How does the body primarily compensate for respiratory acidosis?

• A. Increased ventilation
• B. Retention of bicarbonate
• C. Excretion of hydrogen ions
• D. Decreased metabolic rate

Answer: (B)

In respiratory acidosis, the primary issue is an increase in carbon dioxide (CO2) levels due to inadequate ventilation. The body compensates for this condition primarily through renal mechanisms rather than direct changes in respiratory function. The kidneys adjust by retaining bicarbonate (HCO3^-), which is an essential buffer that helps to neutralize the excess hydrogen ions resulting from the increased acidity. This process increases the blood’s pH toward normal levels over time.

Retaining bicarbonate effectively counteracts the lowered pH from the accumulation of CO2, as bicarbonate can help absorb some of the hydrogen ions in circulation. This compensation is a slower, yet crucial response, as it stabilizes the acid-base balance in the body long-term, especially in chronic respiratory conditions.

While increased ventilation may also attempt to correct the issue, it is typically not the primary compensatory mechanism in cases of respiratory acidosis because ventilation itself is impaired. Excretion of hydrogen ions and decreased metabolic rate are less relevant as they would not directly address the underlying CO2 retention.