Influence of variations in the ambient humidity on insensible water loss and thermoneutral environment of low birth weight infants.

Total evaporative water loss, transepidermal as well as respiratory water loss was measured in 8 infants on day 1, 11 infants from day 2 to 8 and 8 infants after day 8. Measurements were performed at two levels of humidity, either vapor pressure of 16 or 25 mmHg (2 133 or 3 333 Pa). Evaporative water loss was 40% lower at the higher humidity. Neither metabolic rate nor body temperature showed a significant difference between the two levels of humidity. The effect of the change in humidity on the neutral thermal environment was calculated, the neutral temperature being 0.05 degrees C lower when the vapor pressure is increased by 1 mmHg (133.3 Pa). We conclude that a high humidity is of limited value in nursing infants born after 30-40 weeks.