Question

During blood transfusion the needle is inserted in a vein where the gauge pressure is 2000 Pa. At what height must the blood container be placed so that blood may just enter the vein? [Use the density of whole blood from Table 10.1].

Answer 1

Gauge pressure, P = 2000 Pa
Density of whole blood, $\rho =1.06\times {10}^{3}kg{m}^{–3}$
Acceleration due to gravity, $g=9.8m/s^2$
Height of the blood container = h
Pressure of the blood container, $P=h\rho g$
$\therefore h=\frac{P}{\rho g}=\frac{2000}{1.06\times {10}^3\times 9.8}=0.1925m$
The blood may enter the vein if the blood container is kept at a height greater than 0.1925 m, i.e., about 0.2 m.