"In" vivo method for calibrating electromagnetic flowmeter probes.

Abstract

Cannulating and noncannulating electromagnetic flow probes were calibrated using a model 322 dual-channel Carolina Medical Electronics flowmeter. The cannulating probes were calibrated "in vitro" using a constant-flow system and the collected perfusing solution measured over a given interval of time. The results indicated that these probes, which have their electrodes in direct contact with the flowing blood, were relatively insensitive to hematocrit. A single probe factor can be obtained using 0.9% NaCl as a substitute for whole blood. The noncannulating probes were calibrated "in vivo" against the standard cannulating probes by placing them in series on a vessel and adjusting the flowmeter sensitivity (or probe factor) of the channel connected to the uncalibrated probe until the metered flow readings of both channels were identical. The animal''s hematocrit was then changed in order to obtain additional points for the calibration curve.