1. Servo-Controlled Blood Vessel Occluder Ahmed El-Gawish, Alan Chen, Hugo Loo, & Imad Mohammad Advisor: Ki Chon

2. Background Renal autoregulation keeps blood pressure stable in the renal system The device will increase or decrease blood pressure by ~20 mmHg with fast response times The response time should be in order of 100 ms.

3. The Output KI Chon project proposal

4. Design Alternatives Mechanical hydraulic occluder Water based syringe pump occluder Regulated compressed air occluder

5. Regulated Compressed Air Occluder Electrical Regulator Valve

6. Stage Regulation Stage 1: regulator/valve –125 psi → 18 psi –ON/OFF control –Safety feature Stage 2: regulator/controller –Specific control over range –18 psi → 120 mmHg < p < 200 mmHg

7. Regulator Properties < 70 milliseconds response time Analog/digital inputs/outputs available Allow users to develop own software for interface

8. Valve

9. Compressed Air Occluder

10. Limitation of Air System Compliance of air Biocompatibility of gas Budget limit

11. Mechanical Occluder Components i.Occluder ii.Solenoid iii.Spring iv.Jagged teeth v.Hydraulic system

12. Mechanical Occluder

13. Hydraulic System vs Motor Hydraulic system Pros –Compact –Control over distance Cons –Low precision Motor Pros –Precision Cons –Over heating issues –Noise –Bulkiness

14. Forces Involved A – Force of Spring B – Force by Blood Vessel C – Force by flexible Hydraulic Tubing D – Friction force on jagged teeth (from 1 or 2 below) E – Friction force on jagged teeth (from solenoid) F – Friction force on slope (from solenoid) G – Friction force on slope (from 1 and 2 below) 1 > A + B + C + D + E (one click) 2 << A + B + C + D + E (holding)

15. Forces Involved A = B = C = D = E = F = G =

16. Solenoid

17. Solenoid Forces

18. Limitations of Mechanical System Limited resolution Overheating Control limited to occluding Jerky occlusion

19. Syringe Pump Occluder

20. Syringe Pump Reaction Time Syringe pump bottleneck is in withdrawal Change in volume is cylindrical: πr 2 h, where d = 5mm and h = 5mm

21. Syringe Size Calculation Accuracy ▲ as size ▼ Speed ▼ as size ▼ Therefore, accuracy ▼ as speed ▲ Response time is more important than the accuracy, since the accuracy is always within 1%

22. Communication with Syringe Pump Standard RS232 port at 9600 baud 8N1 Text input/output using terminal program Commands change as well as query the rate/volume of injection and withdrawal DASYLab has RS232 input and output

23. Syringe Pump Reaction Time Rate can be changed without stopping pump Communications with computer conducted with 8 data bits and 1 stop bit for 9 bits per byte.

24. Occluder In Action

25. Advantages/Disadvantages Cost effective: pump supplied by customer Water is non-compressible Modular –Use syringes of different sizes –Use occluders of different sizes

26. The Chosen Design Water Based Syringe Pump Occluder! –Simplistic –Low cost –Easily modified

27. Control Software DASYLab Data acquisition hardware Amplifier and filter Virtual Instrumentation PID control ( loop time response <.05 ms)

28. Regulation of PID Controllable effects of PID –Rate to reach set point –Overshoot magnitude –Oscillation

29. System Calibration Required to get optimal results from system Trial runs to get effects relationship (trend) Literature shows relationship is usually linear PID control set to follow trend after each calibration

30. Questions