Standards for filters

Abstract

The risk of an anaphylactic reaction to latex particles in patients undergoing anaesthesia is a serious issue, and techniques to reduce this risk are obviously welcome. The recent study (Barbara et al. Anaesthesia 2001; 56: 231–4) demonstrated that a particular breathing system filter tested reduced the transmission of latex particles. However, it did not, as the authors claimed, ‘suggest that the Pall BB25 filter provides adequate protection of the anaesthetised patient’ since some latex particles penetrated the filter. Hence, it cannot be concluded that an anaphylactic reaction does not occur when the filter is used in an anaesthetic breathing system. The filtration efficiency of breathing system filters varies with the size of the particles in the challenge [1]. The authors did not provide data on either the size of the particles released from gloves or other sources in the operating theatre, or on the size of the particles used in the challenge during the study. The risk of an anaphylactic reaction during anaesthesia was estimated at 1: 13 000, with latex particles responsible for one-sixth of these, giving the risk of a reaction to latex particles of about 1 in 80 000. The primary source of latex particles is from gloves. As no evidence was provided that latex particles are shed from breathing systems, the chance of an anaphylactic reaction to latex particles from sources other than gloves would appear to be extremely remote. The validity of using the Pall BB25 breathing system filter to prevent an anaphylactic reaction during anaesthesia from air-borne latex particles present in breathing systems remains unproven. Hence, because the use of a filter is not without its own risks, the conclusions reached by this paper must be challenged. Finally, we are gravely concerned that the publication of a study co-authored by an employee of Pall Medical advocating the use of a Pall product for this particular purpose would appear to be bordering on advertising by the manufacturer. Further, we wonder whether financial support has been received and if this was the case, appropriate acknowledgement should have been given