Search

The venous hemodynamics of 134 legs were evaluated using a bilateral impedance plethysmograph. Calf venous outflow following the release of proximal occluding cuffs and calf volume changes with ventilation were compared with the results of venography. We found that a two-second outflow of at least 65% indicated a patent deep venous system while an outflow of 50% or less indicated an obstruction of the proximal deep venous system. With outflow between 50% and 65%, a ventilatory wave height greater than 3 mm ruled out proximal deep venous obstruction while a height of 3 mm or less was not diagnostic. These two criteria yielded an accuracy of 92% with no false-negative results and a false-positive rate of only 10%. Thus, this technique can accurately rule out proximal deep venous obstruction and give the clinician considerable confidence in initiating anticoagulant therapy on those suspected cases with positive studies.