Evaluation of a System for On-line Analysis of V̇O2 and V̇CO2 for Clinical Applicability

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Abstract
The accuracy of a system to measure respiratory gas exchange on an on-line basis was evaluated in rabbits, dogs and humans by comparing it with a gas collection method. The system incorporates a hot-wire flowmeter, mass spectrometer and microcomputer. It performs on-line compensation for both transport delay and dynamic response of the mass spectrometer. Compensation of flow measurement for changing gas fractions also is performed. Excellent linear correlations were obtained between the 2 methods. In animals during mechanical ventilation with room air (.ovrhdot.VO2 (oxygen uptake): r = 0.995; .ovrhdot.VCO2 (carbon dioxide output): r = 0.993), and nitrous oxide in O2 (.ovrhdot.VO2: r = 0.975; .ovrhdot.VCO2: r = 0.976); in men spontaneously breathing room air at different workloads (.ovrhdot.VO2: r = 0.999; .ovrhdot.VCO2: r = 0.998), and higher inspired O2 fractions (FIO2: 0.38-0.75) (.ovrhdot.VO2: r = 0.910; .ovrhdot.VCO2: r = 0.988). The system is suited for accurate and continuous measurement of respiratory gas exchange during mechanical ventilation, anesthesia and exercise testing.