Mon22November0925AM 6

Which one of the following options contributes (quantitatively) most to arterial oxygen content?

(Please select 1 option)

Partial pressure of oxygen in plasma

Huffner's constant

Cardiac output

Haemoglobin concentration Correct

Henry's law

Explanation

Arterial oxygen content (CaO2) is the amount of oxygen carried by 100 ml of blood and is normally 17-24 ml/dL.

It can be determined by the following equation:

CaO2 = oxygen bound to haemoglobin + oxygen dissolved in plasma

CaO2 = (1.34 x Hgb x SaO2 x 0.01) + (0.003 x PaO2)

where:

1.34 = Huffner's constant

Hgb is the haemoglobin level in g/dL

SaO2 is the percent oxyhaemoglobin saturation of arterial blood

PaO2 is (0.0225 = ml of O2 dissolved per 100 ml plasma per kPa, or 0.003 ml per mmHg).

Whilst important, quantitatively, the amount of oxygen dissolved in plasma is 0.3 mL/dL.

Henry's law states that at constant temperature, the amount of gas dissolved at equilibrium in a given quantity of a liquid is proportional to the pressure of the gas in contact with the liquid.

Given a haemoglobin concentration of 15 g/dL and a SaO2 of 100% and a PaO2 of 13.3 kPa, the amount of oxygen bound to haemoglobin is 20.4 mL/100mL.

Cardiac output is an important determinant of oxygen delivery but does not influence the oxygen content of blood.

Huffner's constant does not change and its magnitude relatively small.

Answer Statistics

1

10%

2

4%

3

7%

4

81%

5

1%

Times answered: 254