Dental MCQ
Breathing mechanics and gas exchange · Cardio & Respiratory · INBDE Patient Cases

Pulmonary Ventilation INBDE Patient Cases

By Dr. Isaac Sun, DDS

8 ADA INBDE-format patient cases on pulmonary ventilation. Each case is a shared patient box (chief complaint, history, medications, allergies, exam) followed by linked multiple-choice questions with full distractor explanations. Practice the way the real exam is structured.

8 patient cases40 linked questionsADA INBDE formatFull distractor explanations

Eight ADA INBDE-format patient cases on pulmonary ventilation and gas exchange in the dental setting: benzocaine-induced methemoglobinemia with cyanosis and an unreliable pulse oximeter, a COPD patient who cannot recline and needs semi-upright positioning, hypoventilation and oxygen desaturation under sedation with benzodiazepine reversal, restrictive pulmonary fibrosis with limited reserve, aspiration of a dropped crown and rubber-dam prevention, mouth breathing with oral dryness and sleep-disordered breathing, chronic bronchitis in a smoker, and severe anemia with a normal oxygen saturation but low oxygen content. Topics include lung volumes and capacities, surfactant and the pneumocytes, the oxygen-hemoglobin curve and the Bohr effect, dead space, the chemoreceptor control of breathing, ventilation-perfusion matching, and obstructive versus restrictive disease.

Case Coverage Map
What each case is testing
Blue lips after a topical numbing gel:
Benzocaine methemoglobinemia, oxidized hemoglobin, unreliable pulse oximetry, stop-and-refer.
COPD patient who cannot lie back:
Obstructive disease, diaphragm mechanics, semi-upright positioning, rescue inhaler, oxygen judgment.
Falling oxygen saturation under sedation:
Hypoventilation and hypoxemia, airway maneuvers, oxygen, benzodiazepine reversal with flumazenil.
Easily winded with stiff lungs:
Restrictive disease, normal FEV1/FVC, reduced lung volumes, limited reserve, shorter appointments.
A crown slips during try-in:
Aspiration vs swallowing, the cough reflex, chest imaging, rubber dam prevention.
Mouth breathing and chronically dry gums:
Loss of nasal conditioning, oral dryness and caries risk, ENT referral, sleep-disordered breathing.
Years of a wet morning cough in a smoker:
Chronic bronchitis, the mucociliary escalator, the COPD spectrum, smoking and periodontal healing.
Pale and exhausted, but oxygen reads normal:
Anemia, saturation vs oxygen content, compensatory tachycardia, medical coordination before surgery.
Patient case: Blue lips after a topical numbing gel
0 of 5 answered, 0 correct
Patient
Male, 50 years old
Chief Complaint
"My lips and fingertips look blue," he says shortly after the numbing gel.
Background and/or Patient History
  • A generous amount of benzocaine topical gel was applied before an impression
  • Became short of breath and dusky within minutes
  • No chest pain
  • Otherwise healthy
Allergies
NKDA
Medications
  • None
Current Findings
  • Bluish (cyanotic) lips and nail beds
  • Pulse oximeter reads low and barely improves with oxygen
  • Alert but anxious
  • No wheeze or airway swelling
  1. Question 1
    Moderate
    Cyanosis and a low pulse-ox reading soon after benzocaine suggest:
  2. Question 2
    Moderate
    In methemoglobinemia, hemoglobin iron is oxidized so it cannot:
  3. Question 3
    Hard
    Pulse oximetry is unreliable here because it cannot:
  4. Question 4
    Moderate
    The most appropriate action is to:
  5. Question 5
    Moderate
    To prevent recurrence, you should:

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Patient case: COPD patient who cannot lie back
0 of 5 answered, 0 correct
Patient
Male, 70 years old
Chief Complaint
"I can't breathe well lying back, and I breathe through pursed lips," he says.
Background and/or Patient History
  • Presented for multiple restorations
  • Long history of COPD from smoking
  • Uses pursed-lip breathing
  • Short of breath when reclined flat
Allergies
NKDA
Medications
  • Tiotropium inhaler
  • Albuterol rescue inhaler
Current Findings
  • Breathes more comfortably upright
  • Prolonged expiration with mild wheeze
  • SpO2 93% on room air
  • Barrel-shaped chest
  1. Question 1
    Easy
    His prolonged expiration and air trapping are typical of:
  2. Question 2
    Moderate
    He breathes more easily upright mainly because it improves:
  3. Question 3
    Easy
    The best chair position for him is:
  4. Question 4
    Moderate
    Before treatment, you should confirm that he has:
  5. Question 5
    Hard
    If he became short of breath, supplemental oxygen should be:

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Patient case: Falling oxygen saturation under sedation
0 of 5 answered, 0 correct
Patient
Female, 45 years old
Chief Complaint
Pre-sedation: "I'm comfortable, just getting sleepy," she says.
Background and/or Patient History
  • Undergoing sedation for surgical extractions
  • Became deeply relaxed and very quiet
  • Breathing turned shallow and slow
  • No prior sedation problems
Allergies
NKDA
Medications
  • A benzodiazepine given for sedation
Current Findings
  • Pulse oximeter alarms: SpO2 falling to 88%
  • Slow, shallow respirations
  • No stridor
  • Responds to a loud voice
  1. Question 1
    Easy
    A falling SpO2 with shallow breathing under sedation indicates:
  2. Question 2
    Moderate
    The best immediate step is to:
  3. Question 3
    Moderate
    Sedatives lower SpO2 mainly by depressing:
  4. Question 4
    Easy
    If the tongue is obstructing the airway, a useful maneuver is:
  5. Question 5
    Hard
    If a benzodiazepine caused the depression, the reversal agent is:

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Patient case: Easily winded with stiff lungs
0 of 5 answered, 0 correct
Patient
Female, 63 years old
Chief Complaint
"I get winded easily, my doctor says my lungs are stiff," she reports.
Background and/or Patient History
  • Presented for a crown and bridge appointment
  • Diagnosed with pulmonary fibrosis
  • Short of breath with mild exertion
  • Uses no rescue inhaler
Allergies
NKDA
Medications
  • None relevant
Current Findings
  • Dry crackles at both lung bases
  • SpO2 94% at rest
  • Reduced exercise tolerance
  • Speaks in full sentences at rest
  1. Question 1
    Easy
    Pulmonary fibrosis is an example of:
  2. Question 2
    Moderate
    In restrictive disease, the FEV1/FVC ratio is typically:
  3. Question 3
    Moderate
    The main problem in restrictive disease is reduced:
  4. Question 4
    Moderate
    Because her reserve is limited, the best plan is:
  5. Question 5
    Moderate
    Compared with obstructive disease, her difficulty is mainly with:

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Patient case: A crown slips during try-in
0 of 5 answered, 0 correct
Patient
Male, 55 years old
Chief Complaint
"I think I swallowed something," he says after a crown slips during try-in.
Background and/or Patient History
  • A crown slipped from the forceps during try-in
  • He coughed forcefully
  • Now feels something is caught
  • Was reclined during the procedure
Allergies
NKDA
Medications
  • None
Current Findings
  • Persistent cough
  • Mild wheeze on one side
  • SpO2 95%
  • No complete airway obstruction
  1. Question 1
    Moderate
    The forceful cough suggests the object may have entered the:
  2. Question 2
    Easy
    The cough reflex is protective because it helps:
  3. Question 3
    Moderate
    Aspiration into the airway is more dangerous than swallowing because it can cause:
  4. Question 4
    Moderate
    Because aspiration is suspected, the best step is to:
  5. Question 5
    Easy
    The best way to prevent aspiration of small dental objects is to:

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Patient case: Mouth breathing and chronically dry gums
0 of 5 answered, 0 correct
Patient
Female, 16 years old, accompanied by parent
Chief Complaint
Parent: "She breathes through her mouth and her gums always look dry and inflamed."
Background and/or Patient History
  • Presented for a checkup
  • Chronic nasal congestion and mouth breathing
  • Anterior gingiva appears dry and reddened
  • Snores at night per parent
Allergies
NKDA
Medications
  • None
Current Findings
  • Open-mouth resting posture
  • Dry, inflamed anterior gingiva
  • High caries risk on exam
  • Otherwise healthy
  1. Question 1
    Easy
    Chronic mouth breathing bypasses nasal warming, humidifying, and:
  2. Question 2
    Moderate
    Her dry, inflamed anterior gingiva is most likely related to:
  3. Question 3
    Moderate
    Oral dryness raises the risk of:
  4. Question 4
    Easy
    A reasonable referral for the underlying cause is to:
  5. Question 5
    Moderate
    Her snoring and mouth breathing also raise the question of:

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Patient case: Years of a wet morning cough in a smoker
0 of 5 answered, 0 correct
Patient
Male, 60 years old
Chief Complaint
"I've had a wet cough most mornings for years," he says.
Background and/or Patient History
  • Presented for periodontal treatment
  • 30-year smoking history
  • Productive cough most days for several months over two years
  • No fever today
Allergies
NKDA
Medications
  • None
Current Findings
  • Coarse cough with sputum
  • Scattered wheeze
  • SpO2 94%
  • Heavy calculus and periodontal inflammation
  1. Question 1
    Moderate
    A productive cough on most days for at least 3 months over 2 years defines:
  2. Question 2
    Hard
    Chronic bronchitis impairs airway clearance partly by damaging:
  3. Question 3
    Easy
    Chronic bronchitis is part of which disease pattern?
  4. Question 4
    Moderate
    For his periodontal surgery, a sensible step is:
  5. Question 5
    Moderate
    Smoking also affects his periodontal outcome by impairing:

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Patient case: Pale and exhausted, but oxygen reads normal
0 of 5 answered, 0 correct
Patient
Female, 38 years old
Chief Complaint
"I'm exhausted and pale, but they said my oxygen reads normal," she says.
Background and/or Patient History
  • Presented for an extraction
  • Heavy menstrual bleeding and fatigue for months
  • Pale conjunctiva and nail beds
  • Recently told her blood count is very low
Allergies
NKDA
Medications
  • Iron supplement
Current Findings
  • Pulse oximeter reads 98%
  • Marked pallor
  • Resting pulse 100
  • Feels weak with exertion
  1. Question 1
    Moderate
    Her normal pulse-ox reading despite anemia is because pulse oximetry measures:
  2. Question 2
    Moderate
    Even with 98% saturation, her oxygen delivery can be low because of low:
  3. Question 3
    Moderate
    Her resting tachycardia is a compensatory attempt to maintain:
  4. Question 4
    Moderate
    For an elective extraction, the best step is to:
  5. Question 5
    Hard
    This case illustrates that oxygen saturation and oxygen content are:

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Keep studying
Pulmonary Ventilation core recall

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