Automation Of Heart Lung Machine

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First step in controlling a Heart-Lung machine with a computer

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Automation Of Heart Lung Machine

  1. 1. Automation ofCardiopulmonaryBypassAn Autopilot for the Heart-LungMachineKenneth Wilkerson
  2. 2. Theme Improving the safety of open-heart surgery through automation of the heart-lung machine
  3. 3. What is Cardiopulmonary Bypass? Removing heart & lungs from circulation Used during open heart surgery  Heart stopped, opened E.G.:  Coronary Artery Bypass Graft  Valve repair/replacement Function taken over by a machine
  4. 4. What is a Heart-Lung Machine? Replaces function of heart and lungs  Pump blood  Oxygenate blood  Set/maintain body temperature  Other secondary functions
  5. 5. What is a Heart-Lung Machine? Key parts for primary purpose:  Venous reservoir  Arterial pump  Heat exchanger  Oxygenator  Arterial filter Arterial-Venous (A-V) circuit
  6. 6. Key parts of heart-lung machine A-V Circuit
  7. 7. Early Heart-lung Machine
  8. 8. Modern Heart-Lung Machine
  9. 9. How is HLM operated? Manually Constantly monitored by a perfusionist  Reservoir level  Arterial line pressure  Other Perfusionist also recording data  Some sites automated
  10. 10. Attempts at automating 1953 first successful use of HLM Within a few years attempt automating  Measuring reservoir level  Controlling pump based on reservoir level 1990: first attempt to use computer Efforts continue
  11. 11. Why Automate? Improved safety  Humans get tired, distracted;machines don’t  Machines react faster  Aviation automated before HLM  Worst distraction scenario: reservoir empties, pump air into patient Would you still need a person dedicated to running HLM?
  12. 12. This Project Computer control of HLM  Monitor Volume in venous reservoir  Control speed of arterial pump Goal: do not allow reservoir level to drop below critical level Proof of concept/feasibility study Description of possible next steps
  13. 13. Automated heart-lung machine Reservoir Autopilot Arterial pump Heat Heater-cooler exchanger Oxygenator Arterial filter
  14. 14. Test automated HLM
  15. 15. This Project: Technique Monitoring reservoir:  Measure volume by weighing reservoir  Suspend reservoir from strain gage  Computer polls strain gage Control pump speed:  Pump has connection for external control by another pump (master-slave)  Connect to D/A converter in computer  Computer plays part of master
  16. 16. This Project – strain gage
  17. 17. Monitoring reservoir volume Why use this method?  No blood contact  Does not require modifying reservoir  Easily adaptable to different bag reservoirs  Other types of reservoirs have issues
  18. 18. Monitoring reservoir volume Tested three ways  Maximum accuracy  Effect of flow and vibration on accuracy  Sensitivity to change in volume The tests cover patients from a small adult female using a Cardiac Index of 1.8 to a very large adult male using a Cardiac index of 2.4
  19. 19. Cardiac Index Method of indexing blood flow to patient size Size measured by Body Surface Area  Calculated from height, weight E.g., CI 2.4 means 2.4 LPM per M2
  20. 20. This Project – simulated patient
  21. 21. Maximum accuracy Fill reservoir using graduated cylinder 100ml to capacity in 100ml increments Strain gage reads to 0.01 Kg = 10ml Capacity is 1200ml Record value from strain gage Do three times to check repeatability
  22. 22. Maximum accuracy - Results Largest absolute error 0.01 Kg Largest percent error : 2.5 %  0.01 Kg at 400ml Volumes < 400ml no error
  23. 23. Flow and Vibration Build basic circuit  Use another reservoir to simulate patient Add different volumes to circuit  1500ml to 3000ml  500ml Increment Circulate at different flow rates 2 LPM to 7 LPM  1 LPM increment
  24. 24. Flow and Vibration Take multiple readings from strain gage  0.5 second interval Check variations in readings Results:  Largest variation 0.03 Kg (1.12 to 1.15 Kg)  Mostly variation 0.01 Conclusion:  Flow and vibration no effect on accuracy
  25. 25. Sensitivity to change Circulate at different flow rates 2 to 7 LPM, 1 LPM increment Fully or partially occlude input to reservoir Take readings of strain gage  0.5 sec interval  5 seconds Determine correlation coefficient
  26. 26. Sensitivity to change - Results Correlation coefficient: -0.91 to -1.00
  27. 27. Sensitivity to change – worst Full occl. 4 LPM (67 ml/ sec) 1.51.45 1.41.35 1.31.25 1.21.15 1.11.05 1 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Ti m Seconds e
  28. 28. Sensitivity to change – best Full Occl. 7 LPM (120 ml/ sec) 10.90.80.70.60.50.40.3 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Ti m Seconds e
  29. 29. Monitoring Reservoir -Summary This method of monitoring volume is as good as or better than standard of practice which is the perfusionist reading the volume from a scale on the side of reservoir
  30. 30. Reservoir
  31. 31. Autopilot operator interface
  32. 32. Autopilot log Max flow rate 1 LPM, min pct flow 50, low level 300, min level 100 700 1.2 600 1 500 0.8reservoir level ml 400 flow rate LPM Volume 0.6 Flowrate 300 0.4 200 0.2 100 0 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 Time seconds
  33. 33. Demonstration Auto HLM demo
  34. 34. Overall results This method for automated control of a heart-lung machine is feasible
  35. 35. Next steps How to build on this project  Further automation of A-V circuit
  36. 36. Tasks – Part 1 Modern pump Blood monitoring Gas flow and mixture Reservoir Autopilot Arterial pump Heat Heater-cooler exchanger Oxygenator Blood monitor Arterial filter
  37. 37. Modern pump Validate approach Tech support available Test over full range Stress test autopilot Reservoir Autopilot Arterial pump Heat exchanger Heater-cooler Oxygenator Blood monitor Arterial filter
  38. 38. Blood monitoring Inline, real-time PaO2, PaCO2, Sv02, Hgb Calc O2 consumption w/blood flow, show trend Tell if anesthesia wearing off Reservoir Autopilot Arterial pump Heat exchanger Heater-cooler Oxygenator Blood monitor Arterial filter
  39. 39. Gas flow and mixture Tighter control of blood gases Monitor gas/blood flow to O2 consumption ratio Detect impending oxygenator failure Reservoir Autopilot Arterial pump Heat exchanger Heater-cooler Oxygenator Blood monitor Arterial filter
  40. 40. Part 1 - result Key pieces automated Close attention of perfusionist Reservoir Autopilot Arterial pump Heat Heater-cooler exchanger Oxygenator Blood monitor Arterial filter
  41. 41. Tasks – Part 2 Arterial line pressure Occluders Heater-cooler Reservoir Autopilot Arterial pump Heat exchanger Heater-cooler ALP monitorOxygenator Blood monitor Arterial filter
  42. 42. Arterial line pressure Part of perfusionist scan High pressure requires stopping pump Reservoir Autopilot Arterial pump Heat exchanger Heater-cooler ALP monitor Oxygenator Blood monitor Arterial filter
  43. 43. Occluders Standard is scissor clamps Mainly used at initiation & termination Much to monitor Reservoir Autopilot Arterial pump Heat exchanger Heater-cooler ALP monitorOxygenator Blood monitor Arterial filter
  44. 44. Heater-cooler Cool & rewarm blood w/heat exchanger From a few degrees to zero C Severe cooling means care rewarming Rewarm fast as possible without overheating blood Reservoir Autopilot Arterial pump Heat exchanger Heater-cooler ALP monitor Oxygenator Blood monitor Arterial filter
  45. 45. Part 2 - result Allow autopilot to control initiation and termination of bypass as well as monitor Reservoir Autopilot Arterial pump Heat exchanger Heater-cooler ALP monitorOxygenator Blood monitor Arterial filter
  46. 46. Part 2 – Autopilot operator interface
  47. 47. Part 3 – voice recognition More convenient in OR than mouse and keyboard Quicker access Multiple locations Bluetooth headset
  48. 48. Voice recognition Two types of commands  Normal– repeated back for confirmation  Emergency – immediate execution
  49. 49. Voice recognition Sample normal dialog  Perf: “autopilot increase blood flow zero point five”  Auto: “increase blood flow zero point five”  Perf: “yes”  Auto: “blood flow now at five point zero”
  50. 50. Voice recognition Sample emergency dialog  Perf:“autopilot emergency stop”  Auto: “pump stopped, gas flow stopped”
  51. 51. Overall design guidelines Perfusionist ultimate safety device Equipment will fail Always manual backup Switch quick and simple
  52. 52. References 1. Austin Jon W., Harner David L.. The Heart-lung Machine and Related Technologies of Open Heart Surgery. Phoenix: Phoenix Medical Communications1986:7. 2. Chronicle of Aviation, JL International Publishing Inc., 1992:462 3. C CRAFOORD, B NORBERG, and A SENNING. Clinical studies in extracorporeal circulation with a heart-lung machine. Acta Chir Scand, Mar 1957; 112(3-4): 220-45. 4. F OLMSTED, WJ KOLFF, and DB EFFLER. Three safety devices for the heart-lung machine. Cleve Clin Q, Jul 1958; 25(3): 169-76. 5. Murray N. Andersen, M.D., James F Ulrich,P.E.,Christian V. Mouritzen, M.D. An automatic flow control system for extracorporeal circulation. Journal of thoracic and Cardiovascular Surgery, Aug 1965;50(2):260-264 6. A KANTROWITZ, S REINER, and D ABELSON. An automatically controlled, inexpensive pump-oxygenator.J. Thorac. Cardiovasc. Surg., Nov 1959; 38: 586-93. 7. VINCENT L. GOTT, ROBERT D. SELLERS, RICHARD A. DeWALL, RICHARD L. VARCO, and C. WALTON LILLEHEI. A Disposable Unitized Plastic Sheet Oxygenator for Open Heart Surgery. Chest, Dec 1957; 32: 615 - 625. 8. Pierre M. Galletti M.D.,Ph.D,Gerhard A. Brecher, M.D.,Ph.D.. HEART-LUNG BYPASS, Principles and Techniques of Extracorporeal Circulation. Grune & Stratton,1962:199 9. Gerald Moss M.D.,Ph.D. A device to maintain automatically and continuously an absolute or relative constant weight of a subject or container during perfusion. Surgery, June 1961 10 . F. John Lewis,M.D., Sidney J. Horwitz, B.S.,Joseph B. Naines,Jr.,B.S. Semiautomatic control for an extracorporeal blood pump. Journal of thoracic and Cardiovascular Surgery,March 1962,43(3):392-396 11. James J. Roche, Irving Ungar,M.D.,Herman S. Coleman,M.D. An electric apparatus for rapid and precise regulation of the venous blood-reservoir height on heart-lung machines. Surgery, September 1964,56(3):561-564 12. Jeffrey B. Riley, B.A. CCT. A Technique for Computer Assisted Monitoring in the Management of Total Heart-lung Bypass. The Journal of Extra-Corporeal Technology, 1981, 13(1):171-176. 13. Thomas Hankins, C.L.A.,C.C.P. Computer Assisted Bypass Management. The Journal of Extra-Corporeal Technology, 1980, 12(4):95-102 14. J.B. Riley, M.B. Hurdle, B.A. Winn, P.A. Wagoner. Automation of Cardiopulmonary Bypass Data Collection. The Journal of Extra-Corporeal Technology,1985, 17(1):7- 12 15. D. Gaillard,MD, C. Barraud,CCP, O. Bical, MD, L. Detoni,CCP, L.S. Montejo,MD,A. Venetti,MD. Use of an Extracorporeal Circulation Workstation During the Routine Care of Cardiac Patients. Int J Artif Organs,1990 Feb,13(2):35-41 16. N. Chauveau, W. Van Meurs, R. Barthelemy, J.P. Morucci. Automatic modules for extracorporeal circulation control. Int J Artif Organs, 1990,13(10):692-696 17. Toshiyuki Beppu, ME, Yasuharu Imai, MD, Yasuhiro Fukui, PhD. A Computerized control system for cardiopulmonary bypass. The Journal of Thoracic and Cardiovascular Surgery, 1995, 109(3):428-438 18. US Patent No 7022099, A. Kenneth Litzie et al. Extracorporeal blood handling system with automatic flow control and methods of use. File: Mar 17, 2003, Issue: Apr 4, 2006 19. Alfred H Stammers, Brian L Mejak.An update on perfusion safety: does the type of perfusion practice affect the rate of incidents related to cardiopulmonary bypass?. Perfusion, 2001, 16:189-198 20. Bryan V. Lich,CCP, D. Mark Brown, CCP. The Manual of Clinical Perfusion. Perfusion.com, Inc. 2004 21. Glenn P. Gravlee MD, Richard F. Davis MD, Mark Kurusz CCP, Joe R. Utley MD. Cardiopulmonary Bypass Principles and Practice, second edtion. Lippincott Williams & Wilkins 2000. 22. Bryan V. Lich, CCP,D. Mark Brown CCP. The Manual of Clinical Perfusion, Second Edition Updated. Perfusion.Com 2004:47 23. Glenn P. Gravlee MD, Richard F. Davis MD, Mark Kurusz CCP, Joe R. Utley MD. Cardiopulmonary Bypass Principles and Practice, second edtion. Lippincott Williams & Wilkins 2000: 88 24. Bryan V. Lich, CCP, D. Mark Brown CCP. The Manual of Clinical Perfusion, Second Edition Updated. Perfusion.Com 2004:71 25. Bryan V. Lich, CCP, D. Mark Brown CCP. The Manual of Clinical Perfusion, Second Edition Updated. Perfusion.Com 2004:79
  53. 53. Acknowledgement Cardiovascular Science/Perfusion department MWU Glendale, AZ

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