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

INTRODUCTION: 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. MATERIAL AND METHODS: 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. RESULTS: 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. DISCUSSION: 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.

Changes in the Biomechanical Properties of Human Skin in Hyperthermic and Hypothermic Ranges.

INTRODUCTION: The prevalence of thermal skin injuries is high. Despite new research findings, skin burns and acute cold-contact injuries, together with resulting tissue damage, are not entirely understood. In particular, little is known about how these types of injuries alter the biomechanical properties of skin. OBJECTIVE: This study evaluates hyperthermic- and hypothermic-induced alterations in the biomechanical properties of human skin using a skin elasticity measurement device. MATERIALS AND METHODS: In 54 cases, local hypothermia (15°C and 5°C) and local hyperthermia (40°C and 45°C) were induced at the palmar forearm of healthy participants. The biomechanical properties of skin were measured using the skin elasticity measurement device before and after each temperature change at 2 different depths. RESULTS: The skin firmness, pliability, retraction, and elasticity/calculated elasticity showed a continuous decrease in values with decreasing skin temperatures in total skin measurements and an increase in values with increasing skin temperatures in the upper layer and total skin measurements. CONCLUSIONS: As per the results, the investigators believe these hyperthermic- and hypothermic-induced alterations in biomechanical skin properties are due to increased blood flow, in addition to a reversible increase in interstitial and intracellular fluid contents, thermal contraction, and expansion of collagen and elastic fibers, all of which are precursors to irreversible damage.