The effect of volatile anaesthetic agents on the filtration performance of paediatric breathing system filters*

Abstract

Summary The aim of this study was to determine the filtration performance of five commonly used paediatric breathing system filters following exposure to desflurane, isoflurane and sevoflurane. It has been suggested that oil may degrade the performance of filter material. Volatile anaesthetic vapours are organic and hence may affect the filtration performance of breathing system filters during anaesthesia. This has not been tested for various concentrations of volatile agent, type and duration of exposure. The filtration performance of the filters was measured following exposure to desflurane, isoflurane and sevoflurane at 1 and 2 minimum alveolar concentration (MAC) for 1 and 4 h. Penetration of particles through the Clear‐Therm Micro, Clear‐Therm Mini and Humid‐Vent Filter Pedi increased by between 2.4 and 2.8 times after exposure to desflurane at 2 MAC for 4 h compared to that through unexposed filters (p < 0.0001 for all three filters). Further investigation is required to determine whether this reduction in filtration performance by desflurane is clinically significant.

The effect of desflurane on filtration performance of breathing system filters*

“…Only desflurane had a significant effect on filtration performance and this effect was only particularly marked on three of the five different filters tested [9]. The significant effect of desflurane in contrast to other volatile anaesthetics might be due to either its chemical composition or, more likely, that the concentrations used are greater, as the minimum alveolar concentration of desflurane (6%) is much greater than for other volatile anaesthetics.…”

“…In a previous study investigating the effect of three different volatile anaesthetics (desflurane, isoflurane and sevoflurane) on the filtration performance of filters intended for use with children [9], all the filters included in the study were electrostatic. Only desflurane had a significant effect on filtration performance and this effect was only particularly marked on three of the five different filters tested [9].…”

“…Each group of five filters for a particular exposure was exposed to air or air and desflurane in parallel [9]. The flows of air used to deliver the vapour to each group were 5 l.min .…”

“…The reduction in performance was more marked when using desflurane at higher concentrations and for longer duration. The effect of isoflurane and sevoflurane on these paediatric filters was insignificant [9]. All the filters studied by Froom were electrostatic.…”

Heat and moisture exchangers and breathing system filters: their use in anaesthesia and intensive care. Part 2 – practical use, including problems, and their use with paediatric patients

“…There is evidence to suggest that prolonged exposure (>4 h) to high levels of desflurane (2 MAC) reduces the filtration performance of some electrostatic filters intended for use with adults [30] and children [31]. Lawes described other effects that the use of HMEs and filters can have on monitoring patients during anaesthesia [32].…”