Validation of Two Flow Probes Using Bovine, Porcine, Ovine and Human Blood

In-line electromagnetic and doppler flow probes employed in extracorporeal circuits are calibrated for use with human blood. This study was performed to compare the accuracy of the Sarns Delphin II Doppler and the Medtronic Bio-Medicus electromagnetic flow probes to actual flow using bovine, porcine, ovine and human blood. The flow probes were incorporated into an in vitro extracorporeal circuit. Hematocrit, temperature and flow were randomized over ranges of 15-45% (increment 10%), 22-37°C (increment 5°C) and 1-5 L/min (interval 1 L/min), respectively. Probe flow readings were compared to the measured flow. Flow probe readings in all species significantly correlated with actual flow (p <0.05). Doppler and electromagnetic probe flow readings significantly differed within species (p <0.001). The doppler percent error positively correlated with hematocrit (p <0.001) in all species except human. The electromagnetic percent error did not consistently correlate with hematocrit or temperature. Neither of the flow probe percent errors correlated with erythrocyte diameter or mean corpuscular volume utilizing the average population measurement. Regression equations were developed to derive actual flow from the doppler probe readings in ruminants. These data will allow investigators to select a flow probe appropriate for the experimental conditions and animal model