What respiratory response accompanies metabolic acidosis as compensation?

• A. Hypoventilation.
• B. Hyperventilation (increased rate and depth of breathing).
• C. No change in ventilation.
• D. Apnea.

Answer: (B)

When metabolic acidosis occurs, the body tries to compensate by increasing ventilation to blow off carbon dioxide. By expelling more CO2, the equilibrium CO2 + H2O ⇌ H2CO3 ⇌ H+ + HCO3− shifts to produce fewer hydrogen ions, helping raise the pH toward normal. This rapid response is best described as hyperventilation—an increased rate and depth of breathing.

If breathing slowed down (hypoventilation) or stopped (apnea), CO2 would accumulate and acidosis would worsen, which is why those options aren’t the correct compensatory response. In more severe cases, you might see a pronounced form of this response (Kussmaul breathing), reflecting strong CO2 loss to compensate. Renal adjustments in bicarbonate handling occur later, but the immediate respiratory change is hyperventilation.