Exercise strain-gauge venous plethysmography: evaluation of a "new" device for assessing lower limb venous incompetence.

Plethysmography can be used to detect and assess venous incompetence in the lower extremities. The authors recently evaluated a new device designed for this purpose that uses strain gauges to determine changes in lower extremity circumference occurring with (and immediately after) exercise. The device plots a curve of volume against time for each limb and automatically calculates key values such as the volume of blood expelled from the lower limb veins during exercise and the time required for the veins to refill following exercise. The apparatus was incorporated into their noninvasive vascular laboratory and used (along with other standard tests) to study patients referred for suspected venous incompetence. They observed the following: (1) A shortened postexercise refilling time accurately identified limbs with venous incompetence. (2) The clinical severity of venous incompetence was inversely related to the refilling time. (3) Exercise-induced changes in lower extremity volume correlated well with simultaneously determined changes in venous pressure. (4) Valvular incompetence could be localized to the deep or superficial veins based upon the improvement in refilling times seen following placement of elastic tourniquets around the lower limb. (5) The type of exercise performed (knee bends while the patient was standing versus ankle reflexes while sitting) had little effect on results. The authors conclude that exercise venous plethysmography is a useful noninvasive tool for assessing lower limb venous incompetence.