The heat loss coefficients of a group of infants have been calculated
and compared to see if there is a difference in the ability to lose he
at between prone and non-prone sleeping infants. For a group of 43 inf
ants aged 4-29 weeks, a simple mathematical model of exponential cooli
ng in a body has been fitted to the fall in rectal temperature which o
ccurs in infants at bedtime, One of the parameters yielded by the fitt
ing process is the coefficient of thermal heat loss, After validation
against the estimated heat loss from supine sleeping infants, the heat
loss coefficient was compared at different sleep positions and gender
. The mean heat loss coefficient, measured from the non-prone sleeping
infants (0.269 W/degrees C, S.D. 0.197) agreed well with the value ca
lculated for supine sleepers with the same tog levels (0.4 W/degrees C
), Prone sleeping infants were found to have a considerably smaller he
at loss coefficient which was approximately 60% of the value for non-p
rone sleeping infants (P = 0.000097). Female infants were found to hav
e a heat loss coefficient that was approximately 70% of that of male i
nfants but this gender difference was only significant (P = 0.025) for
non-prone sleeping infants. These results suggest that infants sleepi
ng in the prone position may be unable to lose heat as rapidly as thos
e infants sleeping non-prone.