In the CaO2 calculation example, what is the hemoglobin concentration used (g/dL)?

• A. 12 g/dL
• B. 14 g/dL
• C. 16 g/dL
• D. 18 g/dL

Answer: (B)

The main idea here is that CaO2 depends largely on how much hemoglobin is present, since most oxygen is carried bound to hemoglobin. In the CaO2 formula, CaO2 = (Hb × 1.34 × SaO2) + (PaO2 × 0.003), the hemoglobin concentration (Hb) is the key multiplier for the oxygen bound to Hb.

In the example, a hemoglobin concentration of 14 g/dL is used because it’s a typical normal value for an adult and makes the calculation straightforward while staying within a realistic range. Using this value shows how the bound portion drives CaO2 (for example, with SaO2 around 97%, the bound portion is about 14 × 1.34 × 0.97 ≈ 18 mL O2/dL, with only a small additive from dissolved O2). If the Hb were higher or lower, CaO2 would change proportionally, highlighting why Hb concentration is the major factor in this calculation.

So, the hemoglobin concentration used in the CaO2 calculation example is 14 g/dL.