What is the O2 content of whole blood with Hb 10 g/dL, PaO2 60 mm Hg, and SaO2 90%?

What is the O2 content of whole blood with Hb 10 g/dL, PaO2 60 mm Hg, and SaO2 90%?

• A. 10 mL/dL
• B. 12.5 mL/dL
• C. 15 mL/dL
• D. 17.5 mL/dL

Answer: (B)

Oxygen content in blood comes from two parts: the oxygen bound to hemoglobin and the oxygen dissolved in plasma. The bound portion depends on how much hemoglobin is present and how saturated it is, while the dissolved portion depends on the arterial oxygen tension. Use the equation: CaO2 = (Hb × 1.34 × SaO2) + (PaO2 × 0.003) Plug in the values: Hb = 10 g/dL, SaO2 = 90% (0.90), PaO2 = 60 mmHg. Bound oxygen = 10 × 1.34 × 0.90 = 12.06 mL/dL Dissolved oxygen = 60 × 0.003 = 0.18 mL/dL Total O2 content ≈ 12.06 + 0.18 = 12.24 mL/dL, which is about 12.5 mL/dL when rounded to the nearest practical value. Most of the O2 content here comes from Hb-bound oxygen, with only a small contribution from dissolved O2 at this PaO2.

Oxygen content in blood comes from two parts: the oxygen bound to hemoglobin and the oxygen dissolved in plasma. The bound portion depends on how much hemoglobin is present and how saturated it is, while the dissolved portion depends on the arterial oxygen tension.

Use the equation: CaO2 = (Hb × 1.34 × SaO2) + (PaO2 × 0.003)

Plug in the values: Hb = 10 g/dL, SaO2 = 90% (0.90), PaO2 = 60 mmHg.

Bound oxygen = 10 × 1.34 × 0.90 = 12.06 mL/dL

Dissolved oxygen = 60 × 0.003 = 0.18 mL/dL

Total O2 content ≈ 12.06 + 0.18 = 12.24 mL/dL, which is about 12.5 mL/dL when rounded to the nearest practical value.

Most of the O2 content here comes from Hb-bound oxygen, with only a small contribution from dissolved O2 at this PaO2.