Perfusion, tissue oxygenation and peripheral temperature in the skin of heels exposed to pressure of healthy subjects: A quasi-experimental study.

Abstract

AIM\nTo evaluate the relationship between the pressure exerted on the heel of one foot resting directly on a mattress, versus that exerted on the other heel, protected by a pillow beneath the Achilles tendon area and the changes thus produced in perfusion, oxygenation and temperature in the heels skin of healthy volunteers, lying in a supine position.\n\n\nDESIGN\nExperimental study in a preclinical phase, with healthy volunteer subjects and intrasubject control.\n\n\nMETHODS\nThe study was carried out from November 2017 - May 2018. A pressure measurement surface was placed between the subject and the constant low-pressure support surface. Doppler laser devices were used to measure local temperature and perfusion. The degree of oxygenation was determined using an infrared beam close to the pressure zone in each heel. Both feet rested immobile on the bed, in a natural position, for two hours. To ensure intrasubject control, in every case the left heel was raised slightly, compared with the right.\n\n\nRESULTS\nEighteen subjects took part in this study. Analysis of the results obtained showed that capillary blood flow was significantly reduced in the heel subjected to pressure, compared with the other heel, while no significant effects on oxygen saturation or temperature were observed. The variables associated with greater oxygen saturation were capillary blood flow, local temperature and pressure exerted. Fat-free mass, fat mass and duration of exposure to pressure were all significantly associated with reduced oxygen saturation.\n\n\nCONCLUSIONS\nIn healthy subjects, when the heel is subjected to constant pressure against a constant low-pressure support surface, there is a significant reduction in blood flow, compared with the heel where pressure is relieved. However, there are no significant differences in temperature or tissue oxygenation.\n\n\nIMPACT\nSignificant reductions in vascular flow were observed; however, the oxygenation and temperature of the heel tissues remained unchanged. These findings, corroborated in real patients, would advance our understanding and facilitate decision-making on measures to prevent pressure ulcers, such as repositioning or tissue protection.