Thermal Imaging in Detection of Fever for Infectious Diseases
U. Snekhalatha, K. Palani Thanaraj, Kurt Ammer in Artificial Intelligence-Based Infrared Thermal Image Processing and Its Applications, 2023
Measuring body temperature for the detection of a suspected infection is widely practiced in medicine. The procedure has a long history and one of the first and well-documented studies was done by Wunderlich (P. A. Mackowiak and Worden 1994). In his seminal book, Wunderlich reported temperature measurements recorded in a large sample of subjects using thermometry available at that time and concluded that the normal temperature value of healthy individuals falls in the range of 36.2°C (97.2°F) to 37.5°C (99.5°F) based on the different diurnal cycle. It was also reported a mean temperature of 37.0°C (98.6°F) for healthy individuals and any temperature measurement beyond 38°C (100.4°F) was meant febrile. However, Wunderlich understood that the sample size of healthy subjects was rather small and the measurement procedure in healthy subjects sometimes lacked sufficient precision (Wunderlich 1871).
Altitude, temperature, circadian rhythms and exercise
Adam P. Sharples, James P. Morton, Henning Wackerhage in Molecular Exercise Physiology, 2022
Humans have evolved a regulatory system that maintains the temperature of our body within a narrow range. In relation to temperature, our body has two parts. First, our shell includes our skin and extremities, and here the temperature can vary considerably, for example when we have cold hands or feet. Second, our core comprises the vital inner organs and here the temperature is on average close to ≈37°C. Maintaining our core body temperature is important, as temperature has profound effects on the molecules of life. For example, the activity of enzymes increases with temperature before a too hot temperature causes enzymes and other proteins to denature. If we become too hot then we can suffer a heat stroke which is hyperthermia (core body temperature of >40°C) accompanied by systemic inflammation which can cause defects of several organs and eventually death (35). In contrast, when our body cools down, then enzymes are less active, membranes are more rigid and ion fluxes are reduced. Hypothermia is a medical syndrome when the core body temperature falls to below 35°C. When we are hypothermic, we start to shiver and become lethargic and this can progress further to confusion, coma and death.
The immune and lymphatic systems, infection and sepsis
Peate Ian, Dutton Helen in Acute Nursing Care, 2020
Changes in the body’s ability to control its own temperature can occur when infection develops. Fever or pyrexia is derived from the Latin word febris, or febrile. Fever occurs when the body temporarily fails to maintain the temperature within normal limits. Fever accelerates tissue metabolism and the activity of defences. The set-point is elevated by 1–2°C and is a symptom of many medical conditions and one of the oldest indicators of disease. In response to a stimulus, such as inflammation or the release of endotoxins from bacteria, leucocytes release endogenous pyrogens, ‘fire starters’, or cytokines into the bloodstream. These chemicals act directly on the thermostat or ‘set-point’ in the hypothalamus, causing the release of prostaglandin and elevating or resetting the hypothalamic set-point to a higher level. However, hypothermia, a lower-than-normal body temperature, can occur and is often a bad sign, especially in sepsis. 20% of septic patients present with hypothermia rather than hyperthermia, making a drop in temperature an important sign to note. Sepsis patients with hypothermia have twice the mortality of those who are normothermic or pyrexial (Kushimoto et al. 2013; Drewry et al. 2015; Wiewel et al. 2016). The mechanism of sepsis-induced hypothermia, though, is poorly understood. Scientific literature suggests it is the dis-regulated inflammatory cytokine responses, as well as physiological alterations of the temperature regulation centre in the hypothalamus, that are responsible for this response.
Beyond heat exposure — new methods to quantify and link personal heat exposure, stress, and strain in diverse populations and climates: The journal Temperature toolbox
Published in Temperature, 2023
Gisel Guzman-Echavarria, Ariane Middel, Jennifer Vanos
Physiologically, the thermoregulatory system balances the internal heat production and external environmental heat fluxes to maintain a stable internal temperature [1,11,12]. However, the body may or may not compensate during heat stress to return to thermal equilibrium (Figure 1). Compensable heat stress (CHS) occurs when heat loss to the environment is balanced with heat gain; hence, a steady-state core temperature can be sustained [13]. Conversely, uncompensable heat stress (UHS) occurs when evaporative cooling requirements are not supported due to environmental or other conditions (including low sweat production) that impede the body’s ability to cool [13]. In UHS, the internal body temperature rises, which can result in hyperthermia. Generally, hyperthermia is divided by degree of severity into heat cramps, heat exhaustion, and potentially fatal heatstroke, either classic or exertional [1].
The specific heat of the human body is lower than previously believed: The journal Temperature toolbox
Published in Temperature, 2023
Xiaojiang Xu, Timothy P. Rioux, Michael P. Castellani
The muscle contribution to the specific heat of the body is approximately 47%; fat and skin contribute approximately 24%, and each of the remaining tissue types contribute 7% or less. Thus, the specific heat of any individual human body is directly related to body composition. For example, a study in mice demonstrated that the specific heat varied with body fat percentage. The specific heat was 2.65 kJ · kg−1 · °C−1 for obese mice with 53% fat and 3.66 kJ · kg−1 · °C−1 for lean mice with 8% fat [17]. It was proposed that the specific heat of the human body was also adjusted according to fat percentage [18,19]. This indicates that the body heat content, an important parameter in thermoregulation, is related to body composition as well. Thus, when calculating the body heat content, a two-compartment thermometry model (core and shell) predicted the heat content more accurately than one-compartment thermometry model [19] and a three-compartment thermometry model (core, muscle, and shell) predicted the heat content more accurately than a two-compartment thermometry model [1,8,20]. Since skeletal muscle contributes almost 50% of the body specific heat, this tissue should be specifically considered in the calculation and analysis of the body heat content or mean body temperature.
Heat distribution and the condition of hypothermia in the multi-layered human head: A mathematical model
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Ahsan Ul Haq Lone, M.A. Khanday, Saqib Mubarak, Feroze A. Reshi
Variation in the temperature of human head exposed to external cold temperature at different qm (metabolic heat generation) values was plotted against time, as shown in Figure 2. The resulting graph indicates decrease in the temperature of the human head with prolonged exposure to cold environment. This is in consonance with the clinical finding of hypothermia, where the body temperature lowers by about 1–2 degrees than the normal and emerges as a medical condition. The speedy decrease in temperature of head on exposure to cold environment reflects the vulnerability of head to the hypothermia-induced impairment in the body. The variation of temperature in the human head in relation to axial distance from the core of the head also shows decrease in the temperature (Figure 3). This result garners support from the biological organisation of the head, in which the core is insulated from the surrounding environment by multiple protections, with scalp rather directly interfacing with the external environs. As a result, the scalp experiences the temperature more severely than the inner tissues/compartments of the head. The insulating layers of the core head are likely to succumb to the continued exposure of head to cold atmospheric temperature. Continuous exposure of head surface to the cold temperature gradually results in decrease in the temperature of core head 2–3 degrees lower than the normal body temperature. Such a condition is clinically marked as the manifestation of hypothermia.
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