Pollution control in the operating room: a simple device for the removal of expired anaesthesia vapours.

Foe ~ORE TrlAN A CENTLrRy atmospheric pollution in the operating room has been accepted as a necessary accompaniment of inhalation anaesthesia, and halitosis has been the trademark of the practising anaesthetist. Halothane was a pleasant change from the pungent lingering odour of ether, but there have always been a few members of the operating room staff who complained of headache following exposure to the fumes. In recent years the author has himself become increasingly sensitive to the vapour of both halothane and methoxyflurane, the result being undue fatigue at the end of the day, arid, after more prolonged exposure, severe headache and nausea. Various crude devices were used to suck away the vapour ~rom the expiratory valve of the machines, and the subjective observation was made that ff one was persistent in using these devices the above-mentioned symptoms did not occur. The potential hazard of chronic exposure to anaesthetic agents is now being recognized, 1,2 and the need for a correctly designed aspirator attached to the expiratory valve of the anaesthesia machine is apparent. Such an aspirator should be adaptable to each of the wide variety of expiratory valves presently employed on anaesthesia machines, and it must protect the patient from the extremes of positive and negative pressure which can easily be applied to his airway ff the vacuum should be interrupted or incorrectly applied. Two such devices have recently been described. Marrese a applied the vacuum line to the patient circuit below the expiratory valve, and controlled it with a needle valve. While this device was in use the expiratory valve was dosed, but in case of vacuum failure the valve could be opened. Although he stressed that "no patient was subiected to measurable positive pressures except when intentionally used in pulmonary oedema," the device described by him lacks an automatic safety vent to guard against positive pressure. Furthermore, the unintentional application of full suction to the circuit could be of serious consequence to the patients. Schnelle and Nelson 4 have recognized these problems in the design of their exhaust collecting device and have used the same basic principles as guided us in our modification of the Bird Mark II gas balance valve for the same purpose. The gas balance valve of the Bird Mark II respirator was found to be sensitive when used as an expiratory valve in a patient circuit. It has a fine control knob which is placed well away from the exhalation ports, thereby making it possible to modify these ports for the application of vacuum and the attachment of a spill tube. Using the three-way tee adaptor supplied with it, this valve can be inserted in the expiratory side of the breathing circuit of the anaesthesia machine, and