Repeated USMLE Questions Step 1- 307

A 32-year-old woman with a history of generalized anxiety disorder develops numbness of her face particularly around her mouth. Physical examination and x-ray show no abnormalities other than markedly increased respiratory rate.

Laboratory investigations are as follows:

PO2: 100 mmHg

PCO2: 30 mmHg

Bicarbonate: 18 mEq/L

pH of blood: 7.51

Which of these findings shows that the body is compensating to this condition?

A-Elevated arterial PO2

B-Elevated hydrogen ion concentration

C-Elevated hydrogen ion excretion

D-Elevated bicarbonate excretion

E-Elevated respiratory rate


Respiratory alkalosis is the result of increased respiratory rate as in this patient. It is common in patients who suffer from anxiety disorders. The body compensates to it through renal mechanisms by decreased hydrogen ion excretion and decreased reabsorption of bicarbonate.

The correct answer is D

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