Double wall versus single wall incubator for reducing heat loss in very low birth weight infants in incubators

Newborn infants maintained in the appropriate temperature range have a better chance of surviving. When newborn infants are within the appropriate temperature range, they burn less energy and have improved growth. The concept of an incubator with additional insulation, namely a double wall of plexiglass, is appealing as it may help very low birth weight infants maintain this appropriate temperature environment. We assessed the effects of double wall incubators compared to single wall incubators on the energy needs and water balance of very low birth weight infants. In addition, we looked at important clinical outcomes such as growth, length of hospital stay and survival. Three studies were found that met our criteria. The double wall incubators had advantages as far as decreasing heat loss and decreasing heat production. These infants seemed to be in the best temperature range, as their need to burn energy was less. However, these effects were small and did not provide any evidence of any long-term improvement regarding duration of hospitalization or survival. Although it appears that caring for extremely small infants in double wall incubators may result in certain metabolic advantages, this review was unable to find any data in the literature to support or refute this theory. Available data is insufficient to directly guide clinical practice.

Authors' conclusions: 

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.

Read the full abstract...
Background: 

Studies have shown improved survival of newborn infants maintained in the thermoneutral range. Incubators with a double plexiglass wall for additional insulation may help to provide an improved thermoneutral environment for very low birth weight infants.

Objectives: 

To assess the effects of double walled incubator versus a single wall incubator on insensible water loss, rate of oxygen consumption, episodes of hypothermia, time to regain birth weight, duration of hospitalization and infant mortality in premature infants.

Search strategy: 

The standard search strategy of the Cochrane Neonatal Review Group was used. This included searches of electronic databases: Oxford Database of Perinatal Trials, Cochrane Central Register of Controlled Trials (CENTRAL, The Cochrane Library, Issue 1, 2006), MEDLINE (1966 to 2006), EMBASE, previous reviews including cross references, abstracts, conference and symposia proceedings, expert informants in all published languages, and CINAHL (1982 to 2006). The electronic search was updated in July 2009.

Selection criteria: 

Only studies using random or quasi-random methods of allocation were considered for this review. Eligible studies assessed at least one of the outcome variables identified as important to this topic.

Data collection and analysis: 

Independent data extraction and quality assessment of included trials was conducted by the review authors. Data were analyzed using generic inverse variance methodology and weighted mean difference (WMD). Results are presented with 95% confidence intervals. Meta-analysis was undertaken using a fixed effect model.

Main results: 

Three studies met the criteria. Four other studies were excluded, as they did not compare double versus single wall incubators. Double wall incubators have the advantage of decreasing heat loss, decreasing heat production and decreasing radiant heat loss when compared to single wall incubators. There is also the advantage of reduced oxygen consumption. A minimal increase in conductive heat loss was noted when compared to single wall incubators. All of these effects are small and do not support the proposition that double wall incubators have a beneficial effect on long-term outcomes including mortality or the duration of hospitalization.

Share/Save