THE ROLE OF AIR PLETHYSMOGRAPHY IN THE DIAGNOSIS OF CHRONIC VENOUS INSUFFICIENCY

Purpose: The role of air plethysmography (APG) in the diagnosis of ven ous disease is not well defined. We conducted this study to investigat e the value of APG in the diagnosis of chronic venous insufficiency an d to determine its correlation with the clinical severity of disease a nd the anatomic distribution of reflux. Methods: We studied 186 lower extremities with duplex scanning and venography and measured the venou s volume, venous filling index (VFI), ejection fraction, and residual volume fraction with APG. Limbs were categorized according to the Soci ety for Vascular Surgery and International Society for Cardiovascular Surgery classification of clinical severity of disease and according t o the anatomic distribution of valvular incompetence. Results: Sixty-o ne limbs had no evidence of disease (class 0), 60 limbs had mild disea se (classes 1, 2, and 3), and 65 limbs had severe disease (classes 4, 5, and 6). According to the results of duplex scanning and venography, there was no evidence of reflux in 56 limbs. Isolated superficial ven ous reflux occurred in 52 limbs, and perforator reflux, alone or in co njunction with superficial reflux, occurred in 30. Deep reflux, with o r without superficial reflux, was found in 25 limbs. Deep and perforat or reflux, with Or without superficial reflux, was found in 19 limbs. The VFI had a sensitivity of 80% and 99% positive predictive value for any type of reflux. The VFI was significantly different between group s of limbs with different clinical severities of disease or different types of reflux. The incidence of deep or perforator reflux in limbs w ith a normal VFI value was 7%, and it was 82% in limbs with a VFI of m ore than 5. Among 86 limbs with VFI values not corrected with use of a thigh tourniquet, 28% did not have evidence of deep or perforator ref lux, and among 15 limbs with VEI values corrected with the use of a to urniquet, 33% had perforator reflux, deep reflux, or both. All APG par ameters had low positive predictive values for severe disease or ulcer ation. The ejection fraction and residual volume fraction did not infl uence the clinical severity of disease, did not discriminate between t ypes of renw, and in combination with the vm did not improve the predi ctive value of APG. Conclusions: The VFI measured by APG is an excelle nt predictor of venous reflux, provides an estimate of the clinical se verity of disease, and at high levels predicts deep reflux, perforator reflux, or both. Correction of an abnormal VFI with a thigh tournique t is an unreliable predictor of the absence of deep or perforator inco mpetence. The predictive value of APG for severe disease or ulceration is poor. The ejection fraction and residual volume fraction, individu ally or in combination with the VFI, add little to the diagnostic valu e of APG, and their routine performance may not be clinically justifie d.