IPPB: Bennett valve tutorial

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IPPB Bennett valve tutorial

• By Elizabeth Kelley Buzbee AAS, RRT-NPS, RCP

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The PRII

• Pneumatically powered, pneumatically controlled
• Time or pressure, manually triggered on
• In Air-mix has a descending pressure ramp
• Flow or time cycled off.
• when used as a mechanical ventilator

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The Bennett valve

• This valve works on the balancing of gas flow and
  gravity. The valve at rest is closed due to
  gravity, when inspiratory flow exceeds the force
  of gravity, the valve stays open and the breath
  continues. Once the flow drops off as the
  pressure rises, then gravity starts to close the
  valve and the breath is over.

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The Bennett valve
In A, the valve drum is at rest because the
off-center Weight holds it closed. There is
high pressure Above the valve and below the
valve to patient There is zero pressure
ambient The pressure inside the rotating drum
was Vented to ambient during this phase so that
it is at ambient pressure. The pressure just
below the valve will be read on the SYSTEM
PRESSURE manometer. The pressure just above the
valve will be read on the PRESSURE monometer
While there is no gas pressure inside the drum
there is no gas flow down the exhalation drive
line

• This valve works on the balancing of gas flow and
  gravity. The valve at rest is closed due to
  gravity, when inspiratory flow exceeds the force
  of gravity, the valve stays open and the breath
  continues. Once the flow drops off as the
  pressure rises, then gravity starts to close the
  valve and the breath is over.

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The Bennett valve
In B, as the patient inhales on the circuit.
The pressure drops in the Mainline and in the
area just under the drum Once the pressure
exceeds the force of gravity the vane on the
side of the drum is pulled toward the patient
and the Drum begins to open toward both The
patient bottom and the gas inlet top. Gas
starts to flow from above The valve to the
patient circuit. The pressure seen on the
SYSTEM PRESSURE manometer will rise As the
pressure downstream from the drum rises.

• This valve works on the balancing of gas flow and
  gravity. The valve at rest is closed due to
  gravity, when inspiratory flow exceeds the force
  of gravity, the valve stays open and the breath
  continues. Once the flow drops off as the
  pressure rises, then gravity starts to close the
  valve and the breath is over.

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The Bennett valve

In C during inspiration the drum is still open to
both the high Pressure coming from the Dilutor
regulator and the patient circuit. Pressure
rises in the patient circuit and the exhalation
valve is shut so that the gas goes to the
Patient. As long as there is a pressure
Gradient between the two areas There is flow,
but as the pressure Downstream starts to rise,
the flow Starts to slow down

During the breath, the SYSTEM PRESSURE monometer
drops and the PRESSURE monometer rises until it
reaches the same pressure As the SYSTEM PRESSURE

• This valve works on the balancing of gas flow and
  gravity. The valve at rest is closed due to
  gravity, when inspiratory flow exceeds the force
  of gravity, the valve stays open and the breath
  continues. Once the flow drops off as the
  pressure rises, then gravity starts to close the
  valve and the breath is over.

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The Bennett valve

The flow continues to Slow down and once it Is
only 1- 3lpm, the force of gravity is
stronger Than the gas flow and The drum swings
shut The breath is over The drive line to
the Exhalation valve is no longer Charged with
pressure so the exhalation valve opens for
exhaled Vt to exit The patient. PRESSURE
monometer now Reads Zero while the
SYSTEM PRESSURE reads the high pressure

• This valve works on the balancing of gas flow and
  gravity. The valve at rest is closed due to
  gravity, when inspiratory flow exceeds the force
  of gravity, the valve stays open and the breath
  continues. Once the flow drops off as the
  pressure rises, then gravity starts to close the
  valve and the breath is over.

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