Method And Apparatus For Controlling The Delivery Of Humidified Air
An improved humidification method and apparatus for use with a CPAP type machine in which humidified air is delivered to the patient only during the inhalation phase and non-humidified air is delivered to the patient during the exhalation phase. The invention consists of a valve apparatus to switch from humidified air to non-humidified air and a method of determining when to switch the state of the valve.
1 . A breathing gas delivery machine comprising:
a. a blower;
b. a humidification chamber;
c. an airflow pathway for directing airflow from said blower to an airflow outlet; and
d. a valve, positioned in said airflow path, wherein said valve allows airflow to pass through said humidification chamber during an inhalation phase of a breathing cycle of a user of said machine and further wherein said valve diverts said airflow around said humidification chamber during an exhalation phase of a breathing cycle of a user of said machine.
2 . The breathing gas delivery machine of claim 1 further comprising:
a. a microprocessor; and
b. software, execute by said microprocessor, said software performing the functions of:
controlling said blower;
switching said valve between a first state which allows said airflow to pass through said humidification chamber and a second state which divert said airflow away from said humidification chamber; and
detecting transitions between the inhalation phase and the exhalation phase of the breathing cycle of a user of said machine.
3 . The breathing gas delivery machine of claim 1 further comprising one or more sensors, positioned in said airflow path, for providing data to said microprocessor, said data being used to detect the transitions in the breathing cycle.
4 . The breathing gas delivery machine of claim 3 wherein said sensors are selected from a group consisting of a pressure sensor and an air flow sensor.
5 . The breathing gas delivery machine of claim 2 :
a. wherein said valve is switched from said first state to said second state when a transition from the inhalation phase to the exhalation phase of the breathing cycle is detected; and
b. wherein said valve is switched between said second state and said first state when a transition from the exhalation phase to the inhalation phase of the breathing cycle is detected.
6 . The breathing gas delivery machine of claim 2 :
a. wherein said valve is switched from said first state to said second state at a first time prior to the detection of the transition from the inhalation phase to the exhalation phase of the breathing cycle; and
b. wherein said valve is switched between said second state and said first state at a second time prior to the detection of the transition from the exhalation phase to the inhalation phase of the breathing cycle.
7 . The breathing gas delivery machine of claim 6 :
wherein said first time is roughly equal to the time it takes for airflow to travel between said valve and said airflow outlet during said inhalation phase; and
wherein said second time is roughly equal to the time it takes for airflow to travel between said valve and said airflow outlet during said exhalation phase.
8 . The breathing gas delivery machine of claim 7 wherein said first time and said second time may be lengthened or shortened depending upon the amount of leakage being experienced by a user of said machine.
9 . The breathing gas delivery machine of claim 2 wherein said value comprises:
a. a cylindrical body having an inlet, a first outlet and a second outlet defined thereon, said inlet defined at one end of said cylindrical body and said opposite end of said cylindrical body being closed, and said first and second outlets being defined on a wall of said cylindrical body; and
b. a cylindrical shuttle, moveable within said valve body, said shuttle having opening at both ends thereof, and a first hole and a second hole defined in a side wall thereof;
wherein said first state is defined by said shuttle being in a position wherein said first hole is aligned with said first outlet and wherein said second hole is not aligned with said second outlet; and
wherein said second state is defined by said shuttle being in a position wherein said second hole is aligned with said second outlet and wherein said first hole is not aligned with said first outlet.
10 . The breathing gas delivery machine of claim 9 wherein said valve further comprises means for moving said shuttle back and forth within said body.
11 . The breathing gas delivery machine of claim 10 wherein said means for moving is a solenoid.
12 . The breathing gas delivery machine of claim 9 wherein the movement of said shuttle within said body comprises both longitudinal and rotational movement.
13 . The breathing gas delivery machine of claim 9 wherein the movement of said shuttle within said body is guided by a tab defined on the outside wall of said shuttle and a groove define in the inside wall of said body such that said tab rides within said groove.
14 . The breathing gas delivery machine of claim 9 wherein said groove is shaped such as to impart both longitudinal and rotational movement to said shuttle with respect to said body.
15 . The breathing gas delivery machine of claim 9 wherein said inlet, said first outlet and said second outlet define shoulders therearound, to facilitate the connection of hoses comprising said airflow pathway.