Preterm Infant Thermal Care: Differing Thermal Environments Produced by Air Versus Skin Servo-Control Incubators

Abstract

OBJECTIVE:Incubator thermal environments produced by skin versus air servo-control were compared. STUDY DESIGN:Infant abdominal skin and incubator air temperatures were recorded from 18 infants in skin servo-control and 14 infants in air servo-control (26-to 29-week gestational age, 14 Ϯ 2 days postnatal age) for 24 hours. Differences in incubator and infant temperature, neutral thermal environment (NTE) maintenance, and infant and incubator circadian rhythm were examined using analysis of variance and scatterplots. RESULTS:Skin servo-control resulted in more variable air temperature, yet more stable infant temperature, and more time within the NTE. Circadian rhythm of both infant and incubator temperature differed by control mode and the relationship between incubator and infant temperature rhythms was a function of control mode. CONCLUSION:The differences between incubator control modes extend beyond temperature stability and maintenance of NTE. Circadian rhythm of incubator and infant temperatures is influenced by incubator control.Maintenance of body temperature is a primary challenge facing the preterm infant. Preterm infants are vulnerable to both overand under-heating resulting from limited heat production capacity, propensity for heat loss related to body configuration, skin maturation, and immature sudomotor responses. Incubators, the mainstay in providing thermal care for these fragile infants, operate in two modes: air and skin servo-control. 1,2 The choice of air versus skin servo-control is typically based on infant clinical parameters such as birth weight, gestational age, and health status, and unit protocol, individual care provider preference and experience, equipment availability, marketing, purchasing decisions, and trends in neonatal care.The research examining incubator control mode has focused essentially on the description of environmental temperature stability, efficacy in maintaining a neutral thermal environment (NTE), and minimizing oxygen consumption. In general, skin servo-control incubators produce incubator air temperatures that are extremely variable, often exhibiting a lag effect in response to infant temperature change and overshoot and undershoot. Excursions in incubator temperature greater than 2°C have been reported during skin servocontrol operation. 3,4 Variability in air temperature is also related, in part, to the discrepancy between air temperature, measured at the site of the thermostat, and the incubator temperature as a whole; specifically, air temperature recorded mid-incubator differs from temperature measured at the thermostat. 4 The variable air temperatures observed in skin servo-control incubators result in part from probe artifacts. 4 -7 The two types of artifact in skin temperature measurement are: (1) probe insulation, resulting in probe temperature falsely greater than skin surface temperature and consequently lower incubator (or radiant warmer) temperature, and (2) convective and radiant heating or cooling of the skin probe by the surrounding environment. ...

Toward a Fuzzy Logic Control of the Infant Incubator

“…23 With this on-off control, there is an overshoot and undershoot in the air temperature. 2,16,18,[21][22][23][24] Skin control often leads to large fluctuations in air temperature. 5,6,18 Air control leads to skin temperature fluctuations.…”

“…[10][11][12][13]24 The clinician has to choose either the set air temperature mode or the set skin temperature mode. 23 Most devices use the onoff control. 23 With this on-off control, there is an overshoot and undershoot in the air temperature.…”

“…23 Most devices use the onoff control. 23 With this on-off control, there is an overshoot and undershoot in the air temperature. 2,16,18,[21][22][23][24] Skin control often leads to large fluctuations in air temperature.…”

“…Thermo regulation is a major problem in premature infants. 8,9,15,19,[22][23][24] Premature babies and other high risk infants have low ability to regulate temperature and produce heat. Because of low gestation, these infants do not have the developed thermal regulatory control to maintain their body temperature.…”

“…1,12 Pre-term infants are therefore kept in an infant incubator so as to keep the infant warm and provide thermal neutrality. 15,23,24 Convection type incubators are more prevalent.…”