High Frequency Jet

Ventilation

From an Idea to a

Device

"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

"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

Adults were studied

thoroughly . . . but not babies.

The HFJV Story

Dr. Bunnell: “Is it possible to ventilate babies

with smaller tidal volumes and

lower pressures?”

Dr. Bunnell performs early aerosolized

surfactant studies at MIT in early 1970s.

Observes many babies dying or being

severely injured by early mechanical

ventilators.

Convection/DiffusionHenderson, 1915

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.

Physiologic Basis for

Using Small Tidal Volumes

1915: Henderson Smoke StudiesConvection penetrated smoke deeply through

tube

Effect was called “Flow Streaming”,

the sort of flow we try to create with

HFJV

Diffusion occurred when flow stopped or slowed

1915: Henderson Smoke Studies

Forced OscillationsDuBois and Assoc., 1956

Harvard School of Public Health

Resonant Frequency:

4 - 8 Hz

Best Blood Gases

Lowest Pressures

V

VA = f (VT - VD)

VT = 5 - 10 ml/kg

VD anat. = 2 ml/kg

Alveolar Air Equation

Resonant Frequency

fres = 4 to 8 Hz (adult)

fres = ??? Hz (infants)

VT = 5 - 10 ml/kg

fres = 10-15 Hz ?

fres = 4-8 Hz

Dr. Bunnell: “How can you ventilate and

oxygenate with tidal volumes

smaller than deadspace

volume?”

“. . . you probably can’t.”

InfrasoundJohnson, 1973

Wright-Patterson AFB

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Jack Emerson: personal communication

Jack Emerson: personal communication

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Pressure

Jack Emerson: personal communication

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Pressure

Jack Emerson: personal communication

VA = f (VT - VD)

VD anat. = 2 ml/kg

Alveolar Air Equation

VT = ???

Converting Decibels to Tidal Volume

Db = P = k V => 1-2 ml/kg body weight~

VD(ml/kg)

2

1

Size

Small Medium Large

3

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WhalePeeWee

Herman

Pygmy

ShrewChuck Norris

Anatomic Dead Space Volume:The Great Equalizer in Mammals

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.”

VT

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

If one pushes in that same VT

without the strap, it

causes the lungs to burst . . .

even when PIP

is not very

high!

High Frequency Jet VentilationBunnell, 1975

MIT

Volume-Cost of VentilationTidal Volume vs. Frequency

0 200 400 600 800

Frequency (bpm)

0

0.5

1

1.5

2

2.5

3

3.5

Tidal Volume (ml/kg)

Eureka!

“But how is this possible?”

Mathematical Model of

Gas Flow During HFJVEllis, 1984

San Jose

The Nature of Flow

Laminar: stable

Turbulent: stable

Transitional: unstable

A stable flow is one nature can support

Laminar Flow

Turbulent Flow

Transitional Flow

Dr. Bunnell: “How does HFJV create

Transitional Flow?”

- and -

“How does HFJV avoid

Turbulent Flow?”

Pressure

Monitoring

Port

Jet

Port

The LifePort Adapter

Gas accelerates into lungs

Gas injected here

Bernoulli Effect creates Transitional Flow

0.02 Inspiratory Time avoids Turbulent Flow

Text

Dr. Bunnell: “Why does double-helical,

bi-directional flow save babies?”

Ellis: “You’ve found a way to support double-

helical, bi-directional.”

Now For the Making and

Marketing of HFV

Bruce Dern

Forest Ranger in outer space

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The End