Breathing system filters for paediatric practice

Abstract

We wish to draw attention to the discussion section of the paper from Cann and colleagues comparing breathing system filters [1] which contains the following comment: ‘Optimal performance is especially pertinent to the paediatric setting where there are additional considerations like increased dead space. However, the AAGBI recommends that filters are not used for paediatric patients; rather, the breathing system is replaced between each case. This recommendation is endorsed by the Association of Paediatric Anaesthetists’. In fact, the Association of Paediatric Anaesthetists (APA) has not endorsed this recommendation and our position is set out clearly in a statement issued jointly by the APA and the AAGBI [2]. This statement followed a meeting between both organisations and a senior scientific officer from the MHRA to address issues arising from an evaluation of breathing filters by the MHRA published in March 2004 [3]. The MHRA evaluation suggested that some paediatric filters were less efficient than adult filters because they allowed greater penetrance of saline particles during in vitro testing. It was therefore concluded that they did not afford the same degree of protection for the breathing system as adult filters. Subsequently, it was recommended that circuits used for paediatric anaesthesia should be disposed of after use [4]; however, we note that this stipulation is not contained in the latest guidelines on checking equipment. Most of the paediatric filters with higher measured penetration values were designed for use in small infants and were tested with a gas flow of 15 l.min−1, which is disproportionately high when compared with the adult test flow (30 l.min−1). The APA therefore considered that further information obtained at lower, more appropriate flows was required before recommending a significant change in practice. Furthermore, in older children it is common practice to use larger filters together with a variety of adult breathing systems, including circle systems. Therefore, a blanket recommendation to change circuits between each paediatric case is inappropriate. Taking account of these considerations, the AAGBI and the APA issued a joint statement, which included ‘At present there is insufficient evidence to recommend a wholesale change in practice. In order to underpin future recommendations, it has been agreed that further work is required to examine the performance of filters manufactured for use in infants and small children. In the meantime, in order to protect individual anaesthetists, anaesthetic departments should review their practice and policies. There should be a local policy, agreed by the local clinical governance structure, concerning the use of single use items of equipment and filters that takes account of the size of the patient and the existing evidence’[2]. We welcome the presentation of a paper at the recent Annual Scientific Meeting of the Association of Paediatric Anaesthetists by Dr Wilkes and colleagues which reported useful additional information on the performance of infant filters at lower gas flows. We hope that the paper will be published shortly; this should provide further clarification and, together with the original MHRA report, help departments draw up a policy on the safe and rational use of circuits and filters in the paediatric population, which is appropriate to their needs.