Regional heat loss in newborn infants. Part I. Heat loss in healthy newborns at various environmental temperatures.

In 17 newborn infants (gestational age 33-40 weeks, birthweight 1 100-5 560 g) heat flux (HF) from the forehead, chest and calf was measured by HF transducers and heat loss (HL) from those body regions was calculated, taking into account variations in surface area. Both HF and HL were related to operative environmental temperature (Top). Average HF from the forehead, chest and calf was 63.3, 51.5 and 45.7 W/m2 respectively at a Top of 31.2 degrees C and increased by 100%, 66% and 50% as the Top fell to 27.5 degrees C. HL from the head, trunk and limbs contributed about one-third each to total dry HL. These data, in the form of regression equations, permit assessment of heat loss from the various body regions of individual neonates in any thermal environment.