Patent ID: 8251066

Claim:
A valve device for use in a system for delivering a flow of gas to an airway of a patient, the valve device comprising: a valve body having an outlet open to ambient atmosphere; a valve element comprising a ball or a plug disposed in the valve body such that the valve element is moveable between at least two positions including a first position, wherein an exhaust gas flow that passes through the outlet between the valve device and an ambient atmosphere is at a first level of restriction, and a second position, wherein the exhaust gas flow that passes through the outlet is at a second level of restriction that is greater than the first level of restriction, such that a flow rate of the exhaust gas flow when the valve element is in the first position is greater than the flow rate of the exhaust gas flow when the valve element is in the second position, wherein the valve element is disposed in the first position responsive to the flow of gas having an insufficient pressure or rate of flow to overcome a biasing force acting on the valve element, and wherein the valve element is disposed in the second position responsive to the flow of gas having a sufficient pressure or rate of flow to overcome the biasing force acting on the valve element; and a valve structure adapted to prevent the valve element from completely blocking the exhaust gas flow from passing through the outlet regardless of the position of the valve element relative to the valve body, wherein the valve device is constructed and arranged such that when the valve element is in the first position gas is able to flow from the ambient atmosphere to the airway of the patient through the valve body and gas is able to leave a patient interface and flow into the ambient atmosphere through the valve body, and when the valve element is in the second position the flow of gas generated by the system is at a level suitable for treatment of the patient.