WATER-LOSS FROM THE SKIN OF TERM AND PRETERM INFANTS NURSED UNDER A RADIANT HEATER

The rate of evaporation from the skin (g/m(2)/h) was measured in 12 fu ll-term and 16 preterm infants (gestational age 25-34 wk) both during incubator care and when nursed under a radiant heater. The method for evaporation rate measurement is noninvasive and based on determination of the water vapor pressure gradient close to the skin surface. Measu rements were first made with the infant nursed in an incubator with a controlled environment with respect to humidity, temperature, and air velocity. The measurements in the term infants were performed at an am bient relative humidity (RH) of 50%, and in the preterm infants first at 50% and subsequently at 30-40%. Evaporation rate was then measured with the infant nursed under a radiant heater. In term infants, mean e vaporation rate was 3.3 g/m(2)/h during incubator care (RH 50%) and 4. 4 g/m(2)/h during care under the radiant heater. In preterm infants, t he corresponding values were 15.5 g/m(2)/h in the incubator at RH 50%, 16.7 g/m(2)/h at RH 30-40%, and 17.9 g/m(2)/h under the radiant heate r. It is concluded that the evaporative water loss from the skin depen ds on the ambient water vapor pressure, irrespective of whether the in fant is nursed an incubator or under a radiant heater. The higher rate of evaporation during care under a radiant heater is due to the lower ambient water vapor pressure and not to any direct effect of the noni onizing radiation on the skin.