Acid-Base Disorders USMLE Step 1 Practice Question
A 26-year-old man travels from Boston to a ski resort at 3500 meters elevation. On the second day he develops lightheadedness and paresthesias but is otherwise healthy. Arterial blood gas shows pH 7.48, PaCO2 30 mm Hg, and HCO3− 22 mEq/L. Which of the following is the primary cause of his acid-base abnormality?
Answer choices
- AIncreased production of ketoacids
- BDecreased alveolar ventilation due to hypoxia
- CHyperventilation triggered by hypoxemiaCorrect answer
- DExcess renal bicarbonate generation
- ELoss of hydrogen ions from vomiting
- FImpaired renal excretion of bicarbonate at high altitude
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