Electromagnetic Flow Sensor Research Articles

Correlation of maximum aortic and carotid flow acceleration in chronically instrumented dogs.

Peak flow acceleration measured in the common carotid artery was compared with peak flow acceleration measured in the ascending aorta of five chronically instrumented dogs. Electromagnetic flow sensors, myocardial electrocardiographic leads, right atrial catheters, and coronary occluders were implanted through an incision of the chest at the fourth intercostal space and a ventral midline incision of the neck under sterile conditions while the dogs were anesthetized with sodium pentobarbital. Experiments began 10 days after surgery. We investigated the response to exercise, to 60-second occlusions of the circumflex branch, the anterior descending branch, or both branches of the left coronary artery, to induction of short-acting barbiturate anesthesia, and to intravenous infusion of three concentrations each of isoproterenol (0.8, 1.5-3.0, and 4.0 µg/min), l -norepinephrine (0.8, 2.0, and 4.0 µg/min), and acetylcholine (0.3-0.5, 0.8-2.0, and 4.0 mg/ min). During coronary occlusion, exercise, and induction of anesthesia, both accelerations changed in the same direction and approximately to the same extent. During isoproterenol infusion, both accelerations increased, but the maximum carotid flow acceleration increased more than did the maximum aortic flow acceleration. When l -norepinephrine was infused, the changes were small and were not always in the same direction. When acetylcholine was infused, peak carotid flow acceleration decreased. Peak carotid flow acceleration might be useful as an indirect measure of myocardial mechanical performance during coronary occlusion, anesthesia, and exercise, except during potent peripheral vasodilation like that caused by acetylcholine.

A new approach to electromagnetic blood flow determination by means of catheter in an external magnetic field.

Maximal reduction in transverse catheter dimension has been achieved for the purpose of creating an intravascular electromagnetic flow sensor capable of percutaneous introduction into the vascular system. The electrodes are mounted on a flexible frame which collapses as it passes through a small branch blood vessel and expands to span the diameter of the main vascular trunk when entering it. Unlike the catheter flow sensors developed previously, which are velometers, i.e., sensors of fluid velocity, the present one is capable of measuring the volume rate of flow in branch blood vessels as well as in the major sections of the vascular tree. The magnetic field is provided by a large air core electromagnet placed externally to the animal or patient. A special circuit utilizing two electrodes and three leads permits reduction of the unwanted quadrature signal to zero. A standard sine wave electromagnetic flow meter channel designed for use with conventional electromagnetic flow transducers is adequate for flow measurements as well as for power supply to the large magnet. Illustrations of the performance of the apparatus in vitro and in vivo are presented.

The validity of chronic hepatic blood flow measurements obtained by the electromagnetic flow meter

<h2>Summary</h2> Techniques of long term implantation of electromagnetic flow sensors on the canine ascending aorta, thoracic inferior vena cava, hepatic artery, superior mesenteric artery and portal vein are presented, with a method of obtaining zero flow in the vessels being monitored. Technical problems are discussed and solutions outlined. Hepatic blood flow was measured for periods up to 19 days in the unanesthetized animals. EHBF obtained by the BSP method through implanted catheters correlated well with values for hepatic blood flow obtained by the flow meter. Instantaneous cardiac output may be followed simultaneously with hepatic blood flow in the preparations described.