A New Method for Direct Recording of Cardiac Output. ∗

Summary

A modification of a bristle flowmeter is described which permits direct recording of cardiac output and its fluctuations from one heartbeat to another. The device is inserted into the trunk of the pulmonary artery of anesthetized, heparinized dogs without blood loss and without interrupting blood flow. Zero flow can be established by mechanical means without occluding the vessel. Phasic changes during the cardiac cycle consist of a marked forward flow during cardiac ejection and a brief period of backflow following ejection. Mean cardiac output can be directly recorded by electrically averaging the phasic flows.