USE OF LIGHTGUIDE SPECTROPHOTOMETRY TO QUANTIFY SKIN OXYGENATION IN AVARIABLE MODEL OF VENOUS HYPERTENSION

A variable model of venous hypertension was used to examine the immedi ate effect on skin oxygenation and blood flow, Measurements were carri ed out using laser Doppler flowmetry, transcutaneous oximetry and both macro- and micro-lightguide spectrophotometry to measure haemoglobin saturation (S-O2). Assessments were performed on 20 normal subjects an d in ten patients with deep venous insufficiency lying supine with a p ressure cuff left uninflated (P-0), then inflated to 40 mmHg (P-40), 6 0 mmHg (P-60) and 80 mmHg (P-80), All measurements were performed at t he gaiter area of the leg, In normal subjects median Doppler values fe ll significantly at P-40 (P < 0.001) but further pressure increases ha d no more effect. Mean values of transcutaneous partial pressure of ox ygen (P-tcO2) fell steadily (P < 0.001), although the initial fall at P-40 was small. Median S-O2 fell with increasing occlusion pressure wi th both macro- and micro-lightguide spectrophotometry (P < 0.001), alt hough the main reduction occurred predominantly at lower occlusion pre ssures. Higher levels of S-O2 were obtained with local heating up to 4 4 degrees C, with a pattern similar to that of P-tcO2. In patients, th e same pattern of response to increased venous pressure occurred in ar eas of clinically normal skin. These data suggest that small increases in venous hypertension have an immediate and profound influence on sk in blood how and oxygen availability in normal skin.