Dry Heat Loss Research Articles

Dry heat loss in incubator: comparison of two premature newborn sized manikins.

Keeping premature newborns warm is crucial for their survival. Their ability to prevent excessive heat loss to the environment and to control their body temperature is limited. The risk of hypothermia is particularly important for low-birth-weight newborns with a large body surface area in relation to their mass of heat-producing tissues. The present study was performed to assess the body heat loss difference between small and large body-size premature newborns using two anthropomorphic thermal manikins of premature newborns of 900 g and 1,800 g (respective body surface areas of 0.086 and 0.150 m2). The dry heat loss from the six body segments of the small manikin (S) was measured and compared with that of the large manikin (L). The two manikins were exposed to five different environmental temperatures ranging between 29 and 35 degrees C in a single-walled, air-heated closed incubator. The magnitudes of heat loss decreased significantly by 20.4% between the two manikins [small manikin 110.1 (44.3) W/m2 vs large manikin 87.6 (25.8) W/m2, mean values with one standard deviation]. The results obtained from the comparison of the heat loss measures from the two manikins confirm the fact that the heat loss increases with an increase in the ratio of the body surface area to body mass. The thermal manikin appears to provide an accurate method for the assessment of thermal conditions in neonatal care.

Metabolic heat production, heat loss and the circadian rhythm of body temperature in the rat.

Metabolic heat production (calculated from oxygen consumption), dry heat loss (measured in a calorimeter) and body temperature (measured by telemetry) were recorded simultaneously at 6 min intervals over five consecutive days in rats maintained in constant darkness. Robust circadian rhythmicity (confirmed by chi square periodogram analysis) was observed in all three variables. The rhythm of heat production was phase-advanced by about half an hour in relation to the body temperature rhythm, whereas the rhythm of heat loss was phase-delayed by about half an hour. The balance of heat production and heat loss exhibited a daily oscillation 180 deg out of phase with the oscillation in body temperature. Computations indicated that the amount of heat associated with the generation of the body temperature rhythm (1.6 kJ) corresponds to less than 1 % of the total daily energy budget (172 kJ) in this species. Because of the small magnitude of the fraction of heat balance associated with the body temperature rhythm, it is likely that the daily oscillation in heat balance has a very slow effect on body temperature, thus accounting for the 180 deg phase difference between the rhythms of heat balance and body temperature.

Clothing Thermal Insulation During Sweating

Heat transfer through clothing is an important topic related to thermal comfort in environmental engineering and functional clothing design. The total heat transmitted through clothing is commonly considered as the sum of the dry heat transfer and the evaporative heat transfer. Clothing thermal insulation measured in a nonperspiring con dition, e.g., on a dry thermal manikin, is frequently used to calculate the dry heat transfer when the body is perspiring or even sweating heavily. The effect of perspiration on clothing thermal insulation with respect to dry heat transfer is not well understood, although it is widely speculated that perspiration reduces thermal insulation by wetting clothing assemblies. In this investigation, clothing thermal insulation with very low perspiration and very heavy perspiration is measured using a novel perspiring fabric thermal manikin. Clothing thermal insulation decreases during perspiration, and the amount of reduction varies from 2 to 8%, as related to water accumulation within clothing ensembles. This finding suggests the "after chill" effect of wearers after heavy exercise may not only be caused by heat absorption due to the desorption and evaporation of water within clothing, but also to reduced clothing thermal insulation. Also, for clothing that can absorb a large amount of moisture during sweating, clothing thermal insulation measured on dry manikins may need to be corrected when used for calculating dry heat loss (sometimes used for calculating moisture vapor resistance) on a sweating manikin and predicting thermal comfort during sweating.

Thermal Properties of Towelling Fabrics

To obtain guideline for developing new types of clothing used the towelling fabrics, we clarified the heat and moisture transfer properties of the towelling fabrics. The results obtained were as follows:1. Because the towelling fabrics were thick, the dry heat loss Hd of the towelling fabrics was lower than that of cotton fabrics on the market. However, the measured value Hd of the towelling fabrics was higher than that predicted from their thickness and apparent density.2. The thermal conductance Cd of towelling fabrics which were made of cotton fiber was higher than other fibers (except for cotton) in dry or wet conditions. From this fact, it was suggested that using fabrics which were made of other fibers (except for cotton) for clothing for winter was valid, because their Cd was lower than that of cotton.3. The maximum value of heat flux qmax of the towelling fabrics was about half of that of cotton fabrics on the market. Furthermore, it was found that qmax conformed to uses could be controlled by patterning the pile.4. The thicker the fabric's thickness was, the lower the latent heat loss Hw became. And, it was suggested that the body temperature under the sweating with towelling clothing would not decrease rapidly, because the water absorption area in the ground layer was larger than those in the upper and lower pile layers. From these results, it was concluded that applying the towelling fabrics to clothing for infants or elderly persons was to be desirable.

Influence of head position on thermal stress in newborns: simulation using a thermal mannequin.

The influence of head position on thermal stress was assessed by using a heavily clothed thermal mannequin in three different body positions [supine, face straight up (FSU); supine, face to the side (FTS); prone, FTS] and with or without the head covered by a bonnet. The mannequin was exposed to air temperatures of 29, 32, 34, and 36 degrees C. When the head is uncovered, body or head position has no impact on heat loss. When the head is covered, dry heat loss from the mannequin as a whole (and that from the head in particular) is lower (-0.35 to -0.40 W) in the FTS position than in the FSU position as a result of decreased heat loss from the surface area of the face in contact with the mattress. In the FTS position and with the head covered, there was no difference in heat loss between the prone and supine positions. The results suggest that in heavily clothed newborns whose head is covered by a bonnet, thermal stress depends on the head position.

Head insulation and heat loss in naked and clothed newborns using a thermal mannequin.

In newborns, large amounts of heat are lost from the head, due to its high skin surface area. Insulating the head (for example, with a hat or bonnet) can be a simple and effective method of reducing dry heat loss. In the present study, we evaluated the safety aspects of insulating the head of low-birth-weight naked or clothed newborns by using a heated mannequin that simulates a low-birth-weight newborn. Experimental conditions (comprising a nude and three clothed setups) were performed in a closed incubator at three different air temperatures (29 degrees C, 32 degrees C, and 34 degrees C) and with and without the head being covered with a bonnet in each case, i.e., 24 experimental conditions in all. The study shows that added clothing elements and insulating the head decreases the total heat loss of the mannequin as a whole. As regards the dry heat exchange from the head, wearing a bonnet decreases the local heat loss by an average of 18.9% in all clothed and thermal conditions. This phenomenon could be at the origin of brain overheating in heavily dressed newborns, when unrestricted heat loss is limited to the face only. Our results suggest that--apart from accidental hypothermia-in order to achieve thermal equilibrium of the body, it is preferable to leave the head unprotected and to increase the level of clothing insulation over the rest of the body.

Thermoregulation in juvenile red kangaroos (Macropus rufus) after pouch exit: higher metabolism and evaporative water requirements.

The population dynamics of red kangaroos (Macropus rufus) in the Australian arid zone is tightly linked with environmental factors, which partly operate via the survival of juvenile animals. A crucial stage is the young-at-foot (YAF) stage when kangaroos permanently exit the pouch. We have examined the thermal biology of YAF red kangaroos during ages from permanent pouch exit until weaning. Over a wide range of environmental temperatures (ambient temperature [T(a)] -5 degrees to 45 degrees C), YAF red kangaroos had a mass-specific metabolism that was generally twice that of adults, considerably higher than would be expected for an adult marsupial of their body size. The total energy requirements of YAF red kangaroos were 60%-70% of those of adult females, which were three times their size. Over the same range in T(a), YAF red kangaroos also had total evaporative water losses equal to those of adult females. At the highest T(a) (45 degrees C), differences were noted in patterns of dry heat loss (dry conductance) between YAF red kangaroos and adult females, which may partially explain the relatively high levels of evaporative cooling by YAF. By weaning age, young kangaroos showed little change in their basal energy and water requirements (at T(a) 25 degrees C) but did show reduced mass-specific costs in terms of energy and water use at extremes of T(a) (-5 degrees and 45 degrees C, respectively). In their arid environment, typified by unpredictable rainfall and extremes of T(a), young red kangaroos may need to remain close to water points, which, in turn, may restrict their ability to find the high-quality forage needed to meet their high energy demands.

Assessment of dry heat exchanges in newborns: influence of body position and clothing in SIDS.

A dramatic decrease of sudden infant death syndrome (SIDS) has been noted following the issuance of recommendations to adopt the supine sleeping position for infants. It has been suggested that the increased risk could be related to heat stress associated with body position. In the present study, the dry heat losses of small-for-gestational-age newborns nude or clothed were assessed and compared to see whether there is a difference in the ability to lose heat between the prone and supine positions. An anthropomorphic thermal mannequin was exposed to six environmental temperatures, ranging between 25 and 37 degrees C, in a single-walled, air-heated incubator. The magnitudes of heat losses did not significantly differ between the two body positions for the nude (supine 103.46 +/- 29.67 vs. prone 85.78 +/- 34.91 W/m(2)) and clothed mannequin (supine 59.35 +/- 21.51 vs. prone 63.17 +/- 23.06 W/m(2)). With regard to dry heat exchanges recorded under steady-state conditions, the results show that there is no association between body position and body overheating.

A Study on the Development of an Infant-sized Movable Sweating Thermal Manikin

A movable sweating thermal manikin the size of a two-year-old infant was developed in this study. Heat was supplied through manganese wires of 0.3 mm diameter which were glued to the outside of the manikin. The manikin had 32 sweating pores drilled on its surface at the ratio of one per 110 cm2 of surface area. Water was supplied from a water bath through silicone tubes to each sweating pore with peristaltic pumps. The manikin was dressed in a tight-fitting cotton knit suit and a water-resistant/water vapor-permeable material to control body-surface wettedness. Joints such as shoulders, hips, and knees meant the manikin was able to be placed in a standing, sitting, or walking positions. The surface temperature of the sweating thermal manikin was maintained within 33±0.5°C for the duration of the experiment. Dry heat loss from the nude manikin was in good agreement with the value obtained by subtracting the evaporative heat loss from a 2-year-old Japanese infant’s metabolic rate at rest. The manikin’s sweat rate was able to be controlled at ten different sweating rates. The wettedness of the manikin changed from 0.49 when the water was supplied at 294 g/h•m2 to 0.83 when the water was supplied at 2184 g/h•m2. It was confirmed in the present study that the skin temperature and the wettedness of the newly developed manikin were controlled precisely and the heat exchange between the manikin and the environment simulated those of a two-year-old Japanese infant.

Fluid and electrolyte supplementation for exercise heat stress

During exercise in the heat, sweat output often exceeds water intake, resulting in a body water deficit (hypohydration) and electrolyte losses. Because daily water losses can be substantial, persons need to emphasize drinking during exercise as well as at meals. For persons consuming a normal diet, electrolyte supplementation is not warranted except perhaps during the first few days of heat exposure. Aerobic exercise is likely to be adversely affected by heat stress and hypohydration; the warmer the climate the greater the potential for performance decrements. Hypohydration increases heat storage and reduces a person's ability to tolerate heat strain. The increased heat storage is mediated by a lower sweating rate (evaporative heat loss) and reduced skin blood flow (dry heat loss) for a given core temperature. Heat-acclimated persons need to pay particular attention to fluid replacement because heat acclimation increases sweat losses, and hypohydration negates the thermoregulatory advantages conferred by acclimation. It has been suggested that hyperhydration (increased total body water) may reduce physiologic strain during exercise heat stress, but data supporting that notion are not robust. Research is recommended for 3 populations with fluid and electrolyte balance problems: older adults, cystic fibrosis patients, and persons with spinal cord injuries.

Thermoregulation by Kangaroos from Mesic and Arid Habitats: Influence of Temperature on Routes of Heat Loss in Eastern Grey Kangaroos (Macropus giganteus) and Red Kangaroos (Macropus rufus)

We examined thermoregulation in red kangaroos (Macropus rufus) from deserts and in eastern grey kangaroos (Macropus giganteus) from mesic forests/woodlands. Desert kangaroos have complex evaporative heat loss mechanisms, but the relative importance of these mechanisms is unclear. Little is known of the abilities of grey kangaroos. Our detailed study of these kangaroos' thermoregulatory responses at air temperatures (T(a)) from -5 degrees to 45 degrees C showed that, while some differences occur, their abilities are fundamentally similar. Both species show the basic marsupial characteristics of relatively low basal metabolism and body temperature (T(b)). Within the thermoneutral zone, T(b) was 36.3 degrees + or - 0.1 degrees C (X + or - SE) in both species, and except for a small rise at T(a) 45 degrees C, T(b) was stable over a wide range of T(a). Metabolic heat production was 25% higher in red kangaroos at T(a) -5 degrees C. At the highest T(a) (45 degrees C), both species relied on evaporative heat loss (EHL) to maintain T(b); both panting and licking were used. The eastern grey kangaroo utilised panting (76% of EHL) as the principal mode of EHL, and while this was so for red kangaroos, cutaneous evaporative heat loss (CEHL) was significant (40% of EHL). CEHL appeared to be mainly licking, as evidenced from surface temperatures. Both species utilised peripheral vascular adjustments to control heat flow, as indicated by changes in dry conductance (C(dry)). At lower temperatures, C(dry) was minimal, but it increased significantly at T(a) just below T(b) (33 degrees C); in these conditions, the C(dry) of red kangaroos was significantly higher than that of eastern grey kangaroos, indicating a greater reliance on dry heat loss. Under conditions where heat flows into the body from the environment (T(a) 45 degrees C), there was peripheral vasoconstriction to reduce this inflow; C(dry) decreased significantly from the values seen at 33 degrees C in both kangaroos. The results indicated that, while both species have excellent thermoregulatory abilities, the desert red kangaroos may cope better with more extreme temperatures, given that they respond to T(a) 45 degrees C with lower respiratory evaporation than do the eastern grey kangaroos.

Thermal responses to cold wind of thermoneutral and cooled subjects

The effects of initial thermal state on thermoregulatory responses to cold (-10 degrees C) in a 0.2 (still air), 1.0, and 5.0 m. S(-1) wind speed were studied. Eight young male subjects were first preconditioned in thermoneutral (+20 degrees C, TN) or cool (-5 degrees C, CO) environment for 60 min. After preconditioning the subjects were exposed to wind at -10 degrees C in a standing position, facing the wind, for 30 min. Precooling decreased mean skin temperature (Tsk) by 4.0 (SEM 0.1) degrees C (P < 0.001) and increased heat flux by 57 (SEM 2) W x m(-2) (P < 0.001) in comparison to TN. Cooling rate of Tsk was faster (P < 0.001) in TN than in CO at every wind speed. Even so, Tsk ended up at a lower level in CO (P < 0.001-0.01) than in TN at every wind speed. Local skin temperatures of hand, finger, foot and toe were significantly lower in CO than in TN at the end of all exposures to wind. Heat flux from the skin was 8% higher (NS) in TN at 5.0 m x s(-1) wind speed in comparison to CO. A 5.0 m x s(-1) wind speed increased oxygen consumption significantly (P < 0.001) in both CO and TN in comparison to still air. At 5.0 m x s(-1) wind speed the general thermal sensation was the same (cold) in both TN and CO, despite the higher Tsk in TN. In conclusion, Tsk decreased more rapidly in TN, probably due to rapid skin vasoconstriction and redistribution of circulation to the central body. Probably for the same reason, dry heat loss from the skin was at nearly the same level in both TN and CO. Although the initial thermal state did not affect the amount of heat loss, it significantly affected the peripheral temperatures and thermal sensations and should therefore be taken into consideration in the prediction of thermophysiological responses to wind.

Hydration effects on temperature regulation.

During exercise in the heat, sweat output often exceeds water intake which results in a body water deficit (hypohydration) and electrolyte losses. Daily water losses can be substantial and persons need to emphasize drinking during exercise as well as at mealtime. Aerobic exercise tasks are likely to be adversely affected by heat stress and hypohydration; and the warmer the climate the greater the potential for performance decrements. Hypohydration increases heat storage and reduces one's ability to tolerate heat strain. The increased heat storage is mediated by reduced sweating rate (evaporative heat loss) and reduced skin blood flow (dry heat loss) for a given core temperature. Hyperhydration (increased total body water) has been suggested to reduce physiologic strain during exercise heat stress, however, data supporting that notion are not robust.

Direct and indirect calorimetry of thermogenic flowers of the sacred lotus, Nelumbo nucifera

Direct and indirect calorimetric experiments were performed on flowers of the sacred lotus, Nelumbo nucifera, and compared with temperature measurements. To this end, a simple, light and cheap heat-flow calorimeter of the twin type was developed to monitor the heat output of lotus flowers in an outdoor pond. Each side of the calorimeter consisted of a water jacket as a heat sink surrounding a 730 ml concentric can as a calorimetric vessel. The vessel and heat sink were thermally connected via a Peltier element but otherwise thermally isolated. Both water jackets were housed in a styrofoam box and connected in parallel to a thermostated water bath. The calorimeter exhibited a mean sensitivity of 25.8 mV W −1, a time constant of 8 min and a 24 h baseline stability better than 1% of the chosen range. This differential calorimeter was placed around lotus flowers ≈ 1 m above the water level. Direct calorimetry was accompanied with indirect calorimetry by measuring oxygen consumption rates of the flowers with open-flow respirometry, and the patterns of temperature change were recorded with thermocouples. Flowers maintained mean temperatures of ca. 30.7° and 34.2°C at mean calorimeter temperatures of 18.4° and 30.4°C, respectively, demonstrating good thermoregulatory ability. Metabolic heat production averaged ca. 0.51 W at the low temperature and 0.25 W at the high temperature. Dry heat loss to the calorimeter averaged −0.62 W and −0.17 W, respectively, which indicated that there was a small condensation of atmospheric water vapor inside the calorimeter at the low temperature, but net evaporation from the flower at a level of ca. 33% of heat production occurred at the high temperature. In a set of laboratory experiments on cut lotus flowers, a heat-flux budget was constructed from measurements of heat production (open-flow respirometry), heat loss (gradient-layer calorimeter of the Benzinger/Kitzinger type), and evaporative heat loss (gravimetric). Heat production rate was ca. 0.3 W and was balanced almost completely by evaporative heat loss into the calorimeter air (25°C; 37% relative humidity). Therefore, total heat flux by convection, conduction and radiation was essentially zero, despite the flower's heat-producing receptacle prevailing ca. 5†C higher than the calorimeter air. Heat from the receptacle was apparently transferred to the petals which, in turn, lost it mainly through evaporation. Equivalence of direct and indirect calorimetry substantiated the assumed caloric equivalent of oxygen consumption of 21.1 J ml −1 and indicated that there was no conservation of energy in metabolic processes during thermogenesis.

A method for dynamic measurement of the resistance to dry heat exchange by footwear

Five different types of cold protective footwear have been tested with regard to their resistance to dry heat loss (i.e. the insulation) with a new electrically heated foot model. The model is able to simulate ‘walking’ movements in order to provide a more realistic simulation of wear conditions. Thermal insulation of shoes with and without a steel toe cap was the same. The insulating properties during simulated walking movements were 10–25% lower compared with static conditions. For two of the shoe models a significantly lower insulation value for the sole area was obtained when adding a weight of 30 kg. A significant difference could also be found between the insulation values of two different sizes of one of the models. Measurements with the standard method (EN 344) correlated well with the local insulation value of the sole part of the thermal foot. Correlation with the insulation value for the whole shoe was much less, variation was bigger and ranking in terms of cold protection differed between methods. The electrically heated foot model appears to provide a reproducible, accurate and more realistic method for measuring the insulation properties of shoes than EN 344.

The role of behavioral thermoregulation as a thermoeffector during prolonged hypoxia in the rat

Exposing rodents to insults such as hypoxia and chemical toxicants induces regulated hypothermia, characterized by a preference for cooler ambient temperatures ( T a) and reduced core temperature ( T c). This study clarified the efficacy of behavioral thermoregulation to regulate T c when subjected to a steady-state hypoxic insult. T c, selected T a ( ST a), heart rate (HR), and motor activity (MA) were monitored by radiotelemetry in rats housed in a temperature gradient. A 6 to 6.5 h period of hypoxia (6.9% O 2)was induced by diluting the air entering the gradient with nitrogen. During the first hour of hypoxia T c decreased by 2.5°C while ST a decreased from 30 to 24.5°C. As hypoxia progressed, ST a rebounded slightly to 26–27°C while T c remained between 34–35°C. HR increased gradually from 300 to 375 beats min −1 during hypoxia. MA increased transiently but then remained near baseline throughout the remainder of the exposure period. Exposure to hypoxia in a gradient maintained at 31.5°C blocked the hypothermic response, showing that preference for cooler T aS during hypoxia is critical for regulating T c. Calorimetric measurements showed that exposure to hypoxia at a T a of 22°C led to a transient rise in dry heat loss, suppression in metabolic rate, and reduction in T c. At a warmer T a of 32°C, hypoxia led to a suppression in heat loss along with an elevation in CO 2 production and T c. Overall, the data show that behavioral and autonomic thermoeffectors serve to regulate T c at a hypothermic level throughout a prolonged period of hypoxic stress.

Change in heat loss as a part of adaptation to repeated cold exposures in adult and aged male C57BL/6J mice.

Previous studies have shown that adult mice increase cold-induced heat production as a result of repeated exposures to cold, but that aged mice do not. The objective of the present study was to investigate changes in heat loss during repeated cold exposures in adult and aged C57BL/6J mice. Mice were partially restrained for three hours at 6 degrees C, three times at one-week intervals. Dry heat loss was inferred from measurements of differential temperature between the incoming and outgoing air in the experimental chamber. During the first cold exposure, aged mice showed less heat loss (both total and adjusted for body temperature) than adult animals, suggesting greater peripheral vasoconstriction in aged mice. With repeated cold exposures, both age groups showed increased heat loss, but the aged mice showed greater increase of heat loss, so that by the third cold stress test, no significant differences in heat loss between adult and aged mice were observed. The increase of heat loss after repeated cold exposures in aged mice might reflect a lesser peripheral vasoconstriction, serving to reduce the possibility of tissue necrosis in the cold.

Wet and dry season heat loss in two tropical Australian reservoirs

The influence of the wet/dry tropical climate on the seasonal heat pattern for two Australian water bodies is examined. The heat content and volume-weighted mean temperature of the reservoirs (Darwin River Reservoir, DRR; Manton River Reservoir, MRR) were computed for an eight year period which included wet seasons of very high and low rainfall. Because of the large volume changes of the two water bodies and dependence of heat content on volume, volume-weighted mean temperature was a better parameter to assess the heat pattern of DRR and MRR. The surface energy budget for DRR, in common with other tropical water bodies, was primarily controlled by net radiation and evaporative energy fluxes. Both reservoirs experienced two annual temperature minima and maxima in most years. The water bodies reached minimum annual temperatures (22-25°C) in the cool, dry season (June-August), then gained heat rapidly during the dry-wet transition (August-October). In December, temperatures reached 31-32°C. During most wet seasons (January, February), monsoon weather caused significant heat loss, leading to a second temperature minimum of 27-30°C. Subsequent heat gain increased temperatures to 30-32°C in March. When monsoon weather was brief, however, neither reservoir experienced significant wet season cooling, resulting in a single annual minimum and maximum temperature. Between April and June reservoir heat loss was most rapid due to reduced shortwave radiation and increased evaporative energy fluxes. The seasonal heat pattern of DRR and MRR is compared to other water bodies exposed to a tropical climate comprising of distinct high and low rainfall seasons. Minimum annual temperatures and heat contents of DRR and MRR coincided with the hemispheric winter, as experienced by nearly all tropical lakes. No single seasonal heat pattern, however, is representative of these tropical climates, due to variable influences of advective and surface heat fluxes, though two annual temperature and heat content maxima and minima is most common.

Heat loss during cold exposure in adult and aged C57BL/6J mice.

Metabolic heat production (MHP), colonic temperature (Tco), and nonevaporative (dry) heat loss were measured in ADULT and AGED C57BL/6J male mice during cold exposure. Dry heat loss was assessed as a differential temperature (Td) between incoming and outgoing air through the chamber for indirect calorimetry. The average Td during cold exposure normalized to surface area for ADULT mice was significantly higher than that for the AGED animals (0.0618 +/- 0.0003 degree C/cm2 and 0.0553 +/- 0.0005 degree C/cm2, respectively). Linear regression analysis showed that at the same Tco AGED mice showed lower values of Td normalized to surface area, indicating that at the same body temperature they were losing less heat than ADULT animals. It was concluded that age-related decline in cold tolerance in mice is not due to a lack of ability to reduce heat loss during cold exposure. On the contrary, AGED animals had lower heat loss in comparison with ADULT. We suggest that augmentation of heat conservation mechanisms is an adaptive response to diminishing cold-induced heat production.

Skin to skin care:heat balance.

Skin to skin care has been practised in primitive and high technology cultures for body temperature preservation in neonates. Regional skin temperature and heat flow was measured in moderately hypothermic term neonates to quantitate the heat transfer occurring during one hour of skin to skin care. Nine healthy newborns with a mean rectal temperature of 36.3 degrees C were placed skin to skin on their mothers' chests. The mean (SD) rectal temperature increased by 0.7 (0.4) degrees C to 37.0 degrees C. The heat loss was high (70 Wm-2) from the unprotected skin of the head to the surrounding air. Minute heat losses occurred from covered areas; and heat was initially gained from areas in contact with the mother's skin. The total dry heat loss during skin to skin care corresponded to heat loss during incubator care at 32-32.5 degrees C. The reduced heat loss, and to a minor extent, the initial heat flux from the mothers allowed heat to be conserved, leading to rewarming.