In CaO2 calculation, what is the coefficient for PaO2 in the dissolved oxygen term?

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In CaO2 calculation, what is the coefficient for PaO2 in the dissolved oxygen term?

The dissolved oxygen part of CaO2 comes from Henry’s law, which says the amount of O2 dissolved in blood is proportional to the partial pressure of O2 (PaO2) and a small solubility coefficient. That coefficient is 0.003 mL O2 per dL of blood per mmHg. So the dissolved oxygen term is PaO2 × 0.003. This tiny coefficient reflects that only a small fraction of O2 is dissolved in plasma; most O2 is carried by hemoglobin, which is accounted for in the hemoglobin-bound term. For example, with PaO2 ≈ 100 mmHg, the dissolved portion is about 0.3 mL/dL, while the Hb-bound portion contributes much more. The other coefficients would misrepresent the actual solubility of O2 in blood.

The dissolved oxygen part of CaO2 comes from Henry’s law, which says the amount of O2 dissolved in blood is proportional to the partial pressure of O2 (PaO2) and a small solubility coefficient. That coefficient is 0.003 mL O2 per dL of blood per mmHg. So the dissolved oxygen term is PaO2 × 0.003. This tiny coefficient reflects that only a small fraction of O2 is dissolved in plasma; most O2 is carried by hemoglobin, which is accounted for in the hemoglobin-bound term. For example, with PaO2 ≈ 100 mmHg, the dissolved portion is about 0.3 mL/dL, while the Hb-bound portion contributes much more. The other coefficients would misrepresent the actual solubility of O2 in blood.

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