How does the respiratory system compensate for metabolic acidosis?

• A. Decrease ventilation to retain CO2
• B. Increase renal excretion of bicarbonate
• C. Increase bicarbonate production
• D. Increase ventilation to exhale CO2

Answer: (D)

When metabolic acidosis lowers pH by reducing bicarbonate, the respiratory system responds quickly by increasing ventilation to blow off carbon dioxide. Less CO2 in the blood shifts the carbonic acid-bicarbonate balance toward left, decreasing hydrogen ion concentration and raising pH. This rapid respiratory compensation happens while the kidneys adjust more slowly. The other options describe renal changes or actions that would not serve as the immediate respiratory response (retaining CO2 would worsen acidosis; excreting bicarbonate or producing more bicarbonate are kidney-driven adjustments).