Respiratory compensation in response to metabolic acidosis or alkalosis should:

• A. Fully correct (normalize) pH
• B. Result in no change in pH
• C. Worsen pH
• D. Partially correct pH

Answer: (D)

Respiratory compensation for metabolic disturbances works quickly to move pH toward normal by changing CO2 levels. When there’s metabolic acidosis, the body increases ventilation to blow off CO2, which lowers the amount of carbonic acid and raises pH toward normal. When there’s metabolic alkalosis, ventilation is reduced to retain CO2, increasing carbonic acid and lowering pH toward normal. But this adjustment is only partial. The underlying metabolic problem— bicarbonate or nonvolatile acid balance—still exists, and full normalization of pH requires renal compensation, which takes hours to days. So the expected outcome is a partial correction of pH rather than a complete normalization.