The acute impact of local cooling versus local heating on human skin microcirculation using laser Doppler flowmetry and tissue spectrophotometry.

Abstract

Knowledge of thermally induced skin injury has increased, but its pathophysiology remains unclear. Although it is assumed that local cooling may protect tissue, little is known about the impact of local heating on human skin. This study aimed to evaluate acute skin perfusion dynamics following thermal stimuli in healthy human volunteers. In 54 subjects, a TSA-II-NeuroSensory Analyzer was used to induce local hypothermia (15 °C and 5 °C) and local hyperthermia (40 °C and 45 °C) at the palmar forearm of healthy volunteers. Changes in tissue microcirculation were assessed using an O2C device before and after each temperature change. Blood flow and velocity values showed a continuous decrease with decreasing skin temperature, whereas haemoglobin oxygen saturation (SO₂) showed a continuous increase in superficial (2 mm) and deep layers (8 mm). With increasing skin temperature, flow, SO₂ and velocity increased in the superficial and deep layers. The relative amount of haemoglobin (rHB) did not show a continuous alteration. Local cooling may protect damaged tissue due to increased SO₂ (lower oxygen consumption). However, reduced blood flow and velocity in response to local cooling limit nutrient requirements and the transport of metabolites. Despite higher oxygen consumption of tissue at higher temperatures, both blood flow and SO₂ increase. Thus, we hypothesize that not only hypothermia but also hyperthermia may provide tissue protection.