Effect of Relative Humidity on Thermal Balance of the Newborn Infant

Sulyok, E.; Jéquier, E; Ryser, G.

doi:10.1159/000240509

Cited by 26 publications

(6 citation statements)

References 10 publications

(14 reference statements)

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“…Comparison of these data with those obtained in our previous study [36], makes evident that the metabolic rate at ambient temperature of 37° is far lower than that found at "neutral" temperature (at 32° metabolic rate = 2.25 W/kg; SE ±0.06).…”

Section: Metabolic Ratesupporting

confidence: 68%

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Thermal Balance of the Newborn Infant in a Heat-gaining Environment

1973

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ExtractThe thermal balance of 22 full term, 9 small for date, and 8 large premature infants was studied by gradient layer direct calorimetry on the 1st day of life. In addition, the influence of muscular activity on the ability to sweat of 8 full term infants was investigated. The same measurements were repeated in 20 infants on the 3rd day of life.All i nfants were subjected to the same experimental conditions: ambient temperature 37°, restive humidity 50%, and air flow 30 liters/min.It was demonstrated that the evaporation of water was the primary way to dissipate heat in a heat-gaining environment. Active thermoregulatory sweating was elicited at deep body temperatures of 37.45°, 37.8°, and 37.76° in the full term, small for date, and premature infants, respectively.The set-point temperature of sweating tended to be lower with increasing gestational and postnatal age, and with vigorous muscular activity. The physiologic weight loss of about 3%, and the intrauterine growth retardation resulted in significant increase in this threshold temperature.The maximal sweat rate of the premature infants (1.43 W/kg) was significantly lower than that of the full term (1.81 W/kg) and small for date infants (2.32 W/kg): P < 0.05 and 0.01, respectively.Heat loss by radiation and convection was directly related to the mean skin temperature; it was only when the latter reached the value of 37° that radiative plus convective heat loss became positive.There was a close inverse relation between the total heat loss and heat storage. After the beginning of sweating, the heat storage of full term and small for date infants sharply decreased and stabilized around 0, which showed that a new thermal steady state was reached. The premature infant was not able to reach this new equilibrium and the heat storage remained positive.The full term and small for date infants could keep the body temperature at a steady level of 37.66° and 37.98°, respectively, whereas the esophageal temperature of the premature infants kept on increasing.The cutaneous thermal conductance, an indicator of the heat-transferring blood flow, was at first negative, which showed that heat was transferred from the surface to the core. Later, before the evaporative heat loss, it increased and reached the maximal value at a body temperature of 37.6° in the normal, and of 37.9° in both the small for date and premature groups.The metabolic rate for the small for date and premature infants was significantly higher than that for the full term infants, and it directly related to the deep body temperature in each group. Neonatal thermal balance 889In the new thermal equilibrium, the metabolic rate of the full term infants was about 20% lower than that measured under neutral ambient conditions. We suggest that the term "neutral thermal environment" must be reconsidered. SpeculationA new method, gradient layer direct calorimetry, gave us the opportunity to measure directly the different heat losses of the neonate under well controlled experimental conditions, and to compare thes...

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Section: Metabolic Ratesupporting

confidence: 68%

“…In the present study, it has been demonstrated that the metabolic rate at an ambient temperature of 37°d isplays a drop of about 34% when compared with the results obtained under neutral ambient conditions [36].…”

Section: Metabolic Ratesupporting

confidence: 47%

Thermal Balance of the Newborn Infant in a Heat-gaining Environment

1973

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“…The evaporative heat losses amounted to about 17-20 % of the metabolic rate. These findings agree with those of Anderson (1), Levine et al (21), and Sulyok et al (31,32), but the values are a little higher than the esti mates obtained by Hey and Katz (15), and Zweymiiller and Preining (34).…”

Section: Discussionsupporting

confidence: 91%

“…Similar values were found by Ryser and Jequier (25) and by Sulyok et al (31,32) using direct calorimetry. The effective 'cooling constant' which takes into account both dry and evapora tive heat losses, can be obtained by multiplying 5.7 W*m_2,°C_1 by 1.25, which gives 7.1 Wm * L .…”

Section: Cooling Constantsupporting

confidence: 90%

Heat Losses in Newborn Infants of Different Body Size Measured by Direct Calorimetry in a Thermoneutral and a Cold Environment

Kajtár¹,

Jéquier²,

Prod’hom³

1976

Neonatology

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Small-for-date infants (less than the 10th weight percentile, group I), appropriate-for-date (between the 10th and the 90th percentile, group II), and large-for-date infants (above the 90th percentile, group III) were exposed to ambient temperatures (T_a) of 28 and 32 °C in a direct calorimeter. Total heat losses ( + Ċ + Ė) expressed per unit body surface were similar in the three groups, but when expressed per kg of body weight, ( + Ċ + Ė) were more elevated in group I than in groups II and III. At 28 °C T_a ( + Ċ + Ė) was 4.35 ± 0.15, 3.6 ± 0.1, and 3.04 ± 0.09 W/kg in groups I, II and III, respectively. Metabolic rate was higher at 28 than at 32 °C in the three groups. Heat storage (⋅) at 28 °C was negative in the three groups; at 32 °C, ⋅ was negative in group I, but thermal equilibrium was reached in groups II and III (⋅ = 0). Thermal body insulation between the three groups was not significantly different. In order to practically determine the dry heat losses of a newborn infant a cooling constant of 5.7·W·m^––²·°C ^––1 was calculated. Our results show that at low T_a, the surface-body mass ratio of small-sized infants plays a more important role in inducing a negative thermal balance, than a lack of stimulation of heat production or an inefficient thermal body insulation.

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“…Since the pioneering work of Day and Hardy [1942], Day [1943], Mount [1959], Karlberg [1952], Silverman et al [1958Silverman et al [ , 1966, Glass et al [1968Glass et al [ , 1969, Briick [1962], Hey and Mount [1967], Hey [1975] and Jequier's group [Ryser and Jequier, 1972] have added much to our under standing of the interaction between the ther mal environment and energy metabolism by the use of modern direct and indirect calori metric equipment [Ryser and Jequier, 1972;Sulyok et al, 1972Sulyok et al, , 1973a. In order to standardise the thermal environment and to make studies comparable, most investiga tions are now carried out under strict ther moneutral conditions.…”

Section: New Techniques and Directions In Neonatal Nutritional Researchmentioning

confidence: 99%

New Perspectives in Neonatal Nutrition

Swyer¹

1987

Neonatology

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Modern techniques of cardiopulmonary life support, particularly for very low birthweight infants and those suffering from major surgical conditions, has presented the neonatologist with a completely new population of infants for whom continued survival and further normal physical and mental growth and development are critically dependent on adequate nutrition. The uncertainties surrounding the definition of ‘adequacy’ as well as the techniques and difficulties of its attainment and assessment are exposed. This paper examines desirable goals to be aimed for in the nutrition of the neonate in relation to genetic potential for growth, development and body composition. There is discussion of current research into the intermediary metabolism and utilisation of macronutrients and certain minerals for energy production and tissue growth and of methodology for determining body composition. The editor has also allowed a certain licence for speculation concerning future directions in neonatal nutrition.

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Effect of Relative Humidity on Thermal Balance of the Newborn Infant

Cited by 26 publications

References 10 publications

Thermal Balance of the Newborn Infant in a Heat-gaining Environment

Thermal Balance of the Newborn Infant in a Heat-gaining Environment

Heat Losses in Newborn Infants of Different Body Size Measured by Direct Calorimetry in a Thermoneutral and a Cold Environment

New Perspectives in Neonatal Nutrition

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