impedance plethysmography, a technique for detecting blood vessel occlusion that determines volumetric changes in the limb by measuring changes in its girth as indicated by changes in the electric impedance of mercury-containing polymeric silicone (Silastic) tubes in a pressure cuff. The method is based on the principle that any circumferential rate of change in a limb segment is directly proportional to the volumetric rate of change, which in turn reflects occlusion of venous and arterial blood flow. However, the technique does not accurately indicate the presence or absence of partially obstructing thrombi in major vessels.
