Validation of air plethysmography, photoplethysmography, and duplex ultrasonography in the evaluation of severe venous stasis

Abstract

The purpose of this study was to validate the diagnostic capabilities of the most commonly used noninvasive modalities for evaluation of chronic venous insufficiency. Twenty limbs in 20 patients were studied with air plethysmography (APG), photoplethysmography (PPG), and duplex ultrasonography. Ten limbs (group 1) were clinically without any venous disease. Group 2 consisted of 10 limbs with severe, class 3 venous stasis. Duplex ultrasonography, complemented with Doppler color-flow imaging was used to examine the superficial and deep venous systems to identify reflux. Ultrasonography identified deep venous reflux in eight of 10 limbs in group 2. Severe superficial reflux was identified in the two remaining limbs. Seven limbs with deep reflux also demonstrated severe superficial reflux. Superficial venous reflux was identified in one leg in group 1. APG accurately separated normal limbs from those with reflux. Parameters that were significantly different (p < 0.05) between the two groups were the venous filling index, (group 1 = 1.37 +/- 1.16 ml/sec, group 2 = 29.5 +/- 6.2 ml/sec.), venous volume (group 1 = 107 +/- 10.1 ml, group 2 = 220 +/- 22.5 ml), ejection fraction (group 1 = 52.5% +/- 2.3%, group 2 = 32.5% +2- 4.6%), and residual volume fraction (group 1 = 21.4 +/- 2.0%, group 2 = 52.1% +/- 2.5%). PPG refill times were significantly shortened in group 2 versus those of group 1 (6.4 +/- 0.89 sec vs 20.2 +/- 1.1 sec). The sensitivity of PPG refill times to identify reflux was 100%, but the specificity was only 60%, whereas the sensitivity and specificity for the residual volume fraction was 100%. The venous filling index was able to identify reflux and determine whether only superficial reflux was present with a sensitivity of 100% and a specificity of 90%. The kappa coefficient of agreement between duplex scanning and APG was 0.83, whereas between duplex and PPG it was only 0.47. APG accurately identifies limbs with and without venous reflux when compared with duplex ultrasonography. APG is a better method of evaluating clinically significant venous reflux than PPG. PPG is a sensitive method of detecting reflux, but the specificity is poor, and PPG refill times cannot accurately predict the location of reflux. The combination of APG and duplex ultrasonography provides the best means of assessing venous reflux.