Method for releasing controlled amount of aerosol medication

• US 5,743,252 A
• Filed: 11/27/1996
• Issued: 04/28/1998
• Est. Priority Date: 03/05/1991
• Status: Expired due to Fees

• Current Assignee: Aradigm Corporation
• Original Assignee: Aradigm Corporation
• Inventors: Rubsamen, Reid M., Johansson, Eric T.
• Primary Examiner(s): Lewis, Aaron J.
• Application Number:
  US08/756,409
• Time in Patent Office: 517 Days
• Field of Search: 128/200.14, 128/200.23, 128/204.18, 128/204.21, 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 15/0066 with means for varying the dose size
• 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 15/0091 mechanically breath-triggered
• 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 2016/0036 in the breathing tube and used in both inspiratory and expiratory phase
• 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 35/71 : Feed mechanisms with proportioning B01F35/80
• CPC Class Codes: B01F 35/712 : for feeding fluids
• CPC Class Codes: B01F 35/7179 : using sprayers, nozzles or jets
• CPC Class Codes: B01F 35/71805 : using valves, gates, orifices or openings
• CPC Class Codes: B01F 35/7547 : using valves, gates, orifices or openings
• CPC Class Codes: F16H 35/00 : Gearings or mechanisms with other special functional features
• 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 1/44 : Venturi tubes
• 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
• CPC Class Codes: G01F 25/10 : of flowmeters
• CPC Class Codes: G01F 7/005 : by measuring pressure or differential pressure, created by the use of flow constriction

Abstract

A method for releasing a controlled amount of aerosol medication is disclosed. The method of the invention is preferably used in connection with a portable, battery-powered, hand-held system for releasing a controlled dose of aerosol medication for inhalation by a patient. The inhalation breath flow of the user of the apparatus is monitored and the inhalation flow rate is measured, and inhalation volume is determined as a function of the measured flow rate. The measured flow rate is compared to predetermined minimum and maximum flow rate thresholds, and the determined flow volume is compared to predetermined minimum and maximum flow volume thresholds. When both the measured flow rate and the measured flow volume are between their respective the minimum and maximum thresholds, a signal is provided to release a controlled amount of aerosol.

Claims

1. A device for delivering aerosol to a patient, comprising:

a container holding formulation for delivery to a patient;

a means for aerosolizing the formulation;

a flow path;

a transducer having an analog signal corresponding to sensed pressure flow in either direction through the flow path wherein the drift offset of the transducer is corrected by;

an analog to digital converter having a defined range of digital counts and a digital value in the digital range corresponding to the base zero flow in either direction;

means for controlling the analog to digital converter to convert the transducer output signal to a digital value at a given sampling rate;

means for identifying a zero-flow condition through the flow path when the digital values do not vary more than a selected number of digital counts over a first period of time;

first means for determining an offset value based on the difference between the identified base digital count and the digital value output of the analog to digital converter during a zero-flow condition; and

means for adjusting the output of the analog to digital converter by the determined offset value.

2. The apparatus of claim 1 wherein the identifying means further comprises:

a buffer for storing a selected number of digital values corresponding to samples of the transducer output taken over the selected time interval;

means for adding a newly acquired digital value to the buffer and subtracting the oldest acquired digital value from the buffer; and

first means for processing the buffer contents to identify a zero-flow condition through the flow path in response to the digital values stored in the buffer not varying more than a selected number of digital counts.

3. The apparatus of claim 2 wherein the first processing means further comprises second means for determining that a zero-flow condition exists when the difference between the maximum and minimum values in the buffer is less than the selected number of digital counts.

4. The apparatus of claim 3 wherein the analog to digital converter has a digital count range on the order of 65,536 counts, the selected number of digital values in the buffer is on the order of 25, and the second determining means determines that a zero-flow condition exists when the determined difference is less than four digital counts.

5. The apparatus of claim 2 wherein the first determining means further comprises second means for processing the buffer contents to determine a mean value of the selected number of digital values in the buffer and determines the offset value as the difference between the identified base digital count and the determined mean value.

6. The apparatus of claim 5 wherein the analog to digital converter has a digital count range on the order of 65,536 counts, and the selected number of digital values in the buffer is on the order of 25, and the first processing means determines that a zero-flow condition exists when the determined difference is less than four digital counts.

7. The apparatus of claim 1 wherein the analog to digital converter has a digital count range on the order of 65,536 counts, and the identifying means determines that the digital value does not change by more than ±

2 digital counts during a period on the order of one-third of a second.