The reliability of noninvasive cardiac output measurement using the inert gas rebreathing method in patients with advanced heart failure

Abstract

Background: Impaired cardiac output (CO) is a key element of heart failure (HF). So far, there has been no simple, reliable, inexpensive and non-invasive CO measurement method feasible for clinical practice. Not a single diagnostic test has been elaborated to diagnose and monitor HF. The aim of the study was the evaluation of the reliability of a new, non-invasive CO measurement device utilizing an inert gas rebreathing technique and an infrared photoacoustic gas analyzer, in comparison with standard invasive methods.
Methods: In 21 patients with advanced HF (NYHA classes III and IV) undergoing cardiac catheterization as a routine hemodynamic evaluation before heart transplantation, CO measurements with the tested non-invasive method were carried out during invasive examination.
Results: CO measured by the inert gas rebreathing technique (CORB), according to the statistical Bland-Altman method, was, on average, 0.1 L/min higher than that determined by thermodilution (COTD) and 0.006 L/min higher than the CO determined by the Fick formula (COFick). This magnitude of difference equals 2.8% of COTD and 0.15% of COFick values. The limits of agreement between CORB and COTD were ± 1.4 L/min, and between CORB and COFick ± 1.3 L/min. In the subgroup with atrial fibrillation, the mean difference between tested and reference methods (0.3 ± 1.0 L/min for both COTD and COFick) was higher than in the sinus rhythm subgroup (0.06 ± 1.5 L/min for COTD and 0.08 ± 1.5 for COFick).
Conclusions: CO measurement with the inert gas rebreathing method utilizing an infrared photoacoustic gas analyzer seems reliable enough to be employed in clinical practice. Being non-invasive, it may well be used for repeated determinations in patients with HF. (Cardiol J 2008; 15: 63-70)