Thermal balance in term and preterm newborn infants nursed in an incubator equipped with a radiant heat source

A radiant hood warmer, a device that heats the incubator roof independently of the incubator's main heat source, was used to study the thermal balance of 11 full term and 13 preterm (gestational age 25–34 weeks) infants exposed to an isolated elevation of incubator roof temperature at stable ambient air temperature and humidity. After initial measurements without active heating of the incubator roof, the hood warmer was set to 33°C, 36°C and finally (preterm infants only) to 39°C. At least 18 min of measurements with the infant asleep were made at each hood warmer setting. In the term infants an increase in roof temperature from 30.5°C to 35.6°C resulted in an increase in skin temperature from 35.4 to 35.9°C, and a decrease in radiative heat loss from 32.8 to 20.7 W/m² exposed skin. In the preterm infants an increase in roof temperature from 31.0 to 38.4°C led to an increase in skin temperature from 35.7 to 36.3°C and a decrease in radiative heat loss from 34.1 to 13.0 W/m² exposed skin. The increased inner roof surface temperature did not affect evaporative or convective heat loss, skin blood flow, respiratory water loss, oxygen consumption or transepidermal water loss in either group. Thus, at stable ambient air temperature and humidity, the increase in incubator roof temperature resulted in an increase in skin temperature and a decrease in radiative heat loss in both term and preterm infants.