Open-loop gain of evaporative heat loss during radiant heat exposure in the mouse

1982 ◽  
Vol 242 (3) ◽  
pp. R275-R279
Author(s):  
C. J. Gordon
Keyword(s):  
Ambient Temperature ◽  
Heat Exposure ◽  
Radiant Heat ◽  
Open Loop ◽  
Whole Body ◽  
Evaporative Heat Loss ◽  
Loop Gain ◽  
Evaporative Water ◽  
Future Studies ◽  
Ambient Temperatures

Whole-body evaporative water loss of the mouse during radiant heating was determined at ambient temperatures of 20-35 degrees C. The ratio of evaporated to absorbed heat per gram body weight, which is equal to open-loop gain (OLGEHL), increased over sixfold with each 1 degrees C increase in ambient temperature. At 35 degrees C, OLGEHL was equal to 0.8, which implies that the mouse evaporates 80% of the absorbed radiant heat. At 20 degrees C, less than 1% of the absorbed heat is evaporated and the remainder of the heat load is dissipated passively. A previous estimate of OLG for the mouse is similar to the data from this study at an ambient temperature of 35 degrees C. Determining OLG with natural ambient stimulation may make future studies in thermoregulation comparable.

Inhibiting ventilatory evaporation produces an adaptive increase in cutaneous evaporation in mourning doves Zenaida macroura

1999 ◽  
Vol 202 (21) ◽  
pp. 3021-3028 ◽  
Author(s):  
T.C. Hoffman ◽  
G.E. Walsberg
Keyword(s):  
Skin Surface ◽  
The Body ◽  
Evaporative Heat Loss ◽  
Evaporative Water ◽  
Zenaida Macroura ◽  
Ambient Temperatures ◽  
Rapid Adjustment ◽  
Mourning Doves ◽  
A Minor ◽  
Cutaneous Evaporation

We tested the hypothesis that birds can rapidly change the conductance of water vapor at the skin surface in response to a changing need for evaporative heat loss. Mourning doves (Zenaida macroura) were placed in a two-compartment chamber separating the head from the rest of the body. The rate of cutaneous evaporation was measured in response to dry ventilatory inflow at three ambient temperatures and in response to vapor-saturated ventilatory inflow at two ambient temperatures. At 35 degrees C, cutaneous evaporation increased by 72 % when evaporative water loss from the mouth was prevented, but no increase was observed at 45 degrees C. For both dry and vapor-saturated treatments, cutaneous evaporation increased significantly with increased ambient temperature. Changes in skin temperature made only a minor contribution to any observed increase in cutaneous evaporation. This indicates that Z. macroura can effect rapid adjustment of evaporative conductance at the skin in response to acute change in thermoregulatory demand.

Evaporative water loss in domestic fowls and its partition in relation to ambient temperature

1976 ◽  
Vol 87 (3) ◽  
pp. 527-532 ◽  
Author(s):  
S. A. Richards
Keyword(s):  
Ambient Temperature ◽  
Water Loss ◽  
Absolute Humidity ◽  
Evaporative Water Loss ◽  
Linear Functions ◽  
Whole Body ◽  
Water Vapour Pressure ◽  
Evaporative Water ◽  
Open Flow ◽  
Low Levels

SummaryThe rate of evaporative water loss has been studied in domestic fowls in the ambient temperature range from 0 to 40°C.Results for whole-body evaporation were similar when obtained by the open-flow and direct-weighing methods. At low levels of absolute humidity the rate increased by 0·03 mg/(g.h.°C) from 0 to 22 °C and by 0·17 mg/(g.h.°C) from 23 to 40 °C. Wholebody evaporation decreased with rising ambient water vapour pressure by 0·7 mg/(g.h.kPa).Cutaneous water loss was greater than respiratory water loss below 21 °C; it accounted for 78% of whole-body evaporation at 0 °C, falling to 25% at 40 °C.The rates of respiratory and whole-body evaporation could both be expressed as linear functions of respiratory frequency.

Effect of ambient temperature on development of prostaglandin E1 hyperthermia in the rhesus monkey

1978 ◽  
Vol 44 (5) ◽  
pp. 751-758 ◽  
Author(s):  
C. C. Barney ◽  
R. S. Elizondo
Keyword(s):  
Rhesus Monkey ◽  
Metabolic Rate ◽  
Rhesus Monkeys ◽  
Prostaglandin E1 ◽  
Co2 Production ◽  
Evaporative Heat Loss ◽  
Water Losses ◽  
Evaporative Water ◽  
Ambient Temperatures ◽  
Skin Temperatures

Prostaglandin E1 (PGE1) hyperthermia (fever) was studied at ambient temperatures (Ta) of 18, 27, and 35 degrees C in four male unanesthetized rhesus monkeys (Macaca mulatta) implanted with four guide tubes and one reentrant tube within the preoptic anterior hypothalamus (PO/AH). Rectal, hypothalamic, and mean weighted skin temperatures, O2 consumption, CO2 production, and respiratory and total evaporative water losses were measured continuously before and during PGE1 fever at each Ta. The febrile reponse to PO/AH PGE1 injection was dose responsive and was less at a Ta of 35 degrees C than at the other Ta's. At a Ta of 18 degrees C, fever was brought about primarily by an increase in metabolic rate. At a Ta of 27 degrees C, fever was produced by an increase in metabolic rate and by skin vasoconstriction. At a Ta of 35 degrees C, fever was the result of an increase in metabolic rate and a decrease in sweating evaporative heat loss. At each Ta some generalized skin vasconstriction also occurred. During the plateau phase of the fever, the measured heat losses and gains returned to near control levels. The data indicate that the rhesus monkey shows specific thermoregulatory responses to PO/AH PGE1 injection and would be a good model for the study of thermoregulation during fever in higher primates.

scholarly journals Thermoregulation in desert birds: scaling and phylogenetic variation in heat tolerance and evaporative cooling

2021 ◽  
Vol 224 (Suppl 1) ◽  
pp. jeb229211
Author(s):  
Andrew E. McKechnie ◽  
Alexander R. Gerson ◽  
Blair O. Wolf
Keyword(s):  
Heat Tolerance ◽  
Heat Dissipation ◽  
Arid Zone ◽  
Resting Metabolic Rate ◽  
Heat Exposure ◽  
Published Data ◽  
Evaporative Heat Loss ◽  
Evaporative Water ◽  
Data Set ◽  
The Difference

ABSTRACTEvaporative heat dissipation is a key aspect of avian thermoregulation in hot environments. We quantified variation in avian thermoregulatory performance at high air temperatures (Ta) using published data on body temperature (Tb), evaporative water loss (EWL) and resting metabolic rate (RMR) measured under standardized conditions of very low humidity in 56 arid-zone species. Maximum Tb during acute heat exposure varied from 42.5±1.3°C in caprimulgids to 44.5±0.5°C in passerines. Among passerines, both maximum Tb and the difference between maximum and normothermic Tb decreased significantly with body mass (Mb). Scaling exponents for minimum thermoneutral EWL and maximum EWL were 0.825 and 0.801, respectively, even though evaporative scope (ratio of maximum to minimum EWL) varied widely among species. Upper critical limits of thermoneutrality (Tuc) varied by >20°C and maximum RMR during acute heat exposure scaled to Mb0.75 in both the overall data set and among passerines. The slope of RMR at Ta>Tuc increased significantly with Mb but was substantially higher among passerines, which rely on panting, compared with columbids, in which cutaneous evaporation predominates. Our analysis supports recent arguments that interspecific within-taxon variation in heat tolerance is functionally linked to evaporative scope and maximum ratios of evaporative heat loss (EHL) to metabolic heat production (MHP). We provide predictive equations for most variables related to avian heat tolerance. Metabolic costs of heat dissipation pathways, rather than capacity to increase EWL above baseline levels, appear to represent the major constraint on the upper limits of avian heat tolerance.

Thermoregulation, Oxygen-Consumption and Water Turnover in Stubble Quail, Coturnix-Pectoralis, and King Quail, Coturnix-Chinensis

1986 ◽  
Vol 34 (1) ◽  
pp. 25 ◽  
Author(s):  
JR Roberts ◽  
RV Baudinette
Keyword(s):  
Oxygen Consumption ◽  
Body Temperature ◽  
Ambient Temperature ◽  
Water Loss ◽  
Evaporative Water Loss ◽  
Arid Areas ◽  
Water Turnover ◽  
Evaporative Water ◽  
Ambient Temperatures ◽  
Regulate Body Temperature

Stubble quail occur in more arid areas of Australia than king quail; however, the rates of metabolism and the ability to regulate body temperature in response to varying ambient temperature are similar in both birds, and resemble those of other quail species. At high ambient temperatures, rates of heat loss mediated by evaporative water loss are lower than those previously reported for more xerophilic species. Overall rates of water turnover and evaporative water loss at lower ambient temperatures are at the lower end of the range predicted for birds.

The effects of temperature and relative humidity on the thermoregulatory responses of grouped and isolated neonate chicks

1976 ◽  
Vol 86 (1) ◽  
pp. 35-43 ◽  
Author(s):  
B. H. Misson
Keyword(s):  
Body Size ◽  
Relative Humidity ◽  
Rectal Temperature ◽  
Heat Production ◽  
Water Loss ◽  
Evaporative Heat Loss ◽  
Evaporative Water ◽  
Ambient Temperatures ◽  
Metabolic Heat ◽  
Effects Of Temperature

SUMMARYMeasurements of O2 consumption (Vo2), CO2 production (VCO2) evaporative water loss and rectal temperature (Tr) have been made and metabolic heat production (H), evaporative heat loss (—E) and respiratory quotient (RQ) calculated with individual and groups of 1-day-old chicks at constant ambient temperatures (To) in the range 20—43 °C and 80 or 20% relative humidity (R.H.).Minimal metabolism (10·7 kJ/kgJ/h) occurred at 35 °C.One-day-old chicks act as heterotherms outside the zone of minimal metabolism since neither H nor —E are sufficiently developed mechanisms to maintain homeothermy.Huddling allows chicks to maintain a higher TT at a lower H per unit metabolic body size.Reducing E.H. from 80 to 20% raised the upper temperature survival limit (UTSL) from 41·5 to 43 °C.Panting was initiated when Ta = 38 °C and Tr was between 39·5 and 39·9 °C.

593 Ambient Room Temperature in a Burn Intensive Care Unit - A Quality Improvement Project

2020 ◽  
Vol 41 (Supplement_1) ◽  
pp. S139-S140 ◽  
Author(s):  
Alan D Rogers ◽  
Robert Cartotto ◽  
George Ho
Keyword(s):  
Ambient Temperature ◽  
Room Temperature ◽  
Patient Room ◽  
Evaporative Water ◽  
Improvement Project ◽  
Ambient Temperatures ◽  
Ambient Room Temperature ◽  
Medical Order ◽  
Mobile Smartphone ◽  
Observation Period

Abstract Introduction In patients with burns > 20% TBSA, hypermetabolism, evaporative water loss, infection risk and discomfort are all amplified by exposure to cold ambient temperatures. Post-operative patient hypothermia is also detrimental. It is essential to not only maintain a warm patient room temperature, but also to be able to rapidly increase room temperature in the burn ICU. The purpose of this study was to measure typical patient room temperatures in a burn ICU at an adult regional ABA-verified burn center, and to evaluate our ability to intervene and raise room temperature. Methods The ambient temperatures of nine patient rooms were recorded from 14 June to 14 August, 2019. Temperature was measured every minute by a wall-mounted smart sensor placed at standardized positions away from windows or electronic equipment. All devices were tested prior to use, with temperature and humidity accurate and standardized to < 0.2oC and 2% respectively at 18-25oC. Data was transmitted to a mobile smartphone. On 15 August 2019 all room temperatures were manually adjusted to ‘maximum’. This was identified as a sound change initiative, and replicated a potential medical order to increase the ambient temperature should a hypothermic patient be imminently returning from the operating room or resuscitation area after admission. Results Over the baseline observation period (Figure 1) the mean ± SD room temperature was 23.3 ± 1oC. Temperatures deviated below a mean of 22oC during 166 hours per room (11.5%, range 3–362). Following the intervention on 15 August (Figure 2), ambient temperature increased minimally in 6/9 rooms and only by 2–3°C in two rooms (mean rise of 1.03oC; range -0.88oC to 3.26oC). Conclusions The burn ICU rooms are relatively cold and our ability to raise ambient temperature quickly is limited. Further QI change ideas include: 1) a facility engineering assessment 2) set alarms on the smart sensors to alert staff when room temperature falls below a designated threshold. Applicability of Research to Practice This project has identified an important future QI initiative to maintain warm ambient patient room temperatures in the burn ICU.

Mechanisms of temperature regulation in heat-acclimated hamsters

1976 ◽  
Vol 231 (3) ◽  
pp. 707-712 ◽  
Author(s):  
SB Jones ◽  
XJ Musacchia ◽  
GE Tempel
Keyword(s):  
Blood Flow ◽  
Temperature Regulation ◽  
Heat Dissipation ◽  
Regional Distribution ◽  
Heat Exposure ◽  
Flow Distribution ◽  
Peripheral Blood Flow ◽  
Radiative Heat Loss ◽  
Evaporative Water ◽  
Ambient Temperatures

Mechanisms of temperature regulation were assessed by measurements of oxygen consumption (VO2), body temperature (Rre = rectal, Tsk = skin), evaporative water loss (EWL), regional distribution of blood flow, and blood volume. Hamsters (Mesocricetus auratus) were acclimated to ambient temperatures of 34 or 22 degrees C. VO2 of 34 degrees C-exposed animals was reduced to 50% of that of controls at 22 degrees C, whereas EWL with heat exposure was almost double that of controls. Heat-acclimated animals had a slightly elevated Tre in comparison to 22 degrees C-acclimated animals, whereas there was a marked elevation in Tsk with heat exposure, in contrast to control animals at 22 degrees C. Blood flow distribution measurements indicated that with 34 degrees C exposure there was a decreased flow in liver, kidney, and intestine, whereas there was an increase to the carcass. Red cell and plasma volumes in heat-acclimated hamsters were decreased belwo the values of the 22 degrees C controls. Heat acclimation of the fhamster appears to involve reduced VO2 and increased WEL. Convective and radiative heat loss appear to be maintained by increased Tsk with heat exposure. Nonevaporative heat dissipation mechanisms are of primary importance in thermoregulation of the heat-acclimated hamster, and it is suggested that this is mediated by increased peripheral blood flow with reduced flow to the viscera.

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