A noninvasive plethysmographic method for evaluation of the musculovenous pump in the lower extremities

A refinement of plethysmographic musculovenous pump evaluation, with methodologic improvements, is presented. By using a double strain-gauge and knee-bendings, measurement can be made at malleolus level. Use of knee-bending instead of heel-lifting reduced the coefficient of variation in day-to-day determinations from 40% to 12%. A total of 20 knee-bends was found to be ideal for measurements, as a steady state was reached and secondary muscular hyperemia was avoided. The parameters venous return time and expelled volume increased with distal application of strain-gauge, and this must be taken into account in comparisons against reference values obtained with other methods. The coefficient of variation for duplicate determinations with the present method was c. 12% for normal controls and also for patients with varicosity. Reference values derived from 40 normal legs and 68 varicose legs are presented. The investigation demonstrated improvement of a noninvasive method, increasing its reliability for clinical and research purposes.