Hydrophobic versus hygroscopic heat and moisture exchangers

A false alarm with the oxygen failure w d n g device An incident involving a multitone hospital bleep in the anaesthetic room has recently drawn our attention to extraneous sounds simulating the oxygen failure warning device '(Ritchie Whistle)' fitted to our anaesthetic machines.A continuous high pitched sound in the anaesthetic room was assumed to come from the Ritchie Whistle.The machine was examined however, and found to be in order.The noise was eventually traced to a hospital bleep attached to a handbag placed near the sink.The bleep had been splashed with water during routine hand washing and had emitted the continuous noise (apparently characteristic of all wet bleeps) which could only be terminated on removal of the batteries.This incident should reinforce the argument for leaving bleeps at theatre reception rather than in the operating department where their presence is a constant source of annoyance to all the staff who work there.