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EVALUATION OF THE CO 2 REBREATHING METHOD FOR THE NONINVASIVE MEASUREMENT OF RESTING CARDIAC OUTPUT IN MAN
Author(s) -
Hargreaves M.,
Jennings G.
Publication year - 1983
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1983.tb00230.x
Subject(s) - cardiac output , fick principle , reproducibility , arterial blood , cardiology , mean difference , medicine , limits of agreement , significant difference , anesthesia , mathematics , hemodynamics , nuclear medicine , confidence interval , statistics
SUMMARY 1. We have compared the indirect Fick, a non‐invasive CO 2 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 CO 2 content difference were used: (i) from end‐tidal and rebreathing bag equilibrium P co 2 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 Pco 2 and the standard CO 2 dissociation curve; (iii) by direct measurement of arterial P co 2 . 2. Each method was satisfactory in that reproducibility was similar to thermodilution (5‐10%) and the equations relating thermodilution to indirect Fick cardiac output were linear with slope and intercept, close to 1 and 0, respectively. End‐tidal P co 2 accurately predicted arterial Pco 2 except in five patients with liver disease. Direct measurement of arterial P co 2 is recommended in such patients. In other subjects there was no advantage in either correcting non‐invasive measurements of alveolar gas to obtain veno‐arterial CO 2 content difference, or in direct measurement. 3. The indirect Fick is an accurate method for measuring cardiac output at rest in normal subjects and those with cardiovascular disease. Its use can be extended to other groups by a single arterial blood sample.