When corrected for hydrostatic pressure, how do standing leg BP readings compare with lying leg BP readings?

When corrected for hydrostatic pressure, how do standing leg BP readings compare with lying leg BP readings?

• A. They are usually much higher when standing
• B. They are usually much lower when standing
• C. They are similar
• D. They cannot be compared

Answer: (C)

Hydrostatic pressure changes with vertical height, so posture can make leg readings look different. When the leg is dependent and a person is standing, gravity adds a hydrostatic component that raises the measured leg BP compared with when lying. If you subtract that hydrostatic difference and imagine the pressure at the same heart level, the intrinsic arterial pressure at the leg is the same, whether you stood or lied down. Therefore, once you correct for hydrostatic pressure, standing leg BP and lying leg BP are similar.

Hydrostatic pressure changes with vertical height, so posture can make leg readings look different. When the leg is dependent and a person is standing, gravity adds a hydrostatic component that raises the measured leg BP compared with when lying. If you subtract that hydrostatic difference and imagine the pressure at the same heart level, the intrinsic arterial pressure at the leg is the same, whether you stood or lied down. Therefore, once you correct for hydrostatic pressure, standing leg BP and lying leg BP are similar.