An ABG shows pH 7.52, PaCO2 48 mmHg, HCO3- 38 mEq/L. The primary disorder and compensatory response are:

• A Respiratory alkalosis with metabolic compensation
• B Mixed metabolic alkalosis and respiratory acidosis
• C Metabolic alkalosis with respiratory compensation (hypoventilation) ✓
• D Respiratory acidosis with metabolic compensation

Explanation

pH 7.52 (alkalotic), PaCO2 48 mmHg (higher than normal 40 mmHg — CO2 retention reflecting hypoventilation), HCO3- 38 mEq/L (markedly elevated). The primary disorder is metabolic alkalosis (HCO3- elevation to 38). The expected respiratory compensation for metabolic alkalosis: PaCO2 = 0.7 × ΔHCO3- + 21 (Winter's formula for alkalosis) = 0.7 × (38-24) + 21 = 0.7 × 14 + 21 = 30.8 mmHg — but some use: expected PaCO2 ≈ last two digits of pH rule or 0.7 × ΔHCO3 + 40 ± 5 = 0.7(14) + 40 = 49.8 mmHg; observed PaCO2 = 48 mmHg is within expected range, confirming appropriate respiratory compensation. This is simple metabolic alkalosis with expected respiratory compensation, not a mixed disorder.

Reference: Harper's Illustrated Biochemistry, 32nd ed.

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