An evaluation of the Oxylog as a portable device with which to measure oxygen consumption

The Oxylog, a portable device for measuring oxygen consumption, was evaluated under standard, laboratory conditions and with exercising human subjects. The difference in oxygen partial pressure between room air and a series of test gases measured by the Oxylog showed good agreement with results obtained using a paramagnetic analyser and stable values were obtained for at least 6 h. The measurement of oxygen consumption by the Oxylog was assessed under simulated conditions, with an anaesthetic ventilator, and in exercising human subjects. With a simulated steady-state oxygen consumption there was an initial delay of 2 min before any oxygen consumption was recorded. Subsequent increases in simulated oxygen consumption were detected within one minute. The oxygen consumption of exercising human subjects measured with the Oxylog showed very good agreement with simultaneous measurements obtained using the Douglas bag technique. The application of an appropriate conversion factor allows the individual's energy expenditure to be estimated from the oxygen consumption: in this study a factor of 20.08 kJ per litre oxygen consumption gave the best agreement with the Douglas bag estimate.