MICROCIRCULATION IN THE FOOTSOLE AS A FUNCTION OF MECHANICAL PRESSURE

Objective. In this study an experimental set-up for measuring skin mic rovascular responses of the footsole to changes in externally applied pressure was analysed. Design. A clinical study. Skin microvascular bl ood flow was measured in healthy volunteers, during and alter external mechanical pressure of different magnitudes. Background. During stand ing and walking the footsole is commonly exposed to high static and dy namic mechanical pressure, resulting in changes in the microcirculatio n of the footsole, In diabetic patients a disturbed interaction betwee n externally applied pressure and skin microvascular response seems to be involved in the development of a fool ulcer. Methods. Eleven volun teers participated in the study. Static loads were applied to the heel part of the footsole with the person in a supine position, Contact pr essure and skin blood flux, based on the laser Doppler technique, were simultaneously monitored. The pressure used was varied in five discre te steps between 10 and 160 kPa and applied during a period of 5 min e ach, The microcirculation was measured during as well as after pressur e loading. Results. Pressures of 40 kPa and higher do stop the blood f low in the skin microcirculation. Releasing the applied pressure resul ted in a hyperaemic response, This response appears to increase in amp litude at increasing pressures up to 800% of the baseline laser Dopple r fluxmetry level. Beyond a pressure level of 80 kPa the hyperaemic re sponse seems not to be influenced by the pressure level. The time need ed to achieve the maximal laser Doppler fluxmetry level decreased when the pressure was raised from 10 to 80 kPa, but increased again when h igher pressures were applied (P = 0.051). An intraindividual variation of 11-50% was observed for the parameters describing the blood flux b efore, during, and after pressure application. Conclusion. Simultaneou sly measuring changes in contact pressure and laser Doppler flux of th e footsole is a useful method to study the interaction of external mec hanical pressure and skin microvascular reactions. Pressures above 40 kPa stop skin microvascular blood flow. Releasing the applied pressure results in a hyperaemic response, which increases when the applied pr essure increases from 40 to 80 kPa. Higher pressures do not influence the amplitude in skin microvascular response, but result in a longer d elay to maximal hyperaemia. Relevance The study provides information a bout the interaction between externally applied pressures and the micr ocirculation in the footsole. The results of this pilot study offer a possibility for clinical application in research aimed at the aetiolog y of diabetic fool problems. Copyright (C) 1996 Elsevier Science Ltd.