Short-term cocoa bioflavanol supplementation does not improve cold-induced vasodilation in young healthy adults

PURPOSE

Cold-induced vasodilation (CIVD) is an oscillatory rise in blood flow to glabrous skin that occurs in cold-exposed extremities. Dietary flavanols increase bioavailable nitric oxide, a proposed mediator of CIVD through active vasodilation and/or withdrawal of sympathetic vascular smooth muscle tone. However, no studies have examined the effects of flavanol intake on extremity skin perfusion during cold exposure. We tested the hypothesis that acute and 8-day flavanol supplementation would augment CIVD during single-digit cold water immersion (CWI).

METHODS

Eleven healthy adults (24 ± 6 years; 10 M/1F) ingested cocoa flavanols (900 mg/day) or caffeine- and theobromine-matched placebo for 8 days in a double-blind, randomized, crossover design. On Days 1 and 8, CIVD was assessed 2 h post-treatment. Subjects immersed their 3rd finger in warm water (42 °C) for 15 min before CWI (4 °C) for 30 min, during which nail bed and finger pad skin temperature were measured.

RESULTS

Flavanol ingestion had no effect on CIVD frequency (Day 1, Flavanol: 3 ± 2 vs. Placebo: 3 ± 2; Day 8, Flavanol: 3 ± 2 vs. Placebo: 3 ± 1) or amplitude (Day 1, Flavanol: 4.3 ± 1.7 vs. Placebo: 4.9 ± 2.6 °C; Day 8, Flavanol: 3.9 ± 1.9 vs. Placebo: 3.9 ± 2.0 °C) in the finger pad following acute or 8-day supplementation (P > 0.05). Furthermore, average, nadir, and apex finger pad temperatures during CWI were not different between treatments on Days 1 or 8 of supplementation (P > 0.05). Similarly, no differences in CIVD parameters were observed in the nail bed following supplementation (P > 0.05).

CONCLUSION

These data suggest that cocoa flavanol ingestion does not alter finger CIVD. Clinical Trial Registration Clinicaltrials.gov Identifier: NCT04359082. April 24, 2020.

Effect of a vapor barrier in combination with active external rewarming for cold-stressed patients in a prehospital setting: a randomized, crossover field study

BACKGROUND

Use of a vapor barrier in the prehospital care of cold-stressed or hypothermic patients aims to reduce evaporative heat loss and accelerate rewarming. The application of a vapor barrier is recommended in various guidelines, along with both insulating and wind/waterproof layers and an active external rewarming device; however, evidence of its effect is limited. This study aimed to investigate the effect of using a vapor barrier as the inner layer in the recommended "burrito" model for wrapping hypothermic patients in the field.

METHODS

In this, randomized, crossover field study, 16 healthy volunteers wearing wet clothing were subjected to a 30-minute cooling period in a snow chamber before being wrapped in a model including an active heating source either with (intervention) or without (control) a vapor barrier. The mean skin temperature, core temperature, and humidity in the model were measured, and the shivering intensity and thermal comfort were assessed using a subjective questionnaire. The mean skin temperature was the primary outcome, whereas humidity and thermal comfort were the secondary outcomes. Primary outcome data were analyzed using analysis of covariance (ANCOVA).

RESULTS

We found a higher mean skin temperature in the intervention group than in the control group after approximately 25 min (p < 0.05), and this difference persisted for the rest of the 60-minute study period. The largest difference in mean skin temperature was 0.93 °C after 60 min. Humidity levels outside the vapor barrier were significantly higher in the control group than in the intervention group after 5 min. There were no significant differences in subjective comfort. However, there was a consistent trend toward increased comfort in the intervention group compared with the control group.

CONCLUSIONS

The use of a vapor barrier as the innermost layer in combination with an active external heat source leads to higher mean skin rewarming rates in patients wearing wet clothing who are at risk of accidental hypothermia.

TRIAL REGISTRATION

ClinicalTrials.gov identifier: NCT05779722.

Investigating cold Aδ fibers in the 0-40 °C temperature range: A quantitative sensory testing and evoked potentials study

OBJECTIVE

To evaluate the activity of cold Aδ-type fibers to thermal stimuli above human skin temperature (i.e., >32 °C).

METHODS

Twenty young adults aged 20-24 years participated in this study. The cold-detection threshold was measured from a basal temperature of 40 °C using an adaptive staircase method with high-speed cooling ramps (170 °C/s). A total of 150 stimulations at 36 °C, 32 °C, 28 °C, 24 °C, 20 °C, 16 °C, 12 °C, 8 °C, 4 °C and 0 °C (15 each) were performed. After each stimulation, subjects estimated the intensity of cold sensation using a visual analog scale, and evoked potentials were recorded.

RESULTS

The average cold-detection threshold was 35 °C (SD = 1.8). Regardless of the stimulation temperature, subjects reported a cooling sensation. Interestingly, reported increments in sensation were prominent for stimulation temperatures between 32 °C and 20 °C, but below this latter temperature sensations varied only very slightly. Evoked potential recordings revealed that decreasing temperature stimuli from a baseline of 40 °C induced a previously unreported N2P2 component with a mean N2 peak latency of 275 ms (SD = 13.1). The peak-to-peak amplitude of the N2P2 complex increased as the intensity of the cooling stimulation increased, exhibiting a profile comparable to subject-perceived intensity, namely, a major increase up to 20 °C, followed by a plateau to 0 °C.

CONCLUSIONS

The cool sensations reported by subjects were likely conveyed by Aδ fibers rather than by slow-conducting C fibers. Moreover, our rapid stimulation technique starting from a high temperature (40 °C) was capable of a) generating cold sensations at stimulation temperatures between 36 °C and 32 °C, and b) revealing the optimal activation range of Aδ fibers (20 °C-28 °C). Any decrease in temperature below this range did not result in a significant increase in sensation and thus probably did not evoke a significant increase in Aδ fiber activity.

SIGNIFICANCE

The regular assessment of cold sensation in peripheral neuropathies (i.e., with temperatures below 32 °C), could be completed by investigating cold-detection thresholds at temperatures ranging from 40 °C to 32 °C. Indeed, the absolute threshold of cold perception appears to start at 35 °C. Changes in the activation threshold of cold fibers were more easily detectable at this level.

An initial study on the agreement of body temperatures measured by infrared cameras and oral thermometry

The COVID-19 pandemic has led to the rapid adoption and rollout of thermal camera-based Infrared Thermography (IRT) systems for fever detection. These systems use facial infrared emissions to detect individuals exhibiting an elevated core-body temperature, which is present in many symptomatic presentations of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2). Despite the rollout of these systems, there is little independent research supporting their efficacy. The primary objective of this study was to assess the precision and accuracy of IRT screening solutions in a real-world scenario. The method used was a single-centre, observational study investigating the agreement of three IRT systems compared to digital oral thermometer measurements of body temperature. Over 5 days, 107 measurements were taken from individuals wearing facial masks. During each entry, two measurements of the subject's body temperature were made from each system to allow for the evaluation of the measurement precision, followed by an oral thermometer measurement. Each participant also answered a short demographic survey. This study found that the precision of the IRT systems was wider than 0.3 °C claimed accuracy of two of the systems. This study also found that the IRT measurements were only weakly correlated to those of the oral temperature. Additionally, it was found that demographic characteristics (age, gender, and mask-type) impacted the measurement error. This study indicates that using IRT systems in front-line scenarios poses a potential risk, where a lack of measurement accuracy could possibly allow febrile individuals to pass through undetected. Further research is required into methods which could increase accuracy and improve the techniques viability.

Correlation between skin temperature in the lower limbs and biochemical marker, performance data, and clinical recovery scales

The aim of this study was to evaluate the correlation between tools commonly used in the detection of physiological changes, such as clinical complaints, a biochemical marker of muscle injury, and performance data during official matches, with infrared thermography, which has been commonly used in the possible tracking of musculoskeletal injuries in athletes. Twenty-two athletes from a professional soccer club (age 27.7 ± 3.93 years; BMI 24.35 ± 1.80 kg/cm²) were followed during the season of a national championship, totaling 19 matches with an interval of 7 days between matches. At each match, the athletes used a Global Positioning System (GPS) device to collect performance data. Forty-eight hours after each match, every athlete’s perception of recovery, fatigue, and pain was documented. Blood was collected for creatine kinase (CK) analysis, and infrared thermography was applied. Only athletes who presented pain above 4 in either limb were included for thermographic analysis. Each thermographic image was divided into 14 regions of interest. For statistical analysis, we included only the images that showed differences ≥ 1° C. Data normality was verified by the Kolmogorov-Smirnov test with Dallal-Wilkinson-Lilliefors correction. We used the Pearson correlation coefficient to verify the correlation between infrared thermography and the biochemical marker, performance data, and clinical recovery scales. No correlation was observed between mean skin temperature and blood CK levels, pain level, perception of recovery, and fatigue perception (r <0.2, p>0.05). Thus, infrared thermography did not correlate with CK level, pain, fatigue perception, or recovery, nor with performance variables within the field.

Effect of Liothyronine Treatment on Dermal Temperature and Activation of Brown Adipose Tissue in Female Hypothyroid Patients: A Randomized Crossover Study

BACKGROUND

Thyroid hormones are essential for the full thermogenic response of brown adipose tissue (BAT) and have been implicated in dermal temperature regulation. Nevertheless, persistent cold-intolerance exists among a substantial proportion of hypothyroid patients on adequate levothyroxine (LT4) substitution.

MATERIALS AND METHODS

To assess if skin temperature and activation of BAT during treatment with liothyronine (LT3) differs from that of LT4 treatment, fifty-nine female hypothyroid patients with residual symptoms on LT4 or LT4/LT3 combination therapy were randomly assigned in a non-blinded crossover study to receive monotherapy with LT4 or LT3 for 12 weeks each. Change in supraclavicular (SCV) skin temperature overlying BAT, and sternal skin temperature not overlying BAT, during rest and cold stimulation were assessed by infrared thermography (IRT). In addition, abundance of exosomal miR-92a, a biomarker of BAT activation, was estimated as a secondary outcome.

RESULTS

Cold stimulated skin temperatures decreased less with LT3 vs. LT4 in both SCV (mean 0.009°C/min [95% CI: 0.004, 0.014]; P<0.001) and sternal areas (mean 0.014°C/min [95% CI: 0.008, 0.020]; P<0.001). No difference in serum exosomal miR-92a abundance was observed between the two treatment groups.

CONCLUSION

LT3 may reduce dermal heat loss. Thermography data suggested increased BAT activation in hypothyroid patients with cold-intolerance. However, this finding was not corroborated by assessment of the microRNA biomarker of BAT activation.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov, identifier NCT03627611.

Effect on autonomic nervous activity of applying hot towels for 10 s to the back during bed baths

BACKGROUND

Bed baths are a daily nursing activity to maintain patients' hygiene. Those may provide not only comfort but also relaxation. Notably, applying a hot towel to the skin for 10 s (AHT10s) during bed baths helped to reduce the risk of skin tears and provided comfort and warmth in previous studies. However, it is still unclear whether autonomic nervous system is affected by bed baths. Thus, this study investigated the effect on the autonomic nervous activity of applying hot towels for 10 s to the back during bed baths.

METHODS

This crossover study had 50 participants (25 men and women each; average age 22.2 ± 1.6 years; average body mass index 21.4 ± 2.2 kg/m2) who took bed baths with and without (control condition: CON) AHT10s on their back. Skin temperature, heart rate variability (HRV), and blood pressure (BP) were measured. Subjective evaluations and the State-Trait Anxiety Inventory in Japanese were also performed.

RESULTS

A significant interaction of time and bed bath type on skin surface temperature was observed (p < .001). Regarding the means of skin surface temperature at each measurement time point, those for AHT10s were significantly higher than those for CON. Although the total state-anxiety score significantly decreased in both the bed bath types after intervention, the mean values of comfort and warmth were higher for bed baths with AHT10s than for CON (p < .05) during bed baths; AHT10s was significantly higher in warmth than CON after 15 min (p = .032). The interaction and main effects of time on HRV and BP and that of bed bath type were not significant.

CONCLUSION

Bed baths that involved AHT10s caused participants to maintain a higher skin temperature and warmer feeling than under the wiping-only condition; they also provided comfort during the interventions. However, the bed baths with AHT10s did not allow participants to reach a relaxed state; moreover, there was no change in autonomic nerve activity. This may be due to participants' increased anxiety from skin exposure and the intervention being limited to one part of the body.

Bio-heat response of skin tissue based on three-phase-lag model

In this article, the thermal response of skin tissue is investigated based on three-phase-lag (TPL) model of heat conduction. The governing equation of bio-heat conduction is established by introducing both the TPL model of heat conduction and a modified energy conservation equation. The analytical solution is obtained by adopting the method of separation of variables and a parametric study on temperature responses in TPL model is carried out. It is shown that the TPL model can predict both the diffusion and wave characteristics of bio-heat conduction. Increasing the phase-lag of thermal displacement gradient would result in the rise of thermal propagation speed and decrease the temperature in affected zone. The perfusion rate of arterial blood has no obvious effect on thermal propagation velocity and thermal propagation lagging. Increasing of the rate of blood perfusion contributes to decreasing the temperature of steady state.

Temperature-compensated infrared-based low-cost mobile platform module for mass human temperature screening

As fast human temperature screening is needed in large public areas, this paper proposes a low-cost mobile platform module that combines the advantages of analyzing visible and thermal images. In particular, the key idea relies on face detection in the visible image. Then the coordinates of all faces detected are mapped on to the thermal image to determine their corresponding temperatures. Internal temperature compensation and external reference temperature also are employed to reduce the unwanted temperature fluctuation inside the module and in the surrounding environment. Our mobile platform module, called $\unicode{x00B5} {\rm Therm}$, uses a FLIR ONE camera as our visible and thermal imaging cameras. It can simultaneously determine the temperatures of nine people at a speed of 8 frames/second. A field test operation was performed for four days with 1,170 people, with very promising results of 100% sensitivity, 92.6% specificity, and 92.7% accuracy.

The effects of clothing layers on the thermoregulatory responses to short duration babywearing in babies under 12 months old

Carrying babies in a sling, that is, babywearing, is a popular practice among new parents. Babies are thermally vulnerable and public health bodies advise to dress them in one extra layer than the adult. However, these guidelines do not consider babywearing and it is unclear whether babies' clothing insulation should be modified during babywearing. Here we quantified the effects of babies' clothing layers on the thermoregulatory responses to short duration babywearing in babies under 12 months old. Nine babies (4F/5M; 7.3 ± 3.1 months; 9 ± 2.5 kg) and 9 mothers (34 ± 3.0 years) performed two trials in a thermoneutral environment (23°C; 50%RH). During trials, babies wore either 1 (sleepsuit) or 2 (vest + sleepsuit) clothing layers, and mothers performed 15-min stepping exercise while babywearing. We recorded mothers and babies' tympanic temperature (Tty ), babies' local skin temperatures (Tsk ; on the carotid artery area, arm, abdomen, lower back, and thigh), and mothers' perception of babies' thermal state. Babies' Tty did not change after 15-min babywearing (mean change: -0.13°C [-0.30, +0.05]; p = .141), in either clothing trial (difference between trials: +0.05°C [-0.15, +0.25]; p = .591). On the contrary, local Tskin increased across all sites tested (mean increase = +0.71°C [+0.41, +1.01]; p = .038) and similarly between clothing trials, with the abdomen showing the largest change (+1.10°C [+0.32, +1.85]). Mothers did not perceive any change in babies' thermal state. We show that 15-min babywearing increase babies' skin, but not tympanic, temperature by up to 1.1°C on certain body regions, and that this effect is not exacerbated by adding 1 layer of light clothing to the baby.

Effectiveness of a field-type liquid cooling vest for reducing heat strain while wearing protective clothing

This study examined the effectiveness of a field-type liquid cooling vest (LCV) worn underneath an impermeable protective suit on heat strain during walking. Eight men walked for 60 min at a moderate speed (3.0 km/h) wearing the suit in a warm environment (33°C, 60% relative humidity) without (control, CON) or with the LCV. A smaller increase in rectal temperature was recorded in participants in the LCV than in the CON condition (37.6 ± 0.1°C vs. 37.9 ± 0.1°C, p<0.05). Walking while wearing the LCV reduced the level of physiological heat strain, as measured by the mean skin temperature (35.5 ± 0.1°C vs. 36.3 ± 0.1°C), chest sweat rate (13.5 ± 3.0 mg/cm²/h vs. 16.6 ± 3.8 mg/cm²/h), chest cutaneous vascular conductance (349 ± 88% vs. 463 ± 122%), body weight loss (0.72 ± 0.05% vs. 0.93 ± 0.06%), and heart rate (101 ± 6 beats/min vs. 111 ± 7 beats/min) (p<0.05, for all comparisons). These changes were accompanied by a decrease in thermal sensation and discomfort. These results suggest that a field-type LCV attenuates exertional heat strain while wearing impermeable protective clothing.

Efficacy and safety of ucha-shinki-hwan on korean patients with cold hypersensitivity in the hands and feet: Study protocol clinical trial (SPIRIT Compliant)

BACKGROUND

Cold hypersensitivity in the hands and feet (CHHF) is a common complaint in Asian female population especially in Korea. Due to the symptoms of CHHF the quality of individual's daily life can be degraded. Ucha-Shinki-Hwan (UCHA) is widely used in the treatment of various diseases including CHHF by harmonizing Yin and Yang, and improving the vitality of whole body. However, the efficacy of UCHA as a treatment option of CHHF has not been assessed in trials. Thus, we aimed to investigate the efficacy and safety of UCHA in Korean women with CHHF through this trial.

METHODS

This study will be an exploratory, randomized, double-blind, placebo-controlled, parallel-group, multicenter trial. Korean women aged 19 to 59 years who complaint with CHHF will be enrolled from 5 university affiliated Korean medicine hospitals. A total of 164 subjects will be randomly assigned to a treatment group (UCHA) or a placebo group at a 1:1 ratio. The subjects will receive 2.5 g of either UCHA or placebo three times a day for 8 weeks. The primary outcome will be evaluated with the visual analog scale score of CHHF. The secondary outcome measures will be changes in skin temperature in extremities as measured by using a thermometer and the Korean version of the World Health Organization Quality of Life Scale Abbreviated Version.

DISCUSSION

This study will be the first trial to explore the efficacy and safety of UCHA for CHHF patient. This will provide meaningful clinical information on herbal medicine treatment of CHHF and a clinical evidence for planning a full randomized clinical trial.

DISCLOSURES AND ACKNOWLEDGMENTS

The authors report no competing interests.

TRIAL REGISTRATION

This study is registered at ClinicalTrials.gov, ID: NCT03790033. Registered on (31 December 2018) PROTOCOL VERSION:: The final approved version of the trial protocol is V1.3. (25 January 2019).

Whole-body active heating does not preserve finger temperature or manual dexterity during cold-water immersion

BACKGROUND

Cold-water immersion impairs manual dexterity when finger temperature is below 15°C. This exposes divers to increased risk of error. We hypothesized that whole-body active heating would maintain finger temperatures and dexterity during cold-water immersion.

METHODS

Twelve subjects (six males) (22 ± 2 years old; BMI 23.9 ± 2.5; body fat 16 ± 6%) completed 60-minute head-out water immersion (HOWI) wearing a 7mm wetsuit and 3mm gloves in thermoneutral water (TN 25°C) and cold water (CW 10°C) while wearing a water-perfused suit (WP) with 37°C water circulated over the torso, arms, and legs. Gross (Minnesota Manual Dexterity Test [MMDT]) and fine (modified Purdue Pegboard [PPT]) dexterity were assessed before, during and after immersion. Core body and skin temperatures were recorded every 10 minutes.

RESULTS

MMDT (TN -25 ± 14%; CW -72 ± 23%; WP -67 ± 29%; p<0.05) and PPT (TN -16 ± 9%; CW: -45 ± 10%; WP: -38 ± 13%; p<0.05) performance decreased during immersion. MMDT and PPT did not differ between CW and WP. Immediately following immersion gross dexterity was recovered in all conditions. Post-immersion fine dexterity was still impaired in CW (p<0.01), but not WP or TN. Core and skin temperatures decreased during immersion in CW and WP (p<0.05) but did not differ between CW and WP.

CONCLUSION

Manual dexterity decreased during immersion. Dexterity was further impaired during cold-water immersion and was not maintained by water perfusion active heating. Warm water perfusion did not maintain finger temperature above 15°C but hand temperature remained above these limits, suggesting a need to reassess thermal thresholds for working divers in cold-water conditions.

Infrared 3D Thermography for Inflammation Detection in Diabetic Foot Disease: A Proof of Concept

BACKGROUND

Thermal assessment of the plantar surface of the foot using spot thermometers and thermal imaging has been proven effective in diabetic foot ulcer prevention. However, with traditional cameras this is limited to single spots or a two-dimensional (2D) view of the plantar side of foot, where only 50% of the ulcers occur. To improve ulcer detection, the view has to be extended beyond 2D. Our aim is to explore for proof of concept the combination of three-dimensional (3D) models with thermal imaging for inflammation detection in diabetic foot disease.

METHOD

From eight participants with a current diabetic foot ulcer we simultaneously acquired a 3D foot model and three thermal infrared images using a high-resolution medical 3D imaging system aligned with three smartphone-based thermal infrared cameras. Using spatial transformations, we aimed to map thermal images onto the 3D model, to create the 3D visualizations. Expert clinicians assessed these for quality and face validity as +, +/-, -.

RESULTS

We could replace the texture maps (color definitions) of the 3D model with the thermal infrared images and created the first-ever 3D thermographs of the diabetic foot. We then converted these models to 3D PDF-files compatible with the hospital IT environment. Face validity was assessed as + in six and +/- in two cases.

CONCLUSIONS

We have provided a proof of concept for the creation of clinically useful 3D thermal foot images to assess the diabetic foot skin temperature in 3D in a hospital IT environment. Future developments are expected to improve the image-processing techniques to result in easier, handheld applications and driving further research.

Describing Normative Foot Temperatures in Patients With Diabetes-Related Peripheral Neuropathy

BACKGROUND

Prior research shows increased foot temperatures are predictive of diabetes-related foot complications. Our aim was to describe normative skin foot temperatures for individuals with diabetic peripheral neuropathy to better inform new technologies. We also explored for potential risk factors which correlate with changes in foot temperatures.

METHODS

We conducted a retrospective chart review of adult patients >18 years of age with diabetes mellitus and clinically diagnosed diabetic peripheral neuropathy with pedal digital thermometry performed between 2009 and 2018. A total of 58 patients met these criteria. Univariate modeling was based on covariates that may affect foot temperature including age, peripheral arterial disease, toe pressure, seasonality of measurement, smoking pack-years, caffeine use, insulin use, and calcium channel blocker use.

RESULTS

In patients with diabetic peripheral neuropathy, mean toe temperatures of 27.67°C (6.300°C), forefoot of 28.58°C (5.36°C), midfoot of 29.21°C (3.81°C), and rearfoot of 29.88°C(3.83°C) were demonstrated. A modest negative correlation between seasonality and toe and metatarsal temperatures (r = -0.38, P < .05; r = -0.43 P < .01, respectively) was demonstrated. Midfoot temperatures were modestly and positively correlated to the presence of small fiber symptoms (r = 0.33, P = .03). Positive modest correlation with rearfoot temperatures and amount of pack-year history (r = 0.30, P = .03) was seen.

CONCLUSION

Normative foot temperatures in neuropathic patients were found to be inversely associated with seasonality at the toe and metatarsal level. Smoking and pack-year history demonstrate modest correlation previously unseen in temperature analyses and warrant further exploration. Normative temperatures in neuropathic patients can better inform new technologies for the prevention of diabetic foot ulcer and Charcot neuroarthropathy.

Infrared Thermography and Vascular Disorders in Diabetic Feet

AIM

Diabetes mellitus (DM) and related foot complications constitute a growing healthcare burden. Diabetes mellitus is associated with lower-limb amputation, but diabetic foot assessment is challenging. Here, we evaluated a novel noninvasive diagnostic method-infrared thermography (IRT) -assessing its diagnostic potential compared to conventional noninvasive measurements.

METHODS

This study included patients with DM (n = 118) and healthy controls (n = 93). All participants underwent ankle brachial index and toe pressure (TP) measurements, and IRT using a standardized protocol with temperature measurement at five foot areas.

RESULTS

Compared to controls, patients with DM generally had warmer feet and exhibited a significantly greater temperature difference between feet (P < .001). Mean temperatures were highest in patients with DM with neuroischemia, followed by neuropathy. Patients with DM with angiopathy showed the lowest mean temperature-similar to controls and noncomplicated diabetics. Mean temperatures at all measurement sites were significantly higher with abnormal TP (<50 mmHg) than normal TP (≥50 mmHg) (P < .001). Infrared thermography revealed differences between angiosome areas, subclinical infections, and plantar high-pressure areas.

CONCLUSION

Infrared thermography revealed local temperature differences in high-risk diabetic feet. Normal skin surface temperature varies between individuals, but in combination with other tools, IRT might be useful in clinical screening.

CLINICALTRIALS ID

14212016.

Remote Temperature Monitoring in Patients With Visual Impairment Due to Diabetes Mellitus: A Proposed Improvement to Current Standard of Care for Prevention of Diabetic Foot Ulcers

BACKGROUND

Two debilitating sequelae of diabetes are foot ulcerations and vision impairing conditions including retinopathy, open-angle glaucoma, and cataracts. Current standard of care recommends daily visual screening of feet. Despite willingness, many patients are impeded by visual impairment. We investigate whether once-daily remote temperature monitoring can improve self-screening for patients at risk for diabetic foot complications.

METHODS

We followed four male veterans with diabetes mellitus, peripheral neuropathy, impaired visual acuity, and at least one other diabetes-related visual impairment in a high-risk podiatry clinic. Patients received a telemedicine remote temperature monitoring mat and instructed on proper daily use. Each patient developed a "hotspot," defined as a 1.75°C localized temperature difference between matched pedal locations, which resulted in telephone triage outreach.

RESULTS

In three cases, outreach resulted in a sooner appointment where patients were found to have a relevant outcome at the hotspot. Patients in cases 1-3 had University of Texas (UT) 1A ulcerations. The patient in case 4 had inflammation from trauma. All patients had refractive errors plus another vision impairing condition that potentially delayed identification of lesions. Patients in cases 1 and 2 have cataracts, patients in cases 2 and 3 have retinopathy, and patient in case 4 has glaucoma.

CONCLUSIONS

As an adjunct to daily preventative diabetic self-care, once-daily remote temperature monitoring technology can augment self-screening to prompt necessary outreach and treatment and potentially prevent costly and debilitating diabetic foot complications. This case series serves as a pilot study for real-world application of thermometry, where further large-scale research is needed.

Infrared Thermography for Estimating Supraclavicular Skin Temperature and BAT Activity in Humans: A Systematic Review

OBJECTIVE

Brown adipose tissue (BAT) is a thermogenic tissue with potential as a therapeutic target in the treatment of obesity and related metabolic disorders. The most used technique for quantifying human BAT activity is the measurement of 18 F-fluorodeoxyglucose uptake via a positron emission tomography/computed tomography scan following exposure to cold. However, several studies have indicated the measurement of the supraclavicular skin temperature (SST) by infrared thermography (IRT) to be a less invasive alternative. This work reviews the state of the art of this latter method as a means of determining BAT activity in humans.

METHODS

The data sources for this review were PubMed, Web of Science, and EBSCOhost (SPORTdiscus), and eligible studies were those conducted in humans.

RESULTS

In most studies in which participants were first cooled, an increase in IRT-measured SST was noted. However, only 5 of 24 such studies also involved a nuclear technique that confirmed increased activity in BAT, and only 2 took into account the thickness of the fat layer when measuring SST by IRT.

CONCLUSIONS

More work is needed to understand the involvement of tissues other than BAT in determining IRT-measured SST; at present, IRT cannot determine whether any increase in SST is due to increased BAT activity.

Thermoregulation in Ectodermal Dysplasia: A Case Series

Ectodermal dysplasia (ED) is a rare genetic disorder occurring as a consequence of gene mutations that code for the ectoderm of the developing embryo and results in numerous disorders of varying severity. The lack of functioning sweat glands in those affected with ED leads to high infant mortality and frequent complaints of hyperthermia. Temperature control of two adolescents affected with ED was assessed by conducting heat and exercise exposures while monitoring insulated auditory canal (T_ac) and skin temperatures, sweating rates, and skin blood flow. One participant was able to sweat and regulate his T_ac while a second participant could not regulate T_ac without a cooling intervention. The heterogeneous nature of ED, and these cases highlight the need for a case-by-case review of temperature control of individuals affected with ED. This will determine cooling strategies that would be of most benefit to the individual.

Effect of Injection Site Cooling and Warming on Insulin Glargine Pharmacokinetics and Pharmacodynamics

BACKGROUND

In type 1 diabetes (T1D), closed-loop systems provide excellent overnight fasting blood glucose control by adjusting the insulin infusion rate based on corresponding changes in sensor glucose levels. In patients on multiple daily insulin (MDI) injections, such control in overnight glucose levels has not been possible due to the inability to alter the absorption rate of long-acting insulin after injection. In this study, we tested the hypothesis that increases/decreases of fasting glucose levels could be achieved by cooling/warming the skin around the injection site, which would result in lower/higher Glargine absorption rates from its subcutaneous depot.

METHODS

Fourteen subjects with T1D (4 females; age 39.6 ± 16.7 years, HbA1c 7.8 ± 1.1%, BMI 25.4 ± 2.8 kg/m²) on MDI therapy underwent fasting pharmacokinetic and pharmacodynamic studies that started at ~8 am and lasted 240 min on 3 separate days in random order: a control day without warming or cooling of the injection site and two experimental days, one day with injection site warming and the other with cooling.

RESULTS

Cooling the skin around the glargine injection site reduced insulin concentrations by >40% (P < .01 versus the warming study, P = .21 versus the control study), accompanied by a 55 mg/dL increase in serum glucose (P < .01 versus the control study). Conversely, skin warming prevented the fall in serum insulin (P = .2 versus the control study; P < .01 versus the cooling study), resulting in a 40 mg/dL reduction in serum glucose (P < .001 versus the cooling study, P = .11 versus the control study).

CONCLUSIONS

This proof of concept study has shown that cooling and warming the skin around the injection site provides a means to decrease and increase the rate of absorption and action of insulin glargine from its subcutaneous depot.

Nasal skin temperature reveals changes in arousal levels due to time on task: An experimental thermal infrared imaging study

Infrared thermography, thanks to technological developments and lowering prices, is now getting considerable attention as a potential arousal monitor in the safety industry. Nasal skin temperature might be a valid index to track physiological variations due to reduced arousal levels, and its use could prevent a drowsiness-related deterioration of performance. However, the few studies that have investigated nasal skin temperature in applied settings have had inconsistent results. Here, we assessed the validity of nasal skin temperature to monitor changes in arousal levels (from alertness to drowsiness). The participants performed a 2-h simulated driving task while we simultaneously recorded their nasal skin temperature, brain activity (we used frontal delta electroencephalographic [EEG] activity as the reference index of alertness), and driving performance (speeding time). For those variables, we calculated growth curve models. We also collected subjective ratings of alertness and fatigue before and after the driving session. We found that the nasal skin temperature showed a cubic trajectory (it increased for the first 75 min, and then it began to decrease, but such deceleration gradually diminished over time). As expected, frontal delta EEG activity showed an inverted U-shaped quadratic trend (EEG power increased for the first hour and half, and gradually decreased during the last thirty minutes). The speeding time exhibited a similar pattern of change. Subjective sleepiness and fatigue increased after the task. Overall, our results suggest that nasal skin temperature seems to be a valid measure of arousal variations while performing a complex and dynamic everyday task.

Circadian skin temperature rhythms, circadian activity rhythms and sleep in individuals with self-reported depressive symptoms

BACKGROUND

Disturbed circadian rhythms have been associated with depression. New body-worn devices allow the objective recording of circadian parameters such as physical activity, skin temperature and sleep. The objective of this study was to investigate whether circadian skin temperature and circadian activity rhythms are altered in depressed individuals.

METHODS

Data on skin temperature, physical activity and sleep were available for 1610 subjects from a population-based cohort study. In a matching process two groups were formed for analysis: 121 participants with pronounced depression symptoms (CES-D Score > 21) and n = 121 matched non-depressed controls (CES-D Score < 15). Circadian rhythms were investigated by analyzing non-parametric rhythm indicators of 24-h skin temperature and physical activity data. Sleep timing, continuity and quantity were calculated from actigraphy.

RESULTS

No differences between the groups were found when all participants were considered. After excluding antidepressant medicated participants, the depression group was found to have a lower skin temperature amplitude t(208) = 2.45, p = .015 and a less stable skin temperature rhythm t(208) = 2.40, p = .017. The amplitude predicted the group status (beta = -5.529, p = .016). No effects were found for activity or sleep.

CONCLUSION

The results indicate that skin-temperature rhythms are blunted in unmedicated depressed individuals. This could be a promising non-invasive marker for further analysis.

Physiological Differences Between Heat Tolerant and Heat Intolerant Young Healthy Women

Purpose: Heat intolerance (HI) is determined in the Israel Defense Force according to a heat tolerance test (HTT) before returning to duty after an exertional heat stroke (EHS) event. Recently, increased numbers of female combatants resulted in an increased number of EHS cases among women and a higher percentage of heat intolerance (HI) individuals. We aimed to evaluate the differences between tolerance to heat among women performing an HTT in relation to their menstrual cycle phase. Method: Thirty-three female participants were sorted into two groups: HI and heat tolerant (HT) according to two HTTs performed during both the luteal and follicular phases of the menstrual cycle or while consuming and during a break from consuming contraceptives. Results: HT women had an 18% higher maximal oxygen uptake (p < .005, 95% CI [2.6,9.8]) and 1.2% lower skin temperature in the HTT at the during and follicular phases (p < .01, 95% CI [0.12,0.77]) and 1.7% lower at the off and luteal phases (p < .001, 95% CI [0.34,0.92]). The mean sweat rate was 14% lower among the HI group only at the HTT at the during and follicular phases (p < .05, 95% CI (3,88)]). Conclusion: We found that HT can be predicted using aerobic capacity and core body temperature. Moreover, during the luteal phase, women presented altered thermoregulation that decreased the probability of being HT. This emphasizes the importance of considering the HT/HI criteria in the HTT for women, according to their aerobic ability and menstrual-cycle phase.

Model of Steady-state Temperature Rise in Multilayer Tissues Due to Narrow-beam Millimeter-wave Radiofrequency Field Exposure

The assessment of health effects due to localized exposures from radiofrequency fields is facilitated by characterizing the steady-state, surface temperature rise in tissue. A closed-form analytical model was developed that relates the steady-state, surface temperature rise in multilayer planar tissues as a function of the spatial-peak power density and beam dimensions of an incident millimeter wave. Model data was derived from finite-difference solutions of the Pennes bioheat transfer equation for both normal-incidence plane waves and for narrow, circularly symmetric beams with Gaussian intensity distribution on the surface. Monte Carlo techniques were employed by representing tissue layer thicknesses at different body sites as statistical distributions compiled from human data found in the literature. The finite-difference solutions were validated against analytical solutions of the bioheat equation for the plane wave case and against a narrow-beam solution performed using a commercial multiphysics simulation package. In both cases, agreement was within 1-2%. For a given frequency, the resulting analytical model has four input parameters, two of which are deterministic, describing the level of exposure (i.e., the spatial-peak power density and beam width). The remaining two are stochastic quantities, extracted from the Monte Carlo analyses. The analytical model is composed of relatively simple functions that can be programmed in a spreadsheet. Demonstration of the analytical model is provided in two examples: the calculation of spatial-peak power density vs. beam width that produces a predefined maximum steady-state surface temperature, and the performance evaluation of various proposed spatial-averaging areas for the incident power density.

Heat Flux Sensing for Machine-Learning-Based Personal Thermal Comfort Modeling

In recent years, physiological features have gained more attention in developing models of personal thermal comfort for improved and accurate adaptive operation of Human-In-The-Loop (HITL) Heating, Ventilation, and Air-Conditioning (HVAC) systems. Pursuing the identification of effective physiological sensing systems for enhancing flexibility of human-centered and distributed control, using machine learning algorithms, we have investigated how heat flux sensing could improve personal thermal comfort inference under transient ambient conditions. We have explored the variations of heat exchange rates of facial and wrist skin. These areas are often exposed in indoor environments and contribute to the thermoregulation mechanism through skin heat exchange, which we have coupled with variations of skin and ambient temperatures for inference of personal thermal preferences. Adopting an experimental and data analysis methodology, we have evaluated the modeling of personal thermal preference of 18 human subjects for well-known classifiers using different scenarios of learning. The experimental measurements have revealed the differences in personal thermal preferences and how they are reflected in physiological variables. Further, we have shown that heat exchange rates have high potential in improving the performance of personal inference models even compared to the use of skin temperature.

Sacral Skin Temperature and Pressure Ulcer Development: A Descriptive Study

Existing evidence is inadequate to assume increased skin temperature is a risk factor for the development of pressure ulcers (PUs).

PURPOSE

The purpose of this prospective, descriptive study was to examine the relationship between sacral skin temperature and PU development.

METHODS

Using convenience sampling methods, patients who were hospitalized in the tertiary intensive care unit (ICU) of the internal medicine department of a university hospital in İzmir, Turkey, between April and December 2015 were eligible to participate if they were ⟩18 years of age, had an expected hospital stay of at least 5 days, a Braden score ≤12, and were admitted without a PU. Demographic and clinical data collected included age, gender, body mass index, diagnosis, mattress type, length of follow-up (days), systolic and diastolic blood pressure, body temperature, hemoglobin level, sacral skin temperatures in the supine and lateral positions, room temperature, PU stage and duration, and Braden score. Temperature was measured the day of hospitalization as a baseline measurement (day 1) and once every day thereafter up to 22 days, until the patient did or did not develop a PU, died, was no longer undergoing position change, or was discharged. Sacral skin temperature was taken immediately after the patient was moved to a lateral position following 120 minutes of supine position (referred to as supine position sacral skin temperature measurement) and after 30 minutes in lateral position (referred to as lateral position sacral skin temperature measurement). Data were collected using paper-and-pencil questionnaires and entered into a software program for analysis. Descriptive statistics, Student's t test, one-way analysis of variance test, Pearson product-moment correlation analysis, and Spearman's rank-order correlation analysis were used for data analysis.

RESULTS

Of the 37 patients who met the inclusion criteria and were monitored for at least 5 days, 21 (56.8%) developed PUs. No statistically significant difference in supine position sacral skin temperature on day 1 or day 5 was found between patients who did and did not develop a PU (36.90° C ± 0.29° C and 37.15° C ± 0.53° C, respectively, on day 1; t = -1.656, P = .112; and 37.37° C ± 0.53° C and 37.30° C ± 0.79° C, respectively, on day 5; t = 0.259, P = .798). Day 5 lateral position skin temperatures also did not differ significantly between the 2 groups (37.44° C ± 0.44° C and 37.31° C ± 0.75° C, respectively; t = 1.306, P = .621). A statistically significant difference was noted between mean sacral skin temperature in the supine position among patients ages 75 to 90 years compared with patients 38 to 64 years and 65 to 74 years (36.93° C ± 0.39° C; F = 13.221, P = .000) and with use of a viscoelastic mattress compared with an alternating pressure air mattress and continuous lateral rotation alternating pressure air mattress (37.85° C ± 0.54° C; F = 14.039, P = .000). No statistically significant differences in sacral skin temperatures were found for any of the of the other variables assessed.

CONCLUSION

Sacral skin temperatures were not statistically different between ICU patients who did and did not develop a PU. Additional research may help increase understanding of the relationship between skin temperature and PU development.

Heat stress assessment during intermittent work under different environmental conditions and clothing combinations of effective wet bulb globe temperature (WBGT)

This study examined whether different combinations of ambient temperature and relative humidity for the effective wet bulb globe temperature, in conjunction with two different levels of clothing adjustment factors, elicit a similar level of heat strain consistent with the current threshold limit value guidelines. Twelve healthy, physically active men performed four 15-min sessions of cycling at a fixed rate of metabolic heat production of 350 watts. Each trial was separated by a 15-min recovery period under four conditions: (1) Cotton coveralls + dry condition (WD: 45.5 °C dry-bulb, 15% relative humidity); (2) Cotton coveralls + humid condition (WH: 31 °C dry-bulb, 84% relative humidity); (3) Protective clothing + dry condition (PD: 30 °C dry-bulb, 15% relative humidity); and (4) Protective clothing + humid condition (PH: 20 °C dry-bulb, 80% relative humidity). Gloves (mining or chemical) and headgear (helmet or powered air-purifying respirator) were removed during recovery with hydration ad libitum. Rectal temperature (Tre), skin temperature (Tsk), physiological heat strain (PSI), perceptual heat strain (PeSI), and body heat content were calculated. At the end of the 2-hr trials, Tre remained below 38 °C and the magnitude of Tre elevation was not greater than 1 °C in all conditions (WD: 0.9, WH: 0.8, WH: 0.7, and PD: 0.6 °C). However, Tsk was significantly increased by approximately 2.1 ± 0.8 °C across all conditions (all p ≤ 0.001). The increase in Tsk was the highest in WD followed by PD, WH, and PH conditions (all p ≤ 0.001). Although PSI and PeSI did not indicate severe heat strain during the 2-hr intermittent work period, PSI and PeSI were significantly increased over time (p ≤ 0.001). This study showed that core temperature and heat strain indices (PSI and PeSI) increased similarly across the four conditions. However, given that core temperature increased continuously during the work session, it is likely that the American Conference of Governmental Industrial Hygienist's TLV^® upper limit core temperature of 38.0 °C may be surpassed during extended work periods under all conditions.

Seven days of cold acclimation substantially reduces shivering intensity and increases nonshivering thermogenesis in adult humans

Daily compensable cold exposure in humans reduces shivering by ~20% without changing total heat production, partly by increasing brown adipose tissue thermogenic capacity and activity. Although acclimation and acclimatization studies have long suggested that daily reductions in core temperature are essential to elicit significant metabolic changes in response to repeated cold exposure, this has never directly been demonstrated. The aim of the present study is to determine whether daily cold-water immersion, resulting in a significant fall in core temperature, can further reduce shivering intensity during mild acute cold exposure. Seven men underwent 1 h of daily cold-water immersion (14°C) for seven consecutive days. Immediately before and following the acclimation protocol, participants underwent a mild cold exposure using a novel skin temperature clamping cold exposure protocol to elicit the same thermogenic rate between trials. Metabolic heat production, shivering intensity, muscle recruitment pattern, and thermal sensation were measured throughout these experimental sessions. Uncompensable cold acclimation reduced total shivering intensity by 36% (P = 0.003), without affecting whole body heat production, double what was previously shown from a 4-wk mild acclimation. This implies that nonshivering thermogenesis increased to supplement the reduction in the thermogenic contribution of shivering. As fuel selection did not change following the 7-day cold acclimation, we suggest that the nonshivering mechanism recruited must rely on a similar fuel mixture to produce this heat. The more significant reductions in shivering intensity compared with a longer mild cold acclimation suggest important differential metabolic responses, resulting from an uncompensable compared with compensable cold acclimation. NEW & NOTEWORTHY Several decades of research have been dedicated to reducing the presence of shivering during cold exposure. The present study aims to determine whether as little as seven consecutive days of cold-water immersion is sufficient to reduce shivering and increase nonshivering thermogenesis. We provide evidence that whole body nonshivering thermogenesis can be increased to offset a reduction in shivering activity to maintain endogenous heat production. This demonstrates that short, but intense cold stimulation can elicit rapid metabolic changes in humans, thereby improving our comfort and ability to perform various motor tasks in the cold. Further research is required to determine the nonshivering processes that are upregulated within this short time period.

Changes in local skin temperature after the application of a pulsed Nd:YAG laser to healthy subjects: a prospective crossover controlled trial

Pulsed Nd:YAG laser (1064 nm) is a recent modality that is used for the rehabilitation of musculoskeletal disorders, but there is no evidence about its thermal effects. The aim of the study was to investigate the changes in local skin temperature (LST) after the application of a pulsed Nd:YAG laser to healthy subjects. The study participants were 30 male subjects with an average age of 21.96 (± 0.92) years. A rectangular area (15 × 10 cm²) was marked at the front of the dominant thigh and scanned with a laser beam at 3000 J with 20 J/cm² for 15 min. The other thigh was considered as a control side. The minimum, average, and maximum LSTs were measured using a thermographic camera. The measurements were performed before laser application, immediately after, and then every minute until the LST returned to the pre-treatment value. An independent t test and repeated measures ANOVA were used to analyze the changes in LST. The level of significance was set at p < 0.05. The pulsed Nd:YAG laser significantly increased the minimum, average, and maximum LSTs in comparison with the control. The increase was significant for up to 5 min after the application, and it took 10 min to reach the baseline values. The level of increase was 1.23-4.03 °C, and the average increase was 2.6 °C. The pulsed Nd:YAG laser significantly increased the minimum, average, and maximum LSTs of the thigh area in normal subjects, and the thermal effect lasted for 5 min after application.

Central nervous system circuits that control body temperature

Maintenance of mammalian core body temperature within a narrow range is a fundamental homeostatic process to optimize cellular and tissue function, and to improve survival in adverse thermal environments. Body temperature is maintained during a broad range of environmental and physiological challenges by central nervous system circuits that process thermal afferent inputs from the skin and the body core to control the activity of thermoeffectors. These include thermoregulatory behaviors, cutaneous vasomotion (vasoconstriction and, in humans, active vasodilation), thermogenesis (shivering and brown adipose tissue), evaporative heat loss (salivary spreading in rodents, and human sweating). This review provides an overview of the central nervous system circuits for thermoregulatory reflex regulation of thermoeffectors.

Regulation of sensory nerve conduction velocity of human bodies responding to annual temperature variations in natural environments

The extensive research interests in environmental temperature can be linked to human productivity/performance as well as comfort and health; while the mechanisms of physiological indices responding to temperature variations remain incompletely understood. This study adopted a physiological sensory nerve conduction velocity (SCV) as a temperature-sensitive biomarker to explore the thermoregulatory mechanisms of human responding to annual temperatures. The measurements of subjects' SCV (over 600 samples) were conducted in a naturally ventilated environment over all four seasons. The results showed a positive correlation between SCV and annual temperatures and a Boltzmann model was adopted to depict the S-shaped trend of SCV with operative temperatures from 5°C to 40°C. The SCV increased linearly with operative temperatures from 14.28°C to 20.5°C and responded sensitively for 10.19°C-24.59°C, while tended to be stable beyond that. The subjects' thermal sensations were linearly related to SCV, elaborating the relation between human physiological regulations and subjective thermal perception variations. The findings reveal the body SCV regulatory characteristics in different operative temperature intervals, thereby giving a deeper insight into human autonomic thermoregulation and benefiting for built environment designs, meantime minimizing the temperature-invoked risks to human health and well-being.

The effect of menstrual cycle phase on foot skin temperature during mild local cooling in young women

Japanese women can experience a sensation of cold feet in daily life. It is possible that this sensation of coldness in feet may be associated with female hormones, but to date the effect of menstrual cycle phase on the skin temperature (Tsk) of the foot during local cooling is unknown. We therefore examined Tsk and partial cutaneous blood flow in the foot during the follicular (F) and luteal (L) phases of the menstrual cycle in women experiencing local cooling. Tsk was measured in the toes and the dorsum of the left foot using infrared thermography, while cutaneous blood flow was evaluated in the big toe of the left foot using laser Doppler flowmetry (LDF), both at 28 °C. Mild local cooling (24.7 °C) was then applied for 30 min to the right foot. During cooling of the right foot, no significant differences in Tsk were observed between the F and L phases in either the toes of the left foot or the dorsum of the left foot of all subjects. However, cutaneous blood flow determined by LDF in the big toe of the left foot was greater in the F phase than in the L phase. These results suggest that the menstrual cycle phase did not affect Tsk in the foot, but it did affect cutaneous blood flow in the big toe during mild local cooling.

Skin temperature responses to hand-arm vibration in cold and thermoneutral ambient temperatures

Hand-arm vibration (HAV) from hand-held vibrating machines increases the risk of injury in the form of vasoconstriction in the fingers, commonly named as vibration induced white fingers (VWF). Cold temperature may increase that risk. This experimental study examined and compared the effects of the skin temperature of the hands during and after exposure to HAV in thermoneutral and cold conditions. Fourteen subjects were exposed to three conditions: 25°C with HAV, 5°C with HAV or 5°C without HAV. Their skin temperatures were continuously recorded for the thumbs, index fingers, palms, and back of hands. After 20 min of acclimatization, the subjects held, for five min, two handles where the right handle could vibrate at 5 m/s² and the left was stationary. Finally, they released their grip and stood still for 10 more min. HAV had no additional cooling effect in cold during gripping of the handles. After the subjects released the handles there was only a HAV-induced cooling effect in the left palm with on average 0.5°C colder skin temperature. A single exposure to HAV will not cause an injury such as VWF, but as the present study show: short-term exposure to HAV causes some changes in skin temperature.

Multimodal stress detection: Testing for covariation in vocal, hormonal and physiological responses to Trier Social Stress Test

Examining the effects of acute stress across multiple modalities (behavioral, physiological, and endocrinological) can increase our understanding of the interplay among stress systems, and may improve the efficacy of stress detection. A multimodal approach also allows for verification of the biological stress response, which can vary between individuals due to myriad internal and external factors, thus allowing for reliable interpretation of behavioral markers of stress. Here, controlling for variables known to affect the magnitude of the stress response, we utilized the Trier Social Stress Test (TSST) to elicit an acute stress response in 80 healthy adult men and women. The TSST involves an interview-style oral presentation and critical social evaluation, and is highly effective in inducing psychosocial stress. Participants completed the study in individual 2 h sessions, during which we collected voice, polygraph and salivary hormone measures in baseline, stress, and relaxation phases. Our results show sizeable systematic increases in voice pitch (mean, minimum and variation in fundamental frequency, F0), hormone levels (cortisol) and decreases in skin temperature and hand movement during psychosocial stress, with striking similarities between men and women. However, cortisol and skin temperature only weakly predicted changes in voice pitch during stress, in either women or men, respectively. Thus, while our results provide compelling evidence that psychosocial stress manifests itself behaviorally by increasing voice pitch and its variability alongside simultaneous activation of physiological and endocrinological stress systems, our results also highlight a relatively weak degree of intra-individual 'response coherence' across these stress systems, with dissociations among different stress measures related most strongly to sex.

Thermal management of epidermal electronic devices/skin system considering insensible sweating

Thermal management of the system consisting of epidermal electronics devices (EEDs) and skin is critically important since a few degrees in temperature increase may induce thermal discomfort. In this paper, considering insensible sweating, a three-dimensional analytical thermal model, validated by finite element analysis, is developed to derive analytical expressions for the steady temperature distributions in the EED/skin system. The influences of various parameters including the thickness and thermal conductivity of the substrate in EEDs on the maximum skin temperature are investigated. The comfort analysis is then carried out based on the model to provide design guidelines for optimizing the geometric and material properties of EEDs to avoid the adverse thermal effects. These results pave the theoretical foundation for thermal management of EEDs/skin system in practical applications.

An Optical Fiber-Based Data-Driven Method for Human Skin Temperature 3-D Mapping

Human skin temperature mapping provides abundant information of physiological conditions of human body, which provides supplementary or alternative indicators for disease monitoring or diagnosis. The existing models of temperature mapping or temperature field distribution of human skin are generally established by finite element method. Due to the complexity of biological systems, it is challenging to achieve high accuracy mathematical models of temperature field of human skin. The goal of this study is to establish human skin temperature three-dimensional (3-D) mapping platform by integrating optical fibers and improved genetic algorithm-back propagation (GA-BP) neural network. The proposed data-driven method is capable of acquiring entire human skin temperature 3-D mapping by simply measuring a few points on human skin. Multiple experiments were conducted to validate the proposed method on different areas of human skin in different ambient environments. In each experiment setting, the measured data and the model output data were compared. The mean absolute error in all the validation experiments is 0.11 °C, which is lower than that in the state of the art using physical modeling for skin temperature prediction and more close to clinical accuracy. The results show that the proposed approach is accurate and reliable, which may provide a platform technology for human skin temperature mapping that can be used in both medical and scientific studies as well as home monitoring.

Towards a wearable sensor system for continuous occupational cold stress assessment

This study investigated the usefulness of continuous sensor data for improving occupational cold stress assessment. Eleven volunteer male subjects completed a 90-120-min protocol in cold environments, consisting of rest, moderate and hard work. Biomedical data were measured using a smart jacket with integrated temperature, humidity and activity sensors, in addition to a custom-made sensor belt worn around the chest. Other relevant sensor data were measured using commercially available sensors. The study aimed to improve decision support for workers in cold climates, by taking advantage of the information provided by data from the rapidly growing market of wearable sensors. Important findings were that the subjective thermal sensation did not correspond to the measured absolute skin temperature and that large differences were observed in both metabolic energy production and skin temperatures under identical exposure conditions. Temperature, humidity, activity and heart rate were found to be relevant parameters for cold stress assessment, and the locations of the sensors in the prototype jacket were adequate. The study reveals the need for cold stress assessment and indicates that a generalised approached is not sufficient to assess the stress on an individual level.

Physiological responses to acute cold exposure in young lean men

The aim of this study was to comprehensively describe the physiological responses to an acute bout of mild cold in young lean men (n = 11, age: 23 ± 2 years, body mass index: 23.1 ± 1.2 kg/m2) to better understand the underlying mechanisms of non-shivering thermogenesis and how it is regulated. Resting energy expenditure, substrate metabolism, skin temperature, thermal comfort perception, superficial muscle activity, hemodynamics of the forearm and abdominal regions, and heart rate variability were measured under warm conditions (22.7 ± 0.2°C) and during an individualized cooling protocol (air-conditioning and water cooling vest) in a cold room (19.4 ± 0.1°C). The temperature of the cooling vest started at 16.6°C and decreased ~ 1.4°C every 10 minutes until participants shivered (93.5 ± 26.3 min). All measurements were analysed across 4 periods: warm period, at 31% and at 64% of individual´s cold exposure time until shivering occurred, and at the shivering threshold. Energy expenditure increased from warm period to 31% of cold exposure by 16.7% (P = 0.078) and to the shivering threshold by 31.7% (P = 0.023). Fat oxidation increased by 72.6% from warm period to 31% of cold exposure (P = 0.004), whereas no changes occurred in carbohydrates oxidation. As shivering came closer, the skin temperature and thermal comfort perception decreased (all P<0.05), except in the supraclavicular skin temperature, which did not change (P>0.05). Furthermore, the superficial muscle activation increased at the shivering threshold. It is noteworthy that the largest physiological changes occurred during the first 30 minutes of cold exposure, when the participants felt less discomfort.

Characterisation of regional skin temperatures in recreational surfers wearing a 2-mm wetsuit

The purpose of this study was to investigate skin temperatures across surfers' bodies while wearing a wetsuit during recreational surfing. Forty-six male recreational surfers participated in this study. Participants were instrumented with eight wireless iButton thermal sensors for the measurement of skin temperature, a Polar RCX5 heart rate monitor and a 2-mm full wetsuit. Following instrumentation, participants were instructed to engage in recreational surfing activities as normal. Significant differences (p < 0.001) in skin temperature (T_sk) were found across the body while wearing a wetsuit during recreational surfing. In addition, regional skin temperature changed across the session for several regions of the body (p < 0.001), and the magnitude of these changes varied significantly between regions. We show for the first time that significant differences exist in skin temperature across the body while wearing a wetsuit during a typical recreational surfing session. These findings may have implications for future wetsuit design. Practitioner Summary: This study investigated the impact of wearing a wetsuit during recreational surfing on regional skin temperatures. Results from this study suggest that skin temperatures differ significantly across the body while wearing a 2-mm wetsuit during recreational surfing. These findings may have implications for future wetsuit design.

Core and skin temperature influences on the surface electromyographic responses to an isometric force and position task

The large body of work demonstrating hyperthermic impairment of neuromuscular function has utilized maximal isometric contractions, but extrapolating these findings to whole-body exercise and submaximal, dynamic contractions may be problematic. We isolated and compared core and skin temperature influences on an isometric force task versus a position task requiring dynamic maintenance of joint angle. Surface electromyography (sEMG) was measured on the flexor carpi radialis at 60% of baseline maximal voluntary contraction while either pushing against a rigid restraint (force task) or while maintaining a constant wrist angle and supporting an equivalent inertial load (position task). Twenty participants performed each task at 0.5°C rectal temperature (T_re) intervals while being passively heated from 37.1±0.3°C to ≥1.5°C T_re and then cooled to 37.8±0.3°C, permitting separate analyses of core versus skin temperature influences. During a 3-s contraction, trend analysis revealed a quadratic trend that peaked during hyperthermia for root-mean-square (RMS) amplitude during the force task. In contrast, RMS amplitude during the position task remained stable with passive heating, then rapidly increased with the initial decrease in skin temperature at the onset of passive cooling (p = 0.010). Combined hot core and hot skin elicited shifts toward higher frequencies in the sEMG signal during the force task (p = 0.003), whereas inconsistent changes in the frequency spectra occurred for the position task. Based on the patterns of RMS amplitude in response to thermal stress, we conclude that core temperature was the primary thermal afferent influencing neuromuscular response during a submaximal force task, with minimal input from skin temperature. However, skin temperature was the primary thermal afferent during a position task with minimal core temperature influence. Therefore, temperature has a task-dependent impact on neuromuscular responses.

Content validation of the Patient-Reported Hamilton Inventory for Complex Regional Pain Syndrome: Validité de contenu du Hamilton Inventory for Complex Regional Pain Syndrome, une mesure des résultats déclarés par le patient

BACKGROUND

Complex regional pain syndrome (CRPS) is a perplexing neurological condition, and persons with CRPS experience substantial loss of daily roles and activities. A condition-specific measure is being developed to evaluate CRPS.

PURPOSE

We describe the use of cognitive interviews to examine content validity of this patient-reported outcome measure for CRPS.

METHOD

Interviews with 44 persons with CRPS were analyzed to identify problems with wording and support content validation. Item-total correlations were calculated for proposed subscales, and scores were plotted to consider floor/ceiling effects.

FINDINGS

Interviews identified questions where respondents considered factors unrelated to the construct of interest or were underaddressed by the questionnaire, including depression and skin temperature. The symptoms, daily function, and coping/social impact scales demonstrated satisfactory correlations (Cronbach's alpha 0.76-0.86). Despite a sampling bias of severity, no frank floor/ceiling effects were noted.

IMPLICATIONS

This study builds a foundation for continuing development and evaluation of the measurement properties of the Patient-Reported Hamilton Inventory for CRPS. It makes explicit the iterative decisions involved in rigorous instrument development.

Changes in electromyographic signals and skin temperature during standardised effort in volleyball players

PURPOSE

The state of athletes' muscles is not constant, but it differs depending on the stage of sports training, which is associated with different degrees of muscle fatigue. There is thus a need to find a non-invasive and simple method to assess muscle fatigue. The aim of the study was to determine the relationship between muscle fatigue due to physical effort and changes in skin temperature, measured using a thermographic camera.

METHODS

The study involved 12 volleyball players. The participants were to maintain 70% of peak torque in the joint for as long as possible. We measured peak torque and the time of maintaining 70% of its value (tlim) as well as continuously recording skin temperature and electromyographic (EMG) signals in the region of the belly of the rectus femoris. The measurements were taken twice: before and after a series of squats.

RESULTS

The study found that tlim decreased when isometric contraction was per- formed after physical effort. Pre- and post-exercise skin temperature did not differ significantly, however, the increase rates of tempera- ture and the root mean square (RMS) of the EMG signals grew significantly. In most of the players, skin temperature also correlated with the RMS, median frequency (MDF), and mean frequency (MF) of the EMG signals.

CONCLUSIONS

Measuring the time of maintaining submaximal torque during isometric contraction and the slope coefficient for the increase in temperature recorded using a thermographic camera can be a simple, cost-effective, and non-invasive method of assessing fatigue and efficiency decreases in the muscles in volley- ball players.

Nitric oxide-cGMP-PKG signaling in the bed nucleus of the stria terminalis modulates the cardiovascular responses to stress in male rats

The bed nucleus of the stria terminalis (BNST) constitutes an important component of neural substrates of physiological and behavioral responses to aversive stimuli, and it has been implicated on cardiovascular responses evoked by stress. Nevertheless, the local neurochemical mechanisms involved in BNST control of cardiovascular responses during aversive threats are still poorly understood. Thus, the aim of the present study was to assess the involvement of activation in the BNST of the neuronal isoform of the enzyme nitric oxide synthase (nNOS), as well as of signaling mechanisms related to nitric oxide effects such as soluble guanylate cyclase (sGC) and protein kinase G (PKG) on cardiovascular responses induced by an acute session of restraint stress in male rats. We observed that bilateral microinjection of either the nonselective NOS inhibitor Nω-Nitro-L-arginine methyl ester (L-NAME), the selective nNOS inhibitor Nω-Propyl-L-arginine (NPLA) or the sGC inhibitor 1H-[1,2,4]Oxadiazolo[4,3-a]quinoxalin-1-one (ODQ) into the BNST enhanced the tachycardic response and decreased the drop in tail cutaneous temperature evoked by acute restraint stress, but without affecting the increase on blood pressure. Bilateral BNST treatment with the selective PKG inhibitor KT5823 also facilitated the heart rate increase and decreased the drop in cutaneous temperature, in addition to enhancing the blood pressure increase. Taken together, these results provide evidence that NO released from nNOS and activation of sGC and PKG within the BNST play an inhibitory influence on tachycardia to stress, whereas this signaling mechanism mediates the sympathetic-mediated cutaneous vasoconstriction.

Effects of physical exercise in winter training conditions on the thermographic temperature distribution of the horse rider's skin

PURPOSE

The purpose of this work was to assess the impact of a specific equestrian training, conducted in winter weather conditions, on the thermovision temperature distribution of a rider's body surface. The study included a riding pair with 12 years of experience (female rider, aged 25, sports active and 16-year-old horse, Trakehner breed).

METHODS

The study included the temperature distribution of selected parts of the rider's body (the area of the right and left shoulder blade, chest and lumbar section, and the region of the left and right cross) was carried out before and after recreational, jumping and dressage training. Each winter training has been repeated, at dif- ferent times, 10 times, giving a total of 30 workouts. The thermovision measurements were made in a separate room, always under the same conditions.

RESULTS

Research has shown that, along with the increase in the level and intensity of the training, the body surface temperature of the rider increased. After recreational driving, this temperature increased, compared to the pre-workout measurement, by 3.15°C, after jumping through obstacles to 4.39°C, and in dressage to 5.82°C.

CONCLUSIONS

The highest increase in body surface temperature (on the example of dressage training) was recorded in the thoracic and lumbar part of the spine region, then in the area of the left and right scapula, while the smallest in the left and right sacral region of the rider.

Does Temperature Increase by Sympathetic Neurolysis Improve Pain in Complex Regional Pain Syndrome? A Retrospective Cohort Study

BACKGROUND

Lumbar sympathetic neurolysis (LSN) is a treatment option for complex regional pain syndrome (CRPS). We examined whether LSN-related temperature changes are associated with clinical outcome and investigated relationships between the outcome of LSN and clinical variables in patients with CRPS-I.

METHODS

We included 95 patients with CRPS-I affecting a single lower extremity, by the Budapest criteria, and who underwent LSN after successful lumbar sympathetic blocks, in this retrospective study. Fluoroscopy-guided LSN was conducted with 1.5 mL of 99% alcohol at L2 and L3 vertebral levels. Positive outcome was defined as a reduction of ≥50% on a numeric rating scale pain score at 6 months after LSN. The relationship between successful outcome and clinical variables was analyzed.

RESULTS

Positive LSN outcome occurred in 49.5% of patients, and it was suggested that Sympathetically maintained pain may accompany CRPS-I in 28% of patients. The overall temperature in the affected limb was increased after LSN, without contralateral limb temperature changes, but did not differ significantly between the positive and negative outcome groups (P = 0.590). Temperature after LSN in warm-type CRPS was reduced in the affected limb, without contralateral limb temperature changes. The absolute temperature change was significantly greater in cold-type than in warm-type CRPS (P = 0.026). In multivariate analysis, a short duration of pain and concurrent cold intolerance were significant factors predicting a positive outcome after LSN.

CONCLUSIONS

LSN may be effective in some patients with CRPS, irrespective of temperature changes and temperature asymmetry pattern. A short duration of pain and concurrent cold intolerance significantly predict successful LSN.

The regulatory effect of choice in Situation Selection reduces experiential, exocrine and respiratory arousal for negative emotional stimulations

Situation selection is a seldom studied emotion regulation strategy that entails choosing an upcoming emotional situation. Two mechanisms may drive its regulatory effect on emotional responses. One relates to the evaluation of the chosen option, people generally selecting the most positive. The other one implies that having the choice regarding the upcoming emotional situation is already regulatory, independently of what we choose. This research aimed at investigating this latter hypothesis. In a within-subject design, we compared emotional responses of 65 participants when they viewed negative and positive images they could select (use of Situation selection) vs. when they were imposed the exact same images (Situation selection not used). Results show that having the choice in negative contexts decreased negative experience, skin conductance, and respiration reactivity, while enhancing expressivity and cardiovascular reactivity. In positive contexts, choosing generally reinforced the image calming effect. Thus, contrary to other strategies that are efficient for negative but usually impair positive reactions (e.g., distraction), Situation selection may be used widely to reduce negative experience, while avoiding depletion of positive responses. This is particularly notable in emotion experience. Remarkably, these effects are not driven by the content of the situations, but by the act of choosing itself.