Demand gas flow valve apparatus

A breathing circuit system for delivering gas to a user through a face mask, the breathing circuit system comprising:

• an inspiration lumen having a proximal end and a distal end, the proximal end of the inspiration lumen being directly or indirectly coupled to the face mask;
• a demand valve having a proximal end in fluid communication with the distal end of the inspiration lumen and a distal end in fluid communication with a supply of fresh gas;
• the demand valve including a closed position and an open position, the closed position being a default position in the absence of negative pressure in the inspiration lumen, such that the gas from the source of fresh gas cannot enter the inspiration lumen through the demand valve, and the open position occurring in the presence of negative pressure in the inspiration lumen, such that fresh gas from the source of fresh gas can enter the inspiration lumen through the demand valve;
• a flowmeter fluidically coupled between the supply of fresh gas and the demand valve, wherein the flowmeter includes a control panel configured to control the delivery of gas out of the flowmeter;
• a gas reservoir fluidically coupled between the flowmeter and the demand valve, wherein the gas reservoir is configured to receive fresh gas leaving the flowmeter when the demand valve is in the closed position;
• a pressure sensor configured to determine if a pressure in the gas reservoir exceeds a predetermined threshold of pressure to prevent over-inflation of the gas reservoir;
• a conductor electrically coupled to the pressure sensor and to the control panel of the flowmeter, the conductor configured to receive an over-inflation signal from the pressure sensor when the pressure sensor determines that the pressure in the gas reservoir exceeds the predetermined threshold of pressure and transmit a signal to the control panel to reduce the delivery of gas from the flowmeter;
• wherein the over-inflation signal prevents the pressure in the gas reservoir from exceeding the predetermined threshold when the demand valve is in the closed position.