Which expression represents the arterial-venous O2 content difference?

Which expression represents the arterial-venous O2 content difference?

• A. C(a-v)O2 = CaO2 - CvO2
• B. CaO2 - CvO2
• C. CvO2 - CaO2
• D. CaO2 + CvO2

Answer: (A)

The arterial-venous oxygen content difference tells you how much oxygen is extracted by the body's tissues from the arterial blood as it circulates and returns as venous blood. This difference is represented by subtracting the venous O2 content from the arterial O2 content: CaO2 minus CvO2. It’s conventional to denote this as C(a-v)O2. Since tissues take up oxygen, arterial content is higher than venous content, so the result is a positive value that reflects O2 extraction per unit volume of blood. For example, if CaO2 is about 20 mL/dL and CvO2 about 15 mL/dL, the difference is 5 mL/dL, indicating 5 mL of O2 extracted per deciliter of blood. This is the quantity used in the Fick equation for oxygen consumption: VO2 = CO x (CaO2 - CvO2). The other options either reverse the subtraction or add the contents, which does not reflect the actual arterial-venous O2 content difference.

The arterial-venous oxygen content difference tells you how much oxygen is extracted by the body's tissues from the arterial blood as it circulates and returns as venous blood. This difference is represented by subtracting the venous O2 content from the arterial O2 content: CaO2 minus CvO2. It’s conventional to denote this as C(a-v)O2. Since tissues take up oxygen, arterial content is higher than venous content, so the result is a positive value that reflects O2 extraction per unit volume of blood. For example, if CaO2 is about 20 mL/dL and CvO2 about 15 mL/dL, the difference is 5 mL/dL, indicating 5 mL of O2 extracted per deciliter of blood. This is the quantity used in the Fick equation for oxygen consumption: VO2 = CO x (CaO2 - CvO2). The other options either reverse the subtraction or add the contents, which does not reflect the actual arterial-venous O2 content difference.