Premium
Study by Direct Calorimetry of Thermal Balance on the First Day of Life
Author(s) -
Ryser G.,
Jéquier E.
Publication year - 1972
Publication title -
european journal of clinical investigation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.164
H-Index - 107
eISSN - 1365-2362
pISSN - 0014-2972
DOI - 10.1111/j.1365-2362.1972.tb00587.x
Subject(s) - chemistry , calorimetry , relative humidity , calorimeter (particle physics) , thermodynamics , temperature gradient , zoology , meteorology , physics , detector , biology , optics
. Using a gradient layer direct calorimeter, total heat losses were measured in 69 full term new‐borns at 5 different ambient temperatures ( T A ): 28, 30, 32, 34 and 36° C. The relative humidity of the air was kept constant at 50%. Oesophageal temperature ( T eg ) and mean skin temperature ( T̄ s ) were continuously recorded. All experiments lasted at least one hour. The mean total heat loss was at 28° C: 3.55 W/kg; at 30° C: 2.97 W/kg; at 32° C: 2.35 W/kg; at 34° C: 1.92 W/kg and at 36° C: 2.05 W/kg. Dry heat loss was proportional to the external temperature gradient. Evaporative heat loss was constant when new‐borns were not subjected to heat or cold stress, with a mean of 0.39 W/kg. This value is a measurement of insensible perspiration. Sweating was elicited at a T A of 36° C when the internal temperature gradient reached a mean value of 0.68° C. Heat storage ( S ). was calculated and was found to be negative at a T A of 28 and 30° C, and positive at 34 and 36° C. A regression analysis between heat storage and total heat loss showed a mean heat loss of 2.61 W/kg when the new‐borns were in thermal equilibrium ( S = 0). This occured in most babies at a T A slightly below 32° C. A minimal metabolic rate of about 6.0 ml kg ‐1 min ‐1 , determined by direct calorimetry and calculation of S , was found at a T A of 34 and 36° C. The cutaneous thermal conductance, which is an index of cutaneous blood flow was minimal at a T A of 30° C. It increased sharply when T̄ s reached 36.3° C. These data indicate that the range of thermal comfort on the first day of life in normal full‐term new‐borns is very narrow and that there is a perfect thermal balance at a T A slightly below 32° C. However, at this T A , the metabolic rate is not at a minimal level.