Small-for-date infants (less than the 10th weight percentile, group I), appropriate-for-date (between the 10th and the 90th percentile, group II), and large-for-date infants (above the 90th percentile, group III) were exposed to ambient temperatures (Ta) of 28 and 32 °C in a direct calorimeter. Total heat losses ( + Ċ + Ė) expressed per unit body surface were similar in the three groups, but when expressed per kg of body weight, ( + Ċ + Ė) were more elevated in group I than in groups II and III. At 28 °C Ta ( + Ċ + Ė) was 4.35 ± 0.15, 3.6 ± 0.1, and 3.04 ± 0.09 W/kg in groups I, II and III, respectively. Metabolic rate was higher at 28 than at 32 °C in the three groups. Heat storage (⋅) at 28 °C was negative in the three groups; at 32 °C, ⋅ was negative in group I, but thermal equilibrium was reached in groups II and III (⋅ = 0). Thermal body insulation between the three groups was not significantly different. In order to practically determine the dry heat losses of a newborn infant a cooling constant of 5.7·W·m––2·°C ––1 was calculated. Our results show that at low Ta, the surface-body mass ratio of small-sized infants plays a more important role in inducing a negative thermal balance, than a lack of stimulation of heat production or an inefficient thermal body insulation.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.