Assessment of radiant temperature in a closed incubator

Abstract

In closed incubators, radiative heat loss (R) which is assessed from the mean radiant temperature accounts for 40–60% of the neonate’s total heat loss. In the absence of a benchmark method to calculate —often considered to be the same as the air incubator temperature—errors could have a considerable impact on the thermal management of neonates. We compared using two conventional methods (measurement with a black-globe thermometer and a radiative “view factor” approach) and two methods based on nude thermal manikins (a simple, schematic design from Wheldon and a multisegment, anthropometric device developed in our laboratory). By taking the estimations for each method, we calculated metabolic heat production values by partitional calorimetry and then compared them with the values calculated from and measured in 13 preterm neonates. Comparisons between the calculated and measured metabolic heat production values showed that the two conventional methods and Wheldon’s manikin underestimated R, whereas when using the anthropomorphic thermal manikin, the simulated versus clinical difference was not statistically significant. In conclusion, there is a need for a safety standard for measuring in a closed incubator. This standard should also make available estimating equations for all avenues of the neonate’s heat exchange considering the metabolic heat production and the modifying influence of the thermal insulation provided by the diaper and by the mattress. Although thermal manikins appear to be particularly appropriate for measuring , the current lack of standardized procedures limits their widespread use.

Conception d’un logiciel de calcul de la thermoneutralité dans les incubateurs fermés pour nouveau-nés prématurés (projet Pretherm®)

“…Cela est possible grâce à la mesure de la température moyenne de rayonnement par une méthode utilisant le mannequin [14] qui prend en compte les formes anatomiques de l'enfant qui conditionnent ces pertes de chaleur. La détermination de ces dernières est en effet essentielle car elles représentent près de 60 % des pertes totales de chaleur de l'enfant.…”

“…La température moyenne de rayonnement a été mesurée expé-rimentalement en tenant compte de la géométrie de l'incubateur à l'aide d'un modèle mannequin thermique présentant les formes anatomiques d'un nouveau-né prématuré et l'hétérogénéité thermique des températures de surface des différents segments du corps [14]. L'énergie électrique fournie aux éléments chauffants, situés dans chaque segment du mannequin thermique, est régulée de manière à obtenir une température de surface de chaque segment identique à celle mesurée chez le nouveau-né en situation clinique dans une ambiance thermique proche de la neutralité.…”

Can Mathematical Models of Body Heat Exchanges Accurately Predict Thermal Stress in Premature Neonates?

“…As reported by Ultman et al [22] for a single-walled incubator, T r can be 4.0 to 5.5 • C lower than the incubator air temperature. When studying a single-wall incubator with a double-wall roof panel (the Satis + from Médipréma, Tauxigny, France), Décima et al [23] found a difference of 2.7 • C; this is similar to the value of 3.1 • C determined by Wheldon [21] for the Vickers 79 closed incubator (Vickers Medical, UK) and the value of 3.5 • C determined by Sinclair [24] for the Isolette closed incubator, Air-Shields Vickers, UK.…”

“…Mannequins can be used to experimentally determine T r and several factors related to heat transfer coefficients with less uncertainty. For example, Figure 4 compares the (T inc ) calculated from a standard procedure (in which T r is assessed with a standard globe thermometer) with that obtained from experiments on the anthropomorphic, multisegment thermal mannequin [23]. The data showed that the standard procedure underestimated T inc , which increased the risk of body cooling.…”

Warming mattresses for newborns: effectiveness and risks

“…A warming mattress can also supply radiant heat to skin surfaces that are not in direct contact with it. In a study of a black-painted copper manikin representing a small-for-gestational age neonate (body surface area: 0.086 m 2 ; simulated bodyweight: 900 g), lying in a convectively heated closed incubator (ISIS+ from Médipréma, Tauxigny, France), Décima et al [1] showed that the radiant energy provided by the mattress accounted for 42.9% of the body's radiant heat loss as a whole. The mattress can also generate a microclimate by increasing the temperature of the air above the infant, which reduces convective and evaporative heat losses.…”