Changing Hb from 14 to 15 g/dL with SaO2 = 100% increases CaO2 by approximately how much?

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Multiple Choice

Changing Hb from 14 to 15 g/dL with SaO2 = 100% increases CaO2 by approximately how much?

The main idea is how much oxygen is carried by hemoglobin at a given saturation. CaO2 equals the oxygen bound to hemoglobin plus the dissolved oxygen in plasma. The bound portion is Hb × 1.34 × SaO2, and with SaO2 at 100%, the amount carried per gram ofHb is 1.34 mL O2. Increasing hemoglobin by 1 g/dL adds 1 × 1.34 × 1.0 ≈ 1.34 mL/dL to CaO2. The dissolved oxygen term (0.003 × PaO2) stays the same when Hb changes, so it doesn’t contribute to the increase. Rounding to one decimal place gives about 1.3 mL/dL, which is the expected increase in CaO2.

The main idea is how much oxygen is carried by hemoglobin at a given saturation. CaO2 equals the oxygen bound to hemoglobin plus the dissolved oxygen in plasma. The bound portion is Hb × 1.34 × SaO2, and with SaO2 at 100%, the amount carried per gram ofHb is 1.34 mL O2. Increasing hemoglobin by 1 g/dL adds 1 × 1.34 × 1.0 ≈ 1.34 mL/dL to CaO2. The dissolved oxygen term (0.003 × PaO2) stays the same when Hb changes, so it doesn’t contribute to the increase. Rounding to one decimal place gives about 1.3 mL/dL, which is the expected increase in CaO2.

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