Effects of contrast baths on skin blood flow on the dorsal and plantar foot in people with type 2 diabetes and age-matched controls

Effect of Vibration on Alleviating Foot Pressure-Induced Ischemia under Occlusive Compression

Objectives

Foot ulcers often occur in people with diabetes because of pressure-induced tissue ischemia. Vibration has been reported to be helpful in alleviating mechanical damage and promoting wound healing. The objective of this study is to explore whether vibration can relieve reactive hyperemia in foot tissue under occlusive compression.

Methods

Thirteen healthy adults participated in the study. Each foot was placed under occlusive compression without or with vibration intervention, which was randomly assigned every other day. The dorsal foot skin blood flow (SBF) was measured pre- and postintervention for each subject in each test. Temporal variations and spectral features of SBF were recorded for comparison.

Results

The results showed that subjects displayed an obvious reactive hyperemia in the foot tissue after pressure occlusion, whereas they displayed a more regular SBF when vibration was applied along with occlusive compression. Moreover, the amplitude of metabolic, neurogenic, and myogenic pathways for SBF was significantly reduced during the hyperemia process when vibration was applied.

Conclusions

This study demonstrated that vibration can effectively reduce the level of hyperemia in foot tissue under occlusive compression and also induce less protective physiological regulatory activities. This is helpful for protecting foot tissue from pressure-induced ischemic injury and foot ulcers.

Effect of different thermal stimuli on improving microcirculation in the contralateral foot

Background

The lower extremities of the body often suffer from impaired microcirculation, particularly in the elderly or people with underlying conditions such as diabetes. Especially for people suffering from peripheral vascular diseases, skin lesions or wearing an external fixator in one side of limbs, direct contact treatments are not suitable for them to improve microcirculation. Heating the contralateral limb has been reported to improve blood flow in the impaired limb. However, its effect on plantar microvascular responses has not been previously investigated. Thus, the aim of this study was to explore how heating by warm bath and infrared radiation affects the circulations in the contralateral foot. Twelve healthy adults participated in this study and were randomly assigned to either placing the left foot in a warm bath or exposing it to infrared radiation for 10 min intervention every other day. The skin temperature (Temp) and skin blood flow (SBF) in the second metatarsal head of the contralateral foot were measured before and after the intervention.

Results

The results showed that both Temp (Bath: from 29.05 ± 3.56 °C to 31.03 ± 4.14 °C; Infrared: from 29.98 ± 3.86 °C to 31.07 ± 3.92 °C) and SBF (Bath: from 62.26 ± 48.12 PU to 97.76 ± 63.90 PU; Infrared: from 63.37 ± 39.88 PU to 85.27 ± 47.62 PU) in the contralateral foot were significantly increased after heating in both tests (p < 0.05). However, the contralateral SBF increased for 5 min after heating in warm bath test, but only for 1 min in infrared radiation test.

Conclusions

The results of this study show that both heating methods are the effective at increasing contralateral Temp and SBF, but the warm bath has a stronger residual thermal effect.

The Efficacy of Sustained Heat Treatment on Delayed-Onset Muscle Soreness

OBJECTIVE

To assess the impact of heat applied for 8 hours immediately after or 24 hours after exercise on delayed-onset muscle soreness (DOMS) in large skeletal muscle groups measured by subjective and objective means.

DESIGN

Cross-sectional repeated measure design study.

SETTING

Research laboratory.

SUBJECTS

Three groups of 20 subjects, age range 20 to 40 years.

INTERVENTION

Squats were conducted in three 5-minute bouts to initiate DOMS; 3 minutes of rest separated the bouts. One group had heat applied immediately after exercise, and a second group had heat applied 24 hours after exercise. A third group was the control group where no heat was applied.

MAIN OUTCOME MEASURES

Visual analog pain scales, muscle strength of quads, range of motion of quads, stiffness of quads (Continuous Passive Motion machine), algometer to measure quadriceps soreness, and blood myoglobin.

RESULTS

The most significant outcome was a reduction in soreness in the group that had low-temperature heat wraps applied immediately after exercise (P < 0.01). There was benefit to applying heat 24 hours after exercise, but to a smaller extent. This was corroborated by myoglobin, algometer, and stiffness data.

CONCLUSIONS

Low-level continuous heat wraps left for 8 hours just after heavy exercise reduced DOMS in the population tested as assessed by subjective and objective measures.

CLINICAL RELEVANCE

Although cold is commonly used after heavy exercise to reduce soreness, heat applied just after exercise seems very effective in reducing soreness. Unlike cold, it increases flexibility of tissue and tissue blood flow. For joint, it is still probably better to use cold to reduce swelling.

Contrast Therapy and Heat Therapy in Subacute Stage of Grade I and II Lateral Ankle Sprains

Objective This study was conducted to determine the most effective thermal modality; heat or contrast therapy-in reducing pain, reducing swelling, and increasing range of movement (ROM) of the grade I and II lateral ankle sprain in the prechronic stage of the subacute phase. Design Randomized control trail. Methods One hundred and fifteen participants of both genders who were diagnosed as having grade I or II lateral ankle sprain were randomly assigned to the study on the fifth day of injury. Pain, volume, and ROM were recorded before and after treatment continuously for 3 days. Results Effects were evaluated as "Immediately after application" and "3 days after continuous application." Immediately after application, there was no difference between the 2 modalities on ankle ROM; heat reduced pain over contrast therapy, and both modalities increased swelling. When considering the effects after continuous application for 3 days, no difference was found between the 2 modalities on ROM and the reduction of pain. Contrast therapy reduced swelling while heat caused increased swelling even after 3 days. Conclusion The use of different thermal modalities during the transition from the acute to chronic phase of injury can be suggested as effective treatment options according to the objectives of injury management: pain reduction, improve ROM, and swelling management.

LEVELS OF EVIDENCE

Therapeutic, Level II: Randomized clinical trial.

Local cooling reduces regional bone blood flow

Local cooling is very common after bone and joint surgery. Therefore the knowledge of bone blood flow during local cooling is of substantial interest. Previous studies revealed that hypothermia leads to vasoconstriction followed by decreased blood flow levels. The aim of this study was to characterize if local cooling is capable of inducing reduced blood flow in bone tissue using a stepwise-reduced temperature protocol in experimental rabbits. To examine bone blood flow we utilized the fluorescent microsphere (FM) method. In New Zealand white rabbits one randomly chosen hind limb was cooled stepwise from 32 to 2°C, whereas the contra lateral hind limb served as control. Injection of microspheres was performed after stabilization of bone and muscle temperature at each temperature level. Bones were removed, dissected and fluorescence intensity was determined to calculate blood flow values. We found that blood flow of all cooled regions decreased relative to the applied external temperature. At maximum cooling blood flow was almost completely disrupted, indicating local cooling as powerful regulatory mechanism for regional bone blood flow (RBBF). Postoperative cooling therefore may lead to strongly decreased bone blood flow values. As a result external cooling has capacity to both diminish bone healing and reduce bleeding complications.

Moist heat or dry heat for delayed onset muscle soreness

Background

Heat is commonly used in physical therapy following exercise induced delayed onset muscle soreness (DOMS). Most heat modalities used in a clinical setting for DOMS are only applied for 5 to 20 minutes. This minimal heat exposure causes little, if any, change in deep tissue temperature. For this reason, long duration dry chemical heat packs are used at home to slowly and safely warm tissue and reduce potential heat damage while reducing pain associated from DOMS. Clinically, it has been shown that moist heat penetrates deep tissue faster than dry heat. Therefore, in home use chemical moist heat may be more efficacious than dry heat to provide pain relief and reduce tissue damage following exercise DOMS. However, chemical moist heat only lasts for 2 hours compared to the 8 hours duration of chemical dry heat packs. The purpose of this study was to compare the beneficial effect of dry heat versus moist heat on 100 young subjects after exercise induce DOMS.

Methods

One hundred subjects exercised for 15 minutes accomplishing squats. Before and for 3 days after, strength, muscle soreness, tissue resistance, and the force to passively move the knee were recorded. Heat and moist heat were applied in different groups either immediately after exercise or 24 hours later.

Results

The research results of this study showed that immediate application of heat, either dry (8 hours application) or moist (2 hours application), had a similar preservation of quadriceps muscle strength and muscle activity. Results also revealed that the greatest pain reduction was shown after immediate application of moist heat. Never the less, immediate application of dry heat had a similar effect but to a lesser extent.

Conclusion

It should be noted that moist heat had not only similar benefits of dry heat but in some cases enhanced benefits, and with only 25% of the time of application of the dry heat.

Changes of skin temperature of parts of the body and serum asymmetric dimethylarginine (ADMA) in type-2 diabetes mellitus Indian patients

In India, number of people with type 2 Diabetes Mellitus (DM) would be 87 million by the year 2030. DM disturbs autonomic regulation of skin micro-circulation, and causes decrease in resting blood flows through the skin. The skin blood flow has a major effect on its temperature. The aim of the study was to evaluate changes of skin temperature of all parts of the body and serum asymmetric dimethylarginine, ADMA (μmol/L) in type-2 DM Indian patients. Group-I: Normal (n = 17; M/F: 10/15, mean ± SD = 43.2 ± 9.4 years); Group-II: Type-2 DM without cardiovascular (CV) complications (n = 15; M/F: 10/7, mean ± SD = 46.3 ± 14.0 years); Thermograms of all parts of the body were acquired using a non-contact infrared (IR) thermography camera (ThermaCAM T400, FLIR Systems, Sweden). Blood parameters and thyroid hormone were measured biochemically. Indian diabetic risk score (IDRS) was calculated for each subject. In type-2 DM patients without CV group (n = 15), there was a statistically significant (p = 0.01) negative correlations between HbA(1c) and skin temperature of eye and nose (r = -0.57 and r = -0.55 respectively). ADMA was correlated significantly (p = 0.01) with HbA(1c) (r = 0.65) and estimated average glucose, eAG (r = 0.63). In normal subjects, mean minimum and maximum values of skin temperatures were observed at posterior side of sole (26.89 °C) and ear (36.85 °C) respectively. In type-2 DM without CV, mean values of skin temperature in different parts of the body from head to toe were lesser than those values in control group; but this decreases were statistically significant in nose (32.66 Vs 33.99 °C, p = 0.024) as well as in tibia (32.78 Vs 33.13 °C, p = 0.036) regions.

The interrelationship between air temperature and humidity as applied locally to the skin: the resultant response on skin temperature and blood flow with age differences

BACKGROUND

Most studies of the skin and how it responds to local heat have been conducted with either water, thermodes, or dry heat packs. Very little has been accomplished to look at the interaction between air humidity and temperature on skin temperature and blood flow. With variable air temperatures and humidity's around the world, this, in many ways, is a more realistic assessment of environmental impact than previous water bath studies.

MATERIAL/METHODS

Eight young and 8 older subjects were examined in an extensive series of experiments where on different days, air temperature was 38, 40, or 42°C. and at each temperature, humidity was either 0%, 25%, 50%, 75%, or 100% humidity. Over a 20 minute period of exposure, the response of the skin in terms of its temperature and blood flow was assessed.

RESULTS

For both younger and older subjects, for air temperatures of 38 and 40°C., the humidity of the air had no effect on the blood flow response of the skin, while skin temperature at the highest humidity was elevated slightly. However, for air temperatures of 42°C., at 100% humidity, there was a significant elevation in skin blood flow and skin temperature above the other four air humidity's (p<0.05). In older subjects, the blood flow response was less and the skin temperature was much higher than younger individuals for air at 42°C. and 100% humidity (p<0.05).

CONCLUSIONS

Thus, in older subjects, warm humid air caused a greater rise in skin temperature with less protective effect of blood flow to protect the skin from overheating than is found in younger subjects.

Reduced endothelial function in the skin in Southeast Asians compared to Caucasians

BACKGROUND

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.

MATERIAL/METHODS

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.

RESULTS

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).

CONCLUSIONS

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.

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.

Therapeutic modalities--an updated review for the hand surgeon

The number of therapeutic modalities available to the hand surgeon has greatly increased over the past several decades. A field once predicated only on heat, massage, and cold therapy now uses electrical stimulators, ultrasound, biofeedback, iontophoresis, phonophoresis, mirror therapy, lasers, and a number of other modalities. With this expansion in choices, there has been a concurrent effort to better define which modalities are truly effective. In this review, we aim to characterize the commonly used modalities and provide the evidence available that supports their continued use.

The effect of moist air on skin blood flow and temperature in subjects with and without diabetes

BACKGROUND

Endothelial function is known to be impaired in response to heat in people with diabetes, but little has been done to see how air humidity alters the skin blood flow response to heat.

METHODS

Seventeen male and female subjects were divided in two groups, one with type 2 diabetes and the other the control subjects without diabetes, age-matched to the diabetes group. All subjects participated in a series of experiments to determine the effect of the warming of the skin by air on skin temperature and skin blood flow. On different days, skin temperature was warmed with air that was 38°C, 40°C, or 42°C for 20 min. Also, on different days, at each temperature, the air humidity was adjusted to 0%, 25%, 50%, 75%, or 100% humidity. Skin blood flow and temperature were measured throughout the exposure period. This allowed the interactions between air humidity and temperature to be assessed.

RESULTS

For the control subjects, the moisture in the air had no different effect on skin blood flow at air temperatures of 38°C and 40°C (analysis of variance, P>0.05), although skin blood flow progressively increased at each air temperature that was applied. But for the warmest air temperature, 42°C, although the four lower humidities had the same effect on skin blood flow, air at 100% humidity caused the largest increase in skin blood flow. In contrast, in the subjects with diabetes, blood flow was always significantly less at any air temperature applied to the skin than was observed in the control subjects (P<0.05), and skin blood flow was significantly higher for the two higher humidities for the two higher air temperatures. Skin temperature paralleled these findings.

CONCLUSION

These data show that individuals with diabetes do not tolerate moist, warm air above 50% humidity as well as controls without diabetes.

A comparison of the effect of a variety of thermal and vibratory modalities on skin temperature and blood flow in healthy volunteers

BACKGROUND

Circulation plays an essential role in tissue healing. Moist heat and warm water immersion have been shown to increase skin circulation; however, these heating modalities can cause burns. Recent research has shown that passive vibration can also increase circulation but without the risk of burns.

MATERIAL/METHODS

The aim of this study is to compare the effects of short-duration vibration, moist heat, and a combination of the two on skin blood flow (SBF) and skin temperature (ST). Ten (10) subjects, 5 female and 5 male, aged 20-30 years of age, received two interventions a day for 3 consecutive days: Intervention 1--Active vibration only (vibration exercise), Intervention 2--passive vibration only, Intervention 3--moist heat only, Intervention 4--passive vibration combined with moist heat, Intervention 5--a commercial massaging heating pad, and Intervention 6--no intervention, resting in supine only (control). SBF and ST were measured using a laser Doppler imager during the 10 minute intervention and then throughout the nine minute recovery period.

RESULTS

The mean skin blood flow following a ten-minute intervention of the combination of passive vibration and moist heat was significantly different from the control, active vibration, and the commercial massaging heating pad. Skin temperature following the ten-minute interventions of moist heat alone and passive vibration alone were both significantly different from the commercial massaging heating pad and active vibration interventions.

CONCLUSIONS

The combination of passive vibration and moist heat produced the greatest increase in skin blood flow and the second highest increase in skin blood flow nine minutes post application.

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.

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.

A device to measure heat flow through the skin in people with diabetes

INTRODUCTION

As people age, and especially for older people with diabetes, there is increased susceptibility to burns. However, this is not true for all older people or all people with diabetes. The factors that predict burn susceptibility in specific members of the population with diabetes have not been elucidated. To understand the heat transfer properties of the skin in different parts of the body and how it is altered by skin blood flow, age, and glycemic control, a new device was developed.

METHODS

The device was a Plexiglas (Arkema, Colombes, France) capsule (thermode) that has a footprint on the skin of 20 cm(2), with the side contacting the skin made of thin brass. The thermode was machined to allow the free flow of water through the interior with the exception of a small hole for a laser Doppler flow meter to assess blood flow under the capsule. Flow directors kept the water flow even on the under surface of the capsule and minimized turbulent flow until high water flow rates are forced through the capsule.

RESULTS

When tested, the device provided even heat on the brass surface and could show the movement of heat into the skin and the corresponding changes in skin blood flow and temperature. In limited testing, clear differences were seen in heat flux in people with diabetes versus controls.

CONCLUSION

This device might be very useful in determining the early onset of diabetes-related skin damage. Future studies should include examining different regions of the body and variables such as hemoglobin A1c.

Autonomic stress and balance--the impact of age and diabetes

INTRODUCTION

Balance is impaired in the elderly and people with diabetes. However, the effect of attempted balance on the autonomic nervous system has not been investigated.

METHODS

Ten control subjects, 10 subjects with type 2 diabetes (age range, 21-75 years), and 10 older subjects age-matched to the subjects with diabetes were examined to determine the effect of diabetes and age on balance and the associated autonomic stress. Subjects were asked to stand on a balance platform for 1-min periods under four conditions: (1) quiet standing, (2) quiet standing with eyes closed, (3) quiet standing eyes closed with the platform allowed to move side to side over a central pivot that allows the edge of the platform to rotate 4 inches up and down, and (4) the same platform with eyes closed. Blood pressure, electrocardiogram, and sway were recorded.

RESULTS

Balance was worst in the subjects with diabetes, while the cardiovascular stress, as assessed by both heart rate and blood pressure, was greatest in the older group of subjects. But subjects with diabetes, while having a greater blood pressure response to the stress induced by balance, showed a poor heart rate response, probably due to diabetes-induced autonomic damage.

CONCLUSION

Autonomic damage in the subjects with diabetes masked much of the stress of the inability to optimize balance in this population.

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

BACKGROUND

To protect against ischemia, pressure-induced vasodilation (PIV) causes an increase in skin blood flow. Endothelial dysfunction, which is commonly found in older patients and those with diabetes, and global temperatures can affect the resting blood flow in skin, which may reduce the blood flow during and after the application of local pressure. The present study investigated the PIV of the skin with exposure to three global temperatures in younger and older populations and those with diabetes.

MATERIALS AND METHODS

Older subjects (n = 15, mean age 64.2 +/- 14.0 years), subjects with diabetes (n = 15, mean age 62 +/- 5.9 years, mean duration 13.2 +/- 9.1 years), or younger subjects (n = 15, mean age 25.7 +/- 2.9 years) participated. An infrared laser Dopler flow meter was used to measure skin blood flow on the bottom of the foot, lower back, and hand during and after applications of pressure at 7.5, 15, 30, 45, and 60 kPa at 16 degrees C, 24 degrees C, and 32 degrees C global temperatures.

RESULTS

The resting blood flow for all subjects was significantly lower in the 16 degrees C environment (P < 0.05). Blood flow in the group with diabetes was significantly lower at rest, during the application of all pressure, and after the release of pressure in all global temperatures (P < 0.05). The younger group showed a significant increase in blood flow after every pressure application, except 7.5 kPa, in all global conditions (P < 0.001). Older subjects and patients with diabetes did not have a significant reactive hyperemia, especially in the 16 degrees C environment.

CONCLUSION

The protective mechanism of PIV is severely reduced in older populations and those with diabetes, especially in colder environments where skin blood flow is already diminished.

Dry heat, moist heat and body fat: are heating modalities really effective in people who are overweight?

Surface heating modalities are commonly used in physical therapy and physical medicine for increasing circulation, especially in deep tissues, to promote healing. However, recent evidence seems to indicate that in people who are overweight, heat transfer is impaired by the subcutaneous fat layer. The present investigation was conducted on 10 subjects aged 22-54 years, whose body mass index averaged 25.8+/-4.6. Subcutaneous fat above the quadriceps muscle varied from 0.51 to 0.86 cm of thickness. Three heating modalities were examined: the application of dry heat with a commercial chemical heat pack, hydrocollator heat packs (providing a type of moist heat), and a whirlpool, where conductive heat loss through water contact would be very high. The temperature of the skin and the temperature in the muscle (25 mm below the skin surface) were assessed by thermocouples. The results of the experiments showed that for heating modalities that are maintained in skin contact for long periods of time, such as dry heat packs (in place for 6 hours), subcutaneous fat did not impair the change in deep muscle temperature. In contrast, when rapid heat modalities were used, such as the hydrocollator and the whirlpool (15 minutes of sustained skin contact), the transfer of heat from the skin to deep muscle was significantly impaired in people with thicker subcutaneous fat layers. We observed that the greater the impairment in heat transfer to muscle from skin covered by body fat, the warmer the skin temperature increase during the modality.

A device to evaluate motor and autonomic impairment

Various devices have been developed to assess impairment of the autonomic nervous system, while other devices have been developed to evaluate the motor system. However, no devices have been developed to examine the interaction between the autonomic and somatic nervous systems. Therefore, the device described here, a square platform which was 0.7x0.7 m in length and 0.1m thick, was developed to examine somatic-autonomic interaction. The device can be used by placing it directly on the floor or on 1 of 2 pivots; one that allowed the platform to move 0.2m (+/-44.1 degrees) in the front to back or side to side direction and one that allowed both movements together. Strain gauge load cells in the platform measured sway and tremor during the subjects attempt to balance and a continuous blood pressure monitor and the ECG were used to assess the response of the autonomic nervous system (heart rate variability). The device was tested on 5 normal subjects and the following was evaluated: (1) sway during standing, (2) weight shift during standing, (3) frequency of sway and extent of sway during standing, (4) sympathetic and parasympathetic alterations in the ANS during attempted balance, and (5) phase delays between motor and autonomic responses. The results showed that, with increasing balance challenge, sway increased, tremor increased, the sway angle increased and sway was positively correlated with heart rate and negatively correlated with blood pressure. A balance challenge significantly increased sympathetic activity but not parasympathetic activity. This device should have useful applications in assessing motor impairments and sensory and autonomic impairments in a variety of conditions.

Multiple stressors and the response of vascular endothelial cells: the effect of aging and diabetes

BACKGROUND

The present study examined the effects of local heat, global heat, and the interaction between these two endothelial stressors on the blood flow of the skin of the foot in people who are older and who have diabetes.

METHODS

Subjects who were older (mean age 64.2 +/- 5.9 years) and were younger (mean age 25.7 +/- 2.9 years) and subjects who had diabetes (mean age 62 +/- 5.9 years, mean duration 13.2 +/- 9.1 years) participated. Subjects were exposed to three global temperatures (16 degrees C, 24 degrees C, and 32 degrees C), and the blood flow response was recorded on the foot with a laser Doppler flow meter for 30 s following applications of local heat (30 degrees C, 33.5 degrees C, and 37 degrees C) using a Peltier junction to clamp the skin for 2 min.

RESULTS

All three groups significantly increased blood flow from the 16-24 degrees C environments for the 37 degrees C application of local heat (P(Younger) = 0.02, P(Older) = 0.02, P(Diabetes) = 0.01). Those with diabetes and those who were older only increased blood flow 5% and 6% from the 24-32 degrees C environment, which was not statistically significant (P(Older) = 0.12, P(Diabetes) = 0.14).

CONCLUSIONS

There appears to be considerable blood flow reserve in younger subjects to tolerate heat stress. In contrast, older subjects and those with diabetes reach a critical level after which additional heat does not cause in increase in blood flow.

Skin heat dissipation: the influence of diabetes, skin thickness, and subcutaneous fat thickness

BACKGROUND

It is well established that diabetes impairs vascular endothelial function. However, the impact of impaired endothelial function on thermal conductivity of the skin, especially in relation to a constant versus a sudden heat stress, has not been established. Further, there is some evidence that aging reduces skin dermal thickness and subcutaneous fat thickness. Since these are important determinates of heat dissipation by the skin, these parameters also need to be examined in people with diabetes.

METHODS

Ninety subjects (30 younger individuals, 30 patients with diabetes, and 30 patients age-matched to the diabetes subjects) participated in two series of experiments to determine (1) the thickness of the subcutaneous fat layer and skin thickness and the skin response to a sudden heat stress and (2) the response to a continuous heat stress on the lower back. Skin thickness and subcutaneous fat thickness were assessed by ultrasound, and skin blood flow was examined by infrared laser Doppler flow meter.

RESULTS

People with diabetes had significantly less resting blood flow, blood flow in response to a single or continuous heat load, less subcutaneous fat, and thinner skin than either age-matched controls or younger people (P < 0.05). Subjects with diabetes also had the lowest concentration of red blood cells in their skin, implying a reduction in the number of capillaries in the skin.

CONCLUSIONS

Thinning of the skin and probably a reduction in capillaries in the dermal layer contribute to a reduction in the blood flow response to heat. People with diabetes, in particular, have reduced skin heat dissipation because of less resting blood flow and thinner skin than that seen in age-matched controls.