Control Of Skin Blood Flow Research Articles

Using Wavelet Analysis of Blood Flow Oscillations to Investigate Differences in Skin Blood Flow Regulations Between the Upper and Lower Limbs.

The objective of this study was to investigate the differences in skin blood flow regulations between the upper and lower limbs in healthy adults using wavelet analysis of skin blood oscillations. To the best of our knowledge, this is the first study investigating the dominant skin blood flow control of the upper and lower limbs in healthy adults. Skin blood flow of the forearm and leg was simultaneously measured by laser Doppler flowmetry (LDF) in 17 healthy adults. Skin blood flow oscillations were analyzed using wavelet analysis to assess the dominant control among the metabolic endothelial (0.0095-0.02Hz), neurogenic (0.02-0.05Hz), myogenic (0.05-0.15Hz), respiratory (0.15-0.4Hz), and cardiac (0.4-2Hz) origins. Skin blood flow in the leg (11.13 ± 4.90 perfusion unit) was significantly higher than in the forearm (6.90 ± 2.50 perfusion unit, p < 0.001). The metabolic endothelial control is more dominant in the forearm (1.19 ±0.51 au) compared to the leg (0.73 ± 0.41 au, p < 0.01). The myogenic control is more dominant in the leg (1.18 ± 0.28 au) compared to the forearm (0.96±0.18 au, p < 0.05). Through wavelet analysis of skin blood flow oscillations, the results indicate that metabolic endothelial control is more dominant in the forearm (upper limbs) and myogenic control is more dominant in the leg (lower limbs).

Spectral Changes in Skin Blood Flow Do Not Reflect Pressure Manipulations

Skin blood flow is commonly assessed by laser Doppler flowmetry. It has been suggested that pathophysiological conditions can be assessed by analysis of frequency domains of the laser Doppler signals. The frequency range of 0.06‐0.15 Hz has been associated with myogenic control of skin blood flow. We tested the hypothesis that changes in blood pressure would be detectable by short‐time Fourier transform of the myogenic portion of the laser Doppler signal. Laser Doppler sensors were placed on the right ventral forearm of fourteen healthy young volunteers (8 males, 6 females, age 30±6 years, mean ± SD) and a photoplethysmography sensor on the middle finger of the right arm. Measurements of skin blood flow were made with the right arm supported at heart level. Intravascular pressure of the forearm was manipulated by positioning the arm ~50˚ above the heart level to decrease pressure and lowering the arm ~50˚ below the heart level to increase pressure. Short‐time Fourier analyses were computed over the range 0.06 to 0.15 Hz. There were no statistically significant differences (p = 0.526) in spectral densities for baseline (5±7 x 10‐4dB, median ± SD), arm above heart (7±54 x 10‐4dB), and arm below heart (7±14 x 10‐4dB). The results demonstrate that spectral density in the myogenic frequency range is unchanged by manipulation of intravascular pressure. We conclude that spectral analysis of laser Doppler signals in the myogenic range does not reflect changes in blood pressure. These findings suggest that myogenic changes in the skin vasculature cannot be inferred from spectral analysis of laser Doppler signals.

Using laser Doppler flowmetry with wavelet analysis to study skin blood flow regulations after cupping therapy.

The purpose of this study was to use laser Doppler flowmetry (LDF) with wavelet analysis to investigate skin blood flow control mechanisms in response to various intensities of cupping therapy. To the best of our knowledge, this is the first study to assess skin blood flow control mechanism in response to cupping therapy using wavelet analysis of laser Doppler blood flow oscillations. Twelve healthy participants were recruited for this repeated-measures study. Three different intensities of cupping therapy were applied using 3 cup sizes at 35, 40, and 45mm (in diameter) with 300mmHg negative pressure for 5minutes. LDF was used to measure skin blood flow (SBF) on the triceps before and after cupping therapy. Wavelet analysis was used to analyze the blood flow oscillations (BFO) to assess blood flow control mechanisms. The wavelet amplitudes of metabolic and cardiac controls after cupping therapy were higher than those before cupping therapy. For the metabolic control, the 45-mm cupping protocol (1.65±0.09) was significantly higher than the 40-mm cupping protocol (1.40±0.10, P<.05) and the 35-mm cupping protocol (1.35±0.12, P<.05). No differences were showed in the cardiac control among the 35-mm (1.61±0.20), 40-mm (1.64±0.24), and 45-mm (1.27±0.25) cupping protocols. The metabolic and cardiac controls significantly contributed to the increase in SBF after cupping therapy. Different intensities of cupping therapy caused different responses within the metabolic control and not the cardiac control.

Contribution of nucleus raphe magnus to thermoregulation

Thermoregulation is the maintenance of the core body temperature. The regulation of body temperature is one of the most important functions of the nervous system. Nucleus raphe magnus, as a central circuit coordinates the homeostatic response and maintains body temperature during environmental temperature challenges and adjusts body temperature during the inflammatory response and behavioral states and in response to decreasing energy homeostasis. Our aim in this review is the understanding of thermoregulation by raphe magnus in mammals. This review summarizes the basic concepts of thermoregulation and subsequently assesses the physiological responses to cold stress, including skin blood flow control, sweating, sympathetic-derived cutaneous vasoconstriction and peripheral thermoregulatory control in brown adipose tissue.

Normobaric hypoxia does not alter the critical environmental limits for thermal balance during exercise‐heat stress

What is the central question of this study? Hypoxia reportedly does not impair thermoregulation during exercise in compensable heat stress conditions: does it have an impact on maximal heat dissipation and therefore the critical environmental limit for the physiological compensability of core temperature? What is the main finding and its importance? Although skin blood flow was higher in hypoxia, no differences in sweat rates or the critical environmental limit for the physiological compensability of core temperature - an indicator of maximal heat loss - were found compared to exercise in normoxia, indicating no influence of normobaric hypoxia on thermoregulatory capacity in warm conditions. Altered control of skin blood flow (SkBF) in hypoxia does not impair thermoregulation during exercise in compensable conditions, but its impact on maximal heat dissipation is unknown. This study therefore sought to determine whether maximum heat loss is altered by hypoxia during exercise in warm conditions. On separate days, eight males exercised for 90min at a fixed heat production of ∼500W in normoxia (NORM) or normobaric hypoxia (HYP, = 0.13) in a 34°C environment. Ambient vapour pressure was maintained at 2.13kPa for 45min, after which it was raised 0.11kPa every 7.5min. The critical ambient vapour pressure at which oesophageal temperature inflected upward (Pcrit ) indicated that maximum heat dissipation had been reached. Neither local sweat rates on the upper arm, back and forehead (average NORM: 1.46 (0.15) vs. HYP: 1.41 (0.16) mgcm-2 min-1 ; P=0.59) nor whole-body sweat losses (NORM: 1029 (137) g vs. HYP: 1025 (150) g; P=0.95) were different between trials. Laser-Doppler flux values (LDF; arbitrary units), an index of SkBF, were not different between NORM and HYP on the forearm (P=0.23) or back (P=0.73); however, when normalized as a percentage of maximum, LDF values tended to be higher in HYP compared to NORM at the forearm (condition effect, P=0.05) but not back (P=0.19). Despite potentially greater SkBF in hypoxia, there was no difference in Pcrit between conditions (NORM: 3.67 (0.35) kPa; HYP: 3.46 (0.39) kPa; P=0.22). These findings suggest that hypoxia does not independently alter thermoregulatory capacity during exercise in warm conditions.

A Physiological Validation of Spectral Analysis for Skin Flowmotion

In a series of studies, our laboratory has utilized microneurography coupled with laser Doppler flowmetry to examine sympathetic neural control of the cutaneous microvasculature during thermoregulatory stimuli. However, these techniques have limited clinical utility. Spectral analysis of the low frequency periodic oscillations in laser Doppler flowmetry‐derived red blood cell flux (i.e., skin flowmotion) is a noninvasive technique that has been used to quantify cutaneous microvascular control mechanisms (e.g., endothelial, neurogenic, myogenic). To date, conclusions regarding the mechanistic regulation of cutaneous microvascular function derived from spectral analysis have been primarily limited to basal conditions. Thus, the aim here was to examine the validity of spectral analysis to quantify sympathetic neural control of skin blood flow during a dynamic physiological stimulus (local skin heating to 42°C). We hypothesized that pharmacological blockade of sensory nerves would reduce the spectral power of the neurogenic frequency band during local heating. Eleven young healthy adults (7 women; 22±3 yrs, 25±2 kg/m2) participated. Laser Doppler flux was measured continuously during baseline (33°C) and a standardized local heating protocol (42°C) at a non‐treated control site (con) and a site treated with topical lidocaine (lido; 2.5% prilocaine+2.5% lidocaine) to pharmacologically block sensory nerves. Topical lido was applied for a minimum of 45 minutes prior to testing. Cutaneous vascular conductance was calculated and expressed as a percentage of maximum (local heat of 43°C). A raw Fourier transform was used to calculate spectral power around the 0.0095–0.02 Hz, 0.02–0.05 Hz, and 0.05–0.15 Hz frequency intervals, considered to correspond to endothelial, neurogenic, and myogenic activity, respectively. The initial peak of the local heating response was reduced by lido, (con: 62±2% vs. lido: 25±5%, p&lt;0.01), validating adequate sensory nerve blockade. However, there was no difference between sites during baseline (con: 12±1% vs. lido: 9±2%, p=0.07) or the local heating‐induced plateau (con: 95±3% vs. lido: 87±7%, p=0.20). There was no effect of lido on spectral power of any of the frequency intervals at baseline or during local heating. Total spectral power (i.e., the sum of the spectral power for all frequency bands) was significantly related to conductance in both sites at baseline (con: R2=0.69, p&lt;0.01; lido: R2=0.72, p&lt;0.01) and during local heating (con: R2=0.22, p&lt;0.02; lido: R2=0.71, p&lt;0.01). In conclusion, the physiological increase in cutaneous vascular conductance during local heating was mirrored by an increase in total spectral power. Although blockade of sensory nerves reduced the increase in conductance during the initial peak of the local heating response, it did not affect the neurogenic frequency interval derived from spectral analysis. These preliminary data suggest that skin flowmotion may not be a valid approach to evaluate neural control of cutaneous microvascular function during dynamic conditions.Support or Funding InformationAmerican Heart Association Grant #18UFEL33900164; College of Health and Human Development Summer 2019 Undergraduate Research Award; Noll Endowment for Undergraduate Research

Wavelet-based analysis of plantar skin blood flow response to different frequencies of local vibration

Objective: The objectives of this study were to investigate the response of plantar skin blood flow (SBF) to different frequencies of local vibration (LV) and investigate the mechanisms of blood flow control in response to the different frequencies of LV using wavelet analysis. Approach: Twelve healthy participants were recruited to test the effects of three frequencies [0 Hz (sham control), 35 Hz and 100 Hz at 1 mm amplitude] of 10 min LV on the skin of the right first metatarsal head. A repeated measures design was used in this study and the order of vibration frequencies was randomly assigned to participants while they lay on a mat table. Laser Doppler flowmetry was used to measure SBF on the first metatarsal head before and after LV for 10 min. SBF after vibration was expressed as a ratio of SBF before vibration. Wavelet analysis was used to characterize changes in SBF control mechanisms. Main results: Our results showed that the SBF with the 100 Hz protocol (1.56 ± 0.19) was significantly higher than for the 35 Hz (1.29 ± 0.18, p < 0.05) and 0 Hz (0.85 ± 0.11, p < 0.01) protocols. Wavelet analysis demonstrated that metabolic endothelial control (SBF oscillations of 0.0095–0.02 Hz) and neurogenic control (SBF oscillations of 0.02–0.05 Hz) were associated with the increase in SBF after LV at 100 Hz. Significance: LV at 100 Hz results in a significant increase in SBF compared with 35 Hz and 0 Hz vibrations. Such an increase in SBF is related to the regulation of metabolic endothelial (0.0095–0.02 Hz) and neurogenic (0.02–0.05 Hz) controls. This is the first study to demonstrate that 100 Hz LV stimulates an increase in plantar SBF compared with 35 Hz and 0 Hz vibrations through the frequency intervals of 0.0095–0.02 and 0.02–0.05 Hz of SBF oscillations.

Nardilysin in hepatocyte regulates adaptive thermogenesis in brown adipose tissue through the control of skin blood flow.

Nardilysin in hepatocyte regulates adaptive thermogenesis in brown adipose tissue through the control of skin blood flow.

Implementing local cooling to increase skin tolerance to ischemia during normal seating in people with spinal cord injury

The purpose of this study was to investigate the effectiveness of local cooling in reducing reactive hyperemia after ischemia at the ischial tuberosities for people with spinal cord injury (SCI) during normal seating. The degree of the reactive hyperemic response is indicative of the extent of cellular stress caused by the ischemia. We hypothesized that reactive hyperemic skin blood flow (SBF) responses will be lower when local cooling is implemented by the wheelchair seat cushion. This study used a repeated measures design, and each subject underwent two conditions: normal seating with temperature control ‘on’ (cooling) and ‘off’ (non-cooling) for 30 min. Twenty-three participants with traumatic SCI were recruited. SBF and skin temperature were collected before, during and after seating. SBF signals were processed with short-time Fourier analyses to examine the underlying vascular control mechanisms, including the following (corresponding frequency bands): metabolic (0.0095–0.02 Hz), neurogenic (0.02–0.05 Hz), and myogenic (0.05–0.15 Hz) spectral densities. Our results showed that with cooling, skin temperature decreased (range −0.4 ~ −3.1 °C, p = 0.002), and reactive hyperemia parameters (normalized peak SBF and perfusion area) were reduced (p = 0.02, p = 0.033, respectively). In addition, changes in normalized peak SBF (non-cooling – cooling) was moderately correlated with changes in normalized metabolic and neurogenic spectral densities. Our findings suggested that local cooling has a positive effect on reducing the cellular stress caused by ischemia during normal seating. Metabolic and neurogenic SBF control mechanisms may play a minor role. Further exploration of the effect of temperature control on pressure injury prevention is warranted.

Using Multiscale Entropy to Assess the Efficacy of Local Cooling on Reactive Hyperemia in People with a Spinal Cord Injury.

Pressure ulcers are one of the most common complications of a spinal cord injury (SCI). Prolonged unrelieved pressure is thought to be the primary causative factor resulting in tissue ischemia and eventually pressure ulcers. Previous studies suggested that local cooling reduces skin ischemia of the compressed soft tissues based on smaller hyperemic responses. However, the effect of local cooling on nonlinear properties of skin blood flow (SBF) during hyperemia is unknown. In this study, 10 wheelchair users with SCI and 10 able-bodied (AB) controls underwent three experimental protocols, each of which included a 10-min period as baseline, a 20-min intervention period, and a 20-min period for recovering SBF. SBF was measured using a laser Doppler flowmetry. During the intervention period, a pressure of 60 mmHg was applied to the sacral skin, while three skin temperature settings were tested, including no temperature change, a decrease by 10 °C, and an increase by 10 °C, respectively. A multiscale entropy (MSE) method was employed to quantify the degree of regularity of blood flow oscillations (BFO) associated with the SBF control mechanisms during baseline and reactive hyperemia. The results showed that under pressure with cooling, skin BFO both in people with SCI and AB controls were more regular at multiple time scales during hyperemia compared to baseline, whereas under pressure with no temperature change and particularly pressure with heating, BFO were more irregular during hyperemia compared to baseline. Moreover, the results of surrogate tests indicated that changes in the degree of regularity of BFO from baseline to hyperemia were only partially attributed to changes in relative amplitudes of endothelial, neurogenic, and myogenic components of BFO. These findings support the use of MSE to assess the efficacy of local cooling on reactive hyperemia and assess the degree of skin ischemia in people with SCI.

Disruption of TRPV3 Impairs Heat-Evoked Vasodilation and Thermoregulation: A Critical Role of CGRP

Sensing environmental temperature is a key factor allowing individuals to maintain thermal homeostasis via thermoregulatory mechanisms, including changes to skin blood flow. Among transient receptor potential channels, transient receptor potential vanilloid 3 (TRPV3) is a heat-activated cation channel highly expressed in keratinocytes. However, the role of TRPV3 in triggering heat-evoked cutaneous vasodilation is unknown. Using a murine invivo model of local acute environmental heat exposure in the skin, we show that TRPV3 is involved in the local thermoregulatory control of skin blood flow by initiating the release of calcitonin gene-related peptide and nitric oxide in response to local heating of the skin. In addition to their contribution in local heat-evoked vasodilation, TRPV3, calcitonin gene-related peptide, and nitric oxide also contribute to internal body temperature stability during passive whole-body heating. This study provides invivo demonstration of the role of TRPV3 as a strong modulator of cutaneous vascular thermoregulatory mechanisms.

部位別特性を考慮した生体内温度予測プログラムの開発 : 第2報-皮膚血流量調節の数理モデルの検討

部位別特性を考慮した生体内温度予測プログラムの開発 : 第2報-皮膚血流量調節の数理モデルの検討

Autonomic control of body temperature and blood pressure: influences of female sex hormones.

Female reproductive hormones exert important non-reproductive influences on autonomic regulation of body temperature and blood pressure. Estradiol and progesterone influence thermoregulation both centrally and peripherally, where estradiol tends to promote heat dissipation, and progesterone tends to promote heat conservation and higher body temperatures. Changes in thermoregulation over the course of the menstrual cycle and with hot flashes at menopause are mediated by hormonal influences on neural control of skin blood flow and sweating. The influence of estradiol is to promote vasodilation, which, in the skin, results in greater heat dissipation. In the context of blood pressure regulation, both central and peripheral hormonal influences are important as well. Peripherally, the vasodilator influence of estradiol contributes to the lower blood pressures and smaller risk of hypertension seen in young women compared to young men. This is in part due to a mechanism by which estradiol augments beta-adrenergic receptor mediated vasodilation, offsetting alpha-adrenergic vasoconstriction, and resulting in a weak relationship between muscle sympathetic nerve activity and total peripheral resistance, and between muscle sympathetic nerve activity and blood pressure. After menopause, with the loss of reproductive hormones, sympathetic nerve activity, peripheral resistance and blood pressure become more strongly related, and sympathetic nerve activity (which increases with age) becomes a more important contributor to the prevailing level of blood pressure. Continuing to increase our understanding of sex hormone influences on body temperature and blood pressure regulation will provide important insight for optimization of individualized health care for future generations of women.

Control of Skin Blood Flow at the Boundaries of the Thermal Comfort Zone

PURPOSE: The control of skin blood flow in the thermal comfort zone is largely unknown. We tested the hypothesis that skin blood flow at the boundaries of the thermal comfort zone is predominantly under reflex control. METHODS: Ten healthy subjects (age: 26 ± 4 y, 4 females) wearing shorts and a t-shirt underwent a 90 min behavioral test in which they voluntarily moved between a warm (39.9 ± 0.2°C, RH: 20 ± 0%) and a cool (16.9 ± 1.4°C. RH: 49 ± 3%) room when they felt ‘too warm’ or ‘too cool’. This test defined the boundaries of the thermal comfort zone for each subject. Skin blood flow was measured continually on the ventral forearm at two locations using laser Doppler flowmetry. One of these locations was maintained at 34°C, ensuring skin blood flow was under reflex control (RFX). The temperature of the other location was not controlled, and thus, skin blood flow was under local and reflex control (L+RFX). Blood pressure (Finometer), and weighted mean skin and rectal temperatures were also measured continually. Data are reported as a 30 s average immediately prior to moving from cool to warm (C→W) or warm to cool (W→C). Data were averaged across behaviors for a given subject (behaviors/subject = 9 ± 3). Skin blood flow data are reported as absolute values, the change from pre-test baseline, and as cutaneous vascular conductance (CVC). RESULTS: Mean skin temperature was different at C→W (33.5 ± 0.7°C) compared to W→C (36.1 ± 0.5°C, P<0.01), but rectal temperature did not differ at these points (C→W: 36.8 ± 0.2°C, W→C, 36.7 ± 0.2°C, P=0.17). At baseline, C→W and W→C, absolute skin blood flow and CVC were higher at RFX compared to L+RFX (P≤0.01). However, at both locations absolute skin blood flow and CVC were higher (P<0.01) at W→C compared to C→W (P<0.01), which was also consistent with the change from baseline data (P<0.01). Nevertheless, whether expressed as skin blood flow or CVC, the change from baseline at RFX compared to L+RFX was not different at either W→C (RFX: +21 ± 23 PU, +0.27 ± 0.24 mmHg/PU vs. L+RFX: +29 ± 15 PU, +0.33 ± 0.16 mmHg/PU; P≥0.10) or C→W (RFX: -6 ± 15 PU, -0.09 ± 0.16 mmHg/PU vs. L+RFX: -3 ± 6 PU, -0.04 ± 0.06 mmHg/PU; P≥0.39) CONCLUSION: These data indicate that changes in skin blood flow at the boundaries of the thermal comfort zone are largely under reflex control in young healthy adults.

Responses to hyperthermia. Optimizing heat dissipation by convection and evaporation: Neural control of skin blood flow and sweating in humans.

Under normothermic, resting conditions, humans dissipate heat from the body at a rate approximately equal to heat production. Small discrepancies between heat production and heat elimination would, over time, lead to significant changes in heat storage and body temperature. When heat production or environmental temperature is high the challenge of maintaining heat balance is much greater. This matching of heat elimination with heat production is a function of the skin circulation facilitating heat transport to the body surface and sweating, enabling evaporative heat loss. These processes are manifestations of the autonomic control of cutaneous vasomotor and sudomotor functions and form the basis of this review. We focus on these systems in the responses to hyperthermia. In particular, the cutaneous vascular responses to heat stress and the current understanding of the neurovascular mechanisms involved. The available research regarding cutaneous active vasodilation and vasoconstriction is highlighted, with emphasis on active vasodilation as a major responder to heat stress. Involvement of the vasoconstrictor and active vasodilator controls of the skin circulation in the context of heat stress and nonthermoregulatory reflexes (blood pressure, exercise) are also considered. Autonomic involvement in the cutaneous vascular responses to direct heating and cooling of the skin are also discussed. We examine the autonomic control of sweating, including cholinergic and noncholinergic mechanisms, the local control of sweating, thermoregulatory and nonthermoregulatory reflex control and the possible relationship between sudomotor and cutaneous vasodilator function. Finally, we comment on the clinical relevance of these control schemes in conditions of autonomic dysfunction.

Sex hormone effects on autonomic mechanisms of thermoregulation in humans.

Autonomic mechanisms are fundamental to human physiological thermoregulation, and female reproductive hormones have substantial influences on several aspects of these mechanisms. Of these, the best recognized are the thermoregulatory responses that occur at menopause (hot flushes) and the changes in body temperature within the menstrual cycle which may help couples predict ovulation. Our goal in this brief review is to summarize current knowledge regarding the influences of reproductive hormones on autonomic mechanisms in human thermoregulation. In general, estrogens tend to promote lower body temperatures via augmentation of heat dissipation responses, whereas progesterone tends to promote higher body temperatures. Recent evidence suggests specific influences of estrogens on central autonomic nuclei involved in control of skin blood flow and sweating. Estrogens also augment vasodilation by direct effects on peripheral blood vessels. Influences of progesterone are less well understood, but include both centrally regulated changes in thermoregulatory set-point as well as and peripheral effects, including augmented vasoconstriction in the skin. We conclude with a brief discussion of thermoregulatory adjustments associated with changing hormone levels during menopause, pregnancy and polycystic ovary syndrome.

Nitric oxide in the nucleus raphe magnus modulates cutaneous blood flow in rats during hypothermia.

Nucleus Raphe Magnus (NRM) that is involved in the regulation of body temperature contains nitric oxide (NO) synthase. Considering the effect of NO on skin blood flow control, in this study, we assessed its thermoregulatory role within the raphe magnus. To this end, tail blood flow of male Wistar rats was measured by laser doppler following the induction of hypothermia. Intra-NRM injection of SNP (exogenous NO donor, 0.1- 0.2 μl, 0.2 nM) increased the blood flow. Similarly, unilateral microinjection of glutamate (0.1- 0.2 μl, 2.3 nM) into the nucleus increased the blood flow. This effect of L-glutamate was reduced by prior intra NRM administration of NO synthase inhibitor N(G)-methyl-L-arginine or N(G)-nitro-L-arginine methyl ester (L-NAME, 0.1 µl, 100 nM). It is concluded that NO modulates the thermoregulatory response of NRM to hypothermia and may interact with excitatory amino acids in central skin blood flow regulation.

Does the skin of mildly hyperthermic individuals display local variations in thermosensitivity for the control of skin blood flow?

In an accompanying communication, it was revealed that local variations in cutaneous thermosensitivity, with respect to the control of skin blood flow, were not evident in normothermic individuals. Previously, greater thermosensitivity of the face relative to other sites, including the hand and thigh, was observed for sudomotor control in mildly hyperthermic individuals. Therefore, the possibility was tested that such variations may also exist for vasomotor control when subjects were first rendered mildly hyperthermic.

Cutaneous thermosensitivity differences among the face, hand or thigh appear not to exist for skin blood flow during normothermic states

Variations in the volume of the sensory cortex (homunculus) assigned to different skin regions may lead one to postulate that thermal stimulation of some body segments (e.g. face, hand) may evoke more powerful autonomic responses. That is, there may exist a mosaic of cutaneous thermosensitivity. To study thermosensitivity, thermal feedback from sites other than the treated site needs to be minimised. This is achieved via whole-body clamping of deep-body and skin temperatures. Previously, greater sensitivity of the face was observed for sudomotor control in mildly hyperthermic individuals [1], so the aim of this investigation was to explore possible sensitivity variations in the control of skin blood flow during isolated stimulation of three sites, but after a normothermic clamp had been established.

An On-Site Thermoelectric Cooling Device for Cryotherapy and Control of Skin Blood Flow

Cryotherapy involves the surface application of low temperatures to enhance the healing of soft tissue injuries. Typical devices embody a remote source of chilled water that is pumped through a circulation bladder placed on the treatment site. In contrast, the present device uses thermoelectric refrigeration modules to bring the cooling source directly to the tissue to be treated, thereby achieving significant improvements in control of therapeutic temperature while having a reduced size and weight. A prototype system was applied to test an oscillating cooling and heating protocol for efficacy in regulating skin blood perfusion in the treatment area. Data on 12 human subjects indicate that thermoelectric coolers (TECs) delivered significant and sustainable changes in perfusion for both heating (increase by (±SE) 173.0 ± 66.0%, P < 0.005) and cooling (decrease by (±SE) 57.7 ± 4.2%, P < 0.0005), thus supporting the feasibility of a TEC-based device for cryotherapy with local temperature regulation.