Bunnell History and High Frequency Jet Ventilator Theory

1. High Frequency Jet
Ventilation
From an Idea to a
Device

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 which
compresses it, and if the force is removed, it increases
again to its original size."
-- Leonardo da Vinci, late 15th century

3. "The gust of wind driven out of the lung in the
generation of a large breath comes from the aid of
the abdominal wall which compresses the intestines,
and they elevate the diaphragm which compresses
the lungs."
- da Vinci

4. Adults were studied
thoroughly . . . but not babies.

5. The HFJV Story

6. Dr. Bunnell performs early aerosolized
surfactant studies at MIT in early 1970s.
Observes many babies dying or being
severely injured by early mechanical
ventilators.
Dr. Bunnell: “Is it possible to ventilate babies
with smaller tidal volumes and
lower pressures?”

8. Convection/Diffusion
Henderson, 1915

9. Physiologic Basis for
Using 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.

10. 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

11. 1915: Henderson Smoke Studies
Diffusion occurred when flow stopped or slowed

13. Forced Oscillations
DuBois and Assoc., 1956
Harvard School of Public Health

14. V
Resonant Frequency: Best Blood Gases
Lowest Pressures
4 - 8 Hz

15. Alveolar Air Equation
VA = f (VT - VD)
VT = 5 - 10 ml/kg
VD anat. = 2 ml/kg

16. Resonant Frequency
fres = 4 to 8 Hz (adult)
fres = ??? Hz (infants)

17. fres = 4-8 Hz
VT = 5 - 10 ml/kg
fres = 10-15 Hz ?

18. Dr. Bunnell: “How can you ventilate and
oxygenate with tidal volumes
smaller than deadspace
volume?”
“. . . you probably can’t.”

19. Infrasound
Johnson, 1973
Wright-Patterson AFB

20. * *
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*
*
Jack Emerson: personal communication

21. Jack Emerson: personal communication

22. Pressure
*
*
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* *
**
** * * ** *
*** * **
* ** * *
*
* * *
*
** *
*
Jack Emerson: personal communication

23. Pressure
*
* * *
* *
*
* * * * *
* * *
* *
* ** * *
*
*
* * *
* * *
* ** ***
*
Jack Emerson: personal communication

26. Alveolar Air Equation
VA = f (VT - VD)
VD anat. = 2 ml/kg
VT = ???

27. Converting Decibels to Tidal Volume
Db =~ P = k V => 1-2 ml/kg body weight

28. 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

29. 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.”

30. If one pushes a big VT into a critter with a
strapped chest, it doesn’t hurt its lungs . . .
even when PIP
is very high!
VT

31. If one pushes in that same VT without the strap, it
causes the lungs to burst . . .
even when PIP
is not very
high!
VT

32. High Frequency Jet Ventilation
Bunnell, 1975
MIT

33. Volume-Cost of Ventilation
Tidal Volume vs. Frequency
Tidal Volume (ml/kg)
3.5
3
2.5
2
1.5
1
0.5
0
0 200 400 600 800
Frequency (bpm)

35. Eureka!
“But how is this possible?”

36. Mathematical Model of
Gas Flow During HFJV
Ellis, 1984
San Jose

37. The Nature of Flow
A stable flow is one nature can support
Laminar: stable
Turbulent: stable
Transitional: unstable

38. Laminar Flow
Turbulent Flow
Transitional Flow

39. Dr. Bunnell: “How does HFJV create
Transitional Flow?”
- and -
“How does HFJV avoid
Turbulent Flow?”

40. The LifePort Adapter
Pressure
Monitoring Jet
Port Port

41. Bernoulli Effect creates Transitional Flow
0.02 Inspiratory Time avoids Turbulent Flow
Text
Gas accelerates into lungs
Gas injected here

42. Ellis: “You’ve found a way to support double-
helical, bi-directional.”
Dr. Bunnell: “Why does double-helical,
bi-directional flow save babies?”

44. Now For the Making and
Marketing of HFV

46. Bruce Dern
Forest Ranger in outer space

50. + =

52. The End