Showing papers by "Leicester General Hospital published in 1956"

Carbon dioxide concentration in various anaesthetic techniques

Abstract: FOLLOWING the observation of Harrison and Jones (1955) on the concentration of carbon dioxide in gas samples taken from two points on a Boyle's machine during the administration of anaesthesia by a semiclosed method, it was thought that it might be enlightening to extend the investigation to other techniques and machines. For this purpose, use was made of the recently available Carbon Dioxide Analyser made by the British Oxygen Co. Ltd. This apparatus operates on the principle of a colour change in a special solution, the tint of which varies with the concentration of carbon dioxide, in the gas sample. The readings expressed in percentage form, are: 0.3, 0.7, 1.0, 1.5, 2.0, 3.0, 4.0, 5.0. Naturally one would not expect the degree of accuracy with this apparatus that one would from analyses carried out by Haldane's method but, if that claimed by the manufacturer is justified, one can certainly obtain most useful information by which to compare various techniques. Each experiment was repeated in ten consecutive patients when an identical technique was employed and the results tabulated. The readings were taken in the middle of the anaesthetic when the operation was in progress and no attempt has been made to evaluate changes in carbon dioxide concentration during induction, etc., so that the results represent\" running levels \" only. Fresh soda lime was used as, obviously, exhausted soda lime would affect the readings. Using a Coxeter-Mushin absorber, the analyser was plugged into the circuit first at the junction of the expiratory and then of the inspiratory valves with the corrugated tubing leading to the patient. In the first experiment a completely closed circuit was employed with a basal feed of 200 ml of oxygen and the circulating gases passing through the ether chamber. Readings were as follows: