A patient has arterial blood gas results: pH 7.52, PaCO2 30 mm Hg, HCO3- 24 mEq/L. The nurse determines these results indicate which disturbance?

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

Answer: (D)

When the blood is more alkaline (high pH) and the carbon dioxide level is low (low PaCO2), the disturbance is respiratory alkalosis. Here, pH is elevated and PaCO2 is reduced, which fits a pattern caused by hyperventilation that blows off CO2. The bicarbonate is still normal, which is common early in respiratory alkalosis before the kidneys have had time to compensate. If this were metabolic alkalosis, you'd expect a high bicarbonate level. If it were respiratory acidosis, PaCO2 would be high. If it were metabolic acidosis, the pH would be low. So the combination of alkalemia with low PaCO2 points to respiratory alkalosis.