PNEUMATICALLY-OPERATED GAS DEMAND APPARATUS

A pneumatically-operated gas delivery device coupled in interruptible fluid communication between a recipient and at least one course of pressurized respiratory gas controls delivery of the respiratory gas to the recipient as the recipient inhales and exhales. The device includes a regulator mechanism, a supply valve and a sensing valve, wherein the supply valve delivers the respiratory gas to the recipient responsive to movement of the sensing valve. Gas flow to the supply valve is communicated from the gas source, the regulator mechanism and through a plurality of bolus chambers each of which chambers communicates a portion of the recipient's demand gas flow rate from the regulator mechanism to the supply valve. The bolus chambers allow a high-flow pulse of respiratory gas to be delivered to the patient upon initiation of inhalation coupled with steady state flow for the remainder of inhalation. Distribution of the recipient's gas flow rate among the several bolus chambers improves the dynamic performance of the device.