Effect of humidity on production and loss of heat in the newborn baby.

In 1955 Clement Smith wrote: 'Most of us who work in neonatal pediatrics are distressingly familiar with the sight of a small infant surrounded by a fog of vapour within a closed tent or incubator. This situation perhaps symbolizes the present status of this subject, which is essentially a very small body of facts enveloped in a misty atmosphere of speculation, which is walled off from its surroundings by a rigid container of prejudice.' The facts available are still, unfortunately, almost as scanty today as they were in 1955. Since the classic paper of Blackfan and Yaglou appeared in 1933, it has been generally accepted that a moderately high relative humidity is a useful adjunct to the regulation of a baby's body temperature; Day, Curtis, and Kelly, in 1943, showed that up to a quarter of a baby's basal heat loss might be due to evaporation of water from the skin and respiratory tract. We have, therefore, tried to estimate the effect of the relative humidity of the air on total heat production and loss in normal, naked, newborn babies under controlled environmental conditions.