The wide-range ejector flowmeter: calibrated gas evacuation comprising both high and low gas flows

The wide-range ejector flowmeter is an active scavenging system applying calibrated gas removal directly to the anaesthetic circuit. The evacuation rate can be adjusted on the flowmeter under visual control using the calibration scale ranging from 200 ml.min-1. to l5 l.min-1. The accuracy of the calibration was tested on three ejector flowmeters at 12 different presettings. The percentage deviation from presetting varied from + 18 to -19.4 per cent. The ejector flowmeter enables the provision of consistent and accurately calibrated extraction of waste gases and is applicable within a wide range of fresh gas flows.