Potential contamination of side stream capnography systems during regional anaesthesia

Abstract

We would like to highlight the potential for contamination of anaesthetic breathing apparatus via side stream capnography when used for respiratory monitoring during regional anaesthesia. The use of supplemental oxygen and monitoring of respiratory rate during these techniques is common practice. ASA guidelines recommend the use of clinical signs and/or monitoring for the presence of exhaled carbon dioxide [1]. It is common local practice to supply supplemental oxygen using a simple oxygen mask connected to a rotameter while measuring respiratory rate by placing side stream capnography within the oxygen mask. Various techniques have been observed to secure the capnography port to the oxygen mask but most do not include a bacterial filter. This practice increases the potential risk of cross-contamination between patients as the side stream capnography system is not routinely changed between cases. We recommend the off license use of a 5-μm filter included in some Luer lock filter needles (Filter Needle 2; Braun Medical Ltd., Thorncliffe Park, Sheffield, UK.) This filter can be detached from the needle allowing effective bacterial filtration of the sampled gas without the potential trauma caused by the presence of a needle close to the patient’s face. It is small enough to fit into the holes of an oxygen mask without increasing bulk (Fig. 1) and is a cheap way to avoid potentially dangerous and costly sequelae of cross-contamination during subsequent general anaesthetics. Off-license use of a 5-μm filter.