Question

Blood pressure is normally taken on the upper arm at the level of the heart. Suppose, however, that a patient has his arms in a cast, so you cannot take his blood pressure in the usual way. If you have him stand up and take the blood pressure at his calf, which is 95.5 cm below his heart, what would be the magnitude of the difference between this measurement of blood pressure and a normal blood-pressure measurement? The density of blood is 1060 kg/m3 .

Answer 1

Pressure of fluid increases with increase in depth of the fluid.

The increase in the pressure with the depth is given by 'gh'.

Density of blood = = 1060 kg/m³

Gravitational acceleration = g = 9.81 m/s²

Position of the calf below the heart = h = 95.5 cm = 0.955 m

Pressure taken at heart level = P

Pressure taken at calf level when standing = P + gh

Difference of pressure measured = P

P = gh

P = (1060)(9.81)(0.955)

P = 9930.66 Pa

The magnitude of difference between the measurement of blood pressure at the calf and a normal blood pressure measurement is 9930.66 Pa