IPPB: Bennett valve tutorial By Elizabeth Kelley Buzbee AAS, RRT-NPS, RCP

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

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.

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 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.

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. 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.

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 The Bennett valve 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.

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.