A person with normal lungs has an oxygen consumption of 750 mL O₂/min. The hemoglobin concentration is 15 g/dL. The mixed venous saturation is 25%. What is the cardiac output?

Question

Quizplus · Accepted Answer

The cardiac output can be calculated using the Fick principle, which states that the cardiac output is equal to the oxygen consumption divided by the arteriovenous oxygen difference. The oxygen carrying capacity of hemoglobin is approximately 1.34 mL O₂/g. With a hemoglobin concentration of 15 g/dL, the oxygen content in 100 mL of blood is 15 g/dL * 1.34 mL O₂/g = 20.1 mL O₂. Assuming arterial oxygen saturation is 100% and mixed venous saturation is 25%, the arteriovenous oxygen difference is 20.1 mL O₂ * (1 - 0.25) = 15.075 mL O₂ per 100 mL of blood. To find the cardiac output in mL/min, divide the oxygen consumption (750 mL O₂/min) by the arteriovenous oxygen difference in mL O₂ per 100 mL of blood and then multiply by 100 to convert to mL/min: (750 mL O₂/min) / (15.075 mL O₂ per 100 mL of blood) * 100 = 4976.6 mL/min, which is approximately 5,000 mL/min.

A Person with Normal Lungs Has an Oxygen Consumption of 750