Electrolyte and blood gas values indicate a primary respiratory disturbance with CO2 retention. Which acid-base disorder is most compatible?

Electrolyte and blood gas values indicate a primary respiratory disturbance with CO2 retention. Which acid-base disorder is most compatible?

• A. Respiratory alkalosis
• B. Respiratory acidosis
• C. Metabolic alkalosis
• D. Metabolic acidosis

Answer: (B)

When CO2 is retained, the primary issue is a respiratory problem. Higher CO2 shifts the balance of carbonic acid toward more H+ and lower pH, so the most compatible disorder is respiratory acidosis. The kidneys may compensate over time by increasing bicarbonate reabsorption to raise pH, especially if the problem is chronic, but the initiating abnormality is the respiratory retention of CO2. If CO2 were low from overbreathing, that would indicate respiratory alkalosis. Metabolic disorders involve changes in bicarbonate or acid independent of CO2; they wouldn’t present specifically as CO2 retention with a primary respiratory disturbance.

When CO2 is retained, the primary issue is a respiratory problem. Higher CO2 shifts the balance of carbonic acid toward more H+ and lower pH, so the most compatible disorder is respiratory acidosis. The kidneys may compensate over time by increasing bicarbonate reabsorption to raise pH, especially if the problem is chronic, but the initiating abnormality is the respiratory retention of CO2. If CO2 were low from overbreathing, that would indicate respiratory alkalosis. Metabolic disorders involve changes in bicarbonate or acid independent of CO2; they wouldn’t present specifically as CO2 retention with a primary respiratory disturbance.