Bunnell History and High Frequency Jet Ventilator Theory

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Bunnell History and High Frequency Jet Ventilator Theory

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Bunnell History and High Frequency Jet Ventilator Theory

  1. 1. High Frequency Jet VentilationFrom an Idea to a Device
  2. 2. "The substance of the lung is dilatable and extensible like the tinder made from a fungus. But it is spongy and if you press it, it yields to the force whichcompresses it, and if the force is removed, it increases again to its original size." -- Leonardo da Vinci, late 15th century
  3. 3. "The gust of wind driven out of the lung in the generation of a large breath comes from the aid ofthe abdominal wall which compresses the intestines, and they elevate the diaphragm which compresses the lungs." - da Vinci
  4. 4. Adults were studied thoroughly . . . but not babies.
  5. 5. The HFJV Story
  6. 6. Dr. Bunnell performs early aerosolizedsurfactant studies at MIT in early 1970s.Observes many babies dying or beingseverely injured by early mechanicalventilators.Dr. Bunnell: “Is it possible to ventilate babies with smaller tidal volumes and lower pressures?”
  7. 7. Convection/Diffusion Henderson, 1915
  8. 8. Physiologic Basis forUsing Small Tidal Volumes In 1915, Henderson was intrigued by the shallow breathing of panting dogs. He wondered how dogs could pant indefinitely without becoming hypoxic or hypercapnic. So, he designed an experiment to find out.
  9. 9. 1915: Henderson Smoke Studies Convection penetrated smoke deeply through tube Effect was called “Flow Streaming”, the sort of flow we try to create with HFJV
  10. 10. 1915: Henderson Smoke Studies Diffusion occurred when flow stopped or slowed
  11. 11. Forced Oscillations DuBois and Assoc., 1956Harvard School of Public Health
  12. 12. VResonant Frequency: Best Blood Gases Lowest Pressures 4 - 8 Hz
  13. 13. Alveolar Air Equation VA = f (VT - VD) VT = 5 - 10 ml/kg VD anat. = 2 ml/kg
  14. 14. Resonant Frequency fres = 4 to 8 Hz (adult) fres = ??? Hz (infants)
  15. 15. fres = 4-8 HzVT = 5 - 10 ml/kg fres = 10-15 Hz ?
  16. 16. Dr. Bunnell: “How can you ventilate and oxygenate with tidal volumes smaller than deadspace volume?” “. . . you probably can’t.”
  17. 17. Infrasound Johnson, 1973Wright-Patterson AFB
  18. 18. * * * * * * * * * * * * * ** * * ** * * * * * * * * * * *Jack Emerson: personal communication
  19. 19. Jack Emerson: personal communication
  20. 20. Pressure * * * * * * * ** ** * * ** **** * *** ** * * * * * * * ** * * Jack Emerson: personal communication
  21. 21. Pressure * * * * * * ** * * * * * * * * * * ** * * * * * * * * * * * ** *** * Jack Emerson: personal communication
  22. 22. Alveolar Air Equation VA = f (VT - VD) VD anat. = 2 ml/kg VT = ???
  23. 23. Converting Decibels to Tidal VolumeDb =~ P = k V => 1-2 ml/kg body weight
  24. 24. Anatomic Dead Space Volume: The Great Equalizer in Mammals 3 Pygmy Chuck Norris Shrew * * * * ***** ** * * * * * ** **** ** * * * * 2 * * ** * **** * ** * * Blue * * * * PeeWee* * * * * * * VD *(ml/kg) Herman Whale 1 Small Medium Large Size
  25. 25. Dr. Bunnell: “How can you possibly get good blood gases with such small tidal volumes?!”Colonel Johnson: “Why don’t YOU find out?” Dr. Bunnell: “Good idea.”
  26. 26. If one pushes a big VT into a critter with astrapped chest, it doesn’t hurt its lungs . . . even when PIP is very high! VT
  27. 27. If one pushes in that same VT without the strap, itcauses the lungs to burst . . . even when PIP is not very high! VT
  28. 28. High Frequency Jet Ventilation Bunnell, 1975 MIT
  29. 29. Volume-Cost of Ventilation Tidal Volume vs. FrequencyTidal Volume (ml/kg)3.5 32.5 21.5 10.5 0 0 200 400 600 800 Frequency (bpm)
  30. 30. Eureka!“But how is this possible?”
  31. 31. Mathematical Model ofGas Flow During HFJV Ellis, 1984 San Jose
  32. 32. The Nature of FlowA stable flow is one nature can support Laminar: stable Turbulent: stable Transitional: unstable
  33. 33. Laminar FlowTurbulent FlowTransitional Flow
  34. 34. Dr. Bunnell: “How does HFJV create Transitional Flow?” - and - “How does HFJV avoid Turbulent Flow?”
  35. 35. The LifePort AdapterPressureMonitoring Jet Port Port
  36. 36. Bernoulli Effect creates Transitional Flow 0.02 Inspiratory Time avoids Turbulent Flow TextGas accelerates into lungs Gas injected here
  37. 37. Ellis: “You’ve found a way to support double- helical, bi-directional.”Dr. Bunnell: “Why does double-helical, bi-directional flow save babies?”
  38. 38. Now For the Making and Marketing of HFV
  39. 39. Bruce DernForest Ranger in outer space
  40. 40. + =
  41. 41. The End

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