Temperature Changes of Pulmonary Blood During Exposure to Cold

Mather, George W.; Nahas, G; Hemingway, Allan

doi:10.1152/ajplegacy.1953.173.3.390

Cited by 26 publications

(19 citation statements)

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“…In exercising horses, blood temperature decreased by as much as 0.6°C on its passage through the lungs, dissipating up to two-thirds of the total heat load generated (Hodgson et al, 1993;Lund et al, 1996). The temperature of blood in the left atrium or carotid trunk also has been found to be lower than pulmonary artery temperature in resting dogs (Mather et al, 1953) and calves (Bligh, 1957b), albeit by a much smaller amount than that in exercising horses.…”

Section: Discussionmentioning

confidence: 93%

Variability in brain and arterial blood temperatures in free-ranging ostriches in their natural habitat

Fuller

Kamerman

Maloney

et al. 2003

Journal of Experimental Biology

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The main determinant of deep brain temperature, measured in or near the hypothalamus, is the temperature of the arterial blood supplying the brain (Hayward and Baker, 1968). In most mammals, therefore, brain temperature changes in parallel with carotid blood temperature but, because of its high metabolic rate, exceeds the temperature of arterial blood by 0.2-0.5°C (Hayward and Baker, 1969). However, some mammals, particularly artiodactyls and felids, are able to lower brain temperature below carotid blood temperature, a process termed selective brain cooling (for reviews, see Jessen, 2001;Mitchell et al., 2002). In these mammals, selective brain cooling is facilitated by the carotid rete, a bilateral network of intertwining arteries in the main arterial supply to the brain, situated on either side of the pituitary body within cool venous lakes derived from veins draining the nasal mucosa (Gillilan, 1974;Simoens et al., 1987). Moderate exercise on a treadmill or exposure to heat in a laboratory uncouples brain and carotid blood temperatures, so that the gradient between brain and blood temperatures narrows until, at a threshold temperature of approximately 39°C, brain temperature equals carotid blood temperature (Baker, 1982;Kuhnen and Jessen, 1991;Kuhnen and Mercer, 1993). Beyond that threshold, brain temperature rises at a slower rate than does blood temperature, establishing selective brain cooling with a magnitude, at most, of about 1°C.In mammals that are free-living in their natural habitat and exposed to a variety of complex stressors, however, a similar tight thermal relationship between brain and arterial blood temperatures is apparently absent. In free-ranging antelope, selective brain cooling occurs within the normothermic range of body temperature, and only sporadically in response to high heat loads (Jessen et al., 1994;Mitchell et al., 1997;Fuller et al., 1999b;Maloney et al., 2002). During high-intensity exercise, when brain temperatures reach their highest levels, selective brain cooling is abolished. Indeed, for any given blood temperature, brain temperature is highly variable and unpredictable. Large-amplitude, transient deviations in brain temperature, independent of any changes in the temperature of arterial blood supplying the brain, have also been observed in several laboratory animals in response to non-thermal stimuli (Fuller et al., 1999a;Maloney et al., 2001). This variability arises because the efferent arm of the control mechanism We used implanted miniature data loggers to measure brain (in or near the hypothalamus) and carotid arterial blood temperatures at 5 min intervals in six free-ranging ostriches Struthio camelus in their natural habitat, for a period of up to 14 days. Carotid blood temperature exhibited a large amplitude (3.0-4.6°C) circadian rhythm, and was positively correlated with air temperature. During the day, brain temperature exceeded carotid blood temperature by approx. 0.4°C, but there were episodes when brain temperature was lowered below blood temperature. Selecti...

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Section: Discussionmentioning

confidence: 93%

Variability in brain and arterial blood temperatures in free-ranging ostriches in their natural habitat

Fuller

Kamerman

Maloney

et al. 2003

Journal of Experimental Biology

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“…(14,(16)(17)(18)(19) Although there is as yet no scientific evidence to support the idea, the possibility of controlling the loss of heat and humidity through the airways, or even providing heat and humidity via those airways (in order to prevent and treat hypothermia), has been considered.…”

Section: Discussionmentioning

confidence: 99%

“…The device was adjusted as follows: VC to 5000 mL, Vt to 800 mL, initial-and end-expiratory pressures to 20 cmH 2 O, PEEP to 2 cmH 2 O, and air temperature to 37 °C. (13,14,17,18) The safety valve was adjusted to 40 cmH 2 O. The mechanical ventilator was adjusted as follows: Vt to 800 mL, maximal inspiratory pressure to 20 cmH 2 O, inspiratory flow to 40 L.min −1 , PEEP to 2 cmH 2 O, RR to 17 breaths per minute, fraction of inspired oxygen to 0.21, and air temperature to that of the external environment.…”

Section: Adjustmentmentioning

confidence: 99%

“…Air temperature is the principal factor implicated in the heat exchange of the respiratory system, since the temperature of this air can be quite variable, and since heat gain or loss is directly related to the difference in temperature between the inspired air and the surface of the respiratory system. (13,14) Other important factors involved in these thermal reactions are the ventilation rate per minute, airway temperature, vasomotor changes, and changes in the mucous membrane. (15)(16)(17)(18)(19) During inspiration, the air is heated by the mucosa, which reflects the temperature of the blood.…”

Section: Introductionmentioning

confidence: 99%

“…Although there have been studies evaluating the loss of thermal energy and humidity through the airways, none have done so during procedures requiring orotracheal intubation. (13,14,(16)(17)(18)(19) The present study sought to create a device that could be adjusted to simulate the conditioning of air in the respiratory tract with the same normal values of temperature, pressure, and RH as those seen in the respiratory system of healthy individuals on mechanical ventilation. The objective of creating such device is to be useful to other studies on thermoregulation and mechanical ventilation without the need for previous animal studies.…”

Section: Introductionmentioning

confidence: 99%

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Modelo mecânico para simulação do condicionamento pulmonar do ar respirado

et al. 2007

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Objective: To create a mechanical model that could be regulated to simulate the conditioning of inspired and expired air with the same normal values of temperature, pressure, and relative humidity as those of the respiratory system of a healthy young man on mechanical ventilation. Methods: Using several types of materials, a mechanical device was built and regulated using normal values of vital capacity, tidal volume, maximal inspiratory pressure, positive end-expiratory pressure, and gas temperature in the system. The device was submitted to mechanical ventilation for a period of 29.8 min. The changes in the temperature of the air circulating in the system were recorded every two seconds. Results: The statistical analysis of the data collected revealed that the device was approximately as efficient in the conditioning of air as is the respiratory system of a human being. Conclusion: By the study endpoint, we had developed a mechanical device capable of simulating the conditioning of air in the respiratory tract. The device mimics the conditions of temperature, pressure, and relative humidity seen in the respiratory system of healthy individuals.

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