Pulmonary Ventilation MCQ
Lung volumes, mechanics of breathing, gas exchange physiology, the O₂–Hb curve, and obstructive vs restrictive PFT patterns. 11 board-style MCQs.
Concept summary and clinical relevance.
Quick-reference structure first, then detailed coverage. Mnemonics in amber, clinical pearls in blue.
Pulmonary physiology questions on the INBDE focus on three things: lung volumes and what they measure, the obstructive-vs-restrictive PFT pattern, and the O₂–Hb dissociation curve (Bohr effect). Layered on top: clinical scenarios for asthma, COPD, fibrosis, and the hypoventilation/hyperventilation states you'll see in the dental chair.
| Measure | Definition | Notes |
|---|---|---|
| Tidal volume (TV) | Normal breath in/out | ~500 mL |
| Inspiratory reserve volume (IRV) | Extra inhaled after a normal breath | Measurable |
| Expiratory reserve volume (ERV) | Extra exhaled after a normal breath | Measurable |
| Residual volume (RV) | Air left after maximal exhalation | NOT measurable by spirometry |
| Vital capacity (VC) | TV + IRV + ERV | Maximum usable air |
| Total lung capacity (TLC) | VC + RV | All air the lungs can hold |
| FEV₁/FVC ratio | Forced expiratory volume in 1 sec ÷ forced vital capacity | Key obstructive vs restrictive marker |
| Pattern | Examples | FEV₁/FVC | TLC | RV |
|---|---|---|---|---|
| Obstructive | Asthma, COPD, emphysema | ↓ (< 70%) | Normal or ↑ | ↑ (air trapping) |
| Restrictive | Pulmonary fibrosis, sarcoidosis | Normal or ↑ | ↓ | Normal or ↓ |
| Shift | Meaning | Causes |
|---|---|---|
| Right shift | ↓ O₂ affinity → release O₂ to tissues | ↑ CO₂, ↑ H⁺ (acidosis), ↑ temperature, ↑ 2,3-BPG |
| Left shift | ↑ O₂ affinity → hold O₂ | ↓ CO₂, ↓ H⁺ (alkalosis), ↓ temperature, fetal Hb, carbon monoxide |
Mechanics of breathing
- Quiet inspiration: diaphragm contracts → thoracic volume increases → intrathoracic pressure drops → air flows in.
- Expiration at rest: passive: the elastic recoil of the lung tissue and chest wall returns volume to FRC.
- Forced expiration: active, using abdominal muscles and internal intercostals.
- Compliance = ΔV / ΔP; emphysema increases it, fibrosis decreases it.
Gas exchange & transport
- Diffusion across the alveolar-capillary membrane depends on surface area, barrier thickness, and partial pressure gradient.
- Oxygen is transported mostly bound to hemoglobin (~98%); a small fraction is dissolved in plasma.
- Carbon dioxide is transported mainly as bicarbonate (HCO₃⁻); some bound to hemoglobin and some dissolved.
- The S-shaped O₂–Hb curve: cooperative binding gives a steep middle and a flat plateau at high PO₂.
Pulmonary function patterns
- Obstructive (asthma, COPD, emphysema): airflow out is limited → ↓ FEV₁/FVC, ↑ RV from air trapping.
- Restrictive (fibrosis, sarcoidosis): lungs can't fully expand → ↓ TLC; FEV₁/FVC is preserved or even increased because both numerator and denominator fall together.
- Hypoventilation (e.g., opioid overdose): retains CO₂ → respiratory acidosis.
- Hyperventilation (anxiety): blows off CO₂ → respiratory alkalosis with tingling, lightheadedness, possible syncope.
11 board-style MCQs.
Active recall is the highest-yield study method. Pick an answer, check it, and read why every distractor is wrong.
- Question 1EasyWhich lung volume represents the air inhaled or exhaled in a normal breath?
- Question 2EasyWhich lung volume cannot be measured directly by spirometry?
- Question 3EasyWhich muscle is the primary driver of quiet inspiration?
- Question 4EasyExpiration at rest is primarily due to:
- Question 5ModerateWhich condition increases lung compliance?
- Question 6ModerateWhich condition decreases lung compliance?
- Question 7EasyThe main form of CO₂ transport in the blood is:
- Question 8EasyWhich factor causes a right shift of the O₂–hemoglobin dissociation curve?
- Question 9ModerateIn obstructive lung disease (e.g., asthma, COPD), which pulmonary function ratio decreases?
- Question 10ModerateIn restrictive lung disease (e.g., pulmonary fibrosis), the FEV₁/FVC ratio is typically:
- Question 11EasyHyperventilation in an anxious dental patient leads to:
Founder, KYT Dental Services. These MCQs are reviewed by a practicing clinician and offered as an educational reference for dental students.
Other dental MCQ topics.
Same Learning Summary plus Core Recall MCQ format. Every topic includes practice questions with full distractor explanations.
Cranial nerves, bones and foramina, vasculature, mastication, and radiographic landmarks. The structural foundation every dental student returns to.
Brain regions, spinal pathways, autonomic nervous system, and clinical localization for dental patients.
Nephron function, fluid and electrolyte balance, digestion, and GI hormones: what dentists need to understand about the rest of the body.