Measurement of oxygen uptake: a method for use during nitrous oxide in oxygen anaesthesia

A new method for oxygen uptake (VO2) measurement based on a constant volume closed circuit is discussed. The accuracy of the method tested in the laboratory was demonstrated to be +/- 1.8% and estimated to be +/- 2.01% in clinical use during abdominal surgery. The 0-90% rise time of the measurement to step changes in VO2 was found to be 42 s, for a change of 15 ml min-1 with a lag time of less than 30 s.