Forearm to fingertip skin temperature gradients in the thermoneutral zone were significantly related to resting metabolic rate: potential implications for nutrition research

Three dimensional models of human thermoregulation: A review

Numerous human thermoregulatory models have been developed and widely used in various applications such as aerospace, medicine, public health, and physiology research. This paper is a review of three dimensional (3D) models for human thermoregulation. This review begins with a short introduction of thermoregulatory model development followed by key principles for mathematical description of human thermoregulation systems. Different representations of 3D human bodies are discussed with respect to their detail and prediction capability. The human body was divided into fifteen layered cylinders in early 3D models (cylinder model). Recent 3D models have utilized medical image datasets to develop geometrically correct human models (realistic geometry model). The finite element method is mostly used to solve the governing equations and get numerical solutions. The realistic geometry models provide a high degree of anatomical realism and predict whole-body thermoregulatory responses at high resolution and at organ and tissue levels. Thus, 3D models extend to a wide range of applications where temperature distribution is critical, such as hypothermia/hyperthermia therapy and physiology research. The development of thermoregulatory models will continue with the growth in computational power, advancement in numerical methods and simulation software, advances in modern imaging techniques, and progress in the basic science of thermal physiology.

Review of the efficacy of infrared thermography for screening infectious diseases with applications to COVID-19

Purpose: The recent coronavirus disease 2019 (COVID-19) pandemic, which spread across the globe in a very short period of time, revealed that the transmission control of disease is a crucial step to prevent an outbreak and effective screening for viral infectious diseases is necessary. Since the severe acute respiratory syndrome (SARS) outbreak in 2003, infrared thermography (IRT) has been considered a gold standard method for screening febrile individuals at the time of pandemics. The objective of this review is to evaluate the efficacy of IRT for screening infectious diseases with specific applications to COVID-19. Approach: A literature review was performed in Google Scholar, PubMed, and ScienceDirect to search for studies evaluating IRT screening from 2002 to present using relevant keywords. Additional literature searches were done to evaluate IRT in comparison to traditional core body temperature measurements and assess the benefits of measuring additional vital signs for infectious disease screening. Results: Studies have reported on the unreliability of IRT due to poor sensitivity and specificity in detecting true core body temperature and its inability to identify asymptomatic carriers. Airport mass screening using IRT was conducted during occurrences of SARS, Dengue, Swine Flu, and Ebola with reported sensitivities as low as zero. Other studies reported that screening other vital signs such as heart and respiratory rates can lead to more robust methods for early infection detection. Conclusions: Studies evaluating IRT showed varied results in its efficacy for screening infectious diseases. This suggests the need to assess additional physiological parameters to increase the sensitivity and specificity of non-invasive biosensors.

Thermal Sensation in Older People with and without Dementia Living in Residential Care: New Assessment Approaches to Thermal Comfort Using Infrared Thermography

The temperature of the indoor environment is important for health and wellbeing, especially at the extremes of age. The study aim was to understand the relationship between self-reported thermal sensation and extremity skin temperature in care home residents with and without dementia. The Abbreviated Mental Test (AMT) was used to discriminate residents to two categories, those with, and those without, dementia. After residents settled and further explanation of the study given (approximately 15 min), measurements included: tympanic membrane temperature, thermal sensation rating and infrared thermal mapping of non-dominant hand and forearm. Sixty-nine afebrile adults (60-101 years of age) were studied in groups of two to five, in mean ambient temperatures of 21.4-26.6 °C (median 23.6 °C). Significant differences were observed between groups; thermal sensation rating (p = 0.02), tympanic temperature (p = 0.01), fingertip skin temperature (p = 0.01) and temperature gradients; fingertip-wrist p = 0.001 and fingertip-distal forearm, p = 0.001. Residents with dementia were in significantly lower air temperatures (p = 0.001). Although equal numbers of residents per group rated the environment as 'neutral' (comfortable), resident ratings for 'cool/cold' were more frequent amongst those with dementia compared with no dementia. In parallel, extremity (hand) thermograms revealed visual temperature demarcation, variously across fingertip, wrist, and forearm commensurate with peripheral vasoconstriction. Infrared thermography provided a quantitative and qualitative method to measure and observe hand skin temperature across multiple regions of interest alongside thermal sensation self-report. As an imaging modality, infrared thermography has potential as an additional assessment technology with clinical utility to identify vulnerable residents who may be unable to communicate verbally, or reliably, their satisfaction with indoor environmental conditions.

The Utility of Forearm to Fingertip Skin Temperature Gradients During Measurements of Resting Energy Expenditure

The measurement of resting energy expenditure (REE) is important to both human physiology and nutrition. There are several pre-conditions for the proper measurement of REE, but a key criterion is that it takes place in the thermoneutral zone (TNZ). Deciding whether a person is in his or her TNZ is not an easy task, and a suggested way forward is the monitoring of forearm to fingertip skin temperature gradients (FFG). In this commentary, we highlight our recent findings that FFG varies between individuals even when measured at a temperature within TNZ. Interestingly, FFG showed a consistent direct relationship with adjusted REE, in both cross-sectional and longitudinal study designs. In addition, we provide new findings that FFG is sensitive to small ambient temperature variations within the TNZ, in comparison to visual analogue scale (VAS)-derived subjective measures of thermal comfort. While further research is needed in this area, our view is measurements of FFG should be included in REE protocols. This would inform investigators on how their participants are responding to the ambient room temperature and also allow appropriate statistical adjustments in REE for between-group comparisons.