Electromagnetic flow insert design for haemodynamic safety

Higher resolution blood flow measurement in the 40-1000 mL/min range for pediatric and renal therapy established the need for a fivefold increase in the signal-to-noise ratio of a disposable transducer element used with a Faraday-type electromagnetic flowmeter. Magnetic field strength, concentration and electronic gain stability improvements gave only part of the needed gain. Increasing the blood velocity at the measuring point could have introduced unacceptable pressure drops and blood damage. Classical design methods applied to a tapered sensing section produced an insert which was tested in vitro, displaying a 3.5 gain increase with an acceptable increase in pressure drop and no greater hemolysis.<>