Pulmonary Embolism USMLE Step 1 Practice Question
A 38-year-old woman presents with acute dyspnea and pleuritic chest pain after a 12-hour international flight. Vital signs: BP 128/82, HR 102, RR 22, SpO2 91% on room air, temperature 37.2°C. Arterial blood gas shows pH 7.48, PaCO2 30 mmHg, PaO2 72 mmHg, HCO3 22 mEq/L. Chest X-ray is normal. She denies leg swelling. Which acid-base disturbance is present, and what condition does it suggest?
Answer choices
- AAcute respiratory alkalosis, consistent with pulmonary embolismCorrect answer
- BChronic respiratory alkalosis, consistent with high-altitude exposure
- CAcute respiratory acidosis, consistent with COPD exacerbation
- DMixed metabolic alkalosis and respiratory acidosis, consistent with vomiting with COPD
- EMetabolic acidosis, consistent with sepsis
- FAcute metabolic alkalosis, consistent with diuretic use
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