Question

A patient's diastolic blood pressure, measured as usual at the level of her heart, is 80 mmHg. What is her blood pressure at her ankles, which are located 100 cm below her heart? [The density of blood is 1060 kg/m^3 .]

Answer 1

Blood pressure is normally measured on the upper arm but accasionally this is not possible. The presence of fractures,wounds ,vascular access devices and shunts, morbid obesity,surgical procedures, lymphoedema , limb deformities and amputations may prevent the satisfactory cuff placement around the upper arm . In addition ,BP measurement may be inaccurate in the presence of bilateral subclavian artery stenoses such as can occur with Takayasu's arteritis or atherosclerosis. In these circumstances measurement of BP in the leg may be necessary.

A recent systematic review examined the relationship between supine BP measurements in the arm and leg. The review of many patients concluded that ankle systolic BP was on average 17.0 mmHg higher than arm systolic BP,whilst there was NO difference in diastolic BP in the general population.