DETECTION OF DEEP-VEIN THROMBOSIS WITH AN AUTOMATIC ELECTRICALLY CALIBRATED STRAIN-GAUGE PLETHYSMOGRAPH

Abstract

A new strain gauge plethysmograph was developed to permit accurate electrical calibration and automatic calculation of limb blood flow from a panel meter. This instrument was used to quantitate maximum venous outflow (MVO) in both limbs of 20 normal volunteers and 387 limbs of 195 patients with clinically suspected leg vein thrombosis. The MVO of normal subjects averaged 45 .+-. 18 cc[cubic centimeters]/min per 100 cc of calf tissue (mean .+-. 1 SD). In 69 limbs with deep vein thrombosis documented by Doppler ultrasound and/or phlebography, the MVO averaged 17 .+-. 13 cc/min per 100 cc, which was significantly less than that of normal limbs (P < 0.001). Only 3 of 31 limbs with venous thrombosis above the knee had MVO above 20 cc/min per 100 cc, the lower limit of normal, for a diagnostic sensitivity of 90%. The specificity of a normal MVO in excluding deep vein thrombosis was 81%, with only a 1% rate of false-negative diagnoses above the knee. This automatic strain gauge plethysmograph has the attribute of providing rapid quantitation of limb venous hemodynamics which facilitates non-invasive dignosis and follow-up assessment of venous disease.