Patent ID: 7823588

Claim:
A valve system for a breathing assistance apparatus, comprising: a positive pressure port configured communicating with a positive relative pressure gas supply; a negative pressure port configured communicating with a negative relative pressure gas supply; a gas supply port configured for communication with a gas delivery device for delivering at least a portion of the gas from the positive relative pressure gas supply to a patient, the gas supply port communicatively coupled to both the positive pressure port and the negative pressure port; and a valve control system operable to control a valve mechanism to control a gas supply ratio of (a) a gas flow from the positive relative pressure gas supply toward the valve mechanism to (b) a gas flow from the valve mechanism toward the negative relative pressure gas supply, wherein the valve mechanism allows the gas flow from the positive relative pressure gas supply toward the valve mechanism and the gas flow from valve mechanism toward the negative relative pressure gas supply to occur simultaneously to provide a range of gas supply ratios between 0 and 1.