Karen Hammarlund

TRANSEPIDERMAL WATER LOSS IN NEWBORN INFANTS.: VIII. Relation to Gestational Age and Post-natal Age in Appropriate and Small for Gestational Age Infants

ABSTRACT. In 68 appropriate for gestational age (AGA) and 33 small for gestational age (SGA) infants, transepidermal water loss was studied during the first four weeks after birth. The method used to measure evaporation rate is based on measurement of the water vapour pressure gradient close to the skin surface. All measurements were made at an ambient humidity of 50% and with the infants calm and quiet. At all the investigated post‐natal ages in both AGA and SGA infants, an exponential relationship was found between transepidermal water loss (g/m2 h) and gestational age, this loss being much higher in the pre‐term infants than in those born at term. The transepidermal water loss was generally lower in SGA than in AGA infants during the first week of post‐natal life, irrespective of gestational age at birth. There was a gradual decrease in transepidermal water loss with increasing post‐natal age in both pre‐term AGA and pre‐term SGA infants. Three weeks after birth this water loss tended to be higher in pre‐term SGA infants than in pre‐term AGA infants of corresponding gestational age.

TRANSEPIDERMAL WATER LOSS IN NEWBORN INFANTS II. Relation to Activity and Body Temperature

Abstract. Using a method described in a previous article the transepidermal water loss (TEWL) was studied in 10 healthy newborn infants at rest and during activity. On the average TEWL was 37% higher during activity than during rest although no sweating was observed. In 9 infants placed in incubators with an ambient temperature slightly above the thermoneutral range measurements were made as the body temperature rose. TEWL was almost constant until a temperature of 37.1°C was reached whereupon the water loss suddenly increased as the infant started sweating.

Heat Loss from the Skin of Preterm and Fullterm Newborn Infants during the First Weeks after Birth

In 68 infants appropriate for gestational age, born after 25-41 weeks of gestation, the evaporation rate from the skin and ambient, skin and body temperatures were measured repeatedly during the first 4 weeks after birth, and the heat exchange due to evaporation, radiation and convection was calculated. All measurements were made at an ambient humidity of 50%, with the infants calm and quiet. High evaporative heat losses were found in preterm infants on their first days of life, with gradually decreasing values with increasing gestational and postnatal age. It was only during the 1st week of life in infants born at 25-27 weeks of gestation that evaporative heat loss was higher than radiative heat loss. The high evaporative heat losses in very preterm infants were balanced by low losses or even a gain through radiation and convection, because of the high ambient temperature needed to maintain a stable body temperature. Total heat loss increased with increasing gestational and postnatal age.

TRANSEPIDERMAL WATER LOSS IN FULL‐TERM AND PRE‐TERM INFANTS

Sedin, G., Hammarlund, K. and Strömberg, B. (Department of Paediatrics, University Hospital, Uppsala, Sweden). Transepidermal water loss in full‐term and pre‐term infants. Acta Paediatr Scand, Suppl. 305: 27–31, 1983.—The amount of water lost from the skin and the relation of the water loss to environmental factors, activity, body temperature, gestational age, nutritional status at birth and post‐natal age were studied in full‐term and pre‐term newborn infants. The method we used was non‐invasive and based on determination of the water vapour pressure gradient immediately above the skin surface. We found that the transepidermal water loss per unit time and area (TEWL; g/m2 h) could be calculated by using values from only three measurement sites. TEWL increased with activity and when body temperature was elevated above 37.1C. On the first day after birth TEWL in appropriate for gestational age (AGA) infants was exponentially related to gestational age, with much higher values in the most pre‐term infants than in full‐term infants. In full‐term small for gestational age (SGA) infants TEWL was significantly lower than in full‐term AGA infants. In pre‐term and full‐term AGA infants and in full‐term SGA infants we found an inverse linear relationship between ambient humidity and evaporation rate (ER; g/m2 h) from the skin. The level of ER and the slope of the relationship depended on the gestational age of the infant, with higher ER in the more pre‐term infants. Analysis of the relationship between ambient humidity and ER indicated that there is a gradual change in the permeability of the skin with gestational age. In pre‐term infants TEWL gradually decreased during the first weeks of life. In full‐term AGA infants TEWL was almost unchanged during these first weeks.

Water loss from the skin of term and preterm infants nursed under a radiant heater

The rate of evaporation from the skin (g/m2/h) 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 (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 evaporation rate was 3.3 g/m2/h during incubator care (RH 50%) and 4.4 g/m2/h during care under the radiant heater. In preterm infants, the corresponding values were 15.5 g/m2/h in the incubator at RH 50%, 16.7 g/m2/h at RH 30–40%, and 17.9 g/m2/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 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.

Transepidermal water loss in newborn infants. VII. Relation to post-natal age in very pre-term and full-term appropriate for gestational age infants.

ABSTRACT. During the first weeks after birth the transepidermal water loss was determined repeatedly in 7 infants born after 25–27 weeks of gestation, in 13 infants born after 28–30 weeks and in 14 full‐term infants. All infants were appropriate for gestational age. The very pre‐term infants had high evaporative water losses from their skin on their first days after birth. A gradual decrease was then observed, but after four weeks the values were still higher than those in full‐term infants. The transepidermal water loss in full‐term infants was unchanged during the first two weeks of life, but increased during the subsequent two weeks. The relation between evaporation rate from an interscapular skin area and ambient humidity was studied repeatedly during the first week of life in two very pre‐term infants. The magnitude of evaporation decreased with increasing post‐natal age, but was still dependent on the ambient relative humidity.

Insensible water loss from the skin during phototherapy in term and preterm infants

The rate of evaporation from the skin was measured before and during phototherapy in 10 full‐term and seven preterm infants (gestational age 29‐33 weeks). The method for measurement of rate of evaporation was non‐invasive and was based on determination of the water vapour pressure gradient close to the skin surface. All infants were studied naked in an incubator with an ambient relative humidity of 50% and with a controlled environment with respect to temperature and air velocity. In the term infants the mean rate of evaporation, measured from an interscapular skin area, was 3.1 g/m2h both before and after 30 min of phototherapy. In the preterm infants the corresponding value was 9.8 g/m2h before and 9.7 g/m2h after 120 min of phototherapy. Thus, in thermally stable infants, nonionizing radiation from phototherapy equipment does not increase water loss from the skin.

Irregular breathing in young lambs and newborn infants during heat stress

Ten healthy unanaesthetized full‐term lambs, aged 4‐12 days, were studied during moderate radiant heat stress, and 21 full‐term newborn infants were studied during moderate convective heat stress. The rate of breathing and the breathing pattern were recorded, using strain gauges made of mercury‐filled rubber tubing placed around the thorax and abdomen. In both the lambs and the infants the respiratory rate increased during heat stress. When this increase began, both the lambs and infants had short periods of very rapid breathing followed by short apnoeas. The concentrations of carbon dioxide and water in a flow‐through system collecting expired air increased during the short periods of rapid breathing and then decreased again during the subsequent short apnoeic period.

Respiratory Water Loss in Relation to Activity in Fullterm Infants on Their First Day after Birth

ABSTRACT. Respiratory water loss (RWL), oxygen consumption and carbon dioxide production were measured in ten fullterm infants on their first day after birth, using an open flow‐through system with a mass spectrometer, specially equipped with a water channel, for analysis of gas concentrations. Measurements were made both with the infant asleep and during different levels of motor activity. The ambient temperature was maintained at approximately 32.5°C and the ambient relative humidity at 50%. RWL increased from 4.2±0.7 (SD) mg/kg min when the infant was asleep to 6.3±1.0 mg/kg min when he or she was awake but calm; with increasing activity there was a further increase in RWL. The oxygen consumption increased from 5.4±0.9 (SD) ml/kg min during sleep to 6.9±0.8 (SD) ml/kg min when awake, and also increased further with increasing activity.

Respiratory water loss in relation to gestational age in infants on their first day after birth.

Respiratory water loss, oxygen consumption and carbon dioxide production were measured in 32 infants on their first day after birth. Gestational age was between 27 and 41 weeks. All infants were studied in incubators with 50% ambient relative humidity and an ambient temperature that allowed the infant to maintain a normal and stable body temperature. During the measurements the infants were usually asleep. Respiratory water loss was found to be highest in the most preterm infants and lower in more mature infants. Respiratory water loss per breath (mg/kg) was almost the same at all gestational ages and the higher respiratory water loss found in the most preterm as compared with the more mature infants is thus due to a higher rate of breathing. Oxygen consumption was lowest in the most preterm infants and increased with increasing gestational age. Thus, in full‐term infants respiratory water loss and transepidermal water loss are of approximately equal magnitude at an ambient humidity of 50%, while respiratory water loss constitutes a smaller proportion than trans‐epidermal water loss in very preterm infants. Respiratory water loss increases with the rate of breathing. ? Insensible water loss, oxygen consumption, preterm infants, respiratory water loss