ABG interpretation: pH 7.52; pCO2 30; HCO3- 22. Which pattern best fits this result?

ABG interpretation: pH 7.52; pCO2 30; HCO3- 22. Which pattern best fits this result?

• A. Compensated respiratory alkalosis
• B. Compensated metabolic acidosis
• C. Uncompensated metabolic alkalosis
• D. Uncompensated respiratory acidosis

Answer: (A)

The key idea is that the blood gas shows alkalemia with a primary respiratory disturbance and renal compensation. The pH is elevated, indicating alkalosis. The low pCO2 (30) points to a respiratory cause, since CO2 is the volatile acid driving the respiratory component. The bicarbonate is near normal but slightly reduced (22 mEq/L), which is consistent with metabolic compensation by the kidneys for a respiratory alkalosis—the drop in CO2 lowers stimulation for bicarbonate reabsorption and promotes bicarbonate excretion. The magnitude fits acute compensation: a 10 mmHg drop in pCO2 typically yields about a 2 mEq/L fall in HCO3-. So this pattern is respiratory alkalosis with metabolic (renal) compensation. It’s not metabolic alkalosis (bicarbonate would be high) and not respiratory acidosis (pH would be low).

The key idea is that the blood gas shows alkalemia with a primary respiratory disturbance and renal compensation. The pH is elevated, indicating alkalosis. The low pCO2 (30) points to a respiratory cause, since CO2 is the volatile acid driving the respiratory component. The bicarbonate is near normal but slightly reduced (22 mEq/L), which is consistent with metabolic compensation by the kidneys for a respiratory alkalosis—the drop in CO2 lowers stimulation for bicarbonate reabsorption and promotes bicarbonate excretion. The magnitude fits acute compensation: a 10 mmHg drop in pCO2 typically yields about a 2 mEq/L fall in HCO3-.

So this pattern is respiratory alkalosis with metabolic (renal) compensation. It’s not metabolic alkalosis (bicarbonate would be high) and not respiratory acidosis (pH would be low).