An Electromagnetic Catheter-Flowmeter

An electromagnetic flowmeter incorporated into a catheter is described. The catheter is introduced into the aorta via the femoral artery. The flow sensor is located some distance below the catheter tip and is sensitive to flow at right angles to the catheter. A crater-like elevation at one end of the transducer lumen permits funnel-like connection of the transducer to the ostium of an aortic branch. The transducer thus measures the blood flow through a selected branch of the aorta. It is pressed against the branch artery by arching the catheter by means of a pull-wire. A reliable and readily reproducible zero-flow baseline is obtained by slightly withdrawing the lumen of the transducer from the branch ostium, thus closing the lumen by the aortic wall. Records of phasic blood flow in the left renal and superior mesenteric arteries of a dog are presented. The calibration was accomplished by comparison with a calibrated noncannulating electromagnetic flow transducer. Reliable calibration can also be performed in vitro.