Which of the following statements is true about partially compensated respiratory alkalosis?

• A. PCO2 is higher than normal.
• B. HCO3- is higher than normal.
• C. More CO2 is eliminated through the lungs by hyperventilation.
• D. Renal reabsorption of HCO3- is decreased.

Answer: (D)

Partially compensated respiratory alkalosis happens when hyperventilation lowers the arterial CO2, raising pH, and the kidneys respond by reducing bicarbonate reabsorption to lower the bicarbonate level toward normal. The crucial adjustment is that the kidneys excrete more bicarbonate, so renal reabsorption of HCO3- is decreased. This renal response is the defining feature of the partial compensation stage.

The other statements don’t fit this stage: CO2 is not higher than normal in this condition—it’s lower due to hyperventilation. Bicarbonate would not be higher; it’s being reduced by renal excretion as part of compensation. Saying more CO2 is eliminated by the lungs describes the initial cause of the alkalosis, not the compensatory state itself.