A method of controlled ventilation with a circle-absorber breathing system.

A simple method of adapting a pressure-cycled ventilator of the flow generator type to ventilate patients on a circle-absorber anaesthetic system is described. Standard lengths of corrugated black rubber tubing are placed between the ventilator and the circle-absorber is deadspace, replacing the reservoir bag. The performance of this modification was investigated and a functional volume for the tubing calculated. There was a simple relationship between the tidal volume, the length of tubing and the fresh gas flow required to avoid dilution of the anaesthetic gases by the driving gases.