Wed3November0844PM 6

A 59-year-old man is admitted to the critical care unit following a laparotomy for faecal peritonitis. He is being invasively monitored using a pulmonary artery flotation catheter.

The following data are available:

Temperature 38°C

Blood pressure = 80/50 mmHg (mean 60 mmHg)

Pulmonary artery pressure = 20/5 mmHg (mean 10 mmHg)

Pulmonary capillary occlusion pressure = 5 mmHg

CVP = 10 mmHg

Cardiac output = 5 litres/minute

Mixed venous oxygen saturation 80%.

Which one of the following values approximates best to the pulmonary vascular resistance in this patient?

Note: A correction factor of 80 is used to convert mmHg to dynes·s·cm-5

(Please select 1 option)

100 dynes·s·cm-5

80 dynes·s·cm-5 This is the correct answer

40 dynes·s·cm-5

60 dynes·s·cm-5

20 dynes·s·cm-5 Incorrect answer selected

Explanation

Pulmonary vascular resistance (PVR) is a derived value based on the following:

The analogy is Ohm's law:

Potential difference (V) = Flow of current (I) × Resistance (O)

Therefore R = V/I

PVR = MPAP - PCWP × 80

CO

PVR = 10 - 5 × 80 = 80 dynes·s·cm-5

5

Normal values range between 20-130 dynes·s·cm-5

Answer Statistics

1

6%

2

52%

3

19%

4

16%

5

9%

Times answered: 277