Validation of the use of foreign gas rebreathing method for non-invasive determination of cardiac output in heart disease patients.

OBJECTIVE: To compare a new device (Innocor) for non-invasive measurement of cardiac output (CO) by foreign gas rebreathing method with conventional techniques used in the measurements of cardiac function. METHODS: Cardiac outputs measured by Innocor (CO(RB)) were compared with CO obtained by echocardiography (CO(EC)), Swan-Ganz thermodilution (CO(TD)), and left ventricle radiography (CO(LVR)) in 34 patients subjected to cardiac catheterization. Values obtained from the four methods were analyzed by linear regression and paired values were compared by the method of Bland and Altman in SPSS. RESULTS: There was strong positive correlation (r=0.94) between Innocor cardiac output values and the corresponding values obtained by thermodilution and between CO(EC) and CO(LVR) values. Thermodilution appears to overestimate cardiac output when compared to the values obtained with Innocor by (0.66+/-0.22) L/min (P<0.0001). There was no correlation between data obtained by Innocor and the corresponding CO(EC) and CO(LVR) values. CONCLUSION: Innocor CO(RB) is an easy, safe and well established method for non-invasive measurement of cardiac output with good prospects for clinical application in heart disease patients.