Thu18November0253AM 6

The difference between the oxygen content of arterial blood (CaO2) and mixed-venous blood (CvO2) is the arterial-venous oxygen (a-vO2) difference.

Which single organ has the highest a-vO2 difference at rest?

(Please select 1 option)

Kidney

Heart This is the correct answer

Intestine Incorrect answer selected

Skin

Skeletal muscle

Explanation

The heart has the highest a-vO2 difference at rest; high capillary to myocyte ratio with short diffusion distances and high mitochondrial density. There is also very tight control of coronary blood flow. At rest 70-80% of the oxygen available to the cardiac muscle is extracted and during exercise this might increase to 90%.

The a-vO2 difference represents the ability of the body or individual organ to extract oxygen from the blood.

Factors that influence CaO2 include:

Haemoglobin concentration

Partial pressure of oxygen in the alveoli (PAO2)

Pulmonary diffusion capacity.

Factors that influence CvO2 (oxygen extraction) include:

Capillary density

Regional blood flow.

Organ CaO2-CvO2 (volume% or ml O2/100 ml blood)

Heart 10-13

Resting skeletal muscle 2-5

Kidney 2-3

Intestine 4-6

Skin 1-2

Answer Statistics

1

22%

2

60%

3

6%

4

1%

5

12%

Times answered: 245