Impedance plethysmography. Noninvasive diagnosis of deep venous thrombosis and arterial insufficiency

The versatility of impedance plethysmography (IPG) in the diagnosis of arterial and venous disease was evaluated in the clinical setting. Eighty-eight consecutive patients suspected of acute or chronic deep venous thrombosis (DVT) and undergoing ascending venography were evaluated using IPG. Venous capacitance (VC) and venous outflow (VO) were expressed as a per cent impedance change (% Δ I). The evaluation was considered as abnormal if the VC was less than 1.85% Δ I and the VO less than 0.95% Δ I. The overall accuracy was 90 per cent with a sensitivity of 92 per cent and specificity of 93 per cent. Arterial blood flow (ABF) was measured in normal volunteers (20 limbs) and patients with intermittent claudication (20 limbs) and rest pain (16 limbs). Resting ABF (cc/100 ml/min) did not differ (P > 0.05) in the normal volunteer (4.3 ± 0.4) and patients with intermittent claudication (4.6 ± 0.5), but both were significantly greater (P < 0.05) than ABF in patients with rest pain (3.2 ± 0.2). Peak ABF during reactive hyperemia (RH) was significantly greater (P < 0.001) in normal volunteers (24.8 ± 1.6) than in claudicators (10.5 ± 1.3), and both flows were significantly greater (P < 0.001) than the peak ABF in patients with rest pain (5.3 ± 0.5). IPG may be used in the assessment of arterial and venous disease. It provides a sensitive test with which to screen patients with suspected DVT. In addition, it is a valuable adjunct in differentiating normal limbs from those with intermittent claudication and/or rest pain.