Sun28November0333PM 23

A 34-year-old patient with adult respiratory distress syndrome is being ventilated on the critical care unit. A pulmonary artery flotation catheter is being used to optimise his haemodynamic state.

The following data are acquired:

Haemoglobin concentration 10 g/dL

Mixed venous oxygen saturation 70%

Mixed venous oxygen tension (PvO2) 50 mmHg (6.67kPa)

Which one of the following options approximates best to this patient's mixed venous oxygen content (mL/100mL)?

(Please select 1 option)

11.0

9.5 This is the correct answer

9.0 Incorrect answer selected

10.5

10.0

Explanation

Mixed venous oxygen content (CvO2) is the amount of oxygen carried by 100 ml of mixed venous blood and is normally 12-17 mL/dL.

It can be determined by the following equation:

CvO2 = (1.34 × Hgb × SvO2 × 0.01) + (PaO2 × PvO2)

where:

1.34 = Huffner's constant

Hgb is the haemoglobin level in g/dL

SvO2 is the percent oxyhaemoglobin saturation of mixed venous blood

PvO2 is (0.0225 = ml of O2 dissolved per 100 ml plasma per kPa, or 0.003 ml per mmHg)

so:

CvO2 = (1.34 × 10 × 70 × 0.01) + (0.023 x 6.67)

CvO2 = 9.38 + 0.15 = 9.53 mL/100mL

Answer Statistics

1

8%

2

49%

3

13%

4

14%

5

20%

Times answered: 258