Patent ID: 7089938

Claim:
A conserving device for use in delivering gas from a source of gas through a gas line, the conserving device comprising: a main valve operable in an open position for the gas to exit the main valve and in a closed position in which the gas exit is interrupted; a sensing valve operable to open in response to a pressure drop and to close upon sufficient return of pressure; a first pneumatic connection between the source of gas and the main valve to bias the main valve toward the closed position; a second pneumatic connection between the main valve and the sensing valve to receive a portion of the gas exiting the main valve and transmit a sufficient pressure to the sensing valve to close the sensing valve, whereupon the gas from the first pneumatic connection closes the main valve, interrupting delivery of the gas to the patient substantially independently of exhalation, whereby the gas is delivered intermittently and is conserved; and an orifice plate, the orifice plate having a plurality of orifices disposed in spaced relation thereon, a selected one of the orifices positioned between, and in pneumatic communication with, the source of gas and the main valve, the selected orifice corresponding to a rate of flow of the gas.