Oxygen Content (CaO₂) Calculator
The total oxygen carried in arterial blood — the hemoglobin-bound and dissolved fractions together — showing why oxygen content tracks hemoglobin and saturation far more than PaO₂.
Written by Apex Respiratory Editorial Team
Enter as a percent (98) or a fraction (0.98).
Enter hemoglobin, oxygen saturation, and PaO₂ to calculate the arterial oxygen content.
Reading oxygen content
CaO₂ is the sum of oxygen bound to hemoglobin (1.34 mL O₂ per gram of fully saturated Hb — Egan’s teaches 1.34; the theoretical maximum is 1.39) plus the small dissolved fraction (0.003 mL/dL per mmHg of PaO₂).
Because the bound term dominates, content tracks hemoglobin and saturation, notPaO₂ — a reassuring PaO₂ with severe anemia can still mean profound tissue oxygen lack.
Oxygen delivery (DO₂ = CaO₂ × cardiac output × 10) also depends on perfusion, so content is only half the story.
Educational use only. This material supports respiratory therapy education and exam review. It is not medical advice and is not a substitute for clinical judgment, institutional protocols, or physician orders. Always follow facility policies and current provider orders, and verify calculations independently before clinical use.
Sources
- Kacmarek RM, Stoller JK, Heuer AJ. Egan's Fundamentals of Respiratory Care. 12th ed. Elsevier; 2021.
- West JB, Luks AM. West's Respiratory Physiology: The Essentials. 11th ed. Wolters Kluwer; 2020.