Automatic aerosol medication delivery system and methods

• US 5,522,378 A
• Filed: 11/29/1994
• Issued: 06/04/1996
• Est. Priority Date: 03/05/1991
• Status: Expired due to Term

• Current Assignee: Aradigm Corporation
• Original Assignee: Aradigm Corporation
• Inventors: Rubsamen, Reid M., Ritson, Carl
• Primary Examiner(s): Lewis, Aaron J.
• Application Number:
  US08/346,508
• Time in Patent Office: 553 Days
• Field of Search: 128/200.14, 128/200.23, 128/202.22, 128/205.23, 128/204.23
• US Class Current: 128/200.14
• CPC Class Codes: A61J 7/0418 with electronic history memory
• CPC Class Codes: A61M 15/00 Inhalators drug delivery in endotracheal tubes A61M16/04
• CPC Class Codes: A61M 15/0021 Mouthpieces therefor
• CPC Class Codes: A61M 15/008 Electronic counters
• CPC Class Codes: A61M 15/009 using medicine packages with incorporated spraying means, e.g. aerosol cans pocket atomiser of the injector type A61M11/08
• CPC Class Codes: A61M 16/0858 Pressure sampling ports
• CPC Class Codes: A61M 16/202 electrically actuated
• CPC Class Codes: A61M 2016/0021 with a proportional output signal, e.g. from a thermistor
• CPC Class Codes: A61M 2016/0039 in the inspiratory circuit
• CPC Class Codes: A61M 2205/50 with microprocessors or computers
• CPC Class Codes: A61M 2205/60 with identification means
• CPC Class Codes: A61M 2205/6018 providing set-up signals for the apparatus configuration
• CPC Class Codes: A61M 2205/6027 Electric-conductive bridges closing detection circuits, with or without identifying elements, e.g. resistances, zener-diodes
• CPC Class Codes: A61M 2205/6036 characterised by physical shape, e.g. array of activating switches
• CPC Class Codes: A61M 2205/6045 having complementary physical shapes for indexing or registration purposes
• CPC Class Codes: A61M 2205/8206 battery-operated
• CPC Class Codes: A61M 2205/8212 with means or measures taken for minimising energy consumption
• CPC Class Codes: B01F 23/2132 using nozzles
• CPC Class Codes: B01F 35/714 for feeding predetermined amounts B01F35/88 takes precedence
• CPC Class Codes: B01F 35/7179 using sprayers, nozzles or jets
• CPC Class Codes: B01F 35/7547 : using valves, gates, orifices or openings
• CPC Class Codes: G01F 1/363 : with electrical or electro-mechanical indication G01F1/37 and G01F1/38 take precedence
• CPC Class Codes: G01F 1/40 : Details of construction of the flow constriction devices
• CPC Class Codes: G01F 1/50 : Correcting or compensating means
• CPC Class Codes: G01F 13/006 : measuring volume in function of time
• CPC Class Codes: G01F 15/002 : for gases

Abstract

A portable, battery powered, hand-held system for releasing a controlled dose of aerosol medication for inhalation by a patient including a durable body and a medication cassette inserted in the durable body. The cassette includes a housing for containing a canister of medication, bears an identification code, and permits the canister to be manually depressed to release a dose, e.g., a metered dose, when out of the durable body. The durable body includes an actuator mechanism for engaging an inserted cassette and its canister, and an actuator release mechanism for controlling the actuator mechanism to depress the canister for a selected period of time to release the desired dose of medication and then the release the canister. The actuator mechanism, includes a compression spring for depressing the canister and a torsion spring for reloading the compression spring. The torsion spring is reloaded by rotating the cassette from an open position for delivering aerosol to a closed position. The actuator release mechanism includes a motor and trigger pin assembly that controls the release of the compression spring and the torsion spring, and, hence, the time that the canister is depressed. The motor operates in response to sensed flow satisfying a selected delivery threshold. The durable body includes a flow sensor having an asymmetrical orifice that is calibrated, independent of the cassette, to convert the sensed pressure due to flow into a flow rate. The orifice is separately calibrated for an inhalation flow rate range and an exhalation flow rate range over a selected number of known flow rates. The sensed pressure value is corrected for transducer offset drift and converted to a flow rate using the calibration data and piecewise linear interpolation.

Claims

1. A portable, hand-held, battery-operated device for delivering aerosolized medications to a patient, comprising:

a cassette comprising a body member having positioned therein a drug formulation containing canister having a depressible valve stem, the cassette having an identification code thereon and the body member having a shape designed to fit into a receiving chamber of the device;

a durable body which comprises the receiving chamber designed to receive the body member of the cassette;

a mouthpiece having an opening therein from which opening a patient may inhale aerosolized medication released from the canister;

a flow sensor for sensing the patient'"'"'s inhalation breath flow;

a microprocessor connected to the flow sensor for determining a point for the release of an amount of drug formulation to the patient based on a sensed inhalation satisfying a flow delivery threshold;

a release mechanism for releasing which operates an actuator mechanism to open the valve upon receipt of a signal from the microprocessor;

wherein the receiving chamber further comprises a latch for engaging the first protrusion and locking the cassette in the receiving chamber and means for disengaging the latch from the protrusion for removing the cassette from the receiving chamber.

2. The device of claim 1 wherein the cassette identification code further comprises a first series of protrusions and wherein the durable body further comprises a keyplate in the receiving chamber having a first series of slots for passing there through the first series of protrusions so that only cassettes having the first series of protrusions can be passed through the keyplate and inserted in the durable body.

3. The device of claim 1 wherein the cassette further comprises an electronic device containing the identification code and wherein the microprocessor further comprises a means for coupling to and obtaining information from the identification code.

4. The device of claim 3 wherein the identification code includes information corresponding to the number of unit dosages of medication contained in the canister of the cassette when the canister is full.

5. The device of claim 3 wherein the identification code includes information corresponding to the number of unit dosages of medication that have been delivered from the canister.

6. The device of claim 1 wherein the cassette further comprises a first protrusion and the receiving chamber further comprises a first groove for receiving the first protrusion, thereby guiding the cassette into the receiving chamber.

7. The device of claim 1 further comprising:

a driver member for engaging an inserted cassette and its canister, the driver member being translatable along a longitudinal first axis and rotatable about the first axis;

a spring element having one portion fixed and a second portion connected to the driver member and being moveable between a loaded condition position and a released condition, wherein the spring element moving from the loaded condition to the released condition moves the driver element to depress the canister for releasing a dose of medication;

means for allowing the spring element to release and for maintaining the spring element in the loaded condition;

wherein the cassette further comprises a surface for engaging the driver member when the cassette is inserted in the durable body, the cassette is rotatable in the receiving chamber about the first axis between an open and a closed position, and wherein rotating the cassette from the open to the closed position rotates the driver member to place the spring element in a loaded condition.

8. The device of claim 1 wherein the cassette body member fully encloses the canister inside the housing.

9. The device of claim 8 wherein the cassette body member further comprises an aperture positioned to allow for manually depressing the canister.

10. The device of claim 8 wherein the flow sensor tube section is calibrated so that different cassettes may be used without affecting the calibration.

11. The device of claim 10 wherein the flow sensor is calibrated for a first range of flow rates for inspiratory flow on the order of 0 to 720 liters per minute and for a second range of flow rates for expiratory flow on the order of 0 to 200 liters per minute.

12. The device of claim 1 wherein the flow sensor is a tube section having an asymmetrical orifice and a transducer for sensing the pressure in the tube.

13. The device of claim 12 wherein the durable body flow sensor tube section is comprised of a contoured wall of the durable body and an airway cover having a first end with a first cross-sectional area, a second end having a second cross-sectional area, and a throat having a third cross-sectional area that is less than the first and second cross-sectional areas.