Changes in venous blood volume produced by external compression of the lower leg.

Abstract

Experiments have been performed with healthy human volunteers to measure the changes in cross-sectional area of the lower leg for a range of positive external pressures. It was found that area measurements obtained using mercury-silastic strain-gauge loops placed beneath an external pressurising cuff are significantly influenced by artefacts of tissue movement which must be corrected if accurate interpretations of the data are to be made. Most of the changes in vessel area occur in the range of external pressure up to about 3 kPa. As the external pressure increases further, the corresponding area change decreases progressively. At extgernal pressures above about 2 or 3kPa, the changes in venous cross-sectional area are strongly affected by frictional pressure drops. This may even produce, at different measurement locations along the same leg, simultaneous area increases and decreases for increasing external pressures.