The influence of environmental temperature on the response of the skin to local pressure: the impact of aging and diabetes

Heatwaves and diabetes in Brisbane, Australia: a population-based retrospective cohort study

Background

Available data on the effects of heatwaves on hospitalizations for diabetes and the post-discharge status of diabetics are scarce. This study aimed to assess the effects of heatwaves on hospitalizations and post-discharge deaths for diabetes, and to identify the individual- and community-level characteristics [i.e. age, gender, Socio-economic Indexes for Areas (SEIFA), and normalized difference vegetation index (NDVI)] that modified heatwave effects.

Methods

Health data were extracted from a cohort study which included patients in Brisbane, Australia, who were hospitalized due to diabetes from 1st January 2005 to 31st December 2013, and died within 2 months after they were discharged. Data on community-level modifiers, including SEIFA and NDVI (i.e. urban vegetation), were obtained from Australian Bureau of Statistics and Australian Bureau of Meteorology, respectively. Case-crossover design was used to quantify the effects of heatwaves on hospitalizations and post-discharge deaths due to diabetes. Four heatwave definitions incorporating both intensity (i.e. 90th, 95th, 97th and 99th percentiles of mean temperature distribution) and duration (2 days), as well as excess heat factor (EHF), were used. A case-only design was adopted to identify the modifiers of heatwave effects.

Results

There were 10 542 hospitalizations for diabetes, and 513 patients died due to diabetes within 2 months after discharge. During low-intensity heatwave days (i.e. 90th percentile & 2 days), we did not observe a significant increase in hospitalizations for diabetes [9% at lag 0; 95% confidence interval (CI): –3%, 23%; P = 0.146], but we observed a significant increase in post-discharge deaths (46% at lag 2; 95% CI: 3%, 107%; P = 0.036). During middle-intensity heatwave days (i.e. 95th percentile & 2 days), hospitalizations for diabetes increased by 19% at lag 0 (95% CI: 2%, 39%; P = 0.026), and post-discharge deaths increased by 64% at lag 0 (95% CI: 6%, 154%; P = 0.027). During high-intensity heatwave days (i.e. 97th percentile & 2 days), hospitalizations for diabetes increased by 37% at lag 1 (95% CI: 11%, 69%; P = 0.004) and post-discharge deaths increased by 137% at lag 1 (95% CI: 39%, 303%; P = 0.002). When heatwave intensity increased to 99th percentile, we did not observe a significant increase in hospitalizations (–1% at lag 0; 95% CI: –38%, 59%; P = 0.870) or post-discharge deaths (79% at lag 0; 95% CI: –39%, 431%; P = 0.301). When we used EHF to define heatwaves, we observed significant increases of hospitalizations (7%; 95% CI: 1%, 15%; P = 0.039) and post-discharge deaths (68%, 95% CI: 10%, 158%; P = 0.017) during heatwave days, compared with non-heatwave days. Children and male diabetics were particularly vulnerable to heatwave effects, but we did not find any significant modification effect of SEIFA or NDVI on the associations of heatwaves with hospitalizations and post-discharge deaths due to diabetes.

Conclusion

Heatwaves may lead to hospitalizations of diabetics and their premature deaths. Heat-related diabetes burden in children may increase as climate warms and with increasing obesity rates in adolescents.

Blood flow responses over sacrum in nursing home residents during one hour bed rest

Objectives

To describe individual BF responses in a nursing home resident population for one‐hour periods of bed rest.

Methods

BF was measured for one hour over the sacrum in 0° supine position and 30° supine tilt position in 25 individuals aged 65 y or older while lying on a pressure‐redistributing mattress. Measurements were made at three tissue depths (1, 2, and 10 mm) using the noninvasive optical techniques, LDF and PPG.

Results

Eleven participants had a PIV response at 1 mm depth in both positions and seven participants had a lack of this response at this depth and positions. The BF response at 1 mm depth appeared immediately and remained over, or below, baseline for the entire 60 min of loading in both positions. These BF patterns were also seen in deeper tissue layers.

Conclusions

The cutaneous BF response among the nursing home residents was distinct, appeared early, and remained during the one hour of loading.

A new method to evaluate the effects of shear on the skin

Currently, pressure ulcer preventive strategies focus mainly on pressure redistribution. Little attention is paid to reduce the harmful effects of shear-force, because little is known about pathophysiological aspects of shear-force. Even today, no method to measure the effects of shear-force on the skin is available. Therefore, the aim of this study was to investigate the response to shear-forces in terms of analyzing a noninvasive biomarker and reactive hyperemic parameter measured at the skin of healthy participants. A physical model was developed to produce a combination of pressure and shear or pressure alone on the skin. Ten healthy male participants were included and pressure (3.9 kPa) and a combined loading of pressure and shear (2.4 kPa + 14.5 N) was applied at the volar aspect of the forearms for 15 and 30 minutes. A Sebutape sample was used to collect IL-1α and total protein (TP) noninvasively. The reactive hyperemic parameter was derived from a laser Doppler flowmeter. The increase in IL-1α/TP-ratio after a combined loading of pressure and shear for 30 minutes of 6.2 ± 2.5 was significantly higher compared with all other test conditions (p < 0.05). The increase in cutaneous blood cell flux was already significantly higher when a combined loading of pressure and shear was applied for 15 minutes compared with pressure alone. These results shows that the IL-1α/TP-ratio and cutaneous blood cell flux can be used as robust measures of the effect of shear-force on skin in humans. Therefore, this model can be used to evaluate materials aimed at the reduction of shear.

The Effects of Different Lying Positions on Interface Pressure, Skin Temperature, and Tissue Blood Flow in Nursing Home Residents

Background:

Although repositioning is considered an important intervention to prevent pressure ulcers, tissue response during loading in different lying positions has not been adequately explored.

Aim:

To compare the effects of different lying positions on interface pressure, skin temperature, and tissue blood flow in nursing home residents.

Method:

From May 2011 to August 2012, interface pressure, skin temperature, and blood flow at three tissue depths were measured for 1 hr over the sacrum in 30° supine tilt and 0° supine positions and over the trochanter major in 30° lateral and 90° lateral positions in 25 residents aged 65 years or older. Measurement of interface pressure was accomplished using a pneumatic pressure transmitter connected to a digital manometer, skin temperature using a temperature sensor, and blood flow using photoplethysmography and laser Doppler flowmetry.

Results:

Interface pressure was significantly higher in the 0° supine and 90° lateral positions than in 30° supine tilt and 30° lateral positions. The mean skin temperature increased from baseline in all positions. Blood flow was significantly higher in the 30° supine tilt position compared to the other positions. A hyperemic response in the post pressure period was seen at almost all tissue depths and positions.

Conclusion:

The 30° supine tilt position generated less interface pressure and allowed greater tissue perfusion, suggesting that this position is the most beneficial.

Effects of elevated vacuum on in-socket residual limb fluid volume: case study results using bioimpedance analysis

Bioimpedance analysis was used to measure the residual limb fluid volume of seven transtibial amputee subjects using elevated vacuum sockets and nonelevated vacuum sockets. Fluid volume changes were assessed during sessions with the subjects sitting, standing, and walking. In general, fluid volume losses during 3 or 5 min walks and losses over the course of the 30 min test session were less for elevated vacuum than for suction. Numerous variables, including the time of day that data were collected, soft tissue consistency, socket-to-limb size and shape differences, and subject health, may have affected the results and had an equivalent or greater effect on limb fluid volume compared with elevated vacuum. Researchers should well consider these variables in the study design of future investigations on the effects of elevated vacuum on residual limb volume.

Resting blood flow in the skin: does it exist, and what is the influence of temperature, aging, and diabetes?

Measurement of resting blood flow to the skin and other organs is an important indicator of health and disease and a way to assess the reaction to various stimuli and pharmaceutical interventions. However, unlike plasma ions such as sodium or potassium, it is difficult to determine what the proper value for resting blood flow really is. Part of the problem is in the measurement of blood flow; various techniques yield very different measures of skin blood flow even in the same area. Even if there were common techniques, resting blood flow to tissue, such as the skin, is determined by the interaction of a plurality of factors, including the sympathetic nervous system, temperature, pressure, shear forces on blood vessels, tissue osmolality, and a variety of other stimuli. Compounding this variability, the blood flow response to any stressor is reduced by free radicals in the blood and diminished by aging and diabetes. Race also has an effect on resting blood flow to the skin. All these factors interact to make the exact resting blood flow difficult to determine in any one individual and at any one time. This review examines the main techniques to assess blood flow, the factors that alter blood flow in the skin, and how aging and diabetes affect blood flow. Recommendations for the measurement of resting blood flow are presented.

The influence of autonomic dysfunction associated with aging and type 2 diabetes on daily life activities

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.

A method of measuring the interaction between skin temperature and humidity on skin vascular endothelial function in people with diabetes

BACKGROUND

A core defect in people with Type 2 Diabetes is endothelial dysfunction. This defect permeates all organ systems in the body including the ability of the skin to protect itself from thermal injuries by an appropriate increase in skin circulation. Most studies on the local response to heating have been done with dry heat sources. Recent data show that endothelial function is improved in people with diabetes with moist heat. Little is known about 'how' moist heat must be or the mechanisms on why moist heat triggers a better blood flow response than dry heat.

METHODS

In the present investigation, a device was developed to provide variable temperature air and variable humidity as an aid to study the dynamics of the skin circulatory response to heat in people with diabetes. The device consisted of a water bath used to heat air and an air dryer and air bubbler to generate dry and moist air, respectively, at a fixed temperature. The air could then be mixed and the temperature stabilized to produce a variable temperature and humidity air source to expose the skin to in people with diabetes.

RESULTS

The device was validated at different air temperatures and humidities and tested on four subjects to assess operation. The air flows, temperatures and humilities were stable with less than a 5% coefficient of variation.

CONCLUSIONS

Testing on humans showed that there appeared to be a linear relationship between air humidity and blood flow at a given air temperature exposed to the skin.

Comparison of different heat modalities for treating delayed-onset muscle soreness in people with diabetes

BACKGROUND

Delayed-onset muscle soreness (DOMS) is a serious problem for people who do not exercise on a regular basis. Although the best preventive measure for diabetes and for maintaining a low hemoglobin A1c is exercise, muscle soreness is common in people with diabetes. For people with diabetes, DOMS is rarely reported in exercise studies.

RESEARCH DESIGN

One hundred twenty subjects participated in three groups (young, older, and type 2 diabetes) and were examined to evaluate the soreness in the abdominal muscles after a matched exercise bout using a p90x exercise video (Beachbody LLC, Los Angeles, CA) for core fitness. Next, three heating modalities were assessed on how well they could reduce muscle soreness: ThermaCare(®) (Pfizer Consumer Healthcare, Richmond, VA) heat wraps, hydrocollator heat wraps, and a chemical moist heat wrap.

RESULTS

The results showed that people with diabetes were significantly sorer than age-matched controls (P < 0.05). On a 100-mm VAS (100 mm = sorest), the average soreness for the people with diabetes was 73.3 ± 16.2 mm, for the older group was 56.1 ± 15.1 mm, and for the younger group was 41.5 ± 9.3 mm; these differences were significant (analysis of variance, P < 0.05). The greatest reduction in soreness after applying the modalities was using moist heat, both immediately after the modality and up to 2 days after the exercise. Right after the modality, moist heat reduced pain by 52.3% in the older subjects compared with 30.5% in the subjects with diabetes and 33.3% in the younger subjects. Skin blood flow in the abdominal area before exercise was greatest in the younger subjects and lower in the subjects with diabetes after heat application. Skin temperature at rest and after exercise was greatest in the diabetes group.

CONCLUSIONS

Muscle soreness following exercise was greatest in people with diabetes, and the best modality of the three studied to reduce this type of soreness was chemical moist heat.

The effect of type-2-diabetes-related vascular endothelial dysfunction on skin physiology and activities of daily living

A common factor contributing to organ damage in type 2 diabetes mellitus (T2DM) is impaired tissue blood flow caused by damage to vascular endothelial cells (VECs). Damage can occur even before the clinical diagnosis of diabetes. It can be caused by both a high average blood glucose concentration and/or large daily spikes in blood glucose. While much of the present literature focuses on the damage to VECs and organs from these large glucose excursions, this review will focus on the consequence of this damage, that is, how endothelial cell damage in diabetes affects normal daily activities (e.g., exercise, reaction to typical stimuli) and various treatment modalities (e.g.. contrast baths and electrical stimulation therapy). It is important to understand the effects of VEC damage such as poor skin blood flow, compromised thermoregulation, and altered response to skin pressure in designing diabetes technologies as simple as heating pads and as complex as continuous glucose monitors. At the simplest level, people with diabetes have poor circulation to the skin and other organs. In the skin, even the blood flow response to locally applied pressure, such as during standing, is different than for people who do not have T2DM. Simple weight bearing on the foot can occlude the skin circulation. This makes the skin more susceptible to damage. In addition, endothelial damage has far-reaching effects on the whole body during normal activities of daily living, including an impaired response to local heat, such as hot packs and contrast baths, and higher body temperatures during whole body heating due to impaired blood flow and a reduced ability to sweat. Finally, because of multiple organ damage, people with T2DM have poor balance and gait and impaired exercise performance.

The ability of different areas of the skin to absorb heat from a locally applied heat source: the impact of diabetes

BACKGROUND

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.

RESULTS

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.

CONCLUSION

Thus, specific areas of the body are damaged more by diabetes than other areas.

The influence of aging and diabetes on heat transfer characteristics of the skin to a rapidly applied heat source

BACKGROUND

Numerous studies have examined the blood flow of the skin at rest and in response to sustained heat and shown that, in older people and people with diabetes, the skin blood flow response to heat is diminished compared to younger people. It is not sustained heat, however, that usually causes burns; it is a more rapid application of heat.

SUBJECTS AND METHODS

Ten younger subjects, 10 older subjects, and 10 subjects with diabetes were examined before and after applying a water-filled thermode to the skin above the quadriceps muscle to observe the changes in skin temperature and skin blood flow and the ability of the skin to absorb heat after a 2-min heat exposure with water at 44°C.

RESULTS

Skin temperature rose from 31.2°C at rest to 38.3°C after 2 min of heat application in all subjects (P > 0.05 between groups). The calories required in the younger group of subjects was 2.26 times the calories required in the older group of subjects for the same change in skin temperature and 13.8 times the calories needed to increase skin temperature in the subjects with diabetes. Furthermore, the blood flow at rest was lower in people with diabetes than older subjects and both groups less than that seen in younger subjects. The blood flow response to heat was slower in the subjects with diabetes compared to the older subjects and much slower than that seen in the younger subjects.

CONCLUSIONS

Reduced skin blood flow of older and subjects with diabetes, decreased thickness of the dermal layer, and increased subcutaneous fat, as well as damage to transient receptor potential vanilloid 1 receptors, may account for some of the differences between the groups.