Limitations of noninvasive determination of cardiac output in small circulatory systems

Pulsewave velocity analysis is an option for the noninvasive determination of cardiac output and the evaluation of additional haemodynamic parameters. An algorithm we developed ourselves has been established as a method for t he measurement of cardiac output in rabbits. The Effectiveness of this prog ram was investigated by monitoring controlled hypoxia-induced alterations i n the circulatory system. Calculated values were compared with direct measu rements of cardiac output with a Doppler flow probe placed in the ascending aorta. Within the physiological framework of blood gas analysis, a good co rrelation was found between the two methods. In the case of hypoxia-induced depression, however, the two methods showed diverging results, presumably due to arrhythmia-induced wave reflections within the arterial vascular tre e. This makes an extension of the algorithm necessary to take account for t hese case.