Water Loss from the Skin of Term and Preterm Infants Nursed under a Radiant Heater

Abstract

The rate of evaporalion from the skin (g/m 2 jh) was measured in 12 full-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. Measurements 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 ambient relative humidity (RR) 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 evaporation rate was 3.3 g/m 2 jh during incubator care (RH 50%) and 4.4 g/m 2 jh during care under the radiant heater. In preterm infants, the corresponding values were 15.5 g/m 2 jh in the incubator at RH 50%, 16.7 g/m 2 jh at RH 30-40%, and 17.9 g/m 2 j h under the radiant heater. It is concluded that the evaporative water loss from the skin depends on the ambient water vapor pressure, irrespective of whether the infant is nursed Radiant heaters are frequ ently used in the care of newb orn infants and are co nsidere d to be effec tive in rewarming infants exposed to cold stress after birth (1). One possible disad vantage of radiant heaters is that they may ca use de hy dra tion in the new born by incr easin g insensible water loss (2-8). Th e mechanism of such an increase is not understood and appro priate methods for measuring the effect of nonionizing radiat ion have been difficult to find.:In previ ous studies (2-8) co ncerning the effect of non ionizing rad iant energy, produced eit her by radiant heaters or by phot oth erapy, insensibl e wa ter loss wa s determined by ind irect methods (gravimetric methods, usu all y using the Potter sca le) , making it difficult to ascertain whether the observed increase derived fro m an increase in transep idermal or respiratory wa ter Received February 24, 1994; accepted September I , 1994. Correspondence: Professor Gunnar Sedin, Department of Pediatrics, University Chilo dren's Hospital, S-751 85 Uppsala, Sweden.Supported by grants from the Swedish Medical Research Council (Project 19X-04998), the newspaper Expressen's Prenatal Research Foundation, Stockholm, Sweden, and the Swedish Institute (fellowship for SA).lThis was one of Karen Hammarlund's last scientific contributions; she died before publication of the study.in 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 nonionizing radiation on the skin. tPediatr Res 37: 233-238, 1995) Abbrev iations ER, evaporation rate PH zO , water vapor pressure RH, relative humidity HR , heart rate RR, respiratory rate RH a m b , ambient relative humidity PH ZO a m b , ambient water vapor pressure Tbody' rectal temperature T is c> ...

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

“…The subsequent increase in ceiling temperature resulted in an increase in skin temperature and blood flow and a marked decrease in radiative heat exchange, but did not affect the transepidermal or respiratory water loss. This agrees with previous findings (21), and indicates that the 2 before the hood warmer was switched on. increase in insensible water loss found in some earlier studies (22)(23)(24)(25)(26)(27)(28) was not caused by a direct effect of the non-ionized radiation on the infant's skin, but rather by a lower ambient humidity (28), the presence of convective air currents (29) and/or an increase in motor activity (21) or rate of breathing (30)(31)(32).…”

The effect of convective heating on evaporative heat loss in anesthetized children

“…It is unfortunate we were unable to study children in the <1-month age range. In an attempt to understand the likely range of values, we compared our results to those presented on nonanesthetized neonates in a series of publications from the University hospital, Uppsala, Swedensome of which we have referred to in this paper (11,14,15). Assuming a birth length of~50 cm and a similar methodology for calculating BSA, they found that TEWL in full-term infants was~1.1 gÁh À1 (at the lower end of our results) and it did not change until 4 weeks (14).…”

Transepidermal water loss in infants born at 24 and 25 weeks of gestation

“…Since the same ambient RH could not be achieved during the measurements for all infants, and to allow comparisons with previous published data, the values obtained for TEWL were corrected to a RH of 1186 J Å gren et al ACTA PAEDIATR 87 (1998) 50% (TEWL 50 ), using the two-point equation for evaporation rate over Ph 2 o at the ambient temperature of each measurement, as presented in a previously published paper (18).…”