Simultaneous multiple-subject analysis of respiratory gas exchange in humans

Abstract

Respiratory gas collection and analysis with indirect calorimetry allows assessment of energy and substrate use during rest and exercise and aerobic capacity. We have developed a novel system for simultaneous multiple-subject measurement of respiratory gas exchange during rest and exercise for up to five subjects, and validated the system with a series of experiments. Thirteen healthy young men (mean age 22 ± 2 years, height 172 ± 6 cm, weight 67.1 ± 11.6 kg) participated in this study. Memory problems of the mass spectrometer, which are caused by switching analyzed gases of different compositions between channels, was sufficiently eliminated with a washout of 2 s (seconds) with errors of less than 0.3% for O2 and less than 0.4% for CO2. The high-response mass spectrometer and specially designed mixing chamber enabled correct estimation of metabolic measurements, even for gas concentration data from a non-continuous flow of any given 1s of every 10-s interval (spot-sampling method). Diet-induced thermogenesis (DIT) and oxygen consumption (VO2) during maximal incremental exercise were not significantly different between the novel and Douglas bag methods (P = 0.61 and P = 0.56, respectively). The limit of agreement of DIT and VO2 during maximal incremental exercise between the two methods were 2.8 ± 43.6% and 0.9 ± 4.8%, respectively. We concluded that the newly developed system has reasonable validity over a wide range.

Keywords

• indirect calorimetry
• maximal oxygen consumption
• resting metabolic rate
• douglas bag method
• mixing chamber method
• diet-induced thermogenesis