Systems Design Review : Heart Pump and Circulatory System Susan Rhodes, Kevan Bjornson, Blake Suhr, Michael Kromos, Henry Davignon

Agenda Review Problem Definition Requirements Concept Development Functional Decomposition Benchmarking Morph Chart Feasibility Concept Selection Pugh Analysis System Architecture Updated Risks Plans for Next Phase

Project Objective Improve and integrate the current heart pump and circulatory system models. The finished model must be acceptable for a laboratory setting and be accompanied by a user friendly LabVIEW interface. The finished model must demonstrate desired physiological conditions.

Customer Requirements

House of Quality

Concept Development Functional Decomposition Benchmarking Morph Chart Feasibility

Benchmarking (System model)

Benchmarking (Resistance)

Benchmarking (Tubing)

Morph Chart

Ventricle Feasibility most compatible with current system only relative shape accuracy desired 3D printed mold Cost effective relative to piston 3 molds for 30$ with remaining silicone Physiologically accurate

Piston Heart Pump Feasibility -The Heart Pump as it currently sits is a Piston design with a spring loaded plate in a diaphragm. Updating this system would only require minimal changes in design with only a few updates to current parts. The resulting cost is therefore minimal and the system would perform more reliably. -The current design was not physiologically accurate – while it came close, there were some issues with the data being collected. After speaking with Dr. Day, he believes that this type of system does not accurately model the pre-load phase, which would throw off the data slightly. This is due to the spring system which is creating a negative pressure, almost a suction, thus pulling the fluid into the chamber – which is not what we want

Feasibility of Solenoid Use Problem: The current solenoid has a maximum switching frequency and the customer requirements state that the pump must operate at 2.5 Hz. Solenoid was tested by firing relay with an Arduino controller Speed was slowly increased until solenoid was unable to return to closed position Upper limit frequency was calculated by counting number of fires in a ten second period. Upper frequency tapers at 2.8Hz and solenoid fails at 3Hz Conclusion: It is feasible to use the current solenoid to operate the pump efficiently from 2.5-2.8HZ

Feasibility of DAQ Use Problem: There are two types of DAQs available from the BME department for use. Is it feasible to operate the loop using one DAQ? DAQ # of Ai channels # of Ao channels # of D io channels Max input rate myDAQ 2 7 200 kS/s USB-6211 16 4 400 kS/s Device/Sensor Channel Required Relay Analog out Air Regulator Pressure sensor(x2) Analog in Flow sensor(2) Conclusion: Our proposed design will require the use of 2 analog out channels and 4 analog in channels. Therefore, it is feasible for us to operate using one NI USB-6211 DAQ.

Concept Selection Pugh Analysis System Architecture Updated Risks

Pugh Chart

System Architecture

Proposed Lab Exercise 1 (PV loop Observation) Uses real clinical diagnostic techniques learned in coursework Students would observe the impact predetermined simulations have on real-time visual data Pressure volume (PV) loops would be displayed in triplicate to allow for comparison. Required hardware: Pressure sensors, flow-sensor

Proposed Lab Exercise 2 (Starling Curve Plots) Students would collect discrete data points using the labveiw program Small adjustments would be made to the loop to reach required points Data would be exported an analyzed for lab report Requires the use calculation of ventricular volume, cardiac output, right atrial pressure, and flow) Achieved by use of flow and pressure sensors

Updated Risk Assessment

Updated Plans: Silicone Ventricle The idea for the ventricle design started in an SME interview with Dr. Day. The current model was based on a piston and raised some concerns to the biological accuracy of such a model. He presented his heart model loops and the ventricle design appeared to be the most compatible with the current system. Using CAD a draft of a ventricle design was created and brought to Mike Buffalin at the construct. Mike had made the previous molds for Dr. Day’s and Dr. Mix’s loops. The mold is currently in the process of being 3D printed. The ventricle will be made by pouring silicone into the mold. The ventricle has a volume of 120ml. The silicone mix is estimated to cost $30 per pint. Which would provide enough for 3 molds with almost enough for an additional mold remaining. The calculations show the ventricle is approximately $10 per mold, where the diaphragm was $50 per unit. One extra plate is needed to hold the ventricle in place, at a cost of $10. There are very few risks and enough reward to justify a prototype for further testing

Next Steps The major change is a shift of focus from repair to remake. From our previous steps, we determined that many of the systems were either too broken or technologically insufficient to warrant fixing

Team Action Items Create and assemble the ventricle prototype Test the pump against the Engineering Requirements Decide if the ventricle pump should continue to be perused. Identify all material in the circulatory system that needs to be replaced. Test various tubing for compliance and identify the desired tubing Generate preliminary LabVIEW program