In CKD with metabolic acidosis, what is the primary compensatory mechanism and its clinical manifestation?

• A. Decreased respiratory rate to retain CO2
• B. Increased ventilation (hyperventilation) to blow off CO2, often with tachypnea
• C. No respiratory change; bicarbonate therapy only
• D. Increased renal bicarbonate reabsorption

Answer: (B)

Metabolic acidosis prompts the body to compensate primarily through the respiratory system. By increasing ventilation, the lungs blow off carbon dioxide (CO2), which shifts the acid-base balance toward less acidity and helps raise the pH. This rapid, deep breathing is often felt as tachypnea and can be described as hyperventilation. In CKD, the kidneys struggle to excrete acid, so the lungs provide the faster countermeasure to the acid load. Options advocating slower breathing, no respiratory change, or relying only on bicarbonate therapy don’t reflect the immediate compensatory mechanism the body uses. Increased renal bicarbonate reabsorption isn’t the immediate compensatory response, though the kidneys’ ability to handle acid-base changes is impaired in CKD.