A healthy adult has hemoglobin 15 g/dL, SaO2 100%, PaO2 100 mmHg, and PaCO2 40 mmHg breathing room air. What is the approximate total oxygen content of arterial blood?

• A About 30 mL O2 per dL
• B About 12 mL O2 per dL
• C About 20 mL O2 per dL ✓
• D About 6 mL O2 per dL

Explanation

Bound oxygen equals 1.34 mL/g multiplied by Hb 15 g/dL and saturation 1.0, giving about 20 mL/dL. Dissolved oxygen contributes PaO2 times 0.003, roughly 0.3 mL/dL, a negligible addition. Option B would apply if saturation were about 60 percent, and option D ignores hemoglobin entirely, treating dissolved oxygen as the main carrier. Almost all transported oxygen travels bound to hemoglobin.

Reference: Ganong's Review of Medical Physiology, 27th ed.

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