Thermal Physiology and Thermoregulation
James Stewart Campbell, M. Nathaniel Mead in Human Medical Thermography, 2023
Skin temperature is normally a reliable indicator of the heat exchange activity of the body. The average temperature of the skin is about 32.5°C (90.5°F) or 4°C (7.2°F) lower than the body's core temperature under thermoneutral conditions.12 At a room temperature of 25°C (77°F), local skin temperatures may vary within a range of 4–5°C (7.2–9°F) depending on physiologic, anatomic, and pathologic factors.13 In a warmer environment, the temperature of the skin increases toward core temperature as blood flow through the skin increases. The human body is generally warmer than the ambient temperature, allowing a flow of heat from the core to the environment. Even with clothing for insulation, heat is steadily lost from the body. During cold stress, blood flow through exposed skin is reduced, leading to a decrease in skin temperature and conservation of core body heat. Skin temperature in the periphery may approach the ambient temperature during cooling, with the nose, ear, finger, and toe temperatures becoming about 17°C (30.6°F) lower than normal core temperature when the body is equilibrated to an air temperature of 20°C (68°F).
Water and hydration in the workplace *
Jamie Bartram, Rachel Baum, Peter A. Coclanis, David M. Gute, David Kay, Stéphanie McFadyen, Katherine Pond, William Robertson, Michael J. Rouse in Routledge Handbook of Water and Health, 2015
Hypothermia occurs from prolonged exposure to cold water temperatures or cold air which causes the core, internal body temperature to drop below 95 degrees F (35 degrees C). Early symptoms of hypothermia are shivering, fatigue, loss of coordination, and confusion and disorientation. Late symptoms include no shivering, blue skin, dilated pupils, slowed pulse and breathing, and loss of consciousness (NIOSH 2014a). As the core body temperature decreases, physical and mental processes slow down and death may result. Survival time in cold water varies based on water temperature. As the water temperature decreases, so does the expected survival time (US Search and Rescue Task Force, n.d.). Cold water immersion causes immersion hypothermia which develops more quickly than hypothermia as water conducts heat away from the body 25 times faster than air (National Institute for Occupational Safety and Health 2014a). An international hypothermia registry was developed as survival after accidental deep hypothermia (core temperature, <28 0C) and prolonged cardiac arrest is rare, and the long-term survival rate is 47 percent higher than previously reported (Walpoth et al. 1997).
Applied exercise physiology and the environment
Nick Draper, Helen Marshall in Exercise Physiology, 2014
Exposure to cold environments can lead to hypothermia and frostbite. Hypothermia is most commonly diagnosed at a core temperature of 35°C or below. It can be triggered by a sudden water immersion, such as the result of a kayak or canoe capsize, or a slower onset such as might occur during a mountain marathon, adventure/multisport race. The symptoms of hypothermia include shivering, a change to a greyish colour for those with lighter skin colouring, slurred speech, irritability, clumsiness and drowsiness. When the core temperature drops to 31°C shivering will cease, representing a significant point in hypothermia. At this point, an individual is unable to re-warm themself without external heating. In cases of mild hypothermia, removing the person from the wind (an emergency shelter is excellent for this purpose), replacing wet clothing, increasing insulation and providing food and drink can help the person to recover quite quickly. As the person begins to recover, decisions can be made about how best to evacuate. In cases of severe hypothermia, the above measures should be completed where possible but medical assistance should be sought as quickly as circumstances allow. A further problem of exercise in cold environments is frostbite which can occur in skin exposed to sub-zero temperatures. In mild cases, limbs can be rewarmed in body temperature (37°C) water, or in the case of a hand, by placing it under the armpit. In severe cases of frostbite, especially if there is a danger of the limb refreezing if warmed, medical assistance should be sought for treatment.
Stationed in Alaska: Subjective Winter Stress and Mental Health
Published in Military Behavioral Health, 2019
Lynn Alkhalil, Maria E. St. Pierre, Walter J. Sowden, Amy B. Adler
Results also showed that the effect of subjective cold stress appears to outweigh the effect of stress caused by winter darkness for mental health and sleep outcomes. This difference may be attributed to the fact that subjective cold stress is a more salient experience characterized by significant physical discomfort (Roth-Isigkeit, 2005; Coghill, 2010), whereas prolonged darkness is not as readily felt by the individual. Thus, subjective stress from the cold may place more of a strain on soldiers, and this strain may account for the stronger correlation between cold stress and with physical and psychological problems. Another explanation for the cold stress finding may be related to differences in how individuals manage the cold. Soldiers may choose to manage the cold by social hibernation (e.g., avoiding exposure to the outside). This isolation may result in loneliness. Not only is loneliness associated with greater risk for mental health problems (Losada et al., 2012), but it also exacerbates feelings of coldness (Ijzerman et al., 2012; Zhong & Leonardelli, 2008), thus increasing the risk for physical and psychological strain.
Residual effects of short-term whole-body cold-water immersion on the cytokine profile, white blood cell count, and blood markers of stress
Published in International Journal of Hyperthermia, 2021
Milda Eimonte, Henrikas Paulauskas, Laura Daniuseviciute, Nerijus Eimantas, Astra Vitkauskiene, Gintare Dauksaite, Rima Solianik, Marius Brazaitis
Interestingly, respiratory cold shock is maximal during naked immersion at a water temperature of 10–15 °C but is no greater during immersion in water at 5 °C [11]. Cold shock subsides during the first 2–3 min after the initial peak, after which there is a gradual thermoregulatory activation shift via a decrease in discharge frequency of cold-sensitive fibers to a less stressful physiological condition, which can be tolerated for hours [7,12]. The available evidence suggests that even brief exposure to acute cold stress leads to increased circulatory levels of the catecholamine hormones norepinephrine (NE) and epinephrine (Epi), and the glucocorticoid hormone cortisol [13,14]. Immersion in 10 °C water for only 2 min produces a large (2-fold) increase in plasma NE concentration [13].
A mathematical model to study thermoregulation and heat-transfer processes in hypothermic neonates under variable physiological parameters
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2023
Hypothermia is a decrease in the body core temperature. It has negative effects for both term and preterm neonates. Due to insufficient and premature body defence system, neonates cannot resist hypothermic situation. Term-babies have several protective factors which prevent this abnormal decay in their body temperature. They develop brown fat in the last few weeks of gestation. This brown fat burns in order to produce heat in their bodies. They also have protection of more subcutaneous fat which helps them to insulate from the cold around them. But term-babies are still prone to hypothermia because they cannot shiver, as no neonate is capable of shivering. So term-babies can become hypothermic if they are exposed to too much cold or they are sick. During sickness, their brain does not work properly to regulate the body’s physiological processes. So term-babies become hypothermic without any apparent cause. Moreover, if the neonates are septic, their body temperature is usually low instead of high. Other factors by which they become hypothermic are through the problems with their brain such as asphyxia or meningitis and exposure to cold. When the baby is severely septic, the temperature can fluctuate up and down (see Guyton 2000; Keener and Sneyd 2009).
Related Knowledge Centers
- Alcohol Intoxication
- Anorexia Nervosa
- Body Temperature
- Cardiac Arrest
- Extracorporeal Membrane Oxygenation
- Thermoregulation
- Cardiopulmonary Bypass
- Shivering
- Hypoglycemia
- Intravenous Therapy