Question

What is the true mean arterial blood pressure if the pressure transducer for arterial blood pressure monitoring is zeroed at the level of the patient's right atrium when laying supine, then raised 10 cm?

A) 10 mm Hg less than the reported mean arterial blood pressure
B) 10 mm Hg more than the reported mean arterial blood pressure
C) 7.4 mm Hg less than the reported mean arterial blood pressure
D) 7.4 mm Hg more than the reported mean arterial blood pressure
E) Additional information is needed to answer this question

Answer 1

The true mean arterial blood pressure would be 7.4 mm Hg more than the reported value when the pressure transducer is raised 10 cm above the heart level.

Step-by-step explanation:

If the pressure transducer for arterial blood pressure monitoring is zeroed at the level of the patient's right atrium while they're laying supine and then raised 10 cm, the hydrostatic pressure exerted by the column of blood between the transducer and the heart must be accounted for. Given that the density of mercury is such that 1.0 mm Hg equals 133 Pa, and knowing that every 1 cm height of blood column approximately equals 0.74 mm Hg in pressure, we can calculate the difference caused by raising the transducer.

When the transducer is raised 10 cm above the heart level, you effectively reduce the measured pressure by the weight of the column of blood. Since 10 cm of blood column corresponds to approximately 7.4 mm Hg (10 cm x 0.74 mm Hg/cm), the true mean arterial blood pressure would be 7.4 mm Hg more than the reported value.