A DISCIPLINED FLOW ESTIMATION ALGORITHM IN THE DEBAKEY VAD?? SYSTEM

Abstract

PURPOSE A dual-channel flow probe and meter are used to continuously measure real-time blood flow rate in the DeBakey VAD®. The system provides a true, calibrated, and independent metric of blood flow while consuming approximately 0.5 Watts. Power reductions, however, may be obtained by deriving flow directly from intrinsic pump signals. The algorithm's accuracy is ensured by periodically verifying its output to the existing flow meter's output using duty cycle control. METHODS: A primary data table containing the DeBakey VAD®'s flow versus power and speed information was stored into a low-power microntroller. The microcontroller was programmed to sample the pump's analog power and speed signals and, via the primary data table, output the corresponding flow value for display and pump control purposes. The real-time flow meter was periodically energized and its output compared to the derived value. The duty cycle used to control the real-time flow meter was proportional to the difference between the actual measured flow and derived flow values. Additionally, a secondary data table containing actual flow information was stored and used to prove that the algorithm performed correctly over the course of its use. CONCLUSION: A flow estimation algorithm whose accuracy is periodically verified against an independent metric has been realized for use with the DeBakey VADB. This hybrid approach allowed the algorithm to be tested in a safe and controlled manner and reduced power consumption by more than a magnitude while maintaining the precision of the existing real-time acoustic flow meter.