Body Skin Temperature Research Articles

Electroencephalographic and peripheral temperature dynamics during a prolonged psychomotor vigilance task

Attention lapses and fatigue are a main source of impaired performance that can lead to accidents. This study analyzed electroencephalographic (EEG) dynamics and body skin temperature as markers of attentional fluctuations in non-sleep deprived subjects during a 45min Psychomotor Vigilance Task (PVT). Independent Component Analysis and time-frequency analysis were used to evaluate the EEG data. Results showed a positive association between distal and distal-to-proximal gradient (DPG) temperatures and reaction time (RT); increments in EEG power in alpha-, theta- and beta-band frequencies in parieto-occipital, central-medial and frontal components, were associated with poor performance (slower RT) in the task. This generalized power increment fits with an increased activity in the default mode network, associated with attention lapses. This study highlights the potential use of the PVT as a tool to obtain individual physiological indices of vigilance and fatigue that could be applied to other vigilance tasks typically performed in occupational settings.

Cardiovascular and thermal strain during 3\u20134\xa0days of a metabolically demanding cold-weather military operation

BackgroundCardiovascular (CV) and thermal responses to metabolically demanding multi-day military operations in extreme cold-weather environments are not well described. Characterization of these operations will provide greater insights into possible performance capabilities and cold injury risk.MethodsSoldiers from two cold-weather field training exercises (FTX) were studied during 3-day (study 1, n = 18, age: 20 ± 1 year, height: 182 ± 7 cm, mass: 82 ± 9 kg) and 4-day (study 2, n = 10, age: 20 ± 1 year, height: 182 ± 6 cm, mass: 80.7 ± 8.3 kg) ski marches in the Arctic. Ambient temperature ranged from −18 to −4 °C during both studies. Total daily energy expenditure (TDEE, from doubly labeled water), heart rate (HR), deep body (Tpill), and torso (Ttorso) skin temperature (obtained in studies 1 and 2) as well as finger (Tfing), toe (Ttoe), wrist, and calf temperatures (study 2) were measured.ResultsTDEE was 6821 ± 578 kcal day−1 and 6394 ± 544 for study 1 and study 2, respectively. Mean HR ranged from 120 to 140 bpm and mean Tpill ranged between 37.5 and 38.0 °C during skiing in both studies. At rest, mean Tpill ranged from 36.0 to 36.5 °C, (lowest value recorded was 35.5 °C). Mean Tfing ranged from 32 to 35 °C during exercise and dropped to 15 °C during rest, with some Tfing values as low as 6–10 °C. Ttoe was above 30 °C during skiing but dropped to 15–20 °C during rest.ConclusionsDaily energy expenditures were among the highest observed for a military training exercise, with moderate exercise intensity levels (~65% age-predicted maximal HR) observed. The short-term cold-weather training did not elicit high CV and Tpill strain. Tfing and Ttoe were also well maintained while skiing, but decreased to values associated with thermal discomfort at rest.

Total body skin temperature of runners during treadmill exercise

The aim of this study was to investigate the time evolution of total body skin temperature during running exercise on treadmill. A group of physically active subjects performed two different treadmill exercises, at graded load and at constant load, for a duration of 30 min, in a moderate indoor environment. Thermal maps of the anterior and posterior body regions were gathered, before, during and after the exercise, by means of infrared thermography. Skin temperature of total body was calculated as a combination of individual measurements taken over several body regions. Within the limits due to the relatively small size of the sample group, results typically show a fall in total body skin temperature during the early stages of treadmill exercise. As the exercise progresses, the dynamics of the skin temperature response is affected by the type of exercise, showing a further decrease during the graded load exercise and a slight increase during the constant load exercise. Regionally averaged skin temperatures were found to be lower than total body skin temperature over the most peripheral body regions less involved in running (upper limbs) and comparable with or higher than total body skin temperature over calves and thighs.

Non-occlusive knitted linen for atopic dermatitis wearer

PurposeThe purpose of this paper is to investigate the suitability of linen in garments for atopic dermatitis (AD) wearers.Design/methodology/approachIn total, 60 garments were tested with four boys (five to eight years old): two with AD and two healthy kids using circular knitting occlusive structure (OS) 28-gauge and non-occlusive structure (NOS) 12-gauge with cotton, polyester staple and linen yarns. Air and water vapor permeability fabric results were analyzed using ANOVA method and occlusive levels correlated with thickness and UPF rates. Skin irritation levels were evaluated with Patient-Oriented SCORing Atopic Dermatitis (PO-SCORAD) self-assessment tool and for body temperature measurements infrared cameras were used. The authors standardized hygiene products; laundry procedures and soaps were previously identified and measured for their pH and skin irritation history with wearers.FindingsLower skinbody temperature (−2.6°C-−2.8°C) and PO-SCORAD values (16.1-22.8) during use by AD volunteers suggest promoting both wear tolerance (WT) and NOS preference. Air permeability of 3,222 l/m2s with NOS knitted linen as at least 48 percent higher than tested fibers indicating AD volunteers preference during hot climate (24°C to 37°C and 54 to 69 percent RH). Control healthy volunteers were less sensitive to NOS (−1.3°C-−1.6°C) and hot feeling polyester was detected in use. UPF confirms open loops of NOS (NOS UPF 10-5 vs OS UPF 25-15). Thickness (0.6 to 1.0 mm) and RET values (3.1-3.8) were both without significance for this study.Research limitations/implicationsDue to the experimental character of this study with a reduced group of two AD volunteers, wear test conclusion is limited to these specific boys. Work extension aiming at broad AD wears statistics significance should consider more volunteers.Practical implicationsThe study provides specific answers to opening new possibilities for AD wear other than cotton or polyester, both fibers with more availability in the Brazilian garments retail industry that sometimes did not meet their routine needs. This study provides practical daily understanding of correlations of WT and air permeability level of NOS knitted applied to garments in direct contact with the skin in subtropical climates.Social implicationsBoth academically and socially, the results can contribute to increasing information related to textile process and practical knowledge of knits to better accomplish AD clothing in subtropical climates. The practical wear test results with AD volunteers also indicate guidelines to parents who were having trouble identifying base layers, fundamental textiles and options for their kids in search of possible relief and well being mainly on hot days.Originality/valueCircular knitting jersey linen study in direct contact with sensitive skin in a subtropical climate city like São Paulo is unique. The study also considered helping parents of a six-year-old AD boy in attendance to a doctor’s suggestion to find better options of clothings to be used during his daily routines.

Study of data-driven thermal sensation prediction model as a function of local body skin temperatures in a built environment

Current thermal/sensation models primarily rely on predefined formulas or empirically defined recommendations, but fail to consider each individual's physiological characteristics. Such models frequently ignore occupants' diverse physical conditions and, therefore, have critical limitations in estimating each individual's thermal sensation levels. Since the human body is governed by the thermoregulation principle to balance the heat flux between the ambient thermal condition and the body itself, skin temperature has a significant role in maintaining this physiological principle. Therefore, this study investigated the potential use of skin temperature and its technical parameters in establishing a thermal sensation. By using advanced modern sensing technologies, and existing thermal regulation model research, this study selected and validated seven body areas as significant local body segments for determining overall thermal sensation. A series of environmental chamber tests were conducted for 2 h. While the indoor temperature fluctuated between 20 °C and 30 °C, skin temperatures of the seven selected body areas were measured in conjunction with a thermal sensation and comfort survey. Results of this study revealed that combinations of skin temperatures for the arm, back, and wrist provided the significant information needed to accurately estimate the thermal sensations of each user. Most of all, both sides of the wrist generated accurate data more than 94% of the time.Therefore, considering the modern advanced wearable sensing technologies, results of this study confirmed that optimum combinations of skin temperature information from selected body areas, is reliable and generally applicable for estimating individual thermal sensations.

Core and Surface Temperature Modification During Road Transport and Physical Exercise in Horse After Acupuncture Needle Stimulation

In this study, the effect of acupuncture on skin temperature (TSKIN), including six body regions (neck, shoulder, ribs, flank, internal thigh, and back), rectal temperature (TRECTAL), serum levels of total proteins, hematocrit, magnesium, calcium (Ca), phosphorus, and chloride was evaluated in five Thoroughbred horses. Horses competed in two official races. For each race, animals were transported from their stables to the racetrack. Horses transported and competed in the first race represent the control group. Two weeks later, the same horses competed in the second race. Before road transport, they were treated with acupuncture. From animals, the TSKIN, TRECTAL, and blood samples were collected at rest; after unloaded, 30 minutes after unloaded, at rest in the transit box, at the end of the race, and 30 minutes after the race. A significant effect of transport and exercise was found on all studied parameters (P < .01), except for Ca and TSKIN of neck (P > .05), in both groups. Transported and exercised horses subjected to acupuncture treatment showed statistically significant higher values of TRECTAL and TSKIN of flank (P < .01). Thoroughbred horses display a classic hemodynamic response to transport and exercise; acupuncture affects body temperature and skin temperature of flank region in both transported and exercised horses suggesting a controlling effect of acupuncture on thermoregulatory function, probably, by decreasing the activities of sympathetic function and manifested as vasodilatation, arterial blood flow, and skin microcirculation increase.

The effect of body fat percentage and body fat distribution on skin surface temperature with infrared thermography

This study aimed to search for relations between body fat percentage and skin temperature and to describe possible effects on skin temperature as a result of fat percentage in each anatomical site. Women (26.11±4.41 years old) (n =123) were tested for: body circumferences; skin temperatures (thermal camera); fat percentage and lean mass from trunk, upper and lower limbs; and body fat percentage (Dual-Energy X-Ray Absorptiometry). Values of minimum (TMi), maximum (TMa), and mean temperatures (TMe) were acquired in 30 regions of interest. Pearson's correlation was estimated for body circumferences and skin temperature variables with body fat percentage. Participants were divided into groups of high and low fat percentage of each body segment, of which TMe values were compared with Student's t-test. Linear regression models for predicting body fat percentage were tested. Body fat percentage was positively correlated with body circumferences and palm temperatures, while it was negatively correlated with most temperatures, such as TMa and TMe of posterior thighs (r =−0.495 and −0.432), TMe of posterior lower limbs (r =−0.488), TMa of anterior thighs (r =−0.406) and TMi and TMe of posterior arms (r =−0.447 and −0.430). Higher fat percentages in the specific anatomical sites tended to decrease TMe, especially in posterior thighs, shanks and arms. Skin temperatures and body circumferences predicted body fat percentage with 58.3% accuracy (R =0.764 and R2 =0.583). This study clarifies that skin temperature distribution is influenced by the fat percentage of each body segment.

Effect of diet quality and ambient temperature on the use of torpor by two species of neotropical nectar-feeding bats.

Neotropical bats use torpor as a strategy to save energy when they experience a low energy intake and/or low ambient temperature (Ta). Digestive physiology limits the energy intake of several glossophaginid bats, and could play an important role in the onset of torpor in these tropical animals. We measured the effect that diet quality and Ta had on the use of torpor by the nectar-feeding bats Glossophaga soricina and Leptonycteris yerbabuenae Captive bats were fed with 5% (low) or 35% (high) sucrose solutions while exposed to two different Ta (17.7 and 23.2°C; low Ta and high Ta) in four different treatments: (1) high sucrose:high Ta, (2) high sucrose:low Ta, (3) low sucrose:high Ta and (4) low sucrose:low Ta We measured their energy intake, changes in body mass (ΔMb) and skin temperature (Tskin) as response variables. Energy intake (in 10 h) was limited when both species fed on 5% sucrose, but body mass gain was only affected in G. soricina. Energy intake and Ta had a negative effect on the minimum Tskin of both species, and ΔMb affected the time that G. soricina used torpor. Both species remained normothermic on the high sucrose:high Ta treatment, but used torpor on the other three treatments. Bats used torpor during their resting and activity periods. Leptonycteris yerbabuenae spent more time in torpor in the low sucrose:high Ta treatment, while G. soricina used this strategy for longer periods of time in the high sucrose:low Ta treatment. We found that diet quality and Ta played an important role in the use of torpor by nectar-feeding bats.

Safety and tolerability of transcranial direct current stimulation to stroke patients – A phase I current escalation study

Background and objectiveA prior meta-analysis revealed that higher doses of transcranial direct current stimulation (tDCS) have a better post-stroke upper-extremity motor recovery. While this finding suggests that currents greater than the typically used 2 mA may be more efficacious, the safety and tolerability of higher currents have not been assessed in stroke patients. We aim to assess the safety and tolerability of single session of up to 4 mA in stroke patients. MethodsWe adapted a traditional 3 + 3 study design with a current escalation schedule of 1»2»2.5»3»3.5»4 mA for this tDCS safety study. We administered one 30-min session of bihemispheric montage tDCS and simultaneous customary occupational therapy to patients with first-ever ischemic stroke. We assessed safety with pre-defined stopping rules and investigated tolerability through a questionnaire. Additionally, we monitored body resistance and skin temperature in real-time at the electrode contact site. ResultsEighteen patients completed the study. The current was escalated to 4 mA without meeting the pre-defined stopping rules or causing any major safety concern. 50% of patients experienced transient skin redness without injury. No rise in temperature (range 26°C–35 °C) was noted and skin barrier function remained intact (i.e. body resistance >1 kΩ). ConclusionOur phase I safety study supports that single session of bihemispheric tDCS with current up to 4 mA is safe and tolerable in stroke patients. A phase II study to further test the safety and preliminary efficacy with multi-session tDCS at 4 mA (as compared with lower current and sham stimulation) is a logical next step.ClinicalTrials.gov Identifier: NCT02763826.

Abstract 103: A Phase I Current Escalation Study for Transcranial Direct Current Stimulation in Ischemic Stroke Patients

Introduction: Positive dose-response relationship with the use of Transcranial direct current stimulation (tDCS) in post-stroke upper limb motor recovery demands investigating the efficacy of higher tDCS doses. Safety and tolerability of tDCS current higher than typically used 2 mA has not been investigated in stroke patients. Hypothesis: tDCS application up to 4 mA for 30 minutes is safe and tolerable in stroke patients Methods: A 3+3 study design with current escalation schedule of 1, 2, 2.5, 3, 3.5 and 4 mA was adopted for this tDCS safety study ( Fig. A ). Patients with first-ever ischemic stroke and unilateral hemiparesis were recruited. Single session of tDCS and customatory occupational therapy for 30 minutes using a device (Chattanooga Ionto) with 5х7 cm 2 sponge electrodes (Soterix Medical) on a bihemispheric montage (C3/C4, anode on lesional side) were administered. Stopping rules were (1) second degree scalp burn, or (2) seizure, or (3) new lesion(s) on DWI sequence of MRI or decreased ADC. Tolerability was assessed by tDCS questionnaire administered before and after tDCS. Body resistance and skin temperature at electrode contact site were monitored in real time. Results: Eighteen patients were enrolled and completed the study. The current was escalated to 4 mA without any major safety concerns (stopping rule). 50% of patients revealed transient skin redness at anodal site and 17% at cathodal side. No patient had any persistent skin perception issues at the end of tDCS ( Fig. B ). We also present real-time monitoring of body resistance and skin temperature to ensure safety during tDCS administration ( Fig. C ). Skin barrier remained intact through tDCS, as demonstrated by absence of abrupt decrease in body resistance (&lt;400 Ω). Skin temperatures remained well below body temperature (range 26°C-35°C) Conclusion: Our data support that tDCS current up to 4 mA is safe and tolerable in ischemic stroke patients. Efficacy and safety should be further tested in a phase II study.

Early development and the emergence of individual differences in behavior among littermates of wild rabbit pups

The ontogeny of associated individual differences in behavior and physiology during early postnatal life, and in particular the emergence of such differences among litter siblings, has been hardly explored in mammals under natural conditions. We studied such within-litter differences in behavior in European rabbit pups Oryctolagus cuniculus prior to weaning, and whether and how these differences co-varied with other individual characteristics such as postnatal body temperature and early growth. The study was conducted under semi-natural conditions in a colony of rabbits of wild origin, where the young were born and developed in nursery burrows. We equipped two siblings per litter with interscapular skin temperature loggers on postnatal day 2 and recorded temperature profiles for 48h. Individual body (skin) temperatures of pups within litters were repeatable across time, indicating the existence of consistent individual differences. Such differences within litters were associated with relative differences in pre-weaning growth, revealing that relatively warmer pups showed a greater increase in body mass during the nest period. Between postnatal days 12 and 17, after the pups had reached a developmental stage of greater mobility, we carried out different behavioral tests: a handling-restraint test, an open field test and a jump-down test from a platform. Individual responses in the former two tests were associated, as those pups showing a quicker struggling response to restraint during handling also exhibited greater exploratory activity in the open field. This correlation across contexts suggests the existence of personality types in wild rabbits at an early developmental stage. Furthermore, pups' behavioral responses were strongly associated with their relative within-litter body mass at testing. Animals with a lower body mass compared to their siblings showed a relatively quicker struggle response to handling restraint and covered a relatively larger distance in the open field, suggesting greater reactivity and responsiveness of relatively lighter pups in these tests. In contrast, relatively heavier pups jumped sooner from the platform, which may have been due to their greater physical maturation. In conclusion, our study shows that individual differences in behavior and associated differences in body temperature and growth are already present during early postnatal life, although such relationships can be easily overlooked, as they predominantly emerge as relative differences among littermates.

Thermo-physiological impact of different firefighting protective clothing ensembles in a hot environment

It is currently unclear how the assembly of different fabric layers of personal protective clothing (PPC) contributes to differences in thermal comfort among garments. Therefore, we used two different approaches to investigate the effect of PPC on body heat dissipation: a technical characterization of textiles (using sweating Torso methodology) and thermo-physiological wearing trials. We hypothesized that the technical characterization provides a similar outcome compared to the wearing trials and, thus, proves to have high thermo-physiological relevance. Thirteen different PPC were investigated using the sweating Torso methodology. Three out of these thirteen were then selected for inclusion in a series of human subject trials in a hot environment. Results from human trials and Torso testing were related to each other. The thermal and evaporative properties of the selected PPC typically differed and effects were observed for the thermo-physiological responses of human study participants. Differences in Torso surface temperature of up to 9℃ and moisture accumulation in the protective clothing systems of up to 184 g·m–2 were detected using the sweating Torso methodology. Moderate intensity exercise with the human study participants induced textile-dependent differences of up to 0.9 ± 0.2℃ ( P &lt; 0.001) and 1.2 ± 0.2℃ ( P = 0.008) for excessive core body and excessive skin temperature, respectively. Using the sweating Torso methodology, physiologically relevant differences in textile performance could be detected among different PPC. Consequently, sweating Torso is a relevant tool to gain insight into human thermo-physiological responses to different PPC with similar end-use based on their dry and wet heat transfer characteristics.

Multifactorial cycling performance of Cyclists and Non-Cyclists and their effect on skin temperature

Although some studies showed a relationship between skin temperature and physical fitness, it is unclear if cycling experience could have an influence on thermoregulation. The aims of this study were to compare differences in skin temperature between Cyclists and Non-Cyclists and to assess the relationship between varying performance factors and skin temperature. Eleven Cyclists and eleven Non-Cyclists performed an incremental cycling test to exhaustion. Body composition, power output, oxygen consumption, heart rate, neuromuscular activation and skin temperature from Vastus Lateralis, Rectus Femoris, Biceps Femoris and Gastrocnemius Medialis were measured. Cyclists presented lower percentage body fat, greater peak power output and higher oxygen consumption (P 1.4), resulting in a higher heat production (P 1.1). Skin temperature was negatively correlated with body fat and positively correlated with peak power output and heat production (P < 0.05 and ∣r∣ ≥ 0.5). Skin temperature was influenced by cycling training profile and participants with a higher physical fitness (i.e., higher peak power output) presented higher heat production and higher skin temperature. Furthermore, percentage body fat was one of the variables that largely explained the relationship between physical fitness and skin temperature.

Experimental study of thermal comfort on stab resistant body armor.

PurposeThis research aims to investigate the impacts of exercise intensity and sequence on human physiology parameters and subjective thermal sensation when wearing stab resistant body armor under daily working conditions in China [26 and 31 °C, 45–50 % relative humidity (RH)], and to investigate on the relationship between subjective judgments and objective parameters.MethodsEight male volunteers were recruited to complete 3 terms of exercises with different velocity set on treadmill for 90 min at 26 °C and 31 °C, 45–50 % RH. In Exercise 1 volunteers were seated during the test. In Exercise 2, volunteers walked with the velocity of 3 km/h in the first 45 min and 6 km/h in the left 45 min. In Exercise 3, volunteers walked with the velocity of 6 km/h in the first 45 min and 3 km/h in the left 45 min. The body core temperature, skin temperature and subjective judgments were recorded during the whole process. Analysis of variance was performed among all the tests.ResultsIndividual discrepancy of Exercise 1 is larger than that of Exercise 2 and 3. On the premise of the same walking distance and environmental conditions, core temperature in Exercise 3 is about 0.2 °C lower than that in Exercise 2 in the end; and with the velocity decrease from 6 km/h to 3 km/h in the end, thermal tolerance of Exercise 3 is about 1 degree lower than that in Exercise 2. Skin temperatures of human trunk were at least 1 °C higher than that of limbs.ConclusionsActivity narrows the individual discrepancy on core temperature. Within experimental conditions, decreasing of intensity at last stage makes the core temperature lower and the whole process much tolerable. The core temperature is more sensitive to the external disturbance on the balance of the whole body, and it can reflect the subjective thermal sensation and physical exertion.

Normal range and lateral symmetry in the skin temperature profile of pregnant women

Body skin temperature is a useful parameter for diagnosing diseases and infrared thermography can be a powerful tool in providing important information to detect body temperature changes in a noninvasive way. The aim of this work was to study the pattern of skin temperature during pregnancy, to establish skin temperature reference values and to find correlations between these and the pregnant population characteristics. Sixty-one healthy pregnant women (mean age 30.6±5.1years) in the 8th–40th gestational week with normal pregnancies were examined in 31 regions of interest (ROI). The ROIs were defined all over the body in order to determine the most influenced by factors such as age or body mass index (BMI). The results obtained in this work highlight that in normal pregnant women the skin temperature is symmetrically distributed, with the symmetrical areas differing less than 0.5°C, with a mean value of 0.25±0.23°C. This study identified a significant negative correlation between the BMI and temperature. Age has been shown to have great influence on the skin temperature, with a significant increase of temperature observed with age. This work explores a novel medical application of infrared thermography and provides a characterization of thermal skin profile in human pregnancy for a large set of ROIs while also evaluating the effects of age and BMI.

Measuring Human Body Temperature through Temperature Sensing Fabric

Continuous measurement of temperature profiles on the surface of the human body offers various kinds of information valuable for clinical diagnosis and as a useful guide to take suitable action. In this article, the behavior of a newly developed temperature sensing fabric (TSF) over extended periods of time in a practical application and its comparison with a reference temperature sensor was investigated. The performance of the TSF was analyzed by measuring the human body skin temperature under steady-state and dynamic conditions. A dedicated interface was built in the LabVIEW environment to measure and record the temperature readings of the TSF and reference temperature sensor simultaneously. The reference and TSF sensors both followed exactly the same trends and experienced the same type of movement artifacts.

Brown Adipose Tissue Is Linked to a Distinct Thermoregulatory Response to Mild Cold in People.

Brown adipose tissue (BAT) plays an important role in thermoregulation in rodents. Its role in temperature homeostasis in people is less studied. To this end, we recruited 18 men [8 subjects with no/minimal BAT activity (BAT−) and 10 with pronounced BAT activity (BAT+)]. Each volunteer participated in a 6 h, individualized, non-shivering cold exposure protocol. BAT was quantified using positron emission tomography/computed tomography. Body core and skin temperatures were measured using a telemetric pill and wireless thermistors, respectively. Core body temperature decreased during cold exposure in the BAT− group only (−0.34°C, 95% CI: −0.6 to −0.1, p = 0.03), while the cold-induced change in core temperature was significantly different between BAT+ and BAT− subjects (BAT+ vs. BAT−, 0.43°C, 95% CI: 0.20–0.65, p = 0.0014). BAT volume was associated with the cold-induced change in core temperature (p = 0.01) even after adjustment for age and adiposity. Compared to the BAT− group, BAT+ subjects tolerated a lower ambient temperature (BAT−: 20.6 ± 0.3°C vs. BAT+: 19.8 ± 0.3°C, p = 0.035) without shivering. The cold-induced change in core temperature (r = 0.79, p = 0.001) and supraclavicular temperature (r = 0.58, p = 0.014) correlated with BAT volume, suggesting that these non-invasive measures can be potentially used as surrogate markers of BAT when other methods to detect BAT are not available or their use is not warranted. These results demonstrate a physiologically significant role for BAT in thermoregulation in people. This trial has been registered with Clinaltrials.gov: NCT01791114 (https://clinicaltrials.gov/ct2/show/NCT01791114).

The Herschel Heritage to Medical Thermography

The discovery of infrared radiation by William Herschel in 1800 led to John Herschel’s study of solar radiation that he imaged by evaporography. This he termed a thermogram. The measurement of temperature in medicine advanced with Dr Carl Wunderlich, who showed the significance of the use of temperature measurements for diagnosis of fever and for monitoring the course of temperature in relation to disease. It was William and John Herschel’s discovery of infrared radiation that has ultimately opened up many applications for thermal imaging. Radiometric determination of human body (skin) temperature is now achievable. Remote sensing of infrared radiation first developed in the 1940s and has continued to develop steadily since 1960. Modern high speed and high resolution camera systems have now reached a dramatic level of performance at more modest costs, which medicine can now employ for non-invasive and quantifiable imaging. This has applications in many areas of medicine both for diagnostics and monitoring treatment. In recent years the acute threat of pandemic infection has increased, heightened by today’s ever expanding world travel. Special interest has been shown in the potential of thermal imaging for airport and travel screening. This is in effect where Dr Wunderlich’s studies began, and it has yet to be proven that the technique can be responsibly employed for efficient screening of large numbers of the travelling public.

Heat stress and its impacts on occupational health and performance

Workplace heat stress is a well-known occupational health hazard, and climate change characterized by the increased frequency and intensity of extreme heat events has made risks more severe and widespread. Heat stress is prevalent in numerous industrial and commercial occupational settings, either outdoors or indoors. Operations that involve high environmental heat, physically demanding activities or impermeable protective clothing have a high potential for incurring heat stress among exposed workers. Workplaces with such conditions may include firefighting, iron and steel manufacturing, mining, glass factories and food canneries. Outdoor tasks performed in hot weather and under direct exposure to sunlight, such as construction, agriculture, oil and gas well operations, and outdoor horticulture and cleaning, are also likely to induce heat stress to employees. This editorial paper highlights the current progress and needs for research on heat stress and of its impacts on occupational health and performance. Heat stress causes physiological and psychological discomforts, deteriorates performance and productivity, increases incident rates and even threatens survival. Increased thermoregulatory, cardiovascular and perceptual strains on the body promote confusion, irritability and other emotional stress, which may cause workers to become distracted from tasks or ignore safety procedures. Understanding the effects of heat stress and implementing appropriate intervention strategies to relieve the harmful impacts of heat stress has been the focus of a significant amount of research. Studies of this nature require a multi-disciplinary approach involving physiology, management and technology. The effects of heat stress can be described by physiological and psychological responses. Management of heat stress utilizes a set of framework, principles, processes and measures to prevent injuries, accidents and other adverse consequences. Technology in terms of techniques, tools, systems and machineries has been adopted as an effective means to protect workers from the hazardous effects of heat stress. Heat stress could be a result from a combination of factors, including environmental conditions, metabolic heat and thermal effects of clothing ensemble. Heat strain is the physiological response of a person in dissipating heat stress. The international standard, ISO 9886:2004 specifies measurements of body core temperature, heart rate, skin temperature and loss of body mass through sweating for evaluation of body heat strain. The upper limits of these physiological parameters have been prescribed by some regulatory organizations for monitoring of workers’ safety in heat stress occupational environments. So far a number of devices such as Ingestible Core Body Thermometer Pill and Polar Heart Rate Monitor have been used for measurement and monitoring of these physiological parameters. However, application of these devices is limited and inconvenient because they are costly and may disturb workers’ normal activities. The physiological strain experienced by a person can be estimated by the heat stress factors and is evaluated by a single index. A heat stress index is a single value that integrates the effects of the six basic parameters (i.e. ambient temperature, relative humidity, radiant temperature, air velocity, metabolic rate and clothing properties) in any human thermal environment such that its value could vary with the thermal strain experienced by an individual. Measurement of wet bulb globe temperature is by far the most widely used and accepted empirical index for managing occupational heat stress; and is recommended as a heat stress standard. The heat stress standard is calculated using the recordings of wet bulb temperature, globe temperature and dry bulb temperature. However, wet bulb globe temperature measurements are insensitive to the cooling effect due to wind velocity and are incapable of measuring the effect of workers’ metabolic rates.

Interactions of mean body and local skin temperatures in the modulation of human forearm and calf blood flows: a three-dimensional description.

The inter-relationships between mean body and local skin temperatures have previously been established for controlling hand and foot blood flows. Since glabrous skin contains many arteriovenous anastomoses, it was important to repeat those experiments on non-glabrous regions using the same sample and experimental conditions. Mild hypothermia (mean body temperature 31.4°C), normothermia (control: 36.0°C) and moderate hyperthermia (38.3°C) were induced and clamped (climate chamber and water-perfusion garment) in eight males. Within each condition, five localised thermal treatments (5, 15, 25, 33, 40°C) were applied to the left forearm and right calf. Steady-state forearm and calf blood flows were measured (venous occlusion plethysmography) for each of the resulting 15 combinations of clamped mean body and local skin temperatures. Under the normothermic clamp, cutaneous blood flows averaged 4.2mL100mL(-1)min(-1) (±0.28: forearm) and 5.4mL100mL(-1)min(-1) (±0.27: calf). When mildly hypothermic, these segments were unresponsive to localised thermal stimuli, but tracked those changes when normothermic and moderately hyperthermic. For deep-body (oesophageal) temperature elevations, forearm blood flow increased by 5.1mL100mL(-1)min(-1)°C(-1) (±0.9) relative to normothermia, while the calf was much less responsive: 3.3mL100mL(-1)min(-1)°C(-1) (±1.5). Three-dimensional surfaces revealed a qualitative divergence in the control of calf blood flow, with vasoconstrictor tone apparently being released more gradually. These descriptions reinforce the importance of deep-tissue temperatures in controlling cutaneous perfusion, with this modulation being non-linear at the forearm and appearing linear for the calf.