Interpret the arterial blood gas with pH 7.52, PaCO2 30 mmHg, HCO3- 28 mEq/L. How should this be interpreted?

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

Answer: (A)

The main idea here is to identify the primary acid-base disturbance by looking at the pH and the two gas values. The pH is 7.52, which means alkalemia. The PaCO2 is 30 mmHg, which is low and points to a respiratory cause of the alkalemia because reduced carbon dioxide in the blood drives pH upward. In a pure respiratory alkalosis, the bicarbonate usually falls as the kidneys try to compensate, not rises; however, the bicarbonate being 28 mEq/L suggests there could be an additional metabolic process or a chronic/complex picture affecting the bicarbonate level. Despite that, the key driver of the alkalemia in this pattern is the low CO2, so the interpretation is respiratory alkalosis.