Mechanical ventilation system utilizing bias valve
A portable mechanical ventilator having a Roots blower provides a desired gas flow and pressure to a patient circuit. The mechanical ventilator includes a flow meter operative to measure gas flow produced by the Roots blower and an exhalation control module configured to operate an exhalation valve connected to the patient circuit. A bias valve connected between the Roots blower and the patient circuit is specifically configured to generate a bias pressure relative to the patient circuit pressure at the exhalation control module. The bias valve attenuates pulsating gas flow produced by the Roots blower such that gas flowing to the mass flow meter exhibits a substantially constant pressure characteristic. The bias pressure facilitates closing of the exhalation valve at the start of inspiration, regulates positive end expiratory pressure during exhalation, and purges sense lines via a pressure transducer module.
1. An apparatus for attenuating a gas flow from a gas source to a patient circuit, the apparatus comprising a bias valve connected between the gas source and the patient circuit, the bias valve comprising an inlet connected to the gas source and comprising a valve seat, an outlet connected to the patient circuit, a cavity, and a poppet, the poppet configured to reciprocate within the cavity to engage against the valve seat to resist gas flow into the bias valve in a closed position, and disengage from the valve seat to permit gas flow into the bias valve in an open position; wherein a poppet clearance is defined between the poppet and the cavity, the poppet clearance sized to generate viscous damping of the gas flow when gas passes through the poppet clearance during poppet reciprocation.
2. The apparatus of claim 1 , wherein a spring biases the poppet against the valve seat such that an elevated pressure is provided at the bias valve inlet relative to the bias valve outlet.
3. The apparatus of claim 2 , wherein:
a pressure transducer module is fluidly connected to the bias valve, wherein the pressure transducer module receives a bias pressure due to the elevated drive pressure; and
a sense line system including at least one of an airway sense line and a flow sense line is connected between the patient circuit and the pressure transducer module, wherein the pressure transducer module is operative to purge the sense line system using the bias pressure.
4. The apparatus of claim 1 , wherein a mass flow meter is interposed between the gas source and the bias valve inlet, the mass flow meter configured to measure a gas flow rate of the gas source.
5. The apparatus of claim 1 , wherein the gas flow from the gas source is a pulsating gas flow.
6. The apparatus of claim 1 , wherein the gas source includes a blower assembly.
7. The apparatus of claim 6 , wherein the blower assembly includes a Roots blower.
8. The apparatus of claim 1 , wherein the poppet has a mass sufficient to generate inertial damping of the pulsating gas flow.
9. The apparatus of claim 8 , wherein a mass element is connected to the poppet to achieve a desired inertial dampening characteristic.
10. The apparatus of claim 1 , wherein an exhalation control module is connected to the bias valve inlet, and an exhalation valve, controlled by the exhalation control module, is connected to the patient circuit.
11. A method for attenuating a gas flow from a gas source to a patient circuit, comprising:
connecting a bias valve between the gas source and the patient circuit, the bias valve comprising an inlet connected to the gas source, an outlet connected to the patient circuit, a cavity, and a poppet configured to reciprocate within the cavity;
engaging the poppet with a valve seat at the bias valve inlet in a closed position and disengaging the poppet from the valve seat in an open position for respectively resisting and allowing gas to flow out of the bias valve outlet; and
viscously dampening the gas flow when the gas passes through a poppet clearance between the poppet and the cavity during poppet reciprocation.
12. The method of claim 11 , further comprising biasing the poppet against the valve seat such that an elevated pressure is provided at the bias valve inlet relative to the bias valve outlet.
13. The method of claim 12 , further comprising:
receiving, at a pressure transducer module fluidly connected to the bias valve, a bias pressure due to the elevated drive pressure;
connecting a sense line system including at least one of an airway sense line and a flow sense line between the patient circuit and the pressure transducer module; and
purging the sense line system using the bias pressure and the pressure transducer module.
14. The method of claim 11 , further comprising interposing a mass flow meter between the gas source and the bias valve inlet, the mass flow meter configured to measure a gas flow rate of the gas source.
15. The method of claim 11 , further comprising inertially dampening the gas flow using the poppet, wherein the gas flow from the gas source is a pulsating gas flow.
16. The method of claim 15 , further comprising connecting a mass element to the poppet to achieve a desired inertial dampening characteristic.
17. A ventilator system comprising:
a pulsating gas source;
a patient circuit;
an exhalation valve connected to the patient circuit;
an exhalation control module configured to operate the exhalation valve; and
a bias valve connected between the gas source and the patient circuit, the bias valve comprising an inlet connected to the gas source and comprising a valve seat, and an outlet connected to the patient circuit, a cavity fluidly coupled to the inlet and the outlet, and a poppet configured to reciprocate within the cavity to engage against the valve seat to resist gas flow into the bias valve in a closed position, and disengage from the valve seat to permit gas flow into the bias valve in an open position.
18. The system of claim 17 , wherein a poppet clearance is defined between the poppet and the cavity to generate viscous damping of the gas flow when gas passes through the poppet clearance during poppet reciprocation.