Asthma USMLE Step 1 Practice Question
A 22-year-old previously healthy man presents with acute dyspnea and wheezing. Vital signs: BP 118/76 mmHg, HR 112/min, RR 28/min, temperature 37.2°C, SpO2 92% on room air. Chest X-ray shows hyperinflation without infiltrates. Spirometry reveals FEV1 of 58% predicted. He denies fever and recent infection. He uses albuterol inhaler occasionally but takes no daily controller medications. Which of the following best describes the ventilation-perfusion ratio at the lung apex compared with the base during acute bronchospasm?
Answer choices
- AApproximately equal at apex and base because both are zero at end expiration
- BZero at the apex because alveoli are maximally expanded
- CLower at the apex because perfusion exceeds ventilation there
- DHigher at the apex because perfusion decreases more than ventilationCorrect answer
- EInfinite at the base because perfusion is greatest there
- FLower at the apex because ventilation decreases more than perfusion due to increased airway resistance
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