Key result
Equilibrium rebreathing yields ~44% lower variation vs extrapolation for estimating mixed venous CO2 during exercise.
Why the study?
The accuracy and variability of the Defares extrapolation CO2 rebreathing method compared to the Collier equilibrium method for estimating mixed venous CO2 tension during exercise were uncertain.
Does the extrapolation (Defares) CO2 rebreathing method compare favorably to the equilibrium (Collier) method for estimating mixed venous CO2 tension in adult subjects during exercise?
Population
95 adult subjects including 25 with coronary artery disease
Comparison
Defares extrapolation CO2 rebreathing method (uncorrected) vs Collier equilibrium CO2 rebreathing method (corrected)
Design
Experimental comparison study
Authors
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Supports Collier method for lower variability in exercise CO2 estimates; leaves open validation against direct cardiac output measures.
Does the extrapolation (Defares) CO2 rebreathing method compare favorably to the equilibrium (Collier) method for estimating mixed venous CO2 tension in adult subjects during exercise?
Absolute Event Rate: 2.5% vs 4.5%
The equilibrium (Collier) CO2 rebreathing method demonstrates lower variability than the extrapolation (Defares) method, making it superior for evaluating cardiac output during exercise.
Auchincloss et al. (1980) studied Coronary artery disease and healthy subjects (n=95). Equilibrium (Collier) CO2 rebreathing method vs. Extrapolation (Defares) CO2 rebreathing method was evaluated on Coefficient of variation in duplicate determinations of mixed venous CO2 tension. The equilibrium (Collier) CO2 rebreathing method yielded a lower coefficient of variation (2.5%) than the extrapolation (Defares) method (4.5%) for estimating mixed venous CO2 tension during exercise.
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