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 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 transepidermal water loss in very preterm infants. Respiratory water loss increases with the rate of breathing.