Peep control in a piston ventilator

In a ventilator for providing gas under pressure to a user for breathing, the ventilator including a primary piston-driven pressurization system and a patient circuit, the improvement comprising:

• a secondary make-up air pressurization system for supplying pressurized air to said patient circuit;
• and
• an exhalation control system operatively coupled to said secondary make-up air pressurization system, said exhalation control system including a first sensor for sensing a PEEP pressure value in said patient circuit, a gas-venting valve, a exhalation valve including a diaphragm for providing exhalation resistance, and a conduit for conveying a signal to said diaphragm of said exhalation valve,
• said conduit operatively connecting said secondary pressurization system to said diaphragm,
• wherein said first sensor is in operative communication with said gas-venting valve for actuating said gas-venting valve through a range between an open and a closed position in response to said sensed value and thereby control the signal conveyed to said diaphragm through said conduit.

A method of providing breathable gas to a patient comprising the steps of:

• providing a piston ventilator including a patient circuit, a piston and cylinder assembly for providing a primary source of pressurized gas to said patient circuit, a secondary source of pressurized gas in communication with said patient circuit, a pressure sensor in said patient circuit in proximity to said patient, a gas vent valve, a controller, and an exhalation valve having a valve element shiftable between an open position, a closed position and a plurality of intermediate positions;
• providing a pneumatic signal from said patient circuit to said element of said exhalation valve to control the resistance of the exhalation valve during the exhale portion of the patient's breath;
• sensing the PEEP in the patient circuit by said pressure sensor;
• providing a signal from said pressure sensor to said controller corresponding to the sensed PEEP;
• comparing said sensed PEEP to a preselected target PEEP in said controller;
• providing a signal from said controller to said gas vent valve to adjust the venting characteristics of said gas vent valve and thereby alter said pneumatic signal;
• delivering said altered pneumatic signal to said element of said exhalation valve to change the resistance of the exhalation valve to patient exhalation.