Physiologic evaluation of a catheter tip electromagnetic velocity probe: A new instrument

A miniature catheter electromagnetic velocity probe has been designed and enclosed within the tip of a No. 8 F cardiac catheter, 2.67 mm. in external diameter. Peak systolic blood flow rates from 3 to 338 cm. 3/sec. as measured by the catheter probe agreed closely with simultaneous measurements by the perivascular electromagnetic flowmeter probe, in the ascending, descending thoracic and abdominal aorta of 12 anesthetized dogs ( r = 0.97 to 0.99). Catheter and perivascular probe measurements of blood flow, made every 1 100 of a second throughout the cardiac cycle, correlated well with each other in these 12 experimental animals ( r = 0.94 to 0.99). In vitro studies utilizing measured steady blood flow in the physiologic range, 13 to 473 cm. 3/sec., demonstrated that the electrical output of the catheter probe was linear ( r = 0.998). Therefore, the catheter probe can be utilized to record and measure accurately the instantaneous blood velocity and flow in the systemic arterial circulation. In comparison to the perivascular flow probe, the catheter probe has the advantage of (1) not requiring surgical exposure of the blood vessels; (2) not restricting pulsatile expansion of the blood vessel; (3) readily allowing the recording of blood velocity in the larger arteries and veins of the systemic and pulmonary circulation; and (4) having the velocity sensing electrodes in direct contact with the blood.