Validation of Open-Circuit Method for the Determination of Oxygen Consumption.

摘要

Seventy-two measurements of respiratory exchange by both the open- and closed-circuit methods were made on ten subjects at rest or during steady-state treadmill work (5.6 km/hr, 0% and 7% grades) in a post absorptive state or 1-3 hr after eating a 61-g protein meal. Inspired nitrogen minute volume was the same as expired nitrogen minute volume. Oxygen consumption (Vo2), as measured by the open-circuit method, was an average of 1.1% higher, ranging from 5.5% higher to 4.7% lower, than the values obtained by the closed-circuit method. The average difference would have been reduced to 0.5% if the measured room air gas percentages (20.91% O2, 0.03% CO2, and 79.06% N2) had been used for the open-circuit method rather than the classical values. Carbon dioxide production (Vc02) was equal regardless of method, and respiratory exchange ratios varied in relationship to differences in Vo2. The results confirm the validity of using the open-circuit method for determining respiratory exchange in man. (Author)