Cutaneous heat loss shortly after burn injury in children

1992 ◽  
Vol 83 (1) ◽  
pp. 117-126 ◽  
Author(s):  
Charmaine Childs ◽  
H. B. Stoner ◽  
R. A. Little
Keyword(s):  
Body Temperature ◽  
Heat Loss ◽  
Burn Injury ◽  
Heat Content ◽  
Total Heat ◽  
Evaporative Heat Loss ◽  
Healthy Children ◽  
Total Heat Loss ◽  
Control Subjects ◽  
Injured Patients

1. Total heat loss and its components have been studied in cool (20°C) and warm (30°C) environments in 30 healthy children and 21 children who had been burned (10-17% body surface area) 0.5-29 h previously. 2. In healthy naked children at 20°C, the partition of total heat loss was: radiation, 64%; convection, 32%; evaporation, 4%. On transfer to the warm, total heat loss was reduced by approximately 50%, with disproportionate reductions in the contributions from radiation and convection being offset, to some extent, by an increase in evaporative heat loss. 3. In patients during the first 5.5 h after injury, the magnitude and pattern of heat loss at 20°C and 30°C were similar to those in control subjects and were unaffected by bandaging. 4. Ten to twenty-nine hours after injury, when the patients were bandaged and body temperature and heat content were significantly higher than in control subjects, radiant and convective heat losses were increased, but as evaporative heat loss tended to be reduced; total heat loss in the warm was unchanged. However, at this time at 20°C, total heat loss was reduced compared with healthy children at the same ambient temperature. 5. The findings of unchanged or reduced total heat loss and reduced evaporative heat loss in injured patients are interpreted as inappropriate responses to an increased body temperature and heat content in children after burn injury.

Influence of air humidity on the partition of heat exchanges of cattle

1972 ◽  
Vol 78 (2) ◽  
pp. 303-307 ◽  
Author(s):  
J. A. McLean ◽  
D. T. Calvert
Keyword(s):  
Body Temperature ◽  
Heat Loss ◽  
Air Temperature ◽  
Heat Production ◽  
Total Heat ◽  
Evaporative Heat Loss ◽  
Air Humidity ◽  
Total Heat Loss ◽  
Air Temperatures ◽  
Heat Exchanges

SUMMARYThe balance between heat production and heat loss and the partition of heat exchanges of cattle in relation to air humidity has been studied at two different air temperatures using a direct (gradient-layer) calorimeter.Increasing humidity at 35 °C air temperature caused no significant change in heat production or in the level of total heat loss finally attained, but body temperature and respiratory activity were both increased.Increasing humidity at 15 °C air temperature caused a small reduction in heat loss by evaporation but had no effect on sensible heat loss, body temperature or respiratory frequency.Heat loss by evaporation amounted to 18% of the total heat loss at 15 °C and to 84% at 35 °C.Heat loss by respiratory evaporation amounted to 54% of the total evaporative heat loss at 15 °C and to 38% at 35 °C.

scholarly journals Protection against Cold in Prehospital Care: Evaporative Heat Loss Reduction by Wet Clothing Removal or the Addition of a Vapor Barrier—A Thermal Manikin Study

2012 ◽  
Vol 27 (1) ◽  
pp. 53-58 ◽  
Author(s):  
Otto Henriksson ◽  
Peter Lundgren ◽  
Kalev Kuklane ◽  
Ingvar Holmér ◽  
Peter Naredi ◽  
...  
Keyword(s):  
Heat Loss ◽  
Prehospital Care ◽  
Ambient Air ◽  
Total Heat ◽  
Thermal Manikin ◽  
Evaporative Heat Loss ◽  
Loss Reduction ◽  
Total Heat Loss ◽  
Cold Environments ◽  
Wet Heat

AbstractIntroduction: In the prehospital care of a cold and wet person, early application of adequate insulation is of utmost importance to reduce cold stress, limit body core cooling, and prevent deterioration of the patient’s condition. Most prehospital guidelines on protection against cold recommend the removal of wet clothing prior to insulation, and some also recommend the use of a waterproof vapor barrier to reduce evaporative heat loss. However, there is little scientific evidence of the effectiveness of these measures.Objective: Using a thermal manikin with wet clothing, this study was conducted to determine the effect of wet clothing removal or the addition of a vapor barrier on thermal insulation and evaporative heat loss using different amounts of insulation in both warm and cold ambient conditions.Methods: A thermal manikin dressed in wet clothing was set up in accordance with the European Standard for assessing requirements of sleeping bags, modified for wet heat loss determination, and the climatic chamber was set to -15 degrees Celsius (°C) for cold conditions and +10°C for warm conditions. Three different insulation ensembles, one, two or seven woollen blankets, were chosen to provide different levels of insulation. Five different test conditions were evaluated for all three levels of insulation ensembles: (1) dry underwear; (2) dry underwear with a vapor barrier; (3) wet underwear; (4) wet underwear with a vapor barrier; and (5) no underwear. Dry and wet heat loss and thermal resistance were determined from continuous monitoring of ambient air temperature, manikin surface temperature, heat flux and evaporative mass loss rate.Results: Independent of insulation thickness or ambient temperature, the removal of wet clothing or the addition of a vapor barrier resulted in a reduction in total heat loss of 19-42%. The absolute heat loss reduction was greater, however, and thus clinically more important in cold environments when little insulation is available. A similar reduction in total heat loss was also achieved by increasing the insulation from one to two blankets or from two to seven blankets.Conclusion: Wet clothing removal or the addition of a vapor barrier effectively reduced evaporative heat loss and might thus be of great importance in prehospital rescue scenarios in cold environments with limited insulation available, such as in mass-casualty situations or during protracted evacuations in harsh conditions.

Comparison of non-evaporative heat transfer in different cattle breeds

1985 ◽  
Vol 36 (3) ◽  
pp. 497 ◽  
Author(s):  
VA Finch
Keyword(s):  
Heat Loss ◽  
Air Temperature ◽  
Heat Storage ◽  
Absolute Humidity ◽  
Total Heat ◽  
Evaporative Heat Loss ◽  
Excessive Sweating ◽  
Total Heat Loss ◽  
Evaporative Water ◽  
Rate Of Increase

Tissue conductance and non-evaporative heat loss from the skin were determined from measurements of body temperature, evaporative water loss, metabolic rate and heat storage in six steers in each of three breeds, Brahman (B), Brahman x Hereford-Shorthorn (BX) and Shorthorn (S). A group of six steers, two from each breed, remained in a climate room set at 25�C overnight, and during the following day all were exposed for 1 h to sequential increases in air temperature (28, 32, 37, 41, 43, 45�C). Each steer was measured at 25�C and after a 30-min exposure to each temperature. Tissue conductance increased with air temperature (Ta), reaching maximum values at 41�C, the rate of increase (W m-2 'C-I per degree rise in Ta) being for B 3.95, for BX 2.33 and for S 2,09. Between 41 and 45�C, tissue conductance remained constant in B but declined in BX and S with a concurrent increase in heat storage. Mean tissue conductance (W m-2 �C-1) of B was 63.5; BX, 56.1; and S, 47.8, values that were significantly different (P < 0.01). Expressed in terms of metabolic weight, the breed means of tissue conductance (litres O2 h-1 W-0.75 �C-1) were also significantly different: B, 0.56; BX, 0.43; and S, 0.33 (P < 0.005), with the relative differences similar to those calculated per unit area. Breed differences in tissue conductance may be related to variations in ability to redirect blood from the core to the skin. Non-evaporative heat loss comprised 55-65% of the total heat loss from the skin in all breeds at Ta of 25�C. The remaining heat was lost through sweating. As Ta increased and approached skin temperature, non-evaporative heat loss decreased but in B and BX remained 25% of the total heat loss from the skin. S steers, in contrast, sustained little non-evaporative heat loss as Ta increased because sweating rates increased 50% more than that required to dissipate the heat at the skin. The increase in absolute humidity of the chamber was associated with the excessive sweating in this breed.

Human heat balance during postexercise recovery: separating metabolic and nonthermal effects

2008 ◽  
Vol 294 (5) ◽  
pp. R1586-R1592 ◽  
Author(s):  
Ollie Jay ◽  
Daniel Gagnon ◽  
Michel B. DuCharme ◽  
Paul Webb ◽  
Francis D. Reardon ◽  
...  
Keyword(s):  
Heat Loss ◽  
Core Temperature ◽  
Heat Production ◽  
Heat Balance ◽  
Heat Content ◽  
Total Heat ◽  
Whole Body ◽  
Active Recovery ◽  
Total Heat Loss ◽  
Body Heat

Previous studies report greater postexercise heat loss responses during active recovery relative to inactive recovery despite similar core temperatures between conditions. Differences have been ascribed to nonthermal factors influencing heat loss response control since elevations in metabolism during active recovery are assumed to be insufficient to change core temperature and modify heat loss responses. However, from a heat balance perspective, different rates of total heat loss with corresponding rates of metabolism are possible at any core temperature. Seven male volunteers cycled at 75% of V̇o2peak in the Snellen whole body air calorimeter regulated at 25.0°C, 30% relative humidity (RH), for 15 min followed by 30 min of active (AR) or inactive (IR) recovery. Relative to IR, a greater rate of metabolic heat production (Ṁ − Ẇ) during AR was paralleled by a greater rate of total heat loss (ḢL) and a greater local sweat rate, despite similar esophageal temperatures between conditions. At end-recovery, rate of body heat storage, that is, [(Ṁ − Ẇ) − ḢL] approached zero similarly in both conditions, with Ṁ − Ẇ and ḢL elevated during AR by 91 ± 26 W and 93 ± 25 W, respectively. Despite a higher Ṁ − Ẇ during AR, change in body heat content from calorimetry was similar between conditions due to a slower relative decrease in ḢL during AR, suggesting an influence of nonthermal factors. In conclusion, different levels of heat loss are possible at similar core temperatures during recovery modes of different metabolic rates. Evidence for nonthermal influences upon heat loss responses must therefore be sought after accounting for differences in heat production.

Heat losses from young pigs at three environmental temperatures, measured in a direct calorimeter

1968 ◽  
Vol 10 (2) ◽  
pp. 135-147 ◽  
Author(s):  
C. W. Holmes
Keyword(s):  
Heat Loss ◽  
Coefficient Of Variation ◽  
Thermal Conductance ◽  
Heat Losses ◽  
Total Heat ◽  
Whole Body ◽  
Evaporative Heat Loss ◽  
Experimental Conditions ◽  
Total Heat Loss ◽  
Mean Values

1. A direct calorimeter is described, capable of partitioning the total heat loss from individual pigs into its evaporative and non-evaporative components; tests revealed that the instrument measured non-evaporative heat loss with a coefficient of variation of 3%, and evaporative heat loss with a coefficient of variation of 5·0% at 10° and 20°C, and 5·6% at 30°C.2. Experiments were carried out to measure the differences between heat losses at 20° and 9°C, or at 20° and 30°C, for pigs weighing approximately 26 kg and 64 kg; each measurement lasted 20 minutes and was made after an equilibration period of 3–4 hr.3. Heat loss was proportional to body weight raised to the power of 0·6, under the present experimental conditions, over the range 26–64 kg at 20°C.4. Total heat loss at 9°C was significantly greater than at 20°C for pigs of both sizes; total heat loss at 30°C was smaller than at 20°C for pigs of both sizes, the decrease being significant for the heavier pigs only. Nonevaporative heat loss increased significantly with decrease in temperature. Evaporative heat loss at 30°C was significantly greater than at 20°C. The increases in total and non-evaporative heat losses at 9°C when compared with 20°C, were significantly greater for the lighter pigs than for the heavier pigs. The small decrease in total heat loss at 30°C, compared with 20°C, may have been due to non-attainment of thermal equilibrium at 30°C.5. Values for whole body thermal conductance were calculated from the measurements of non-evaporative heat loss, and these indicated that a change in tissue conductance took place between 20° and 30°C; the mean values at 9°C were 3·78 and 3·15 kcal/°C.m2.hr for the lighter and heavier pigs respectively.6. Evaporative heat loss at 20°C amounted to 280 and 330 kcal/m2. 24. hr for the lighter and heavier pigs respectively. This component of heat loss amounted to 8% and 13% of the total heat loss at 9° and 20°C respectively for all pigs; the corresponding values at 30°C were 32% and 25% for the lighter and heavier pigs respectively. The increased evaporative loss at 30°C was accompanied by an increase in respiratory rate.7. These results agreed well with the results of previous work with groups of pigs, for heat loss at 20°C. Comparisons with that work indicate that the increase in heat loss at 9°C, when compared with 20°C, was greater for individual pigs than for groups of pigs, of both sizes.

Effects of environmental temperature and humidity on evaporative heat loss through firefighter suit materials made with semi-permeable and microporous moisture barriers

2021 ◽  
pp. 004051752110265
Author(s):  
Huipu Gao ◽  
Anthoney Shawn Deaton ◽  
Xiaomeng Fang ◽  
Kyle Watson ◽  
Emiel A DenHartog ◽  
...  
Keyword(s):  
Heat Loss ◽  
Environmental Temperature ◽  
Moisture Absorption ◽  
Evaporative Heat Loss ◽  
Total Heat Loss ◽  
Evaporative Resistance ◽  
Environmental Testing ◽  
Permeable Barrier ◽  
Moisture Condensation ◽  
Moisture Barriers

The goal of this research was to understand how firefighter protective suits perform in different operational environments. This study used a sweating guarded hotplate to examine the effect of environmental temperature (20–45°C) and relative humidity (25–85% RH) on evaporative heat loss through firefighter turnout materials. Four firefighter turnout composites containing three different bi-component (semi-permeable) and one microporous moisture barriers were selected. The results showed that the evaporative resistance of microporous moisture barrier systems was independent of environmental testing conditions. However, absorbed moisture strongly affected evaporative heat loss through semi-permeable moisture barriers coated with a layer of nonporous hydrophilic polymer. Moisture absorption in mild environment (20–25°C) tests, or when testing at high humidity (>85% RH), significantly increased water vapor transmission in semi-permeable turnout systems. It was also found that environmental conditions used in the total heat loss (THL) test (25°C and 65% RH) produced moisture condensation in bi-component barrier systems, making them appear more breathable than could be expected when worn in hotter environments. Regression models successfully qualified the relationships between moisture uptake levels in semi-permeable barrier systems and evaporative resistance and THL. These findings reveal the limitations in relying on THL, the heat strain index currently called for by the NFPA 1971 Standard for Structural Firefighter personal protective equipment, and supports the need to measure turnout evaporative resistance at 35°C (Ret), in addition to THL at 25°C.

Respiratory water and heat loss of the black duck during flight at different ambient temperatures

1971 ◽  
Vol 49 (5) ◽  
pp. 767-774 ◽  
Author(s):  
M. Berger ◽  
J. S. Hart ◽  
O. Z. Roy
Keyword(s):  
Heat Loss ◽  
Water Loss ◽  
Pulmonary Ventilation ◽  
Evaporative Heat Loss ◽  
Total Heat Loss ◽  
Ambient Temperatures ◽  
Black Duck ◽  
Respiratory Heat Loss ◽  
Metabolic Water ◽  
Expired Air

Pulmonary ventilation and temperature of expired air and of the respiratory passages has been measured by telemetry during flight in the black duck (Anas rubripes) and the respiratory water and heat loss has been calculated.During flight, temperature of expired air was higher than at rest and decreased with decreasing ambient temperatures. Accordingly, respiratory water loss as well as evaporative heat loss decreased at low ambient temperatures, whereas heat loss by warming of the inspired air increased. The data indicated respiratory water loss exceeded metabolic water production except at very low ambient temperatures. In the range between −16 °C to +19 °C, the total respiratory heat loss was fairly constant and amounted to 19% of the heat production. Evidence for the independence of total heat loss and production from changes in ambient temperature during flight is discussed.

Cavity receiver thermal performance analysis based on total heat loss coefficient and efficiency factor

2018 ◽  
Vol 42 (6) ◽  
pp. 2284-2289 ◽  
Author(s):  
Qiangqiang Zhang ◽  
Xin Li ◽  
Zhifeng Wang ◽  
Zhi Li ◽  
Hong Liu ◽  
...  
Keyword(s):  
Performance Analysis ◽  
Heat Loss ◽  
Thermal Performance ◽  
Efficiency Factor ◽  
Loss Coefficient ◽  
Total Heat ◽  
Total Heat Loss
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