[Difficulties in noninvasive cardiac stroke volume determination in "small" blood circulation 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 the measurement of cardiac output in rabbits. The effectiveness of this program was investigated by monitoring controlled hypoxia-induced alterations in the circulatory system. Calculated values were compared with direct measurements of cardiac output with a Doppler flow probe placed in the ascending aorta. Within the physiological framework of blood gas analysis, a good correlation 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 tree. This makes an extension of the algorithm necessary to take account for these case.