A method for allowing a patient to breathe out only with a pressure at least as great as a selected pressure, said method comprising:
- a) providing a device for providing resistance in an air pathway for the patient exhaling, the device comprising:
- 1) a central tube region;
- 2) a first passageway for passing air into the central tube region when the patient breathing through the device inhales;
- 3) a second passageway for passing air out of the central tube region when the patient breathing through the device exhales, wherein the second passageway has an upper portion defined by an upper wall, a lower portion defined by a lower wall, and a transitional wall connecting the lower wall to the upper wall, and wherein the transitional wall is slanted at an angle α with respect to a line perpendicular to the vertical axis of the second passageway, thus providing a second passageway having a valve seat angle of the angle α;
- 4) a third passageway for passing air from the central tube region and into the patient when the patient breathing through the device inhales, and for passing air from the patient to the central tube when the patient breathing through the device exhales;
- 5) a valve in the first passageway that allows air to flow in through the first passageway to the central tube when the patient using the device inhales, and that prevents air from flowing out through the first passageway when the patient using the device exhales;
- 6) a valve in the second passageway that allows air to flow out from the second passageway when the patient using the device exhales with an expiratory air pressure greater than the selected pressure, but that prevents air from flowing out through the second passageway when the patient exhales with an expiratory air pressure that is less than said selected air pressure, and that prevents air from flowing in through the second passageway when the patient using the device inhales, wherein the valve in said second passageway includes:
- i) a stopper to close the second passageway and to prevent air from flowing through the second passageway when the stopper is biased to a closed position, and
- ii) a stopper-biasing spring to maintain the stopper in its closed position unless the expiratory air pressure in the second passageway is greater than the selected pressure, wherein the stopper-biasing spring is a coil spring having a first end connected to the stopper, a second end opposite the first end, and an interior;
- and
- 7) a spring housing cap connected to the second end of the stopper-biasing spring and effective to retain the stopper-biasing spring and to partially compress the spring to a length shorter than its free length, wherein the spring housing cap is movable with respect to the transitional wall of the second passageway so that movement of the spring housing cap is effective for varying the compression length of the spring, and thus is effective for varying the expiratory air pressure that will cause the valve of the second passageway to open, and wherein the stopper-biasing spring is attached at its first end to the spring housing cap, and at its second end to the stopper, with the spring interior being free from any structure that would inhibit “side-to-side” movement of the spring within the second passageway;
- wherein the stopper has an exterior surface defining a stopper angle β with respect to a line perpendicular to the vertical axis of the stopper;
- and
- b) breathing out through said device with sufficient expiratory air pressure to cause the valve of the second passageway to open, allowing air to exit the device.