An instrument for the long-term continuous measurement of oxygen uptake

We developed an instrument for the continuous measurement of oxygen uptake. The instrument consists of a hood which covers the whole head of the subject, a flowmeter, an oxygen meter and a microcomputer. A servocontrolled blower draws room air through the hood, adjusting its volume flow so that the oxygen concentration in the hood is kept constant. The flow rate of the blower is measured with a heated-air transfer-type flowmeter, and oxygen concentration is measured by a solid electrolyte oxygen meter. Oxygen uptake can be calculated from the flow rate and oxygen concentration using the microcomputer, and each of these values is stored on a floppy disk. By this technique the instrument is able to measure oxygen uptake continuously for a prolonged period of time. We then compared the oxygen uptake measurements obtained with this instrument and those obtained with the Douglas bag method. The relationship between the volumes obtained by the two methods showed a high correlation (r = 0.98). The instrument was shown to be capable of measuring the slight change occurring in oxygen uptake between a subject at rest and performing isometric exercise.