The Effect of Probe Position, Calf Muscle Function and Lipodermatosclerosis on Photoplethysmographic Venous Refilling Time
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Objective: To assess the influence of probe position, lipodermatosclerosis and method of calf muscle emptying on the venous refilling time as measured by photoplethysmography in both normal limbs and limbs with chronic venous disease. Design: Prospective evaluation of age- and sex-matched control and study groups. Setting: University Department of Surgery, Vascular Research Laboratory, Fremantle Hospital, Western Australia. Patients: There were 38 controls and 31 patients with venous ulceration. Interventions: Venous refilling times were measured in six positions on the leg in all subjects: the foot, 5 cm below medial tibial condyle in the upper calf, and in the gaiter region on the medial, lateral, anterior and posterior positions at 7.5 cm above the medial malleolus. Measurements were undertaken on active exercise and after bimanual calf compression in the medial gaiter region. Measurements were also undertaken in areas of lipodermatosclerotic skin and in normal-appearing adjacent skin. Results: In normal legs, the lowest refilling times were in the anterior and lateral gaiter positions. Venous patients had a shorter refilling time in the dorsal foot, medial gaiter, posterior gaiter and medial below-knee positions, when compared with controls (Mann–Whitney U-test, p<0.01). The shortest refilling time in patients with venous disease was in the medial gaiter region. Refilling time was slightly prolonged over Hpodermatosclerotic skin compared with adjacent normal-looking skin. Refilling time measured after passive emptying of the calf muscle by external compression was significantly prolonged compared with calf emptying by active calf compression ( p<0.01). This change was similar for both groups. Conclusions: When using venous refilling time on photoplethysmography to distinguish venous from normal limbs, the best separation is in the medial gaiter position. If other probe sites or methods of calf emptying are to be employed, it is imperative that individual laboratory normal ranges be established for the particular method being employed.
