Gas Flow Measurements with a Gas Dilution Technique

A new method for gas flow measurements, based on a gas dilution technique, is described. A known amount of fresh room air is injected as a tracer gas into a carrier gas stream. The downstream concentration profile of the tracer gas is recorded with a portable mass-spectrometer. The flow rate of the carrier gas is calculated from the area under the tracer gas curve as electronically integrated. The method was tested against precision spirometers, one of the rolling seal type and one of the fluidistor type. It was shown that any rapid gas analyser might be used for the analyses, either of the tracer gas or of the carrier gas. The applicability of this method during general Anaesthesia and in other clinical situations is discussed.