A double-walled incubator alters the partition of body heat loss of premature infants. Oxygen consumption and temperature control of premature infants in a double-wall incubator. Oxygen consumption and insensible water loss in premature infants in single-versus double-walled incubators.
Partitional calorimetry was used to assess the influence of a double-walled incubator (Air-Shields C-86 Isolette) on the body heat loss of eight premature newborn infants (birth weights 1.44-1.89 kg, ages 6-19 days). Each infant was studied in the same incubator with and without the inner wall. Incubator heater output was regulated by servocontrol to maintain the abdominal skin temperature at 36.5 degrees C. Operative environmental temperature was the same (mean 33.0 degrees C) in both incubators. There were no differences in body temperatures, oxygen consumption, carbon dioxide production, respiratory quotient, or evaporative water and heat losses. The double-walled incubator reduced radiant heat loss but increased convective heat loss, so that the total rate of body heat loss was unchanged. The effects of a double wall in a forced convection-heated incubator were studied on ten naked, nondistressed, premature infants by measuring their mean skin temperature, esophageal temperature, and oxygen consumption when they were in thermal steady state, with, and without, the double wall in place. The incubator air temperature was maintained within the recommended thermoneutral zone during the consecutive paired experiments. Ambient room temperature and relative humidity were constant and the infant's activity (quiet sleep) and postprandial state were the same in both conditions. Together with a significant rise in operative temperature (P less than .05) induced by the double wall (accounted for by a 0.9 C mean increased in incubator wall temperature nearest the baby), their mean skin temperature and esophageal temperatures increased (P less than .025), while a decrease in oxygen consumption occurred in nine of the ten infants (P less than .05). These findings suggest that the double wall reduced radiant and total heat loss from the baby by diminishing the temperature gradient between the skin and incubator surfaces and that metabolic heat production (oxygen consumption) was reduced when the double wall was in place. Fifteen studies were performed in ten premature infants whose birth weight (mean +/- SD) was 1,444 +/- 250 gm, gestational age 32.7 +/- 1.0 weeks, and postnatal age 10.7 +/- 3.3 days. Each study consisted of three hours simultaneous measurement of insensible water loss and oxygen consumption under two conditions for the same infant: (1) inside a single-walled incubator and (2) inside a double-walled incubator. The double-walled incubator provided significantly (P < 0.001) higher operative temperature and incubator wall temperature than did the single-walled incubator. Infants inside the double-walled incubator had significantly lower (P < 0.01) IWL (30% reduction) and lower (P < 0.05) VO2 (17% reduction) than inside the single-walled incubator--a net caloric saving of 11.8 kcal/kg/day. This saving of energy expenditure may be important in affecting the growth and outcome of the low-birth-weight infants.
Although it appears that caring for extremely small infants in double wall incubators may theoretically result in shorter hospitalization and may have metabolic advantages, this review was unable to find any data in the literature to support or refute this hypothesis. The studies do not provide any evidence that the small decrease in heat loss improves clinical outcome. Therefore, the available data is insufficient to directly guide clinical practice.