The Ability of Different Areas of the Skin to Absorb Heat from a Locally Applied Heat Source: The Impact of Diabetes

Department of Physical Therapy, Loma Linda University, Loma Linda, California, USA.
Diabetes Technology & Therapeutics (Impact Factor: 2.11). 02/2011; 13(3):365-72. DOI: 10.1089/dia.2010.0161
Source: PubMed


When heat is applied to the skin, heat is conducted away because of the latent heat transfer properties of the skin and an increase in skin circulation, but little attention has been paid to the heat transfer properties of skin in different areas of the body and in people with diabetes. research design: Thirty subjects in the age range of 20-75 years had a thermode (44°C) applied to the skin of their arm, leg, foot, and back for 6 min to assess the heat transfer characteristics of skin in these four areas of the body. Skin blood flow and skin temperature were monitored over the 6-min period.
For the younger subjects, blood flow was not statistically different in response to heat in three areas of the body, starting at less than 200 flux measured by a laser Doppler imager and ending at approximately 1,200 flux after heat exposure. The foot had higher resting blood flow and higher blood flow in response to heat. Temperature and the rate of rise of temperature were also not different in any of the areas. The heat added to raise temperature, however, varied by body region. The arm required the least, whereas the leg and foot required the most. For the older group and subjects with diabetes, the heat required for any region of the body was much less to achieve the same increase in skin temperature, and blood flows were also much less; the subjects with diabetes showed the least blood flow and required the fewest calories to heat the skin. Whereas the foot required the greatest number of calories to heat the tissue in younger and older subjects, in subjects with diabetes, the foot took proportionally fewer calories.
Thus, specific areas of the body are damaged more by diabetes than other areas.

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    • "Many studies indicated that it was both the conductive heat loss through the skin itself and skin blood flow that are important in dissipating heat from the skin [16,18,35]. However, conductive heat loss for living skin is not constant (a second or less) and the skin blood flow does play a progressively greater role in continually removing heat for protecting the skin from burns [14,16,35]. According to a recent study from this laboratory, older people and people with diabetes are more susceptible to skin damage and burns due to changes in the structures of the skin and a reduction in skin blood flow linked to reduced bioavailability of nitric oxide by free radicals in vascular endothelial cells [14]. "
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    ABSTRACT: The vascular endothelium plays an integral role in maintaining vascular homeostasis, including the regulation of blood flow, vascular tone, and platelet aggregation. The aim of this study was to see if there were any differences in endothelial function between Koreans and Caucasians. This was accomplished by 2 measures of endothelial function--the response to local heat and the response to vascular occlusion. Ten Caucasian and 10 Korean male and female subjects participated (<35 years old). Endothelial function was assessed by the skin blood flow response to local heat using a thermode for 6 minutes at 3 temperatures (38°C, 40°C and 42°C) and by vascular occlusion for 4 minutes followed by release and measurement of skin blood flow for 2 minutes. When applying 6 minutes of local heat at 3 different temperatures (38°C, 40°C, and 42°C), the skin blood flows were significantly higher for all temperatures in Caucasians as compared with Koreans, with peak blood flow of 223±48.1, 413.7±132.1, and 517.4±135.8 flux in Caucasians and 126.4±41.3, 251±77.9, and 398±97.2 flux in Koreans, respectively (p=0.001). Results of this study support the idea that the skin blood flow response to occlusion was significantly higher in Caucasians (peak 411.9±88.9 flux) than Koreans (peak 332.4±75.8 flux) (p=0.016). These findings suggest that Koreans may have lower endothelial function than Caucasians, which may be explained, in part, by genetic variations between the 2 ethnic groups.
    Full-text · Article · Jun 2012 · Medical science monitor: international medical journal of experimental and clinical research
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    • "The predominance of vasoconstrictors over vasodilators released from vascular endothelial cells in people with diabetes and older individuals causes skin blood flow to be lower at rest in people with diabetes than in age-matched controls compared to younger people [29]. Numerous studies have shown resting skin blood flow to be as little as one third (1/3) that of age-matched controls [56, 63–66]. Making matters worse, various protective mechanisms in the body at the level of the vascular endothelial cell are also damaged in diabetes. "
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    ABSTRACT: Type 2 diabetes (T2D) and ageing have well documented effects on every organ in the body. In T2D the autonomic nervous system is impaired due to damage to neurons, sensory receptors, synapses and the blood vessels. This paper will concentrate on how autonomic impairment alters normal daily activities. Impairments include the response of the blood vessels to heat, sweating, heat transfer, whole body heating, orthostatic intolerance, balance, and gait. Because diabetes is more prevalent in older individuals, the effects of ageing will be examined. Beginning with endothelial dysfunction, blood vessels have impairment in their ability to vasodilate. With this and synaptic damage, the autonomic nervous system cannot compensate for effectors such as pressure on and heating of the skin. This and reduced ability of the heart to respond to stress, reduces autonomic orthostatic compensation. Diminished sweating causes the skin and core temperature to be high during whole body heating. Impaired orthostatic tolerance, impaired vision and vestibular sensing, causes poor balance and impaired gait. Overall, people with T2D must be made aware and counseled relative to the potential consequence of these impairments.
    Full-text · Article · Apr 2012 · Experimental Diabetes Research
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    • "For example, the response to occlusion is blunted in people from Thailand compared to Caucasians [2]. While occlusion is a useful clinical test, it is more practical to examine the response to other stressors such as to heat since heat is used as a therapeutic modality [23–25]. Many of the same genes as seen in people from Thailand are found in Southeast Asian Indians. "
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    ABSTRACT: The reaction of vascular endothelial cells to occlusion and heat in Southeast Asian Indians (SAI) compared to Caucasians (C) has not been studied, although genetic differences are found in endothelial cells between the races. Ten C and Ten SAI (<35 years old) male and female subjects participated. There was no difference in the demographics of the subjects except that the SAI group had been in the United States for 6 months; C was natives to the US. Endothelial function was assessed by the response of the circulation (BF) to local heating and the response to vascular occlusion. The effects of local heat on circulation in the skin on the forearm was assessed by applying heat for 6 minutes at temperatures, 38, 40 and 42°C on 3 separate days. On different days, vascular occlusion was applied for 4 minutes to the same arm and skin blood flow was measured for 2 minutes after occlusion; skin temperature was either 31°C or 42°C. When occlusion was applied at a skin temperature of 31°C, the BF response to occlusion was significantly lower in the SAI cohort compared to C (peak BF C = 617 ± 88.2 flux, SAE = 284 ± 73 flux). The same effect was seen at skin temperatures of 42°C. The circulatory response to heat was also significantly less in SAI compared to C at each temperature examined (p<0.05)(for temperatures of 38, 40 and 42°C, peak blood flow for C was 374.7 ± 81.2, 551.9 ± 91.3 and 725.9 ± 107 flux respectively and 248.5 ± 86.2, 361.4 ± 104.3 and 455.3 ± 109.7 flux respectively for SAI. (p<0.05). Thus there seems to be big differences in these 2 populations in endothelial response to these stressors. The difference may be due to genetic variations between the 2 groups of subjects.
    Full-text · Article · Dec 2011 · Medical science monitor: international medical journal of experimental and clinical research
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