EVALUATION OF THE CO2 REBREATHING METHOD FOR THE NON-INVASIVE MEASUREMENT OF RESTING CARDIAC-OUTPUT IN MAN

Abstract

We have compared the indirect Fick, a non-invasive CO2 rebreathing method for measuring resting cardiac output, with the thermodilution method in eleven subjects including some with cardiac and pulmonary disease. Three alternative methods for calculating veno-arterial CO2 content difference were used: (i) from end-tidal and rebreathing bag equilibrium PCO2 modified from the equations developed for use during exercise by Jones et al. (1975); (ii) by using the uncorrected difference between end-tidal and equilibrium PCO2 and the standard CO2 dissociation curve; (iii) by direct measurement of arterial PCO2. Each method was satisfactory in that reproducibility was similar to thermodilution (5-10..