Foundations · Chair-Side Physiology

300 practice MCQs

Cardiovascular & Respiratory Physiology MCQs

Cardiovascular and respiratory physiology drive what's safe in the dental chair, from anesthetic dose limits to recognizing when a routine visit becomes a medical emergency.

How to use this section

Four passes through cardio-respiratory physiology.

Step 1
Learn the map
Start with the Clinical Map below to see how the pump, the rhythm, the breath, and the chair-side emergencies connect.
Step 2
Drill Core Recall
Move to the Core Recall Bank to lock in the facts: hemodynamic formulas, ECG waves and conduction, lung volumes and gas exchange, and acid-base balance.
Step 3
Study the modules
Work through the Clinical Modules: cardiac cycle, ECG, pulmonary ventilation, and clinical correlations. Each module pairs a learning summary with board-style MCQs and full distractor explanations.
Step 4
Apply at chair-side
Finish with the Clinical Correlations module: it ties pump, rhythm, and breathing back to dental emergencies and anesthetic safety.

Clinical Map

The cardio-respiratory clinical map.

Organized around the question every dental visit quietly asks of the heart and lungs: is this patient safe to treat, and would you recognize it if they weren't? The four areas below move from the pump, to the rhythm, to the breath, to the chair-side emergencies they create.

Cardiovascular and respiratory physiology decide what is safe in the dental chair: how much epinephrine you can give, how a patient tolerates lying back, and what a sudden change in pulse, color, or breathing actually means. The four areas below mirror how you read a patient. The pump (output and pressure), the rhythm (the electrical signal), the breath (ventilation and gas exchange), and the chair-side emergencies where all three show up at once.

The Pump: Output and Pressure

Cardiac output is stroke volume times heart rate, and almost every cardiac question reduces to one of those two levers or the pressure the pump works against. Know the formulas and you can predict how disease, anxiety, and epinephrine move a patient's vital signs.

Hemodynamic parameters and why they matter chair-side

Parameter	Definition	Normal	Chair-side relevance
Stroke volume (SV)	EDV minus ESV	~70 mL	Falls with poor preload (dehydration, vasodilation) or weak contractility
Cardiac output (CO)	SV times heart rate	~5 L/min	Anxiety and pain raise HR and CO; a failing heart cannot keep up with demand
Ejection fraction (EF)	SV divided by EDV	55 to 70%	A low EF marks heart failure and limited reserve for stress or sedation
Preload	Venous return and end-diastolic stretch	Varies	Supine positioning raises it; it can overwhelm a failing heart (orthopnea)
Afterload	Resistance the ventricle ejects against	Varies	Uncontrolled hypertension raises it and the heart's oxygen demand
Mean arterial pressure (MAP)	Diastolic plus one third of pulse pressure	70 to 100 mmHg	The perfusion number; below ~60 organs are underperfused

Clinical pearl, Dental Door Rule

For a patient with significant cardiovascular disease, the cardiac dose limit of epinephrine is about 0.04 mg, roughly two carpules of 1:100,000 lidocaine, versus 0.2 mg in a healthy adult. Epinephrine raises rate, contractility, and oxygen demand through beta-1, so a heart with little reserve is exactly the one that tolerates an overdose least. Aspirate, inject slowly, and respect the limit.

Deep dive

Cardiac Cycle & Hemodynamics →

Diastole versus systole, the EDV/ESV/SV/CO/EF formulas, preload-afterload-contractility, and the S1 to S4 heart sounds.

The Rhythm: Reading the Electrical Signal

The ECG is the conduction system drawn out in time. Each wave and interval maps to one step, so a widened, prolonged, or missing piece localizes the problem and tells you whether the rhythm is benign, dangerous, or shockable.

ECG components and what each represents

Component	Represents	Normal	Read when abnormal
P wave	Atrial depolarization	Upright, < 0.12 s	Absent or chaotic in atrial fibrillation
PR interval	AV node conduction delay	0.12 to 0.20 s	Prolonged in first-degree AV block
QRS complex	Ventricular depolarization	< 0.12 s	Wide in bundle branch block and ventricular rhythms
ST segment	Early ventricular repolarization	Isoelectric	Elevation suggests acute injury (MI)
QT interval	Total depolarization and repolarization	Rate-dependent	Prolonged QT predisposes to torsades

Clinical pearl, Dental Door Rule

Only two arrest rhythms are shockable: ventricular fibrillation and pulseless ventricular tachycardia. Asystole and pulseless electrical activity are not, so they get CPR and epinephrine, not the defibrillator. Separately, a patient in atrial fibrillation is almost always anticoagulated, so confirm the regimen before any extraction or surgical procedure and plan local hemostasis accordingly.

Deep dive

ECG Basics →

P-QRS-T waves, intervals, the conduction system, AFib/VT/VF, AV blocks, and the rhythms that need defibrillation.

The Breath: Ventilation and Gas Exchange

Breathing is two jobs: moving air (ventilation mechanics and lung volumes) and trading gas (the oxygen-hemoglobin curve at the alveolus and the tissue). Obstructive and restrictive patterns split nearly every pulmonary patient you will treat.

Obstructive versus restrictive lung disease

Pattern	FEV1/FVC	Examples	Chair-side relevance
Obstructive	Reduced (< 70%)	Asthma, COPD, chronic bronchitis	Air trapping; confirm a rescue inhaler is on hand and treat triggers before they flare
Restrictive	Normal or increased	Pulmonary fibrosis, obesity, neuromuscular disease	Low total lung volume and reserve; watch tolerance of a reclined chair

Clinical pearl, Dental Door Rule

The oxygen-hemoglobin curve shifts right (releasing more oxygen to tissue) with rising CO2, acid, temperature, and 2,3-BPG, the Bohr effect, and left when those fall or carbon monoxide is present. In practice: never withhold oxygen from a hypoxic, distressed patient out of fear of a COPD hypoxic drive, and give albuterol first for an acute asthma attack in the chair.

Deep dive

Pulmonary Ventilation →

Lung volumes, breathing mechanics, gas transport, the O2-Hb curve and Bohr effect, and obstructive versus restrictive PFT patterns.

Chair-Side: When Physiology Becomes an Emergency

The clinical correlations module is the synthesis: it pulls pump, rhythm, and breath into the handful of events that turn a routine visit into a medical emergency, and into the recognition cues that tell you which one you are looking at.

Angina versus MI: angina eases with rest or nitroglycerin in minutes; chest pain that persists, radiates, and comes with diaphoresis is an MI until proven otherwise. Activate emergency services.
Heart failure: orthopnea (worsening when supine) and paroxysmal nocturnal dyspnea signal a pump that cannot handle the preload of lying flat. Treat these patients more upright.
Asthma attack: wheeze, prolonged expiration, and accessory muscle use. Stop, sit the patient up, and give the short-acting beta-2 agonist (albuterol).
Hyperventilation syndrome: anxiety-driven rapid breathing causing perioral and finger tingling from respiratory alkalosis. Coach slow breathing; do not give supplemental oxygen.
Opioid hypoventilation: sedation plus a slow respiratory rate and pinpoint pupils. Support ventilation and reverse with naloxone.
AFib on an anticoagulant: not an acute emergency but a bleeding-risk decision; confirm the drug and INR where relevant before surgery.

Deep dive

Clinical Correlations →

Heart failure, angina versus MI, AFib and anticoagulation, asthma, COPD oxygen, hyperventilation, and opioid hypoventilation: the chair-side emergencies physiology creates.

Clinical Modules

4 clinical modules in Cardio & Respiratory.

Each module bridges the physiology to a clinical job: pump mechanics, rhythm reading, gas exchange, and recognizing the chair-side emergencies. Every module pairs a learning summary and board-style MCQs with full distractor explanations.

Pump mechanics

Available

Cardiac Cycle & Hemodynamics MCQ

Diastole vs systole, EDV/ESV/SV/CO/EF formulas, preload-afterload-contractility, and the S1–S4 heart sounds. 11 board-style MCQs.

P-QRS-T waves, intervals, conduction system, AFib/VT/VF, AV blocks, and the rhythms that need defibrillation. 11 board-style MCQs.

Start practice →

Breathing mechanics and gas exchange

Available

Pulmonary Ventilation MCQ

Lung volumes, breathing mechanics, gas transport, the O₂–Hb curve and Bohr effect, and obstructive vs restrictive PFT patterns. 11 board-style MCQs.

Start practice →

Chair-side emergencies

Available

Cardio & Respiratory Clinical MCQ

Heart failure, angina vs MI, AFib + anticoagulation, asthma, COPD oxygen, hyperventilation, opioid hypoventilation, and the dental emergencies they create. 11 board-style MCQs.

Start practice →

Core Recall Bank

300 Cardio & Respiratory Physiology Questions

Use this bank to drill the facts: the cardiac cycle and hemodynamic formulas, ECG waves and conduction, lung volumes and gas exchange, and the chair-side correlations. These questions build the foundation; the clinical modules show how the facts are used in diagnosis, anesthetic safety, and recognizing dental emergencies.

001
Cardiac Output Definition
Cardiac output is calculated as:
- A.Heart rate × stroke volume
- B.Blood pressure × heart rate
- C.Venous return ÷ blood pressure
- D.Stroke volume ÷ heart rate
Answer: A.Heart rate × stroke volume
Why
Cardiac output is the amount of blood pumped by one ventricle per minute. It equals heart rate multiplied by stroke volume.
002
Stroke Volume Definition
Stroke volume is the amount of blood:
- A.Pumped by one ventricle per beat
- B.Pumped by both ventricles per minute
- C.Remaining in the ventricle after contraction only
- D.Returning to the heart per hour
Answer: A.Pumped by one ventricle per beat
Why
Stroke volume is the volume of blood ejected by one ventricle with each heartbeat. It depends on preload, contractility, and afterload.
003
End-Diastolic Volume
End-diastolic volume refers to the volume of blood in the ventricle:
- A.During isovolumetric relaxation only
- B.At the end of contraction
- C.In the atrium after systole
- D.At the end of filling
Answer: D.At the end of filling
Why
End-diastolic volume is the ventricular volume after filling is complete, just before systole begins. It is closely related to preload.
004
End-Systolic Volume
End-systolic volume refers to the volume of blood in the ventricle:
- A.Leaving through the vena cava
- B.Entering from the atrium
- C.Before filling begins
- D.Remaining after contraction
Answer: D.Remaining after contraction
Why
End-systolic volume is the blood left in the ventricle after systole. A stronger contraction usually lowers end-systolic volume.
005
Ejection Fraction
Ejection fraction is calculated as:
- A.Stroke volume ÷ end-diastolic volume
- B.End-systolic volume ÷ heart rate
- C.Cardiac output ÷ venous pressure
- D.Heart rate ÷ stroke volume
Answer: A.Stroke volume ÷ end-diastolic volume
Why
Ejection fraction is the fraction of filled ventricular blood that is ejected during systole. It is commonly used to assess systolic function.
006
Normal Left Ventricular Ejection Fraction
A normal left ventricular ejection fraction is usually closest to:
- A.60 percent
- B.25 percent
- C.95 percent
- D.10 percent
Answer: A.60 percent
Why
A normal ejection fraction is typically around 55 to 70 percent. Very low values suggest impaired systolic function.
007
Preload
Preload is most closely related to:
- A.Heart rate only
- B.Ventricular filling before contraction
- C.Blood viscosity only
- D.Arterial pressure opposing ejection
Answer: B.Ventricular filling before contraction
Why
Preload reflects stretch of ventricular muscle before contraction. It is closely related to venous return and end-diastolic volume.
008
Afterload
Afterload is best described as:
- A.Strength of atrial contraction only
- B.Resistance the ventricle must overcome to eject blood
- C.Volume of blood in the veins only
- D.Amount of blood returning to the heart
Answer: B.Resistance the ventricle must overcome to eject blood
Why
Afterload is the pressure or resistance the ventricle works against during ejection. In the left ventricle, it is closely related to arterial pressure.
009
Contractility
Cardiac contractility means:
- A.Strength of contraction at a given preload
- B.Pressure inside the veins only
- C.Amount of blood returning to the heart only
- D.Electrical delay in the AV node only
Answer: A.Strength of contraction at a given preload
Why
Contractility is the intrinsic force-generating ability of cardiac muscle. Sympathetic stimulation increases contractility.
010
Frank-Starling Mechanism
The Frank-Starling mechanism states that increased ventricular filling leads to:
- A.Increased stroke volume
- B.Stopped cardiac conduction
- C.Complete AV valve closure failure
- D.Decreased venous return
Answer: A.Increased stroke volume
Why
More filling stretches cardiac muscle fibers, which increases contraction force within physiologic limits. This helps match cardiac output to venous return.
011
SA Node Function
The sinoatrial node normally acts as the heart's:
- A.Main ventricular muscle
- B.Main valve between atria and ventricles
- C.Primary pacemaker
- D.Pressure sensor in the aorta
Answer: C.Primary pacemaker
Why
The SA node generates spontaneous electrical impulses that set the normal heart rhythm. It is located in the right atrium.
012
AV Node Function
The AV node is important because it:
- A.Produces red blood cells
- B.Delays conduction from atria to ventricles
- C.Opens the aortic valve
- D.Oxygenates blood
Answer: B.Delays conduction from atria to ventricles
Why
The AV node delays conduction so the ventricles have time to fill after atrial contraction. This improves ventricular filling before systole.
013
Purkinje Fibers
Purkinje fibers are specialized for:
- A.Blood filtration
- B.Valve attachment
- C.Oxygen diffusion in alveoli
- D.Rapid ventricular conduction
Answer: D.Rapid ventricular conduction
Why
Purkinje fibers rapidly distribute electrical impulses through the ventricles. This allows coordinated ventricular contraction.
014
ECG P Wave
The P wave on an ECG represents:
- A.Ventricular repolarization
- B.AV valve closure
- C.Ventricular depolarization
- D.Atrial depolarization
Answer: D.Atrial depolarization
Why
The P wave reflects electrical activation of the atria. Atrial contraction follows shortly after.
015
ECG QRS Complex
The QRS complex represents:
- A.Atrial repolarization only
- B.Ventricular depolarization
- C.Ventricular filling
- D.Aortic valve closure
Answer: B.Ventricular depolarization
Why
The QRS complex reflects depolarization of the ventricles. Ventricular contraction follows this electrical event.
016
ECG T Wave
The T wave represents:
- A.Ventricular repolarization
- B.SA node firing only
- C.AV valve opening
- D.Atrial depolarization
Answer: A.Ventricular repolarization
Why
The T wave reflects recovery of ventricular electrical activity. Abnormal T waves may occur with ischemia, electrolyte problems, or other cardiac issues.
017
PR Interval
The PR interval mainly reflects conduction through the:
- A.Aortic valve only
- B.Alveoli
- C.AV node and atrioventricular conduction system
- D.Pulmonary capillaries only
Answer: C.AV node and atrioventricular conduction system
Why
The PR interval measures the time from atrial depolarization to ventricular depolarization. It includes AV nodal delay.
018
QT Interval
The QT interval represents the time of:
- A.SA node recovery only
- B.Ventricular depolarization and repolarization
- C.Venous return only
- D.Atrial filling only
Answer: B.Ventricular depolarization and repolarization
Why
The QT interval reflects the total electrical activation and recovery time of the ventricles. Prolonged QT can increase risk of dangerous arrhythmias.
019
S1 Heart Sound
The first heart sound is caused mainly by closure of the:
- A.Aortic and pulmonary valves
- B.Mitral and tricuspid valves
- C.Coronary arteries
- D.Pulmonary veins
Answer: B.Mitral and tricuspid valves
Why
S1 occurs when the AV valves close at the start of ventricular systole. It is usually heard as "lub."
020
S2 Heart Sound
The second heart sound is caused mainly by closure of the:
- A.Aortic and pulmonary valves
- B.Mitral and tricuspid valves
- C.Vena cava openings
- D.Coronary sinus
Answer: A.Aortic and pulmonary valves
Why
S2 occurs when the semilunar valves close at the end of systole. It is usually heard as "dub."
021
Isovolumetric Contraction
During isovolumetric contraction:
- A.Aortic valve is fully open
- B.Blood flows from ventricle to atrium normally
- C.Ventricular pressure rises while all valves are closed
- D.Ventricles fill rapidly
Answer: C.Ventricular pressure rises while all valves are closed
Why
After the AV valves close and before semilunar valves open, the ventricles contract without changing volume. Pressure rises quickly during this phase.
022
Ventricular Ejection
Ventricular ejection begins when:
- A.Venous return stops
- B.Atrial pressure exceeds venous pressure
- C.Ventricular pressure exceeds arterial pressure
- D.The AV node stops firing
Answer: C.Ventricular pressure exceeds arterial pressure
Why
The aortic and pulmonary valves open when ventricular pressure becomes greater than the pressure in the aorta and pulmonary artery. Blood then leaves the ventricles.
023
Isovolumetric Relaxation
During isovolumetric relaxation:
- A.Ventricles relax while all valves are closed
- B.Blood is ejected into the aorta
- C.The mitral valve remains open
- D.Atria cannot fill
Answer: A.Ventricles relax while all valves are closed
Why
After semilunar valves close and before AV valves open, ventricular pressure falls without a change in volume. This is isovolumetric relaxation.
024
Coronary Perfusion Timing
Most coronary blood flow to the left ventricle occurs during:
- A.Early systole only
- B.Diastole
- C.Atrial systole only
- D.Isovolumetric contraction only
Answer: B.Diastole
Why
During systole, left ventricular muscle compresses coronary vessels. Coronary flow is greatest during diastole when the myocardium relaxes.
025
Coronary Artery Function
Coronary arteries supply blood to the:
- A.Liver sinusoids
- B.Alveoli
- C.Brainstem only
- D.Myocardium
Answer: D.Myocardium
Why
The myocardium needs its own blood supply through the coronary arteries. Even though the heart contains blood, cardiac muscle still depends on coronary circulation.
026
Mean Arterial Pressure
Mean arterial pressure is most closely related to:
- A.Stroke volume ÷ airway resistance
- B.Heart rate ÷ oxygen saturation
- C.Tidal volume × respiratory rate
- D.Cardiac output × systemic vascular resistance
Answer: D.Cardiac output × systemic vascular resistance
Why
Mean arterial pressure depends mainly on cardiac output and systemic vascular resistance. It reflects average driving pressure for blood flow through tissues.
027
Blood Pressure Equation
Arterial blood pressure rises when:
- A.Cardiac output or systemic vascular resistance increases
- B.Tidal volume decreases only
- C.Hemoglobin is completely absent
- D.Alveolar ventilation stops only
Answer: A.Cardiac output or systemic vascular resistance increases
Why
Blood pressure is influenced by how much blood the heart pumps and how much resistance exists in systemic vessels. Either increased cardiac output or increased resistance can raise pressure.
028
Systemic Vascular Resistance
Systemic vascular resistance is controlled mainly by the diameter of:
- A.Arterioles
- B.Pulmonary alveoli
- C.Capillaries only
- D.Large veins only
Answer: A.Arterioles
Why
Arterioles are the major resistance vessels in systemic circulation. Small changes in arteriolar radius produce large changes in resistance.
029
Vessel Radius and Resistance
If vessel radius decreases, vascular resistance:
- A.Increases greatly
- B.Becomes zero
- C.Decreases greatly
- D.Does not change
Answer: A.Increases greatly
Why
Resistance is highly sensitive to vessel radius. Vasoconstriction greatly increases resistance and can raise blood pressure.
030
Sympathetic Effect on Heart
Sympathetic stimulation of the heart increases:
- A.Only red blood cell size
- B.Only venous oxygen content
- C.Heart rate and contractility
- D.Only pulmonary surfactant
Answer: C.Heart rate and contractility
Why
Sympathetic stimulation activates beta-1 receptors in the heart. This increases heart rate, conduction, and contractility.
031
Parasympathetic Effect on Heart
Parasympathetic stimulation through the vagus nerve mainly decreases:
- A.Alveolar oxygen diffusion
- B.Hemoglobin concentration
- C.Pulmonary surfactant
- D.Heart rate
Answer: D.Heart rate
Why
The vagus nerve slows SA node firing and reduces AV node conduction. Its strongest cardiac effect is decreased heart rate.
032
Beta-1 Receptor Location
Beta-1 adrenergic receptors are especially important in the:
- A.Red blood cell membrane only
- B.Heart
- C.Enamel organ
- D.Alveolar air space only
Answer: B.Heart
Why
Beta-1 receptors in the heart increase heart rate and contractility when stimulated. This is why epinephrine can increase pulse and cardiac workload.
033
Alpha-1 Receptor Effect
Alpha-1 receptor activation in blood vessels generally causes:
- A.Decreased heart rate only
- B.Vasoconstriction
- C.Bronchodilation only
- D.Increased oxygen binding only
Answer: B.Vasoconstriction
Why
Alpha-1 receptors on vascular smooth muscle cause vasoconstriction. This can increase systemic vascular resistance and blood pressure.
034
Beta-2 Receptor Effect
Beta-2 receptor activation in the lungs generally causes:
- A.Bronchoconstriction
- B.Valve closure
- C.AV node block
- D.Bronchodilation
Answer: D.Bronchodilation
Why
Beta-2 receptor activation relaxes bronchial smooth muscle. This widens airways and improves airflow.
035
Baroreceptors
Baroreceptors primarily detect changes in:
- A.Alveolar oxygen only
- B.Blood glucose only
- C.Arterial pressure
- D.Tooth pressure only
Answer: C.Arterial pressure
Why
Baroreceptors in the carotid sinus and aortic arch sense stretch caused by arterial pressure. They help rapidly regulate blood pressure through autonomic reflexes.
036
Carotid Sinus Afferent
The carotid sinus baroreceptor afferent pathway travels mainly through:
- A.Hypoglossal nerve
- B.Glossopharyngeal nerve
- C.Trigeminal nerve
- D.Facial nerve
Answer: B.Glossopharyngeal nerve
Why
The carotid sinus sends pressure information through CN IX. This input helps regulate heart rate and blood vessel tone.
037
Aortic Arch Baroreceptor Afferent
Aortic arch baroreceptor afferents travel mainly through:
- A.Hypoglossal nerve
- B.Facial nerve
- C.Mandibular nerve
- D.Vagus nerve
Answer: D.Vagus nerve
Why
The aortic arch sends baroreceptor information through CN X. This helps the brainstem adjust autonomic output to maintain blood pressure.
038
Response to Low Blood Pressure
When blood pressure falls, the baroreceptor reflex causes:
- A.Increased urine loss immediately
- B.Decreased vascular tone only
- C.Increased sympathetic output
- D.Complete stoppage of heart rate
Answer: C.Increased sympathetic output
Why
Low blood pressure reduces baroreceptor firing. The brainstem responds by increasing sympathetic tone, raising heart rate, contractility, and vasoconstriction.
039
Response to High Blood Pressure
When blood pressure rises, the baroreceptor reflex usually causes:
- A.Increased parasympathetic output and reduced sympathetic output
- B.Severe bronchoconstriction only
- C.Increased heart rate only
- D.Complete venous collapse
Answer: A.Increased parasympathetic output and reduced sympathetic output
Why
High pressure increases baroreceptor firing. This promotes vagal activity and reduces sympathetic tone to lower heart rate and vascular resistance.
040
Venous Return
Venous return is the amount of blood returning to the:
- A.Left ventricle only
- B.Aorta only
- C.Right atrium
- D.Pulmonary alveoli
Answer: C.Right atrium
Why
Venous return is blood flow back to the heart, usually measured as flow into the right atrium. In steady state, venous return equals cardiac output.
041
Skeletal Muscle Pump
The skeletal muscle pump helps increase:
- A.Venous return
- B.Alveolar dead space
- C.Airway resistance only
- D.Aortic valve thickness
Answer: A.Venous return
Why
Contracting skeletal muscles compress veins and push blood toward the heart. Venous valves prevent backward flow.
042
Respiratory Pump
During inspiration, venous return to the heart generally increases because thoracic pressure:
- A.Increases greatly
- B.Decreases
- C.Stops changing
- D.Becomes equal to arterial pressure
Answer: B.Decreases
Why
Inspiration lowers intrathoracic pressure, helping draw venous blood into the chest. This supports venous return to the right heart.
043
Capillary Exchange
Fluid movement out of capillaries is promoted by:
- A.Hemoglobin saturation only
- B.Plasma oncotic pressure only
- C.Surfactant only
- D.Capillary hydrostatic pressure
Answer: D.Capillary hydrostatic pressure
Why
Capillary hydrostatic pressure pushes fluid out into the interstitial space. Plasma oncotic pressure pulls fluid back into capillaries.
044
Plasma Oncotic Pressure
Plasma oncotic pressure is mainly produced by:
- A.Oxygen only
- B.Platelets only
- C.Sodium only
- D.Albumin
Answer: D.Albumin
Why
Albumin is the major plasma protein that creates oncotic pressure. This helps retain fluid inside blood vessels.
045
Edema Mechanism
Edema can result from:
- A.Increased capillary hydrostatic pressure or decreased plasma oncotic pressure
- B.Decreased heart rate only
- C.Increased enamel mineralization
- D.Increased alveolar oxygen only
Answer: A.Increased capillary hydrostatic pressure or decreased plasma oncotic pressure
Why
Edema occurs when too much fluid leaves capillaries or not enough returns. Increased hydrostatic pressure, low albumin, lymphatic obstruction, and inflammation can all contribute.
046
Hemoglobin Function
Hemoglobin primarily transports:
- A.Insulin
- B.Saliva
- C.Bile
- D.Oxygen
Answer: D.Oxygen
Why
Hemoglobin in red blood cells carries most oxygen in the blood. Only a small amount of oxygen is dissolved directly in plasma.
047
Oxygen Content in Blood
Most oxygen in blood is carried:
- A.In white blood cells
- B.Attached to platelets
- C.Bound to hemoglobin
- D.Dissolved freely in plasma
Answer: C.Bound to hemoglobin
Why
Hemoglobin carries the vast majority of oxygen. Dissolved oxygen contributes very little to total oxygen content under normal conditions.
048
Oxygen Saturation
Oxygen saturation refers to the percentage of hemoglobin binding sites occupied by:
- A.Carbon dioxide
- B.Oxygen
- C.Bicarbonate
- D.Nitrogen
Answer: B.Oxygen
Why
Oxygen saturation measures how much hemoglobin is loaded with oxygen. Pulse oximeters estimate arterial oxygen saturation.
049
Carbon Dioxide Transport
Most carbon dioxide in blood is transported as:
- A.Bicarbonate
- B.Dissolved oxygen
- C.Nitrogen gas
- D.Carbaminohemoglobin only
Answer: A.Bicarbonate
Why
Most carbon dioxide is converted into bicarbonate in red blood cells. Smaller amounts are dissolved in plasma or bound to hemoglobin.
050
Carbonic Anhydrase
Carbonic anhydrase is important because it helps convert carbon dioxide and water into:
- A.Carbonic acid
- B.Oxygen
- C.Hemoglobin
- D.Albumin
Answer: A.Carbonic acid
Why
Carbonic anhydrase rapidly converts carbon dioxide and water into carbonic acid, which can dissociate into hydrogen ions and bicarbonate. This is central to CO2 transport and acid-base balance.
051
Bohr Effect
The Bohr effect describes how increased CO2 or decreased pH causes hemoglobin to:
- A.Turn into bicarbonate
- B.Bind oxygen more tightly
- C.Stop carrying oxygen completely
- D.Release oxygen more easily
Answer: D.Release oxygen more easily
Why
In active tissues, CO2 rises and pH falls. This shifts hemoglobin toward oxygen unloading where oxygen is needed.
052
Left Shift of Oxyhemoglobin Curve
A left shift of the oxyhemoglobin dissociation curve means hemoglobin has:
- A.No response to pH
- B.Increased oxygen affinity
- C.Decreased oxygen affinity
- D.No oxygen-binding ability
Answer: B.Increased oxygen affinity
Why
A left shift means hemoglobin holds oxygen more tightly. This can impair oxygen unloading to tissues.
053
Right Shift of Oxyhemoglobin Curve
A right shift of the oxyhemoglobin dissociation curve means hemoglobin:
- A.Becomes albumin
- B.Holds oxygen more tightly
- C.Cannot bind carbon dioxide
- D.Releases oxygen more easily
Answer: D.Releases oxygen more easily
Why
A right shift lowers hemoglobin oxygen affinity. This helps oxygen unload to active tissues.
054
Cause of Right Shift
Which condition shifts the oxyhemoglobin dissociation curve to the right?
- A.Increased CO2
- B.Increased pH
- C.Decreased 2,3-BPG
- D.Decreased temperature
Answer: A.Increased CO2
Why
Increased CO2, increased temperature, increased 2,3-BPG, and decreased pH shift the curve right. This promotes oxygen unloading.
055
Carbon Monoxide Effect
Carbon monoxide is dangerous because it:
- A.Directly produces saliva
- B.Increases alveolar surfactant only
- C.Binds hemoglobin with high affinity and reduces oxygen delivery
- D.Blocks all carbon dioxide formation
Answer: C.Binds hemoglobin with high affinity and reduces oxygen delivery
Why
Carbon monoxide binds hemoglobin much more strongly than oxygen. It reduces oxygen-carrying capacity and impairs oxygen unloading.
056
Pulse Oximetry Limitation
Pulse oximetry may appear falsely normal in poisoning by:
- A.Sodium chloride
- B.Nitrogen
- C.Carbon monoxide
- D.Albumin
Answer: C.Carbon monoxide
Why
Pulse oximetry cannot reliably distinguish oxyhemoglobin from carboxyhemoglobin. A patient with carbon monoxide poisoning may look falsely well oxygenated on pulse ox.
057
Respiratory System Main Function
The main function of the respiratory system is to:
- A.Pump blood through arteries
- B.Exchange oxygen and carbon dioxide
- C.Filter plasma proteins
- D.Produce red blood cells only
Answer: B.Exchange oxygen and carbon dioxide
Why
The respiratory system brings oxygen into the body and removes carbon dioxide. This supports cellular metabolism and acid-base balance.
058
Inspiration Muscle
The primary muscle of quiet inspiration is the:
- A.Internal intercostal muscle
- B.Rectus abdominis
- C.Buccinator
- D.Diaphragm
Answer: D.Diaphragm
Why
The diaphragm contracts and moves downward during quiet inspiration. This increases thoracic volume and draws air into the lungs.
059
Quiet Expiration
Quiet expiration is usually:
- A.Caused by active jaw movement
- B.Driven mainly by diaphragm contraction
- C.Impossible without accessory muscles
- D.Passive
Answer: D.Passive
Why
Quiet expiration occurs as inspiratory muscles relax and elastic recoil pushes air out. Active expiration uses abdominal and internal intercostal muscles.
060
Lung Compliance
Lung compliance refers to how easily the lungs:
- A.Pump blood
- B.Expand
- C.Make hemoglobin
- D.Conduct electricity
Answer: B.Expand
Why
Compliance is the change in volume for a given pressure change. High compliance means lungs expand easily, while low compliance means stiff lungs.
061
Surfactant Function
Pulmonary surfactant reduces:
- A.Heart rate only
- B.Alveolar surface tension
- C.Hemoglobin concentration
- D.Blood pressure
Answer: B.Alveolar surface tension
Why
Surfactant reduces surface tension in alveoli. This helps prevent alveolar collapse and improves lung compliance.
062
Surfactant-Producing Cell
Pulmonary surfactant is produced by:
- A.Red blood cells
- B.Platelets
- C.Type I pneumocytes
- D.Type II pneumocytes
Answer: D.Type II pneumocytes
Why
Type II pneumocytes produce surfactant. Type I pneumocytes are thin cells specialized for gas exchange.
063
Type I Pneumocytes
Type I pneumocytes are mainly responsible for:
- A.Mucus production only
- B.Hemoglobin synthesis
- C.Surfactant production
- D.Gas exchange
Answer: D.Gas exchange
Why
Type I pneumocytes are thin cells that form most of the alveolar surface. Their thinness supports diffusion of oxygen and carbon dioxide.
064
Alveolar Macrophages
Alveolar macrophages mainly function to:
- A.Generate cardiac impulses
- B.Close the glottis
- C.Produce hemoglobin
- D.Remove inhaled particles and pathogens
Answer: D.Remove inhaled particles and pathogens
Why
Alveolar macrophages are immune cells that clean the alveoli. They remove particles, debris, and microbes.
065
Tidal Volume
Tidal volume is the amount of air:
- A.In the anatomic dead space only
- B.Exhaled after forced expiration only
- C.Moved in or out during a normal quiet breath
- D.Remaining after maximal expiration
Answer: C.Moved in or out during a normal quiet breath
Why
Tidal volume is the normal breath volume. In an average adult, it is often around 500 mL.
066
Respiratory Rate
Minute ventilation is calculated as:
- A.Vital capacity ÷ heart rate
- B.Residual volume × oxygen saturation
- C.Tidal volume × respiratory rate
- D.Heart rate × stroke volume
Answer: C.Tidal volume × respiratory rate
Why
Minute ventilation is total air moved in or out per minute. It depends on breath size and breathing frequency.
067
Alveolar Ventilation
Alveolar ventilation is lower than minute ventilation because some air remains in the:
- A.Left ventricle
- B.Dead space
- C.Coronary sinus
- D.Pleural fluid only
Answer: B.Dead space
Why
Dead space air does not participate in gas exchange. Alveolar ventilation equals the air reaching functioning alveoli per minute.
068
Anatomic Dead Space
Anatomic dead space includes air in the:
- A.Alveoli with perfect perfusion
- B.Pulmonary capillaries
- C.Conducting airways
- D.Left atrium
Answer: C.Conducting airways
Why
Anatomic dead space is air in the nose, pharynx, trachea, bronchi, and other conducting airways. It does not reach alveoli for gas exchange.
069
Physiologic Dead Space
Physiologic dead space includes:
- A.Only blood in pulmonary veins
- B.Only oxygen bound to hemoglobin
- C.Anatomic dead space plus alveoli that are ventilated but not perfused
- D.Only air in the stomach
Answer: C.Anatomic dead space plus alveoli that are ventilated but not perfused
Why
Physiologic dead space includes all ventilated areas that do not exchange gas effectively. It increases in conditions such as pulmonary embolism.
070
Vital Capacity
Vital capacity is the maximum amount of air that can be:
- A.Exhaled after maximal inspiration
- B.Held in dead space only
- C.Left after maximal expiration
- D.Dissolved in blood
Answer: A.Exhaled after maximal inspiration
Why
Vital capacity includes inspiratory reserve volume, tidal volume, and expiratory reserve volume. It reflects the usable volume range of the lungs.
071
Residual Volume
Residual volume is the air remaining in lungs after:
- A.Normal quiet expiration only
- B.Maximal forced expiration
- C.Normal quiet inspiration
- D.One heartbeat
Answer: B.Maximal forced expiration
Why
Residual volume prevents complete lung collapse. It cannot be measured by simple spirometry.
072
Total Lung Capacity
Total lung capacity equals vital capacity plus:
- A.Cardiac output
- B.Tidal volume only
- C.Dead space only
- D.Residual volume
Answer: D.Residual volume
Why
Total lung capacity is the total air in the lungs after maximal inspiration. It includes residual volume.
073
Obstructive Lung Disease
Obstructive lung disease is characterized mainly by:
- A.Difficulty getting air out
- B.Complete absence of dead space
- C.No change in airflow
- D.Increased lung stiffness only
Answer: A.Difficulty getting air out
Why
Obstructive disease narrows airways and makes expiration difficult. Examples include asthma, COPD, and chronic bronchitis.
074
Restrictive Lung Disease
Restrictive lung disease is characterized mainly by:
- A.Reduced lung expansion
- B.Increased airway mucus only
- C.Bronchodilation only
- D.Increased residual volume always
Answer: A.Reduced lung expansion
Why
Restrictive disease limits lung expansion and reduces lung volumes. Examples include pulmonary fibrosis, chest wall restriction, and neuromuscular weakness.
075
FEV1
FEV1 measures the volume of air forcibly exhaled in:
- A.Five seconds
- B.One minute
- C.The first second
- D.One heartbeat
Answer: C.The first second
Why
FEV1 is the forced expiratory volume in the first second. It is especially reduced in obstructive lung disease.
076
FVC
Forced vital capacity is the total amount of air exhaled during:
- A.Passive expiration only
- B.Forced expiration after maximal inspiration
- C.One cardiac cycle
- D.Normal quiet breathing
Answer: B.Forced expiration after maximal inspiration
Why
FVC measures the maximum air a person can forcefully exhale after a full inspiration. It is used with FEV1 to evaluate lung disease.
077
FEV1/FVC in Obstructive Disease
In obstructive lung disease, the FEV1/FVC ratio usually:
- A.Cannot change
- B.Becomes exactly 100 percent
- C.Decreases
- D.Increases sharply
Answer: C.Decreases
Why
FEV1 falls more than FVC in obstructive disease because air exits slowly. This lowers the FEV1/FVC ratio.
078
FEV1/FVC in Restrictive Disease
In restrictive lung disease, the FEV1/FVC ratio is usually:
- A.Unrelated to lung volume
- B.Normal or increased
- C.Severely decreased only
- D.Always zero
Answer: B.Normal or increased
Why
Both FEV1 and FVC decrease in restrictive disease, but FVC often decreases proportionally or more. The ratio is usually normal or increased.
079
Asthma Mechanism
Asthma involves reversible airway obstruction mainly due to:
- A.Destruction of the SA node
- B.Bronchoconstriction and inflammation
- C.Pulmonary valve failure only
- D.Loss of hemoglobin
Answer: B.Bronchoconstriction and inflammation
Why
Asthma causes airway narrowing due to smooth muscle constriction, inflammation, and mucus production. This makes expiration difficult.
080
COPD Feature
COPD is commonly associated with:
- A.Chronic airflow limitation
- B.No gas exchange impairment ever
- C.Complete absence of coughing
- D.Increased ejection fraction always
Answer: A.Chronic airflow limitation
Why
COPD includes chronic bronchitis and emphysema. It causes persistent airflow limitation and can impair gas exchange.
081
Emphysema
Emphysema is characterized by destruction of:
- A.Type II pneumocytes only
- B.Alveolar walls
- C.AV node tissue only
- D.Red blood cells only
Answer: B.Alveolar walls
Why
Emphysema destroys alveolar walls, reducing elastic recoil and gas exchange surface area. This causes air trapping and shortness of breath.
082
Chronic Bronchitis
Chronic bronchitis is defined clinically by chronic productive cough for:
- A.10 years without sputum
- B.1 day after exercise
- C.At least 3 months in 2 consecutive years
- D.1 week after a cold only
Answer: C.At least 3 months in 2 consecutive years
Why
Chronic bronchitis is a clinical diagnosis based on long-term productive cough. It is associated with mucus hypersecretion and airway inflammation.
083
Pulmonary Fibrosis
Pulmonary fibrosis primarily causes:
- A.Complete bronchodilation
- B.Increased airway diameter only
- C.Decreased lung compliance
- D.Increased lung elasticity always
Answer: C.Decreased lung compliance
Why
Fibrosis stiffens lung tissue. This makes the lungs harder to expand and produces a restrictive pattern.
084
Gas Diffusion
Gas exchange across the alveolar-capillary membrane occurs mainly by:
- A.Active transport only
- B.Filtration only
- C.Muscle contraction only
- D.Diffusion
Answer: D.Diffusion
Why
Oxygen and carbon dioxide move down partial pressure gradients. Thin alveolar and capillary walls support rapid diffusion.
085
Oxygen Diffusion Direction
In the lungs, oxygen normally diffuses from:
- A.Veins into the trachea
- B.Alveoli into pulmonary capillary blood
- C.Blood into alveoli
- D.Left ventricle into alveoli
Answer: B.Alveoli into pulmonary capillary blood
Why
Alveolar oxygen partial pressure is higher than venous blood oxygen partial pressure. Oxygen therefore diffuses into blood.
086
Carbon Dioxide Diffusion Direction
In the lungs, carbon dioxide normally diffuses from:
- A.Pulmonary capillary blood into alveoli
- B.Alveoli into blood
- C.Aorta into the pleural cavity
- D.Bronchi into red blood cells only
Answer: A.Pulmonary capillary blood into alveoli
Why
Venous blood entering pulmonary capillaries has higher carbon dioxide partial pressure than alveolar air. Carbon dioxide diffuses into alveoli to be exhaled.
087
Partial Pressure
Partial pressure refers to the pressure exerted by:
- A.Airway mucus only
- B.An individual gas in a gas mixture
- C.Plasma proteins only
- D.Blood cells only
Answer: B.An individual gas in a gas mixture
Why
Each gas in a mixture contributes part of the total pressure. Gas movement depends on partial pressure gradients.
088
Alveolar PO2
Alveolar PO2 is normally lower than atmospheric PO2 because alveolar air contains:
- A.Water vapor and carbon dioxide
- B.Only oxygen
- C.No carbon dioxide
- D.No nitrogen
Answer: A.Water vapor and carbon dioxide
Why
Inspired air is humidified and mixed with carbon dioxide in alveoli. This lowers alveolar oxygen partial pressure compared with dry atmospheric air.
089
Ventilation-Perfusion Ratio
The ventilation-perfusion ratio compares:
- A.Oxygen saturation to hemoglobin only
- B.Heart rate to stroke volume
- C.Airflow to blood flow in the lungs
- D.Blood pressure to tidal volume only
Answer: C.Airflow to blood flow in the lungs
Why
V/Q matching is essential for efficient gas exchange. Ventilation brings air to alveoli, while perfusion brings blood to alveolar capillaries.
090
Low V/Q
A low V/Q ratio means alveoli are:
- A.Fully blocked from blood and air
- B.Filled only with oxygen
- C.Perfused but poorly ventilated
- D.Ventilated but not perfused
Answer: C.Perfused but poorly ventilated
Why
Low V/Q occurs when blood reaches alveoli but ventilation is inadequate. This can happen with airway obstruction or pneumonia.
091
High V/Q
A high V/Q ratio means alveoli are:
- A.Completely collapsed always
- B.Perfused but not ventilated
- C.Filled with blood only
- D.Ventilated but poorly perfused
Answer: D.Ventilated but poorly perfused
Why
High V/Q occurs when ventilation is present but blood flow is reduced. Pulmonary embolism is a classic cause.
092
Shunt
A physiologic shunt occurs when blood:
- A.Stops flowing through veins
- B.Never reaches systemic tissues
- C.Carries too much oxygen only
- D.Passes through the lungs without being oxygenated well
Answer: D.Passes through the lungs without being oxygenated well
Why
A shunt is perfusion without adequate ventilation. Oxygen therapy may only partially improve severe shunt physiology.
093
Pulmonary Embolism
Pulmonary embolism creates a problem best described as:
- A.Perfusion without ventilation
- B.Ventilation without perfusion
- C.Increased surfactant only
- D.Increased vital capacity only
Answer: B.Ventilation without perfusion
Why
A pulmonary embolus blocks blood flow to ventilated alveoli. This increases dead space and creates high V/Q regions.
094
Hypoxemia
Hypoxemia means low oxygen level in the:
- A.Arterial blood
- B.Saliva only
- C.Tooth enamel
- D.Pulmonary valve only
Answer: A.Arterial blood
Why
Hypoxemia refers to low arterial oxygen. It is different from hypoxia, which means low oxygen delivery or use at the tissue level.
095
Hypoxia
Hypoxia means low oxygen availability at the level of:
- A.Tooth enamel only
- B.Tissues
- C.Airway cartilage only
- D.Salivary ducts only
Answer: B.Tissues
Why
Hypoxia occurs when tissues do not get or use enough oxygen. It can result from hypoxemia, anemia, poor circulation, or cellular poisoning.
096
Cyanosis
Cyanosis is a bluish discoloration caused by increased:
- A.Plasma albumin
- B.Deoxygenated hemoglobin
- C.Platelets only
- D.Carbon monoxide only
Answer: B.Deoxygenated hemoglobin
Why
Cyanosis becomes visible when deoxygenated hemoglobin increases in blood. It may be seen in lips, nail beds, or mucosa.
097
Central Chemoreceptors
Central chemoreceptors respond mainly to changes in:
- A.Blood oxygen only
- B.Hemoglobin concentration only
- C.CO2 through changes in CSF pH
- D.Blood glucose only
Answer: C.CO2 through changes in CSF pH
Why
CO2 crosses the blood-brain barrier and changes CSF pH. Central chemoreceptors are very important for regulating ventilation.
098
Peripheral Chemoreceptors
Peripheral chemoreceptors are located mainly in the:
- A.Alveoli only
- B.Dental pulp only
- C.Carotid and aortic bodies
- D.Left ventricle only
Answer: C.Carotid and aortic bodies
Why
Peripheral chemoreceptors respond to low oxygen, high CO2, and low pH. They send signals to the brainstem to adjust breathing.
099
Main Driver of Ventilation
Under normal conditions, ventilation is driven most strongly by:
- A.Blood calcium only
- B.Plasma albumin only
- C.Arterial CO2 level
- D.Tooth pain
Answer: C.Arterial CO2 level
Why
CO2 is the main physiologic driver of ventilation in most healthy people. Rising CO2 increases ventilation.
100
Hyperventilation Effect
Hyperventilation causes arterial CO2 to:
- A.Stay exactly the same
- B.Increase
- C.Decrease
- D.Turn into oxygen
Answer: C.Decrease
Why
Hyperventilation blows off carbon dioxide. This can cause respiratory alkalosis and symptoms such as lightheadedness or tingling.
101
Hypoventilation Effect
Hypoventilation causes arterial CO2 to:
- A.Increase
- B.Become zero
- C.Decrease
- D.Stop affecting pH
Answer: A.Increase
Why
When ventilation is too low, carbon dioxide is retained. This can cause respiratory acidosis.
102
Respiratory Acidosis
Respiratory acidosis is usually caused by:
- A.Increased hemoglobin only
- B.Hyperventilation
- C.Excessive oxygen unloading only
- D.Hypoventilation
Answer: D.Hypoventilation
Why
Hypoventilation retains CO2, which increases hydrogen ion concentration and lowers pH. This produces respiratory acidosis.
103
Respiratory Alkalosis
Respiratory alkalosis is usually caused by:
- A.Carbon monoxide poisoning only
- B.Hypoventilation
- C.Hyperventilation
- D.Complete airway obstruction only
Answer: C.Hyperventilation
Why
Hyperventilation removes too much CO2. Lower CO2 reduces hydrogen ion concentration and raises blood pH.
104
Metabolic Acidosis Compensation
Respiratory compensation for metabolic acidosis is:
- A.Increased ventilation
- B.Stopped breathing
- C.Decreased oxygen diffusion only
- D.Decreased ventilation
Answer: A.Increased ventilation
Why
In metabolic acidosis, the body increases ventilation to blow off CO2. This helps raise pH toward normal.
105
Metabolic Alkalosis Compensation
Respiratory compensation for metabolic alkalosis is:
- A.Increased oxygen consumption only
- B.Increased surfactant only
- C.Decreased ventilation
- D.Increased ventilation
Answer: C.Decreased ventilation
Why
In metabolic alkalosis, the body may reduce ventilation to retain CO2. This helps lower pH toward normal, but compensation is limited by the need for oxygen.
106
Normal Blood pH
Normal arterial blood pH is closest to:
- A.6.20
- B.5.00
- C.8.50
- D.7.40
Answer: D.7.40
Why
Normal arterial pH is about 7.35 to 7.45. Values outside this range can affect enzyme function, cardiac rhythm, and neurologic status.
107
Normal PaCO2
Normal arterial PaCO2 is closest to:
- A.40 mmHg
- B.200 mmHg
- C.100 mmHg
- D.10 mmHg
Answer: A.40 mmHg
Why
Normal PaCO2 is about 35 to 45 mmHg. It reflects the balance between CO2 production and alveolar ventilation.
108
Normal PaO2
Normal arterial PaO2 in a healthy young adult breathing room air is closest to:
- A.40 mmHg
- B.200 mmHg
- C.95 mmHg
- D.20 mmHg
Answer: C.95 mmHg
Why
Normal PaO2 is often around 80 to 100 mmHg in healthy adults breathing room air. It can be lower with age or lung disease.
109
Bicarbonate Buffer
The major extracellular buffer system is the:
- A.Surfactant system only
- B.Bicarbonate buffer system
- C.Platelet system only
- D.Myoglobin system only
Answer: B.Bicarbonate buffer system
Why
The bicarbonate buffer system is central to blood pH control. The lungs regulate CO2, and the kidneys regulate bicarbonate.
110
Kidney Role in Acid-Base Balance
The kidneys help regulate acid-base balance mainly by controlling:
- A.Heart valve closure directly
- B.Oxygen binding to hemoglobin directly
- C.Bicarbonate and hydrogen ion excretion
- D.Alveolar airflow directly
Answer: C.Bicarbonate and hydrogen ion excretion
Why
The kidneys reabsorb and generate bicarbonate while excreting hydrogen ions. This is slower than respiratory compensation but powerful over time.
111
Anxiety Hyperventilation
A nervous dental patient breathes rapidly and develops tingling around the mouth. What acid-base change is most likely?
- A.Metabolic alkalosis
- B.Respiratory alkalosis
- C.Respiratory acidosis
- D.Metabolic acidosis
Answer: B.Respiratory alkalosis
Why
Hyperventilation lowers CO2. Low CO2 raises blood pH, causing respiratory alkalosis and symptoms such as lightheadedness, tingling, and chest tightness.
112
Panic Breathing
A patient having a panic attack in the dental chair is breathing fast. Arterial CO2 is expected to:
- A.Become unchanged
- B.Become equal to oxygen saturation
- C.Increase
- D.Decrease
Answer: D.Decrease
Why
Rapid breathing removes CO2 faster than the body produces it. This can produce hypocapnia and respiratory alkalosis.
113
Sedation Hypoventilation
A sedated dental patient becomes very sleepy and breathes slowly. Which change is most likely?
- A.Increased PaCO2
- B.Increased pH only
- C.Decreased PaCO2
- D.Increased oxygen saturation always
Answer: A.Increased PaCO2
Why
Slow breathing reduces CO2 removal. CO2 retention can lead to respiratory acidosis and dangerous respiratory depression.
114
Opioid Respiratory Depression
Opioid overdose is dangerous because it can suppress:
- A.Enamel formation
- B.Saliva pH only
- C.Coronary valve closure only
- D.Brainstem respiratory drive
Answer: D.Brainstem respiratory drive
Why
Opioids can reduce responsiveness of respiratory centers to CO2. This can cause hypoventilation, hypoxemia, and death if untreated.
115
Pulse Oximeter Use
During dental sedation, pulse oximetry is used mainly to monitor:
- A.Stroke volume directly
- B.Plasma albumin
- C.Blood glucose
- D.Oxygen saturation
Answer: D.Oxygen saturation
Why
Pulse oximetry estimates hemoglobin oxygen saturation. It helps detect hypoxemia but does not directly measure ventilation or CO2.
116
Capnography Use
Capnography is useful during sedation because it monitors:
- A.Blood glucose
- B.Enamel oxygen content
- C.Exhaled CO2
- D.Platelet function
Answer: C.Exhaled CO2
Why
Capnography helps assess ventilation by measuring exhaled carbon dioxide. It can detect hypoventilation earlier than pulse oximetry in some settings.
117
Asthma Attack in Dental Chair
A patient with asthma develops wheezing and difficulty exhaling. The main physiologic problem is:
- A.Loss of hemoglobin
- B.Low plasma albumin only
- C.Ventricular fibrillation
- D.Bronchoconstriction
Answer: D.Bronchoconstriction
Why
Asthma causes airway smooth muscle constriction, inflammation, and mucus production. This narrows airways and makes expiration difficult.
118
Rescue Inhaler Mechanism
Albuterol improves an asthma attack mainly by stimulating:
- A.Nicotinic receptors only
- B.Alpha-1 receptors
- C.Muscarinic receptors only
- D.Beta-2 receptors
Answer: D.Beta-2 receptors
Why
Albuterol is a beta-2 agonist that relaxes bronchial smooth muscle. This causes bronchodilation and improves airflow.
119
Epinephrine in Local Anesthetic
Epinephrine is added to dental local anesthetic mainly to:
- A.Destroy bacteria directly
- B.Increase alveolar ventilation only
- C.Cause local vasoconstriction and prolong anesthesia
- D.Increase bleeding
Answer: C.Cause local vasoconstriction and prolong anesthesia
Why
Epinephrine constricts local blood vessels through alpha-1 effects. This slows anesthetic absorption, prolongs anesthesia, and reduces bleeding.
120
Epinephrine Cardiovascular Effect
If too much epinephrine enters systemic circulation, it may cause:
- A.Severe hypoventilation only
- B.Complete loss of oxygen binding
- C.Decreased sympathetic activity only
- D.Increased heart rate and blood pressure
Answer: D.Increased heart rate and blood pressure
Why
Systemic epinephrine can stimulate beta-1 receptors in the heart and alpha-1 receptors in vessels. This may increase pulse, contractility, and blood pressure.
121
Dental Epinephrine and Beta-1
A patient feels palpitations after local anesthetic with epinephrine. This is most related to stimulation of:
- A.Type II pneumocytes
- B.Alveolar macrophages
- C.Plasma albumin
- D.Beta-1 receptors in the heart
Answer: D.Beta-1 receptors in the heart
Why
Beta-1 receptor stimulation increases heart rate and contractility. This can be felt as palpitations when epinephrine reaches systemic circulation.
122
Vasoconstrictor and Bleeding Control
A vasoconstrictor reduces bleeding during dental surgery by decreasing:
- A.Respiratory rate only
- B.Oxygen saturation only
- C.Local blood flow
- D.Plasma bicarbonate only
Answer: C.Local blood flow
Why
Vasoconstriction narrows blood vessels in the surgical area. This reduces bleeding and improves visibility.
123
Orthostatic Hypotension
A patient stands up quickly after a long dental appointment and feels dizzy. The immediate problem is usually reduced:
- A.Pulmonary surfactant
- B.Venous return to the heart
- C.Hemoglobin production
- D.Airway resistance
Answer: B.Venous return to the heart
Why
Standing causes blood to pool in the legs, reducing venous return and cardiac output. Baroreflexes normally compensate by increasing sympathetic tone.
124
Vasovagal Syncope
A patient faints after seeing the dental needle. The likely mechanism is:
- A.Increased vagal tone and decreased sympathetic tone
- B.Increased beta-1 stimulation only
- C.Increased coronary perfusion only
- D.Increased alveolar oxygen only
Answer: A.Increased vagal tone and decreased sympathetic tone
Why
Vasovagal syncope causes bradycardia, vasodilation, and low blood pressure. Fear, pain, or needles can trigger this reflex.
125
Early Syncope Signs
Which sign may occur before vasovagal syncope?
- A.Pallor and sweating
- B.Severe hypertension only
- C.Increased enamel hardness
- D.Improved oxygen delivery always
Answer: A.Pallor and sweating
Why
Patients may feel warm, nauseated, sweaty, pale, and lightheaded before fainting. Recognizing early signs helps prevent injury.
126
Supine Position for Syncope
Placing a fainting patient supine with legs elevated helps increase:
- A.Airway resistance
- B.Alveolar dead space
- C.Plasma potassium only
- D.Venous return
Answer: D.Venous return
Why
A supine position with legs elevated helps return blood to the heart and brain. This improves cardiac output and cerebral perfusion.
127
Angina Mechanism
Angina occurs when the myocardium has:
- A.Excessive alveolar ventilation only
- B.Oxygen demand greater than oxygen supply
- C.Too much CSF
- D.Too much surfactant
Answer: B.Oxygen demand greater than oxygen supply
Why
Angina is chest discomfort from myocardial ischemia. It occurs when coronary blood flow cannot meet cardiac oxygen demand.
128
Nitroglycerin Effect
Nitroglycerin helps angina mainly by:
- A.Bronchoconstriction
- B.Blocking oxygen binding
- C.Vasodilation and reduced cardiac workload
- D.Increasing blood clotting
Answer: C.Vasodilation and reduced cardiac workload
Why
Nitroglycerin dilates veins and coronary vessels. Venodilation reduces preload and myocardial oxygen demand.
129
Myocardial Infarction Concern
Chest pain with sweating, shortness of breath, and nausea during dental treatment should raise concern for:
- A.Hyperventilation only
- B.Chronic gingivitis only
- C.Mild dentin sensitivity only
- D.Myocardial infarction
Answer: D.Myocardial infarction
Why
Myocardial infarction can present with chest pressure, diaphoresis, nausea, dyspnea, and radiation to arm, jaw, or back. Dental providers must recognize this as an emergency.
130
Referred Cardiac Pain
Cardiac ischemia can refer pain to the jaw because visceral pain pathways converge with:
- A.Somatic sensory pathways in the CNS
- B.Salivary glands only
- C.Alveolar macrophages only
- D.Enamel rods
Answer: A.Somatic sensory pathways in the CNS
Why
Visceral pain can be perceived in somatic regions due to convergence of sensory pathways. Jaw pain can rarely be a symptom of cardiac ischemia.
131
Hypertension Definition Concept
Hypertension increases risk mainly by increasing stress on:
- A.Blood vessels and the heart
- B.Enamel only
- C.Saliva only
- D.Pulmonary surfactant only
Answer: A.Blood vessels and the heart
Why
High blood pressure increases workload on the heart and damages blood vessels over time. It raises risk of stroke, heart disease, kidney disease, and other complications.
132
High Blood Pressure Before Procedure
A patient has very high blood pressure before dental surgery. The major concern is increased risk of:
- A.Faster enamel repair
- B.Complete pain elimination
- C.Cardiovascular or cerebrovascular event
- D.Increased lung compliance only
Answer: C.Cardiovascular or cerebrovascular event
Why
Severely elevated blood pressure increases risk during stressful or invasive procedures. Stress, pain, and epinephrine can further raise cardiovascular demand.
133
Heart Failure Physiology
Systolic heart failure is mainly a problem with:
- A.Excess oxygen binding only
- B.Increased alveolar surfactant only
- C.Complete absence of venous return
- D.Reduced ventricular pumping ability
Answer: D.Reduced ventricular pumping ability
Why
Systolic heart failure involves reduced contractile function and reduced ejection fraction. The ventricle cannot pump blood effectively.
134
Left Heart Failure
Left-sided heart failure commonly causes fluid backup into the:
- A.Lower legs only
- B.Lungs
- C.Dental pulp only
- D.Liver only
Answer: B.Lungs
Why
If the left heart cannot pump effectively, pressure backs up into pulmonary veins and capillaries. This can cause pulmonary congestion and shortness of breath.
135
Right Heart Failure
Right-sided heart failure commonly causes:
- A.Isolated tooth pain
- B.Peripheral edema
- C.Decreased venous pressure only
- D.Increased FEV1 always
Answer: B.Peripheral edema
Why
Right-sided heart failure causes systemic venous congestion. This can lead to leg swelling, jugular venous distension, and liver congestion.
136
Pulmonary Edema
Pulmonary edema impairs gas exchange because fluid accumulates in or around:
- A.Alveoli
- B.Coronary arteries only
- C.Aortic valve only
- D.Tooth pulp only
Answer: A.Alveoli
Why
Fluid in the lungs increases diffusion distance and reduces effective gas exchange. Patients may develop dyspnea and low oxygen saturation.
137
COPD Dental Chair Position
A patient with COPD may breathe better in a more upright position because it improves:
- A.Diaphragm mechanics and ventilation
- B.Enamel strength
- C.Saliva flow only
- D.Tooth proprioception
Answer: A.Diaphragm mechanics and ventilation
Why
Many COPD patients breathe better upright because the diaphragm can move more effectively. Lying flat may worsen dyspnea.
138
Oxygen in COPD
A COPD patient with chronic CO2 retention requires oxygen carefully because ventilation may be influenced partly by:
- A.Blood glucose only
- B.Low oxygen drive
- C.Enamel oxygen level
- D.Platelet count only
Answer: B.Low oxygen drive
Why
Some chronic CO2 retainers rely more on hypoxic drive than healthy patients. Oxygen is still given when needed, but monitoring is important.
139
Obstructive Sleep Apnea
Obstructive sleep apnea is caused by repeated collapse of the:
- A.Alveolar capillary membrane only
- B.Left ventricle during systole
- C.Coronary sinus only
- D.Upper airway during sleep
Answer: D.Upper airway during sleep
Why
Obstructive sleep apnea occurs when the upper airway repeatedly collapses during sleep. This causes intermittent hypoxia and sleep fragmentation.
140
Sleep Apnea Cardiovascular Risk
Untreated obstructive sleep apnea increases risk of:
- A.Enamel regeneration
- B.Increased vital capacity always
- C.Hypertension and cardiovascular disease
- D.Complete immunity to arrhythmias
Answer: C.Hypertension and cardiovascular disease
Why
Repeated hypoxia and sympathetic activation increase cardiovascular strain. OSA is linked to hypertension, arrhythmias, stroke, and heart disease.
141
Mandibular Advancement Device
A mandibular advancement device can help some sleep apnea patients by:
- A.Reducing alveolar surfactant
- B.Moving the mandible forward to improve airway patency
- C.Blocking pulmonary blood flow
- D.Increasing hemoglobin production
Answer: B.Moving the mandible forward to improve airway patency
Why
Mandibular advancement can pull the tongue and soft tissues forward. This may reduce upper airway collapse in selected patients.
142
Respiratory Infection and Dental Treatment
A patient with fever, productive cough, and shortness of breath may have reduced oxygen exchange due to:
- A.Lung infection and inflammation
- B.Increased enamel formation
- C.Increased salivary buffering only
- D.Increased cardiac ejection fraction only
Answer: A.Lung infection and inflammation
Why
Respiratory infections can inflame airways and alveoli, impairing ventilation and gas exchange. Elective care may need to be delayed depending on severity.
143
Pneumonia V/Q Problem
Pneumonia often causes hypoxemia because affected alveoli are:
- A.Completely removed from circulation
- B.Filled only with oxygen
- C.Ventilated but not perfused
- D.Perfused but poorly ventilated
Answer: D.Perfused but poorly ventilated
Why
Inflamed or fluid-filled alveoli receive blood but have poor ventilation. This creates low V/Q or shunt-like physiology.
144
Pulmonary Embolism Dental Emergency
Sudden shortness of breath, chest pain, and low oxygen saturation may suggest:
- A.Simple dentin sensitivity
- B.Pulmonary embolism
- C.Mild gingivitis
- D.Normal response to brushing
Answer: B.Pulmonary embolism
Why
Pulmonary embolism blocks blood flow to parts of the lung. It can cause sudden dyspnea, chest pain, tachycardia, and hypoxemia.
145
Anemia and Oxygen Delivery
A patient with severe anemia may have normal oxygen saturation but reduced oxygen delivery because of low:
- A.Hemoglobin concentration
- B.Airway resistance
- C.Alveolar ventilation only
- D.Blood pH only
Answer: A.Hemoglobin concentration
Why
Oxygen saturation measures the percentage of hemoglobin binding sites filled. If there is not enough hemoglobin, total oxygen content can still be low.
146
Shock Physiology
Shock is best described as inadequate:
- A.Tissue perfusion
- B.Saliva production only
- C.Lung compliance only
- D.Tooth eruption
Answer: A.Tissue perfusion
Why
Shock occurs when tissues do not receive enough blood flow and oxygen. It can result from low volume, poor pump function, vasodilation, or obstruction.
147
Anaphylaxis Physiology
Anaphylaxis can cause life-threatening hypotension mainly due to:
- A.Increased enamel mineralization
- B.Reduced alveolar surface tension only
- C.Systemic vasodilation and increased vascular permeability
- D.Increased heart valve closure
Answer: C.Systemic vasodilation and increased vascular permeability
Why
Anaphylaxis releases mediators that cause vasodilation, capillary leakage, airway swelling, and bronchoconstriction. This can rapidly impair circulation and breathing.
148
Epinephrine in Anaphylaxis
Epinephrine helps anaphylaxis because it causes vasoconstriction, supports the heart, and produces:
- A.Lower cardiac contractility
- B.Bronchoconstriction
- C.Bronchodilation
- D.Reduced oxygen binding
Answer: C.Bronchodilation
Why
Epinephrine stimulates alpha-1, beta-1, and beta-2 receptors. It raises blood pressure, improves cardiac output, and opens airways.
149
Allergic Airway Swelling
A patient develops facial swelling, wheezing, and difficulty breathing after medication exposure. The most urgent concern is:
- A.Tooth discoloration
- B.Airway compromise
- C.Increased saliva buffering
- D.Gingival recession
Answer: B.Airway compromise
Why
Allergic reactions can cause airway edema and bronchoconstriction. Difficulty breathing after exposure to a medication is a medical emergency.
150
Dental Stress and Cardiovascular Demand
Pain and fear during dental treatment can increase cardiac workload mainly by activating the:
- A.Parasympathetic lacrimal pathway
- B.Sympathetic nervous system
- C.Bicarbonate buffer only
- D.Pulmonary surfactant system
Answer: B.Sympathetic nervous system
Why
Stress and pain increase sympathetic output, raising heart rate, contractility, and blood pressure. Good pain control and calm communication reduce physiologic stress during dental care.
151
Pulse Pressure
Pulse pressure is calculated as:
- A.Mean arterial pressure minus heart rate
- B.Cardiac output divided by stroke volume
- C.Systolic pressure minus diastolic pressure
- D.Diastolic pressure minus systolic pressure
Answer: C.Systolic pressure minus diastolic pressure
Why
Pulse pressure reflects the difference between systolic and diastolic pressure. It is influenced mainly by stroke volume and arterial compliance.
152
Wide Pulse Pressure
A wide pulse pressure is most likely caused by:
- A.Increased venous oxygen content only
- B.Decreased heart rate only
- C.Increased stroke volume or decreased arterial compliance
- D.Decreased respiratory rate only
Answer: C.Increased stroke volume or decreased arterial compliance
Why
Pulse pressure widens when systolic pressure rises, diastolic pressure falls, or arteries become stiff. Aging and aortic regurgitation can widen pulse pressure.
153
Narrow Pulse Pressure
A narrow pulse pressure may occur with:
- A.Low stroke volume
- B.Increased alveolar oxygen only
- C.High tidal volume only
- D.Increased surfactant
Answer: A.Low stroke volume
Why
When stroke volume falls, systolic pressure may drop while diastolic pressure is relatively preserved. This narrows pulse pressure and may occur in shock or severe heart failure.
154
Arterial Compliance
Arterial compliance refers to the ability of arteries to:
- A.Exchange oxygen directly
- B.Produce red blood cells
- C.Generate electrical impulses
- D.Stretch when pressure rises
Answer: D.Stretch when pressure rises
Why
Compliant arteries expand during systole and recoil during diastole. Stiff arteries increase systolic pressure and widen pulse pressure.
155
Venous Compliance
Compared with arteries, veins generally have:
- A.Higher compliance
- B.Higher pressure
- C.Thicker smooth muscle walls
- D.Lower blood volume capacity
Answer: A.Higher compliance
Why
Veins are highly compliant and serve as blood reservoirs. They hold much of the blood volume at low pressure.
156
Venoconstriction
Sympathetic venoconstriction increases cardiac output mainly by increasing:
- A.Residual lung volume only
- B.Alveolar dead space
- C.Venous return
- D.Airway mucus
Answer: C.Venous return
Why
Venoconstriction shifts blood from venous reservoirs toward the heart. This increases preload and can increase stroke volume through the Frank-Starling mechanism.
157
Right Atrial Pressure
If right atrial pressure rises too much, venous return generally:
- A.Stops depending on pressure gradients
- B.Becomes unrelated to cardiac output
- C.Increases without limit
- D.Decreases
Answer: D.Decreases
Why
Venous return depends on the pressure gradient between peripheral veins and the right atrium. Higher right atrial pressure reduces that gradient.
158
Contractility and End-Systolic Volume
Increased cardiac contractility usually causes end-systolic volume to:
- A.Increase
- B.Decrease
- C.Become equal to end-diastolic volume
- D.Stay fixed
Answer: B.Decrease
Why
A stronger ventricle ejects more blood during systole. This lowers end-systolic volume and increases stroke volume.
159
Increased Afterload Effect
An acute increase in afterload usually causes stroke volume to:
- A.Become unrelated to blood pressure
- B.Become zero immediately
- C.Decrease
- D.Increase sharply
Answer: C.Decrease
Why
Afterload is the pressure the ventricle must overcome to eject blood. If afterload rises suddenly, the ventricle ejects less blood unless contractility compensates.
160
Increased Preload Effect
Within normal physiologic limits, increased preload usually causes:
- A.Increased stroke volume
- B.Complete valve failure
- C.Decreased ventricular filling
- D.Decreased myocardial stretch
Answer: A.Increased stroke volume
Why
Increased preload stretches ventricular muscle fibers. This improves force generation and increases stroke volume through the Frank-Starling mechanism.
161
Pressure-Volume Loop Width
On a left ventricular pressure-volume loop, the width of the loop represents:
- A.Stroke volume
- B.Pulmonary ventilation
- C.Heart rate
- D.Diastolic blood pressure only
Answer: A.Stroke volume
Why
The pressure-volume loop shows ventricular pressure and volume during one cardiac cycle. The difference between end-diastolic volume and end-systolic volume is stroke volume.
162
Pressure-Volume Loop Area
The area inside a ventricular pressure-volume loop represents:
- A.Plasma oncotic pressure
- B.Airway resistance
- C.Stroke work
- D.Oxygen saturation
Answer: C.Stroke work
Why
The loop area reflects mechanical work performed by the ventricle during one beat. Larger loops usually mean more work and higher myocardial oxygen demand.
163
Aortic Stenosis Physiology
Aortic stenosis increases left ventricular afterload because the ventricle must eject blood through:
- A.A low-resistance pulmonary vein
- B.A widened valve
- C.A collapsed vena cava
- D.A narrowed valve
Answer: D.A narrowed valve
Why
Aortic stenosis creates an obstruction to outflow. The left ventricle must generate higher pressure to eject blood into the aorta.
164
Aortic Regurgitation Physiology
Aortic regurgitation increases left ventricular volume load because blood flows back into the ventricle during:
- A.Atrial depolarization only
- B.Diastole
- C.Isovolumetric contraction only
- D.Inspiration only
Answer: B.Diastole
Why
In aortic regurgitation, the aortic valve does not close properly. Blood leaks from the aorta back into the left ventricle during diastole.
165
Mitral Regurgitation Physiology
Mitral regurgitation causes blood to flow backward from the left ventricle into the:
- A.Superior vena cava
- B.Right atrium
- C.Left atrium
- D.Pulmonary artery
Answer: C.Left atrium
Why
The mitral valve sits between the left atrium and left ventricle. If it leaks during systole, blood is pushed backward into the left atrium.
166
Mitral Stenosis Physiology
Mitral stenosis primarily impairs blood flow from the:
- A.Left ventricle to aorta
- B.Left atrium to left ventricle
- C.Pulmonary veins to lungs
- D.Right ventricle to pulmonary artery
Answer: B.Left atrium to left ventricle
Why
A narrowed mitral valve limits ventricular filling. Pressure can build up in the left atrium and pulmonary circulation.
167
Left Atrial Enlargement
Long-standing mitral stenosis can enlarge the left atrium and increase risk of:
- A.Pulmonary surfactant excess
- B.Complete airway dilation
- C.Atrial fibrillation
- D.Increased lung compliance
Answer: C.Atrial fibrillation
Why
Pressure overload in the left atrium can stretch atrial tissue. Atrial enlargement increases risk of atrial fibrillation.
168
Atrial Fibrillation Physiology
Atrial fibrillation reduces ventricular filling efficiency because the atria:
- A.Do not contract effectively
- B.Contract too strongly in sequence
- C.Stop receiving venous blood
- D.Become the main oxygen exchange site
Answer: A.Do not contract effectively
Why
Atrial fibrillation causes disorganized atrial electrical activity. The atrial kick is reduced, which can matter more in older patients or those with stiff ventricles.
169
Atrial Kick
Atrial contraction contributes most to ventricular filling when:
- A.The lungs are hyperinflated only
- B.Ventricular compliance is reduced
- C.The patient is not breathing
- D.Oxygen saturation is 100 percent
Answer: B.Ventricular compliance is reduced
Why
When ventricles are stiff, passive filling is less efficient. Atrial contraction becomes more important for filling.
170
Tachycardia and Filling Time
Severe tachycardia can reduce cardiac output because it shortens:
- A.Alveolar diffusion distance
- B.Diastolic filling time
- C.Red blood cell lifespan
- D.Oxygen binding time only
Answer: B.Diastolic filling time
Why
At very high heart rates, the ventricles have less time to fill. Stroke volume may fall enough to reduce cardiac output.
171
Bradycardia and Cardiac Output
Severe bradycardia may reduce cardiac output mainly because:
- A.Heart rate is too low
- B.Stroke volume becomes infinite
- C.Alveolar ventilation becomes zero automatically
- D.Venous return stops completely
Answer: A.Heart rate is too low
Why
Cardiac output equals heart rate times stroke volume. If heart rate is extremely low, stroke volume may not compensate enough.
172
First-Degree AV Block
First-degree AV block is characterized by:
- A.Prolonged PR interval
- B.Wide pulse pressure only
- C.Absent P waves always
- D.Shortened QT interval always
Answer: A.Prolonged PR interval
Why
First-degree AV block means conduction from atria to ventricles is delayed but still occurs. On ECG, this appears as a prolonged PR interval.
173
Complete Heart Block
In complete heart block, atria and ventricles:
- A.Always beat faster together
- B.Stop all electrical activity
- C.Become synchronized by the lungs
- D.Beat independently
Answer: D.Beat independently
Why
Complete heart block means atrial impulses do not conduct to the ventricles. The ventricles rely on a slower escape rhythm.
174
Ventricular Fibrillation
Ventricular fibrillation is dangerous because ventricular contraction becomes:
- A.Limited to atrial tissue
- B.Chaotic and ineffective
- C.Too coordinated
- D.Normal but slower
Answer: B.Chaotic and ineffective
Why
In ventricular fibrillation, the ventricles quiver instead of pumping blood. This causes circulatory collapse unless treated quickly.
175
Defibrillation Purpose
Defibrillation works by:
- A.Depolarizing many cardiac cells at once to reset rhythm
- B.Increasing surfactant production
- C.Increasing blood glucose
- D.Closing the mitral valve manually
Answer: A.Depolarizing many cardiac cells at once to reset rhythm
Why
Defibrillation delivers an electrical shock that interrupts chaotic electrical activity. This can allow the normal pacemaker system to regain control.
176
Myocardial Oxygen Demand
Myocardial oxygen demand increases most directly with increased:
- A.Saliva pH only
- B.Lung surfactant only
- C.Heart rate, contractility, and wall stress
- D.Venous oxygen saturation only
Answer: C.Heart rate, contractility, and wall stress
Why
The heart uses more oxygen when it beats faster, contracts harder, or works against greater pressure or volume load.
177
Diastolic Coronary Filling
A very fast heart rate can reduce coronary perfusion because it shortens:
- A.Atrial depolarization only
- B.Diastole
- C.Inspiration
- D.The QRS complex only
Answer: B.Diastole
Why
Left coronary blood flow occurs mainly during diastole. Tachycardia shortens diastole and can reduce myocardial oxygen supply.
178
Stable Angina Trigger
Stable angina is usually triggered when myocardial oxygen demand increases during:
- A.Low body temperature only
- B.Quiet sleep only
- C.Normal chewing only in all patients
- D.Exertion or stress
Answer: D.Exertion or stress
Why
Stable angina occurs when fixed coronary narrowing limits oxygen supply during increased demand. Rest or nitroglycerin often relieves it.
179
Unstable Angina Concern
Unstable angina is concerning because it may reflect:
- A.Increased lung compliance only
- B.Increased saliva production only
- C.Normal coronary circulation
- D.Acute plaque disruption and reduced coronary blood flow
Answer: D.Acute plaque disruption and reduced coronary blood flow
Why
Unstable angina is more dangerous than stable angina. It can occur at rest and may progress to myocardial infarction.
180
Troponin Meaning
Elevated cardiac troponin suggests injury to:
- A.Alveolar macrophages
- B.Myocardial cells
- C.Platelets only
- D.Type II pneumocytes
Answer: B.Myocardial cells
Why
Troponin is released when cardiac muscle cells are injured. It is an important marker for myocardial infarction.
181
RAAS Activation
The renin-angiotensin-aldosterone system is activated mainly by:
- A.Increased saliva flow
- B.Low renal perfusion pressure
- C.Increased surfactant only
- D.High oxygen saturation only
Answer: B.Low renal perfusion pressure
Why
Low blood pressure, low renal perfusion, or sympathetic activation can trigger renin release. RAAS helps restore blood pressure and volume.
182
Angiotensin II Effect
Angiotensin II raises blood pressure partly by causing:
- A.Bronchodilation only
- B.Alveolar collapse
- C.Vasoconstriction
- D.Reduced aldosterone release
Answer: C.Vasoconstriction
Why
Angiotensin II is a powerful vasoconstrictor. It also stimulates aldosterone release, increasing sodium and water retention.
183
Aldosterone Effect
Aldosterone increases blood volume mainly by increasing renal reabsorption of:
- A.Carbon dioxide only
- B.Hemoglobin only
- C.Oxygen and nitrogen
- D.Sodium and water
Answer: D.Sodium and water
Why
Aldosterone promotes sodium reabsorption in the kidney. Water follows sodium, increasing blood volume and blood pressure.
184
ADH Effect
Antidiuretic hormone increases blood volume by increasing renal reabsorption of:
- A.Oxygen
- B.Carbon dioxide
- C.Water
- D.Platelets
Answer: C.Water
Why
ADH acts on the collecting ducts to increase water reabsorption. This helps conserve fluid and support blood pressure.
185
ANP Effect
Atrial natriuretic peptide is released with atrial stretch and generally causes:
- A.Increased aldosterone release
- B.Increased venous return only
- C.Severe bronchoconstriction
- D.Sodium and water loss
Answer: D.Sodium and water loss
Why
ANP promotes sodium excretion and water loss, helping reduce blood volume and blood pressure.
186
Exercise Cardiac Response
During exercise, cardiac output increases mainly due to increased heart rate and:
- A.Dead space only
- B.Plasma oncotic pressure only
- C.Stroke volume
- D.Residual volume
Answer: C.Stroke volume
Why
Exercise increases sympathetic output, venous return, and contractility. These changes raise both heart rate and stroke volume.
187
Exercise Blood Flow Redistribution
During exercise, blood flow increases most to:
- A.Hair follicles only
- B.Tooth enamel
- C.Active skeletal muscle
- D.Resting salivary glands only
Answer: C.Active skeletal muscle
Why
Local metabolic factors dilate arterioles in active muscle. Blood is redistributed toward tissues with higher oxygen demand.
188
Local Metabolic Vasodilation
Active tissues increase blood flow mainly by releasing local factors such as CO2, H+, adenosine, and:
- A.Bile salts
- B.Enamel proteins
- C.Low oxygen signals
- D.Surfactant granules
Answer: C.Low oxygen signals
Why
Active tissue metabolism changes the local chemical environment. These signals relax arterioles and increase blood flow where it is needed.
189
Reactive Hyperemia
Reactive hyperemia is increased blood flow after:
- A.A temporary period of reduced blood flow
- B.A permanent loss of all capillaries
- C.Increased surfactant secretion
- D.Complete AV node failure only
Answer: A.A temporary period of reduced blood flow
Why
When blood flow is temporarily blocked, metabolic vasodilators accumulate. Once flow returns, blood flow increases above baseline.
190
Active Hyperemia
Active hyperemia occurs when blood flow increases because tissue:
- A.Arterioles fully constrict
- B.Metabolic activity increases
- C.Venous return becomes zero
- D.Oxygen demand disappears
Answer: B.Metabolic activity increases
Why
Active tissue needs more oxygen and nutrient delivery. Local metabolites dilate arterioles and increase blood flow.
191
Endothelial Nitric Oxide
Nitric oxide released by endothelial cells causes vascular smooth muscle:
- A.Contraction only
- B.Calcification
- C.Relaxation
- D.Electrical depolarization of the SA node only
Answer: C.Relaxation
Why
Nitric oxide diffuses into smooth muscle and promotes relaxation. This causes vasodilation and improves blood flow.
192
Endothelin Effect
Endothelin released by endothelial cells generally causes:
- A.Vasoconstriction
- B.Bronchodilation only
- C.Increased oxygen saturation directly
- D.Increased surfactant production
Answer: A.Vasoconstriction
Why
Endothelin is a strong vasoconstrictor. It helps regulate vascular tone but can contribute to vascular disease when overactive.
193
Lymphatic Function
The lymphatic system helps return excess interstitial fluid to the:
- A.Left ventricle directly
- B.Tooth pulp chamber
- C.Venous circulation
- D.Alveolar air spaces
Answer: C.Venous circulation
Why
Lymphatic vessels collect excess interstitial fluid and proteins. They eventually return lymph to the venous system.
194
Lymphatic Obstruction
Lymphatic obstruction can cause edema because fluid cannot:
- A.Return efficiently from tissues to circulation
- B.Diffuse into alveoli normally
- C.Activate the SA node
- D.Bind hemoglobin normally
Answer: A.Return efficiently from tissues to circulation
Why
Blocked lymph drainage allows fluid and proteins to accumulate in tissues. This can cause persistent swelling.
195
Orthopnea
Orthopnea means difficulty breathing when:
- A.Lying flat
- B.Drinking cold water only
- C.Standing only
- D.Chewing only
Answer: A.Lying flat
Why
Orthopnea is common in heart failure and some lung diseases. Lying flat increases venous return and can worsen pulmonary congestion.
196
Paroxysmal Nocturnal Dyspnea
Paroxysmal nocturnal dyspnea is sudden shortness of breath that occurs:
- A.Only after brushing
- B.During sleep
- C.Only during forced expiration testing
- D.Only during chewing
Answer: B.During sleep
Why
Patients wake up short of breath, often due to fluid redistribution and pulmonary congestion. It is commonly associated with left-sided heart failure.
197
Pulmonary Hypertension
Pulmonary hypertension increases workload mainly on the:
- A.Left atrium only
- B.Aortic valve only
- C.Coronary sinus only
- D.Right ventricle
Answer: D.Right ventricle
Why
The right ventricle pumps blood into the pulmonary circulation. High pulmonary pressure increases right ventricular afterload.
198
Cor Pulmonale
Cor pulmonale refers to right heart dysfunction caused by:
- A.Low salivary pH only
- B.Primary enamel failure
- C.Lung disease or pulmonary hypertension
- D.Mitral valve infection only
Answer: C.Lung disease or pulmonary hypertension
Why
Chronic lung disease can raise pulmonary vascular resistance. This stresses the right ventricle and can lead to right-sided heart failure.
199
Hypoxic Pulmonary Vasoconstriction
In the lungs, low alveolar oxygen causes nearby pulmonary arterioles to:
- A.Constrict
- B.Produce surfactant
- C.Dilate strongly
- D.Stop carrying blood permanently
Answer: A.Constrict
Why
Hypoxic pulmonary vasoconstriction redirects blood away from poorly ventilated alveoli toward better ventilated regions.
200
Systemic Response to Local Hypoxia
In systemic tissues, local hypoxia usually causes arterioles to:
- A.Dilate
- B.Stop blood flow completely
- C.Collapse alveoli
- D.Constrict strongly
Answer: A.Dilate
Why
Systemic tissues respond to low oxygen by vasodilation to improve oxygen delivery. This is opposite of the pulmonary vascular response.
201
Alveolar Gas Equation Purpose
The alveolar gas equation is used to estimate:
- A.Alveolar oxygen partial pressure
- B.Plasma oncotic pressure only
- C.Hemoglobin synthesis rate
- D.Cardiac stroke work only
Answer: A.Alveolar oxygen partial pressure
Why
The alveolar gas equation helps estimate alveolar PO2 based on inspired oxygen, atmospheric pressure, water vapor, PaCO2, and respiratory quotient.
202
A-a Gradient
The A-a gradient compares oxygen pressure in the alveoli with oxygen pressure in the:
- A.Left ventricle muscle
- B.Venous blood only
- C.Arterial blood
- D.Pleural space
Answer: C.Arterial blood
Why
The A-a gradient helps determine whether hypoxemia is due to hypoventilation, low inspired oxygen, or impaired gas exchange.
203
Increased A-a Gradient
An increased A-a gradient suggests a problem with:
- A.Increased hemoglobin concentration only
- B.Pure hyperventilation only
- C.Low atmospheric oxygen only
- D.Gas exchange across the lungs
Answer: D.Gas exchange across the lungs
Why
An increased A-a gradient can occur with V/Q mismatch, diffusion limitation, or shunt. It means alveolar oxygen is not transferring normally into arterial blood.
204
Normal A-a Gradient With Hypoventilation
Pure hypoventilation usually causes hypoxemia with:
- A.No rise in PaCO2
- B.Very high A-a gradient always
- C.Normal A-a gradient
- D.No change in alveolar oxygen
Answer: C.Normal A-a gradient
Why
In pure hypoventilation, alveolar oxygen falls because CO2 rises, but gas exchange across the lung may still be normal. The A-a gradient can remain normal.
205
Diffusion Limitation
Diffusion limitation is more likely when the alveolar-capillary membrane is:
- A.Filled with dental plaque
- B.Thickened
- C.Replaced by hemoglobin
- D.Thinner than normal
Answer: B.Thickened
Why
Thicker membranes make it harder for gases to diffuse. Pulmonary fibrosis is a classic example.
206
Diffusion Limitation During Exercise
Diffusion limitation may become more obvious during exercise because capillary transit time:
- A.Becomes unrelated to blood flow
- B.Stops entirely
- C.Decreases
- D.Increases greatly
Answer: C.Decreases
Why
During exercise, blood moves faster through pulmonary capillaries. If diffusion is impaired, oxygen may not fully equilibrate before blood leaves the lungs.
207
Oxygen Therapy and Shunt
A true right-to-left shunt responds poorly to oxygen because some blood:
- A.Is converted to lymph
- B.Has no carbon dioxide
- C.Has too much hemoglobin
- D.Never reaches ventilated alveoli
Answer: D.Never reaches ventilated alveoli
Why
In a true shunt, blood bypasses ventilated alveoli. Since that blood never contacts alveolar oxygen, supplemental oxygen has limited effect.
208
Dead Space and Oxygen
Increased dead space means a larger portion of each breath:
- A.Raises hemoglobin concentration
- B.Does not participate in gas exchange
- C.Enters the left ventricle directly
- D.Becomes pure oxygen
Answer: B.Does not participate in gas exchange
Why
Dead space ventilation moves air but does not exchange gases with blood. This reduces effective alveolar ventilation.
209
Airway Resistance Main Site
Most airway resistance in healthy lungs occurs in the:
- A.Pulmonary veins only
- B.Pleural cavity only
- C.Alveoli only
- D.Medium-sized bronchi
Answer: D.Medium-sized bronchi
Why
Medium-sized bronchi contribute significantly to airway resistance. Small airways have a large combined cross-sectional area, so resistance there is normally lower.
210
Bronchoconstriction Effect
Bronchoconstriction increases airway resistance most directly by decreasing airway:
- A.Oxygen content only
- B.Radius
- C.Surfactant protein size
- D.Blood volume only
Answer: B.Radius
Why
Resistance rises sharply when airway radius decreases. This is why bronchoconstriction can make breathing difficult.
211
Pursed-Lip Breathing
Pursed-lip breathing helps patients with obstructive lung disease by increasing airway pressure during:
- A.Inspiration only
- B.Swallowing only
- C.Expiration
- D.Cardiac systole
Answer: C.Expiration
Why
Pursed-lip breathing creates back pressure that helps prevent small airway collapse during exhalation. This can reduce air trapping.
212
Dynamic Airway Compression
Dynamic airway compression is most likely during forced expiration in patients with:
- A.Pulmonary fibrosis only
- B.Mitral stenosis only
- C.Increased hemoglobin only
- D.Emphysema
Answer: D.Emphysema
Why
Emphysema destroys elastic tissue and reduces airway support. During forced expiration, small airways can collapse, trapping air.
213
Air Trapping
Air trapping in obstructive lung disease tends to increase:
- A.Vital capacity only
- B.Diffusion surface area
- C.Residual volume
- D.Lung stiffness only
Answer: C.Residual volume
Why
When patients cannot fully exhale, more air remains in the lungs after expiration. This increases residual volume.
214
Barrel Chest Physiology
A barrel chest in emphysema reflects chronic:
- A.Pulmonary fibrosis only
- B.Hyperinflation
- C.Low lung volume only
- D.Complete airway closure at rest
Answer: B.Hyperinflation
Why
Emphysema causes air trapping and hyperinflation. Over time, the chest wall may assume a more expanded shape.
215
Restrictive Disease Lung Volumes
In restrictive lung disease, total lung capacity usually:
- A.Becomes equal to dead space
- B.Stays exactly normal
- C.Increases greatly
- D.Decreases
Answer: D.Decreases
Why
Restrictive disorders prevent full lung expansion. This decreases total lung capacity and vital capacity.
216
Neuromuscular Respiratory Failure
A neuromuscular disorder can cause respiratory failure mainly by weakening:
- A.Pulmonary veins only
- B.Type II pneumocytes only
- C.Alveolar macrophages only
- D.Ventilatory muscles
Answer: D.Ventilatory muscles
Why
The diaphragm and intercostal muscles are required for ventilation. Weakness can cause hypoventilation and CO2 retention.
217
Diaphragm Innervation
The diaphragm is innervated by the:
- A.Facial nerve
- B.Vagus nerve only
- C.Hypoglossal nerve
- D.Phrenic nerve
Answer: D.Phrenic nerve
Why
The phrenic nerve arises from C3 to C5 and innervates the diaphragm. Injury can impair breathing.
218
Accessory Muscles of Inspiration
During respiratory distress, patients may recruit accessory muscles such as the:
- A.Buccinator only
- B.Masseter only
- C.Sternocleidomastoid
- D.Orbicularis oris only
Answer: C.Sternocleidomastoid
Why
Accessory muscles help expand the thorax when breathing effort increases. Visible use of these muscles can suggest respiratory distress.
219
Tripod Position
A patient leaning forward with hands supported during respiratory distress is using a position that helps:
- A.Reduce oxygen diffusion
- B.Close the upper airway
- C.Accessory muscles assist breathing
- D.Stop venous return completely
Answer: C.Accessory muscles assist breathing
Why
The tripod position stabilizes the shoulder girdle and helps accessory muscles improve ventilation. It is commonly seen in significant respiratory distress.
220
Pleural Pressure
During quiet inspiration, intrapleural pressure becomes:
- A.Equal to alveolar oxygen pressure
- B.Zero in all patients
- C.More positive than arterial pressure
- D.More negative
Answer: D.More negative
Why
The diaphragm expands the thoracic cavity, making intrapleural pressure more negative. This helps expand the lungs.
221
Pneumothorax Physiology
A pneumothorax can collapse a lung because air enters the:
- A.Pulmonary capillary only
- B.Left atrium
- C.Pleural space
- D.Choroid plexus
Answer: C.Pleural space
Why
Air in the pleural space disrupts the pressure gradient that keeps the lung expanded. The affected lung may partially or fully collapse.
222
Tension Pneumothorax
Tension pneumothorax is dangerous because pressure in the chest can impair:
- A.Saliva production only
- B.Venous return and cardiac output
- C.Enamel formation
- D.Oxygen binding to hemoglobin directly
Answer: B.Venous return and cardiac output
Why
Air trapped under pressure can shift mediastinal structures and compress great veins. This reduces venous return and can cause shock.
223
Atelectasis
Atelectasis means:
- A.Increased cardiac output only
- B.Excess hemoglobin production
- C.Increased alveolar ventilation everywhere
- D.Collapse of alveoli
Answer: D.Collapse of alveoli
Why
Atelectasis reduces ventilated lung units and can impair oxygenation. It may occur after surgery, shallow breathing, obstruction, or loss of surfactant.
224
Surfactant Deficiency Effect
Surfactant deficiency increases the tendency for alveoli to:
- A.Overproduce hemoglobin
- B.Collapse
- C.Become blood vessels
- D.Stop receiving CO2 entirely
Answer: B.Collapse
Why
Surfactant lowers surface tension. Without enough surfactant, alveoli are harder to keep open and more likely to collapse.
225
Laplace Law in Alveoli
Surfactant is especially important in small alveoli because smaller alveoli would otherwise have higher:
- A.Hemoglobin concentration
- B.Oxygen affinity
- C.Blood pressure
- D.Collapsing pressure
Answer: D.Collapsing pressure
Why
By Laplace law, smaller radius increases collapsing pressure if surface tension is unchanged. Surfactant lowers surface tension and stabilizes alveoli.
226
Fetal Hemoglobin
Fetal hemoglobin has a higher affinity for oxygen than adult hemoglobin, causing the curve to shift:
- A.Down to zero
- B.Into a flat line only
- C.Right
- D.Left
Answer: D.Left
Why
Fetal hemoglobin binds oxygen more tightly, which helps pull oxygen from maternal blood across the placenta.
227
2,3-BPG Effect
Increased 2,3-BPG causes hemoglobin to:
- A.Become carboxyhemoglobin
- B.Hold oxygen more tightly
- C.Stop binding CO2
- D.Release oxygen more easily
Answer: D.Release oxygen more easily
Why
2,3-BPG shifts the oxyhemoglobin curve to the right. This supports oxygen unloading to tissues.
228
Anemia and Pulse Oximetry
A patient with anemia can have a normal pulse oximeter reading because pulse oximetry measures:
- A.Total hemoglobin concentration
- B.Percent saturation of available hemoglobin
- C.Total oxygen content directly
- D.Cardiac output directly
Answer: B.Percent saturation of available hemoglobin
Why
Pulse oximetry estimates the percentage of hemoglobin binding sites occupied by oxygen. It does not tell you how much hemoglobin is present.
229
Methemoglobinemia
Methemoglobinemia impairs oxygen delivery because iron in hemoglobin is oxidized and cannot bind oxygen normally. It is associated with:
- A.Functional anemia
- B.Increased alveolar ventilation only
- C.Increased cardiac valve closure
- D.Excess surfactant
Answer: A.Functional anemia
Why
Methemoglobin cannot carry oxygen effectively. Even if PaO2 is normal, tissues may not receive adequate oxygen.
230
Dental Drug and Methemoglobinemia
Which dental topical anesthetic has been associated with methemoglobinemia risk?
- A.Amoxicillin
- B.Benzocaine
- C.Acetaminophen
- D.Ibuprofen
Answer: B.Benzocaine
Why
Benzocaine can rarely cause methemoglobinemia. This matters clinically because cyanosis or low oxygen saturation after topical anesthetic exposure may not be a simple lung problem.
231
Cyanosis Without Low PaO2
A patient with methemoglobinemia may appear cyanotic even when PaO2 is normal because oxygen cannot be properly:
- A.Inspired into the trachea
- B.Carried by hemoglobin
- C.Made by platelets
- D.Produced by alveoli
Answer: B.Carried by hemoglobin
Why
PaO2 measures dissolved oxygen in plasma, not hemoglobin function. Methemoglobin reduces functional oxygen-carrying capacity.
232
Carbon Monoxide and Oxyhemoglobin Curve
Carbon monoxide poisoning shifts the oxyhemoglobin curve to the left, making remaining hemoglobin:
- A.Hold oxygen more tightly
- B.Stop binding oxygen completely
- C.Turn into bicarbonate
- D.Release oxygen more easily
Answer: A.Hold oxygen more tightly
Why
Carbon monoxide reduces available binding sites and makes remaining hemoglobin hold oxygen more tightly. This worsens tissue oxygen delivery.
233
Tissue Hypoxia With Normal PaO2
Which condition can cause tissue hypoxia despite normal arterial PaO2?
- A.Increased tidal volume only
- B.Mild hyperventilation only
- C.Carbon monoxide poisoning
- D.Increased surfactant only
Answer: C.Carbon monoxide poisoning
Why
PaO2 reflects dissolved oxygen, not total oxygen content. Carbon monoxide blocks hemoglobin binding and reduces tissue oxygen delivery.
234
Histotoxic Hypoxia
Histotoxic hypoxia occurs when tissues cannot use oxygen properly, classically due to:
- A.Low hemoglobin only
- B.Cyanide poisoning
- C.Airway obstruction only
- D.Low atmospheric oxygen only
Answer: B.Cyanide poisoning
Why
Cyanide blocks cellular oxygen use in mitochondria. Blood oxygen may be present, but tissues cannot use it effectively.
235
Stagnant Hypoxia
Stagnant hypoxia is caused by:
- A.Poor tissue blood flow
- B.Abnormal hemoglobin only
- C.High atmospheric pressure only
- D.Low hemoglobin only
Answer: A.Poor tissue blood flow
Why
Stagnant hypoxia occurs when circulation is inadequate. Even oxygenated blood cannot meet tissue needs if flow is too low.
236
Hypoxic Hypoxia
Hypoxic hypoxia is caused by low oxygen entering arterial blood, such as with:
- A.Severe anemia only
- B.Carbon monoxide only
- C.Cyanide only
- D.High altitude
Answer: D.High altitude
Why
At high altitude, inspired oxygen partial pressure is lower. This can reduce arterial oxygen and cause hypoxic hypoxia.
237
Hypercapnia
Hypercapnia means increased:
- A.Arterial oxygen only
- B.Plasma albumin only
- C.Hemoglobin concentration only
- D.Arterial CO2
Answer: D.Arterial CO2
Why
Hypercapnia occurs when ventilation is inadequate relative to CO2 production. It can cause acidosis, confusion, and respiratory distress.
238
Hypocapnia
Hypocapnia means decreased:
- A.Blood pressure only
- B.Oxygen saturation only
- C.Arterial CO2
- D.Hemoglobin only
Answer: C.Arterial CO2
Why
Hypocapnia usually results from hyperventilation. It can cause dizziness, tingling, and cerebral vasoconstriction.
239
Cerebral Blood Flow and CO2
Increased arterial CO2 causes cerebral blood vessels to:
- A.Dilate
- B.Collapse permanently
- C.Constrict
- D.Stop receiving blood
Answer: A.Dilate
Why
CO2 strongly affects cerebral blood flow. High CO2 causes cerebral vasodilation, while low CO2 causes cerebral vasoconstriction.
240
Hyperventilation and Dizziness
Hyperventilation can cause dizziness partly because low CO2 causes cerebral blood vessels to:
- A.Dilate strongly
- B.Rupture immediately
- C.Constrict
- D.Become veins
Answer: C.Constrict
Why
Low CO2 causes cerebral vasoconstriction, which can reduce cerebral blood flow and contribute to lightheadedness.
241
Respiratory Compensation Speed
Respiratory compensation for metabolic acid-base disorders occurs:
- A.Only after kidney failure
- B.Never
- C.Within minutes
- D.Only after months
Answer: C.Within minutes
Why
The lungs can adjust CO2 quickly by changing ventilation. Renal compensation takes longer.
242
Renal Compensation Speed
Renal compensation for respiratory acid-base disorders usually takes:
- A.No time at all
- B.Seconds only
- C.One heartbeat
- D.Hours to days
Answer: D.Hours to days
Why
Kidneys regulate bicarbonate and hydrogen ion handling slowly compared with respiratory changes. Full renal compensation takes time.
243
Chronic Respiratory Acidosis Compensation
In chronic respiratory acidosis, the kidneys compensate by increasing:
- A.Bicarbonate retention
- B.Hemoglobin destruction
- C.Oxygen excretion
- D.CO2 production only
Answer: A.Bicarbonate retention
Why
Chronic CO2 retention lowers pH. The kidneys help buffer this by retaining and generating bicarbonate.
244
Diabetic Ketoacidosis Breathing
Deep, rapid breathing in metabolic acidosis is called:
- A.Kussmaul breathing
- B.Apnea only
- C.Cheyne-Stokes breathing
- D.Orthopnea
Answer: A.Kussmaul breathing
Why
Kussmaul breathing is a compensatory pattern seen in severe metabolic acidosis. The body tries to blow off CO2 to raise pH.
245
Cheyne-Stokes Breathing
Cheyne-Stokes breathing is characterized by cycles of increasing and decreasing ventilation with periods of:
- A.Normal breathing only
- B.Constant hyperventilation only
- C.Forced expiration only
- D.Apnea
Answer: D.Apnea
Why
Cheyne-Stokes breathing is a periodic breathing pattern. It can be seen in heart failure, neurologic disease, or during sleep.
246
Central Sleep Apnea
Central sleep apnea differs from obstructive sleep apnea because central sleep apnea involves reduced:
- A.Respiratory drive
- B.Tonsil size only
- C.Upper airway size only
- D.Mandibular advancement only
Answer: A.Respiratory drive
Why
Central sleep apnea occurs when the brain temporarily fails to send proper breathing signals. Obstructive sleep apnea occurs when airflow is blocked despite respiratory effort.
247
Obstructive Apnea Effort
During obstructive sleep apnea, respiratory effort is usually:
- A.Replaced by cardiac contraction
- B.Completely absent always
- C.Present but airflow is blocked
- D.Not related to airway anatomy
Answer: C.Present but airflow is blocked
Why
In obstructive sleep apnea, the patient tries to breathe, but the upper airway collapses. This differs from central apnea, where drive is reduced.
248
Mallampati Concept
A high Mallampati score suggests a potentially more difficult airway because the oropharyngeal view is:
- A.Unrelated to soft tissue
- B.More crowded
- C.Always normal
- D.More open
Answer: B.More crowded
Why
Mallampati classification estimates visibility of oropharyngeal structures. A crowded airway can increase risk during sedation and airway management.
249
Supine Position and OSA
Supine positioning can worsen obstructive sleep apnea because gravity may move the tongue and soft tissues:
- A.Anteriorly away from the airway only
- B.Into the nasal cavity
- C.Into the esophagus permanently
- D.Posteriorly toward the airway
Answer: D.Posteriorly toward the airway
Why
When lying on the back, soft tissues can fall backward and narrow the upper airway. This can worsen obstruction in susceptible patients.
250
Mandibular Advancement Physiology
Mandibular advancement improves upper airway size partly by moving the tongue base:
- A.Forward
- B.Into the nasal cavity
- C.Into the larynx
- D.Backward
Answer: A.Forward
Why
Moving the mandible forward can pull the tongue and attached soft tissues forward. This can reduce airway collapse in selected sleep apnea patients.
251
Bruxism and Arousal
Sleep bruxism is often associated with brief sleep arousals and activation of the:
- A.Visual cortex only
- B.Alveolar surfactant system
- C.Renal filtration barrier only
- D.Autonomic nervous system
Answer: D.Autonomic nervous system
Why
Sleep bruxism episodes often occur around micro-arousals with changes in heart rate and autonomic activity. This connects dental findings to sleep physiology.
252
REM Sleep Breathing
Breathing can become more irregular during REM sleep because respiratory control is influenced by:
- A.Loss of oxygen from hemoglobin only
- B.Closure of all alveoli
- C.Variable autonomic and brainstem activity
- D.Complete diaphragm paralysis in all people
Answer: C.Variable autonomic and brainstem activity
Why
REM sleep has variable autonomic activity and irregular breathing patterns. This can worsen sleep-disordered breathing in some patients.
253
Upper Airway Dilator Muscles
Upper airway patency during sleep depends partly on activity of muscles controlled by cranial nerves, especially the:
- A.Hypoglossal nerve
- B.Abducens nerve only
- C.Olfactory nerve
- D.Optic nerve
Answer: A.Hypoglossal nerve
Why
The hypoglossal nerve controls tongue muscles, including muscles that help maintain upper airway space. Reduced tone during sleep can contribute to obstruction.
254
Genioglossus Function
The genioglossus helps maintain airway patency by pulling the tongue:
- A.Forward
- B.Superiorly into the palate only
- C.Laterally into the cheek only
- D.Backward
Answer: A.Forward
Why
The genioglossus protrudes the tongue. Its activity helps prevent posterior tongue collapse into the airway.
255
Hypoglossal Stimulation Therapy
Hypoglossal nerve stimulation for sleep apnea aims to improve airway patency by activating:
- A.Pulmonary veins
- B.Tongue protrusion muscles
- C.Facial expression muscles only
- D.Alveolar macrophages
Answer: B.Tongue protrusion muscles
Why
Stimulating the hypoglossal nerve can activate tongue muscles that move the tongue forward. This can reduce upper airway obstruction in selected patients.
256
Nasal Resistance
Increased nasal resistance can worsen sleep-disordered breathing by increasing:
- A.Cardiac ejection fraction only
- B.Hemoglobin affinity only
- C.Work of breathing
- D.Pulmonary capillary oxygen content only
Answer: C.Work of breathing
Why
Nasal obstruction increases the effort needed to move air. This can contribute to mouth breathing, sleep fragmentation, and airway instability.
257
Mouth Breathing Physiology
Chronic mouth breathing bypasses normal nasal functions such as warming, humidifying, and:
- A.Filtering inspired air
- B.Closing the mitral valve
- C.Producing hemoglobin
- D.Pumping venous blood
Answer: A.Filtering inspired air
Why
The nose conditions inspired air. Mouth breathing bypasses some filtration and humidification, which can affect oral dryness and airway comfort.
258
Nitric Oxide in Nasal Breathing
Nasal breathing may support airway physiology partly because the nasal cavity produces:
- A.Nitric oxide
- B.Bicarbonate only
- C.Albumin
- D.Hemoglobin
Answer: A.Nitric oxide
Why
The nasal passages and paranasal sinuses produce nitric oxide, which may contribute to airway and vascular regulation.
259
Oral Dryness From Mouth Breathing
Mouth breathing can increase dental risk mainly because it promotes:
- A.Oral dryness
- B.Increased enamel regeneration
- C.Increased salivary buffering always
- D.Complete bacterial elimination
Answer: A.Oral dryness
Why
Mouth breathing can dry oral tissues. Reduced moisture can affect plaque control, comfort, breath, and caries risk.
260
Respiratory Rate and Alveolar Ventilation
If tidal volume becomes very shallow, alveolar ventilation may fall even if respiratory rate increases because:
- A.Dead space disappears
- B.Hemoglobin rises instantly
- C.Cardiac output becomes zero
- D.More of each breath is wasted in dead space
Answer: D.More of each breath is wasted in dead space
Why
Shallow breaths may mostly ventilate conducting airways instead of alveoli. Rapid shallow breathing can be inefficient.
261
Effective Breathing Pattern
For the same minute ventilation, slower deeper breathing usually improves alveolar ventilation because it:
- A.Increases anatomic dead space greatly
- B.Reduces the proportion of dead space ventilation
- C.Stops CO2 removal
- D.Prevents oxygen from reaching alveoli
Answer: B.Reduces the proportion of dead space ventilation
Why
Each breath includes dead space. Larger breaths deliver a greater fraction of air to alveoli, improving gas exchange.
262
Airway Obstruction Sound
Wheezing is caused by airflow through:
- A.The esophagus only
- B.Narrowed lower airways
- C.Fully open alveoli only
- D.Coronary arteries
Answer: B.Narrowed lower airways
Why
Wheezing is a musical sound from narrowed airways, often during expiration. It is common in asthma and other obstructive conditions.
263
Stridor
Stridor suggests obstruction mainly in the:
- A.Alveolar capillaries
- B.Upper airway
- C.Pulmonary veins
- D.Left ventricle
Answer: B.Upper airway
Why
Stridor is a high-pitched sound often heard with upper airway narrowing. It is more concerning than simple mild wheezing because it can signal airway compromise.
264
Dental Sedation Airway Risk
During dental sedation, airway obstruction commonly occurs when soft tissues relax and the tongue falls:
- A.Into the stomach immediately
- B.Posteriorly
- C.Anteriorly
- D.Into the maxillary sinus
Answer: B.Posteriorly
Why
Sedation reduces muscle tone. The tongue and soft palate can fall backward, narrowing the upper airway.
265
Head Tilt-Chin Lift
The head tilt-chin lift maneuver helps open the airway by moving the tongue and soft tissues:
- A.Away from the posterior pharynx
- B.Into the nasal cavity
- C.Into the esophagus
- D.Into the airway
Answer: A.Away from the posterior pharynx
Why
Repositioning the head and chin can relieve soft tissue obstruction. It is a basic airway maneuver in unconscious or sedated patients.
266
Jaw Thrust
The jaw thrust maneuver improves airway patency by moving the mandible:
- A.Backward
- B.Laterally only
- C.Down into the neck
- D.Forward
Answer: D.Forward
Why
Moving the mandible forward can pull the tongue and soft tissues away from the posterior airway. This is especially useful when cervical spine movement should be minimized.
267
Laryngospasm
Laryngospasm is dangerous because it causes reflex closure of the:
- A.Alveoli
- B.Vocal cords
- C.Coronary arteries
- D.Pulmonary veins
Answer: B.Vocal cords
Why
Laryngospasm can block airflow at the level of the larynx. It may occur with airway irritation, secretions, or stimulation under sedation.
268
Aspiration Physiology
Aspiration becomes dangerous when material enters the:
- A.Left ventricle
- B.Coronary sinus
- C.Dental pulp only
- D.Lower airway and lungs
Answer: D.Lower airway and lungs
Why
Aspirated material can obstruct airways, trigger inflammation, or cause aspiration pneumonia. Protective reflexes normally help prevent this.
269
Cough Reflex Purpose
The cough reflex protects the respiratory system by clearing:
- A.Irritants and secretions from the airway
- B.Bile from the stomach only
- C.Enamel plaque only
- D.Blood from the left ventricle
Answer: A.Irritants and secretions from the airway
Why
Coughing helps remove foreign material, mucus, and irritants from the airway. Sedation can reduce this protective reflex.
270
Swallowing and Airway Protection
During swallowing, the airway is protected partly by closure of the laryngeal inlet and movement of the:
- A.Aortic valve
- B.Nasal septum only
- C.Epiglottis
- D.Mitral valve
Answer: C.Epiglottis
Why
Swallowing coordinates tongue, pharyngeal, laryngeal, and esophageal actions. The epiglottis and vocal folds help protect the airway.
271
Oxygen Delivery Equation Concept
Oxygen delivery to tissues depends mainly on cardiac output and:
- A.Saliva pH
- B.Arterial oxygen content
- C.Residual lung volume only
- D.Tooth enamel thickness
Answer: B.Arterial oxygen content
Why
Tissue oxygen delivery depends on how much oxygen the blood carries and how much blood reaches tissues. Low hemoglobin or low cardiac output can reduce delivery.
272
Arterial Oxygen Content
Arterial oxygen content depends most on oxygen saturation and:
- A.Platelet count only
- B.Blood glucose only
- C.Respiratory rate only
- D.Hemoglobin concentration
Answer: D.Hemoglobin concentration
Why
Most oxygen is carried on hemoglobin. Oxygen saturation tells how full hemoglobin is, but hemoglobin concentration determines carrying capacity.
273
Oxygen Extraction
When tissue oxygen delivery falls, tissues may compensate by increasing oxygen:
- A.Destruction
- B.Conversion into CO2 before arrival
- C.Extraction
- D.Production
Answer: C.Extraction
Why
Tissues can remove a greater fraction of oxygen from blood when delivery is limited. If delivery falls too much, compensation fails and hypoxia develops.
274
Mixed Venous Oxygen Saturation
Low mixed venous oxygen saturation suggests tissues are extracting more oxygen because delivery may be:
- A.Excessive
- B.Completely normal in all cases
- C.Unrelated to blood flow
- D.Inadequate
Answer: D.Inadequate
Why
Mixed venous oxygen saturation reflects the oxygen left after tissues extract what they need. Low values can suggest reduced oxygen delivery or increased demand.
275
Lactate Production
Lactate rises during shock because tissues shift toward:
- A.Increased surfactant metabolism
- B.Anaerobic metabolism
- C.Excess oxygen storage
- D.Complete CO2 elimination
Answer: B.Anaerobic metabolism
Why
When oxygen delivery is inadequate, cells rely more on anaerobic glycolysis. This increases lactate production.
276
Cardiogenic Shock
Cardiogenic shock is caused primarily by:
- A.Pump failure
- B.Severe vasodilation only
- C.Fluid loss only
- D.Upper airway obstruction only
Answer: A.Pump failure
Why
Cardiogenic shock occurs when the heart cannot pump enough blood to meet tissue needs. Myocardial infarction is a common cause.
277
Hypovolemic Shock
Hypovolemic shock results from:
- A.Upper airway dilation only
- B.Loss of circulating volume
- C.Excess cardiac contractility
- D.Increased surfactant production
Answer: B.Loss of circulating volume
Why
Bleeding, dehydration, or fluid loss can reduce venous return, preload, stroke volume, and tissue perfusion.
278
Distributive Shock
Distributive shock involves severe:
- A.Increased hemoglobin concentration only
- B.Vasodilation
- C.Alveolar collapse only
- D.Increased arterial stiffness only
Answer: B.Vasodilation
Why
In distributive shock, blood volume is poorly distributed due to widespread vasodilation. Examples include septic and anaphylactic shock.
279
Obstructive Shock
Obstructive shock occurs when circulation is blocked by a mechanical problem such as:
- A.Low saliva flow only
- B.Increased enamel thickness
- C.Mild gingivitis
- D.Massive pulmonary embolism
Answer: D.Massive pulmonary embolism
Why
Obstructive shock happens when blood flow is physically blocked. Massive pulmonary embolism, tension pneumothorax, and cardiac tamponade are examples.
280
Cardiac Tamponade
Cardiac tamponade reduces cardiac output by limiting:
- A.Ventricular filling
- B.Oxygen diffusion only
- C.Hemoglobin formation only
- D.Alveolar ventilation only
Answer: A.Ventricular filling
Why
Fluid in the pericardial space compresses the heart. This prevents normal filling and reduces stroke volume.
281
Pericardial Pressure
In cardiac tamponade, pressure around the heart increases in the:
- A.Alveolar space
- B.Pericardial space
- C.Oral vestibule
- D.Pulmonary airway only
Answer: B.Pericardial space
Why
The pericardial sac surrounds the heart. Excess fluid or blood in this space can compress the heart.
282
Heart Failure Compensation
In heart failure, sympathetic activation initially helps by increasing heart rate and contractility, but chronically it can:
- A.Decrease oxygen demand permanently
- B.Increase cardiac workload
- C.Eliminate pulmonary congestion always
- D.Cure valve disease
Answer: B.Increase cardiac workload
Why
Short-term sympathetic activation supports blood pressure and output. Long-term activation increases myocardial oxygen demand and can worsen remodeling.
283
Ventricular Remodeling
Chronic pressure or volume overload can cause ventricular remodeling, meaning changes in ventricular:
- A.Enamel prism direction only
- B.Size, shape, or wall thickness
- C.Airway diameter only
- D.Salivary protein content only
Answer: B.Size, shape, or wall thickness
Why
The heart adapts to chronic stress by changing structure. Remodeling can initially compensate but may eventually worsen function.
284
Concentric Hypertrophy
Concentric hypertrophy is most associated with chronic:
- A.Pressure overload
- B.Excess lung compliance
- C.Decreased afterload only
- D.Low blood volume only
Answer: A.Pressure overload
Why
Pressure overload, such as chronic hypertension or aortic stenosis, causes the ventricle to thicken inward to generate higher pressure.
285
Eccentric Hypertrophy
Eccentric hypertrophy is most associated with chronic:
- A.Volume overload
- B.Low venous return only
- C.Reduced blood volume only
- D.Decreased preload only
Answer: A.Volume overload
Why
Volume overload, such as regurgitant valves, causes chamber dilation with increased muscle mass.
286
Diastolic Dysfunction
Diastolic dysfunction means the ventricle has difficulty:
- A.Producing hemoglobin
- B.Depolarizing the atria only
- C.Ventilating alveoli
- D.Relaxing and filling
Answer: D.Relaxing and filling
Why
A stiff ventricle cannot fill normally during diastole. Ejection fraction may be preserved, but filling pressures can rise.
287
Systolic Dysfunction
Systolic dysfunction means the ventricle has difficulty:
- A.Receiving oxygen in alveoli only
- B.Making bicarbonate
- C.Filtering lymph
- D.Contracting and ejecting blood
Answer: D.Contracting and ejecting blood
Why
Systolic dysfunction reduces pumping ability and often lowers ejection fraction. It can reduce cardiac output and cause congestion.
288
BNP Release
B-type natriuretic peptide is released mainly in response to ventricular:
- A.Airway narrowing
- B.Oxygen binding
- C.Stretch
- D.Salivary gland stimulation
Answer: C.Stretch
Why
BNP is released when ventricles are stretched by pressure or volume overload. It is commonly elevated in heart failure.
289
Dental Patient With Orthopnea
A patient who cannot tolerate lying back because of shortness of breath may have increased risk from:
- A.Normal physiology only
- B.Enamel hypocalcification only
- C.Pulmonary congestion or heart failure
- D.Mild plaque accumulation only
Answer: C.Pulmonary congestion or heart failure
Why
Orthopnea suggests that lying flat worsens breathing. Dental treatment may require upright positioning and medical caution.
290
Supine Hypotensive Syndrome
In late pregnancy, lying supine can reduce venous return because the uterus compresses the:
- A.Inferior vena cava
- B.Aortic valve
- C.Pulmonary vein only
- D.Carotid sinus only
Answer: A.Inferior vena cava
Why
The gravid uterus can compress the inferior vena cava when the patient lies flat. This reduces venous return and can cause hypotension.
291
Pregnancy Positioning
A pregnant dental patient feeling dizzy while supine may improve by turning slightly to the:
- A.Fully inverted position
- B.Prone position
- C.Right side only always
- D.Left side
Answer: D.Left side
Why
Left uterine displacement can reduce compression of the inferior vena cava. This improves venous return and blood pressure.
292
Fainting Versus Seizure
Brief loss of consciousness from vasovagal syncope is usually due to temporary reduction in:
- A.Enamel oxygenation
- B.Lung compliance only
- C.Salivary secretion only
- D.Cerebral perfusion
Answer: D.Cerebral perfusion
Why
Syncope occurs when blood flow to the brain temporarily falls. Vasovagal events reduce blood pressure and heart rate.
293
Cerebral Autoregulation
Cerebral autoregulation helps maintain brain blood flow despite changes in:
- A.Alveolar surfactant only
- B.Saliva viscosity only
- C.Mean arterial pressure
- D.Tooth pressure only
Answer: C.Mean arterial pressure
Why
The brain adjusts vessel diameter to keep blood flow relatively stable over a range of pressures. Extreme pressure changes can overwhelm this system.
294
Hypertensive Emergency Concept
Severe blood pressure elevation with acute organ damage is called:
- A.Mild orthostasis
- B.Hypertensive emergency
- C.Normal baroreflex
- D.Simple anxiety only
Answer: B.Hypertensive emergency
Why
The key issue is not just the number. Severe hypertension with acute brain, heart, kidney, or vascular injury is an emergency.
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White Coat Hypertension
A patient's blood pressure is high in the dental office but normal at home. This pattern is called:
- A.Respiratory alkalosis only
- B.Cardiogenic shock
- C.Pulmonary embolism
- D.White coat hypertension
Answer: D.White coat hypertension
Why
Anxiety in medical or dental settings can temporarily raise blood pressure. Rechecking after rest and comparing home readings can clarify the pattern.
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Pain Control and Blood Pressure
Good local anesthesia can reduce cardiovascular stress during dental procedures by reducing:
- A.Pain-driven sympathetic activation
- B.Hemoglobin production
- C.Renal bicarbonate excretion only
- D.Alveolar surface tension
Answer: A.Pain-driven sympathetic activation
Why
Pain increases sympathetic output, raising heart rate and blood pressure. Effective anesthesia can reduce physiologic stress.
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Uncontrolled Pain and Myocardial Demand
In a cardiac patient, uncontrolled dental pain can increase myocardial oxygen demand by increasing:
- A.Saliva flow only
- B.Residual lung volume only
- C.Heart rate and blood pressure
- D.Alveolar macrophage activity only
Answer: C.Heart rate and blood pressure
Why
Pain and anxiety activate the sympathetic nervous system. This raises cardiac workload and oxygen demand.
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Beta Blocker Physiology
Beta blockers reduce cardiac workload mainly by decreasing heart rate and:
- A.Contractility
- B.Alveolar ventilation directly
- C.Hemoglobin concentration
- D.Plasma bicarbonate only
Answer: A.Contractility
Why
Beta blockers reduce beta-1 effects in the heart. This lowers heart rate, contractility, and myocardial oxygen demand.
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Nonselective Beta Blocker and Epinephrine
A patient taking a nonselective beta blocker may have exaggerated blood pressure response to epinephrine because alpha-mediated vasoconstriction is:
- A.Converted into bronchodilation
- B.Unopposed
- C.Unrelated to vascular tone
- D.Completely blocked
Answer: B.Unopposed
Why
Nonselective beta blockers block beta effects while alpha-1 vasoconstriction can remain active. This can produce a stronger pressor response to epinephrine.
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Cardiopulmonary Dental Risk Integration
The safest physiologic goal for medically complex dental patients is to minimize stress, maintain oxygenation, and avoid sudden increases in:
- A.Salivary buffering only
- B.Lung compliance only
- C.Cardiac workload
- D.Enamel thickness
Answer: C.Cardiac workload
Why
Dental pain, fear, hypoxia, and excessive vasoconstrictor exposure can increase cardiopulmonary stress. Careful monitoring, positioning, anxiety control, and good anesthesia help protect vulnerable patients.