U.S. patent application number 12/437306 was filed with the patent office on 2009-08-27 for detection system and method for aerosol delivery.
This patent application is currently assigned to DEKA Products Limited Partnership. Invention is credited to David E. Altobelli, Larry B. Gray, Derek G. Kane.
Application Number | 20090213373 12/437306 |
Document ID | / |
Family ID | 34396640 |
Filed Date | 2009-08-27 |
United States Patent
Application |
20090213373 |
Kind Code |
A1 |
Altobelli; David E. ; et
al. |
August 27, 2009 |
Detection System and Method for Aerosol Delivery
Abstract
An apparatus comprises a detector, a pressure sensor and a
processor. The detector is operable to detect light that is
scattered by an aerosol that is associated with a pressure. The
pressure sensor is operable to measure the pressure. The processor
is coupled to the detector and to the pressure sensor, and is
configured to receive at least a signal from the detector and the
pressure sensor. The processor is further configured to use the
received signals to calculate a volume of the first aerosol, and to
output an output signal associated with the calculated volume. The
various measurements can be repeated and compared, and the output
signal can be a feedback signal for metering subsequent amounts of
the aerosol, based on the comparison.
Inventors: |
Altobelli; David E.;
(Hollis, NH) ; Gray; Larry B.; (Merrimack, NH)
; Kane; Derek G.; (Manchester, NH) |
Correspondence
Address: |
Michelle Saquet Temple
DEKA Research & Development Corporation, 340 Commercial Street
Manchester
NH
03101-1129
US
|
Assignee: |
DEKA Products Limited
Partnership
Manchester
NH
|
Family ID: |
34396640 |
Appl. No.: |
12/437306 |
Filed: |
May 7, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12045386 |
Mar 10, 2008 |
7548314 |
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12437306 |
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|
10675278 |
Sep 30, 2003 |
7342660 |
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12045386 |
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10670655 |
Sep 25, 2003 |
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10675278 |
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Current U.S.
Class: |
356/338 |
Current CPC
Class: |
G01N 15/0205 20130101;
A61M 2016/0021 20130101; G01N 2021/4707 20130101; A61M 15/0065
20130101; G01N 15/02 20130101; A61M 2205/3306 20130101; A61M
15/0003 20140204; A61M 15/009 20130101; A61M 2205/3331 20130101;
A61M 2205/3379 20130101; G01N 1/2202 20130101; A61B 5/08 20130101;
A61M 2016/0039 20130101; G01F 13/006 20130101; G01N 21/53 20130101;
G01N 15/1456 20130101; G01N 2001/2223 20130101; G01F 1/34
20130101 |
Class at
Publication: |
356/338 |
International
Class: |
G01N 21/53 20060101
G01N021/53 |
Claims
1. An apparatus comprising: a detector operable to detect light
originating at a light source and scattered by an aerosol; a sensor
operable to determine a pressure of the aerosol; and a processor
coupled to the detector, the processor configured to receive a
signal associated with light scattering from a first aerosol that
is associated with a first airflow; receive a signal representing
the first airflow; and calculate a volume of the first aerosol, the
calculation being based on the signal associated with light
scattering from the first aerosol and the signal representing the
first airflow.
2. The apparatus of claim 1, wherein the processor is further
configured to receive a signal associated with light scattering
from a second aerosol that is associated with a second airflow;
receive a signal representing the second airflow; calculate a
volume of the second aerosol, the calculation being based on the
signal associated with light scattering from the second aerosol and
the signal representing the second airflow; and output a signal
associated with a comparison of the volume of the first aerosol and
the volume of the second aerosol.
3. The apparatus of claim 2, further comprising dose-selection
means coupled to the processor, and wherein the output signal can
be received by the dose-selection means, and wherein the output
signal includes information useful for metering a third
aerosol.
4. The apparatus of claim 2, wherein the output signal comprising
information for metering a third aerosol.
5. The apparatus of claim 1, further comprising a light source.
6. The apparatus of claim 2, wherein the first airflow is
associated with inhalation and the second airflow is associated
with exhalation.
7. An aerosol delivery device comprising: a housing having an
orifice for delivery of the aerosol to the mouth of a user; an
aerosol producing device in fluid communication with the housing; a
detector within the housing operable to detect light originating at
a light source and scattered by the aerosol producing device; a
sensor operable to determine a pressure of the aerosol; and a
processor coupled to the detector, the processor configured to
receive a signal associated with light scattering from a first
aerosol that is associated with a first airflow; receive a signal
representing the first airflow; and calculate a volume of the first
aerosol, the calculation being based on the signal associated with
light scattering from the first aerosol and the signal representing
the first airflow.
8. The device of claim 7 wherein the aerosol producing device is an
atomizer.
9. The device of claim 7 wherein the aerosol aerosolizes a
therapeutic agent.
10. The device of claim 7, wherein the processor is further
configured to receive a signal associated with light scattering
from a second aerosol that is associated with a second airflow;
receive a signal representing the second airflow; calculate a
volume of the second aerosol, the calculation being based on the
signal associated with light scattering from the second aerosol and
the signal representing the second airflow; and output a signal
associated with a comparison of the volume of the first aerosol and
the volume of the second aerosol.
11. The device of claim 10, further comprising dose-selection means
coupled to the processor, and wherein the output signal can be
received by the dose-selection means, and wherein the output signal
includes information useful for metering a third aerosol.
12. The device of claim 10, wherein the first airflow is associated
with inhalation and the second airflow is associated with
exhalation.
13. The device of claims 11 wherein said device is configured to
deliver a predetermined volume of the therapeutic agent.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of co-pending U.S. patent
application Ser. No. 12/045,386, filed Mar. 10, 2008 as Attorney
Docket No. F13, entitled "Detection system and Method for Aerosol
Delivery" which is a continuation of U.S. Pat. No. 7,342,660
entitled "Detection System and Method for Aerosol Delivery", which
is a continuation-in-part of U.S. patent application Ser. No.
10/670,655, filed Sep. 25, 2003 as Attorney Docket No. D42,
entitled "Detection System and Method for Aerosol Delivery", and
now abandoned, all of which are also incorporated herein by
reference in their entireties. U.S. Pat. No. 7,305,984 entitled
"Metering System and Method for Aerosol Delivery"; U.S. patent
application Ser. No. 10/102,484, Attorney Docket No. D44, entitled
"System and Method for Improve Volume Measurement"; and now
abandoned. U.S. Pat. No. 7,021,560, entitled "System and Method for
Aerosol Drug Delivery"; and U.S. Pat. No. 7,146,977, entitled
"Valve System and Method for Aerosol Drug Delivery", all of which
are also incorporated herein by reference in their entireties.
NOTICE OF COPYRIGHT PROTECTION
[0002] A section of the disclosure of this patent document contains
material subject to copyright protection. The copyright owner has
no objection to the facsimile reproduction by anyone of the patent
document, but otherwise reserves all copyright rights
whatsoever.
TECHNICAL FIELD
[0003] The present invention generally relates to systems and
methods for measuring quantities of aerosolized compounds. More
particularly, embodiments of the present invention can relate to
systems and methods for accurately delivering atomized substances,
such as therapeutic agents.
BACKGROUND INFORMATION
[0004] A variety of substances, such as therapeutic agents, may be
delivered by inhalation, including aerosolized liquids and powder
drugs, for the therapeutic treatment of the lungs and inhalation
passageways and/or for the delivery of systemic agents. The
inhalation of systemic therapeutic agents is considered a potential
alternative to injections and other types of drug delivery systems.
For example, insulin may be delivered by inhalation in aerosolized
form, thus avoiding the need for the injection of insulin into a
patient,
[0005] Inhaling aerosols, however, typically lacks the accuracy of
injections, and so may be inappropriate for use in situations where
accurate dosing is critical with aerosolized drugs, the proper
amount; required for delivery is often not properly metered for
delivery. For example, asthma inhalers typically have an acceptable
accuracy of plus or minus 25% of the nominal dose. For systemic
drug delivery of insulin, cm the other hand, such a level of
accuracy is considered too unpredictable to allow for appropriate
use, even though aerosolized delivery may be preferable to
intravenous delivery for a variety of reasons.
[0006] Thus, a need exists for accurately and predictably
delivering a predetermined dose of aerosolized drugs.
SUMMARY
[0007] An embodiment comprises a light detector, a pressure sensor
and a processor. The light detector is operable to detect light
that is scattered by an aerosol that is associated with a pressure.
The pressure sensor is operable to measure the pressure. The
processor is coupled to the light detector and to the pressure
sensor, and is configured to receive at least a signal from the
detector and the pressure sensor. The processor is further
configured to use the received signals to calculate a volume of the
first aerosol, and to output, a signal associated with the
calculated volume.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a schematic diagram of a system for delivering
aerosol according to an embodiment of the invention.
[0009] FIG. 2 is a block diagram of a light scatter detector
according to an embodiment of the invention.
[0010] FIG. 2A is a block diagram of a light scatter detector
including a beam dump, according to an embodiment of the
invention.
[0011] FIG. 3 is a schematic diagram of a system for delivering
aerosol according to an embodiment of the invention.
[0012] FIG. 4 is a block-diagram of a method of measuring the
physical characteristics of an aerosol according to an embodiment
of the invention.
[0013] FIG. 5 is a block diagram of a method of measuring the
physical characteristics of an aerosol according to an embodiment
of the invention.
DETAILED DESCRIPTION
[0014] Embodiments of the invention include systems and methods for
measuring, analyzing, and metering aerosols. For purposes of this
application, the term aerosol includes airflows containing
particles, such as aerosolized liquids, powders, and combinations
of these, as well as airflows that do not contain any aerosolized
particles. One use for the invention is as a real time aerosol
volume transducer. With this use, aerosol density (for example,
aerosol particles per liter) in a system can be measured by light
scatter. If airflow (for example, liters per second) is also
determined, then these two parameters multiplied together yield the
number of aerosol particles per second passing through the chamber.
The number of particles per second can then be integrated to
calculate the total number of aerosol particles (i.e. volume) that
passed through the system. The volume measurement can be repeated,
and a comparison of volume measurements can be fed back to a system
to, for example, meter subsequent amounts of aerosol.
[0015] FIG. 1 shows a block diagram of a contextual overview for
employing embodiments of the present invention. In this overview, a
substance, which can be a liquid or solid form of a therapeutic
agent, or which can be any liquid or solid capable of being
converted to an aerosol, is contained in aerosol selector 101.
Aerosol selector 101 includes atomizer 102, and is coupled to
aerosol flow path 103 such that an aerosol can be introduced from
atomizer 102 into aerosol flow path 103. For purposes of the
application, the term atomizer includes any devise or component
that is capable of producing an aerosol from solids, liquids, or
any combination thereof.
[0016] In one embodiment of the invention, aerosol flow path 103
includes a light source 104, a light detector 105 and a pressure
sensor 107. Light detector 105 and pressure sensor 107 are coupled
to processor 106. Processor 106 can be configured to receive a
signal from light detector 105 and a signal from pressure sensor
107. The respective signals can be sent to processor 106 in
substantially real time, or in some way that associates the
respective signals.
[0017] Processor 106 can be further configured to calculate a
volume of the first aerosol, the calculation being based on the
signal received from light detector 105 and on the signal received
from pressure sensor 107. In one embodiment, processor 106 can
calculate aerosol volume by receiving a signal from detector 105
that is associated with aerosol density, receiving a signal from
pressure sensor 107 that is associated with pressure or flow rate,
and multiplying the aerosol density (i.e., number of particles per
unit volume) by the pressure or flow rate. The result is a
representation of the number of particles per second that traverses
aerosol flow path 103, or that traverses some subvolume of aerosol
flow path 103. The number of particles per second can then be
integrated over time to calculate the total number of aerosol
particles (i.e. volume) that passed through the system.
[0018] Alternatively, airflow can be measured in a variety of way
other than utilizing pressure sensor 107. For example, airflow can
be measured by a turbine-type meter or a hot-wire anemometer.
[0019] In one embodiment, processor 106 can be configured to repeat
the volume calculation for aerosols that are subsequently
introduced into aerosol flow path 103, and compare previous and
subsequent volume calculations. The comparison can be used to
create a feedback signal, output from processor 106 and received by
aerosol selector 101, for metering subsequent aerosols.
[0020] In another embodiment, processor 106 is configured to
receive a first signal and a second signal from light detector 105.
The first signal is associated with light scattering from a first
aerosol that is associated with a first pressure. For the purposes
of the invention, the phrase "first aerosol" means an aerosol with
distinct properties such as composition, number of particles per
unit volume, and particle size. The second signal is associated
with light scattering from a second aerosol that is associated with
a second pressure. For the purposes of the invention, the phrase
"second aerosol" means an aerosol with a number of particles per
unit volume, a particle size or a general composition that may or
may not be different from the first aerosol.
[0021] One skilled in the art will understand that the first
pressure and the second pressure may or may not be the same
pressure, and may or may not occur in the same region, or in
different regions that have the same general geometry.
[0022] In one embodiment, the first aerosol is a medicine to be
inhaled, the first pressure is associated with inhalation, and the
second pressure is associated with exhalation. In other
embodiments, the first and second pressures can be from sources not
associated with inhalation and exhalation. Processor 106 is further
configured to output an output signal associated with a comparison
of the first signal and the second signal. For the purposes of the
invention, the term "comparison" may include any measure of
difference between the first aerosol and the second aerosol. For
example, the comparison may include subtracting the number of
particles per unit volume in the first aerosol from the number of
particles per unit volume in the second aerosol. Alternatively, the
comparison may include, for example, determining the ratio of such
numbers of particles, or comparing input particle size to output
particle size. In one embodiment, breath pause timing can be
measured.
[0023] The output signal can be fed back to aerosol selector 101 to
improve, refine, or otherwise assist in any function performed by
aerosol selector 101. In addition, the output signal can be used to
alter the user's flow pattern for optimal deposition. For example,
the output signal can contain information used to indicate to a
patient to breath longer, deeper, shorter and/or shallower.
[0024] In one embodiment, aerosol selector 101 can receive the
output signal, and can use the information contained in the output
signal to meter a third aerosol. For the purposes of the invention,
the term "third aerosol" means an aerosol with a number of
particles per unit volume, a particle size, or a general
composition that may or may not be different from the first
aerosol. In another embodiment, the output signal can include
comparison information to assist in metering subsequent doses such
that the total dose delivered to a patient can be delivered in
predictable and/or measurable quantities.
[0025] Light source 104 can be a laser, or any light source that is
practicable for the present invention. For example, light source
104 can be a light emitting diode (with or without a collimator),
or can be a fluorescence of the aerosol itself. Light from light
source 104 can be polarized and/or collimated in such a way that,
after scattering from the aerosol, the light can be detected in
detector 105. Light detector 105 can be any light detector, or
multiple light detectors, or an array of light detectors, or any
combination of light detectors in any geometry operable to detect
scattered light, and to send a signal to processor 105. For
example, light detector 105 can be any practicable number and
combination of photomultiplier tubes, CCDs, silicon photodetectors,
pyroelectric detectors, etc. Examples of appropriate geometries
include concentric circles, grid patterns, or any geometry
practicable for the purposes of a particular measurement. For the
purposes of the present invention, the term "scatter" includes, but
is not limited to, scattering due to diffraction.
[0026] For the purposes of the invention, the term processor
includes, for example, any combination of hardware, computer
programs, software, firmware and digital logical processors capable
of processing input, executing algorithms, and generating output as
necessary to practice embodiments of the present invention. Such a
processor may include a microprocessor, an Application Specific
Integrated Circuit (ASIC), and state machines. Such a processor can
include, or can be in communication with, a processor readable
medium that stores instructions that, when executed by the
processor, causes the processor to perform the steps described
herein as carried out, or assisted, by a processor.
[0027] For the purposes of the invention, "processor readable
medium," or simply "medium," includes but is not limited to,
electronic, optical, magnetic, or other storage or transmission
devices capable of providing a processor with processor readable
instructions. Other examples of suitable media include, but are not
limited to, a floppy disk, CD-ROM, magnetic disk, memory chip, ROM,
RAM, ASIC, configured processor, all optical media, all magnetic
tape or other magnetic media, or any other medium from which a
processor can read. Also, various other forms of processor readable
media may transmit or carry instructions to a computer, including a
router, private or public network, or other transmission device or
channel. Also, various other forms of processor readable media may
transmit or carry instructions to a computer, including a router,
private or public network, or other transmission device or
channel.
[0028] Aerosol flow path 103 can further include a region of
variable pressure resistance 108, and a region of fixed pressure
resistance 109.
[0029] FIG. 2 shows a block diagram of a light scatter detector
according to an embodiment of the invention. In this embodiment,
light source 201 is coupled to scatter chamber 202 by aperture 203.
Light source 201 can be, for example, a laser diode emitting a
laser beam. Aperture 203 is configured to remove stray light
emitted by the laser diode, and has a length that provides room for
properly focusing the laser beam within scatter chamber 202. The
laser beam can exit the chamber through aperture 204 in light
detector 205.
[0030] When light passes through the aerosol, the light can scatter
away from the optical path. Accordingly, scatter chamber 202 can be
a polished aluminum tube, or can be any material that allows
scattered light to be directed toward light detector 205.
[0031] Because air and vapor do not scatter as much light as an
aerosol, the amount of light scattered depends largely on the
density of the aerosolized particles in the light path. Thus,
knowledge of the airflow rate, provided by a pressure sensor, and
the amount of light scattered from a laser beam, allows the mass
flow of aerosol to be determined. Ideally, the amount of light
scattered by a monodispersed aerosol is represented by the
following equation:
I.sub.m=I.sub.0(1-e.sup.-.alpha.r-ho.)+I.sub.DC. In this equation,
the variables I.sub.m, I.sub.0, and I.sub.DC are the measured
intensity, the incident intensity, and the background intensity.
The variable .alpha., with units of m.sup.3, is a coefficient
converting the density of scatterers, .rho., having units of
#scatterers/m.sup.3, into the probability that a photon will pass
through the chamber without scattering. The coefficient .alpha. is
essentially independent of all factors except for physical
characteristics of the aerosol and the geometry of the chamber.
When the aerosol is sufficiently similar to the calibration
standard, the measured intensity only depends upon the amount of
incident light, the background light, and the density of
scatters.
[0032] Again ideally, the density of scatterers is given by
.rho.=.gamma.(.mu..sub.m/Q), where .mu..sub.m is the volume flow
rate of the aerosolized particles .mu.L/s, Q is the volume flow
rate of air, L/s, and .gamma. is a coefficient relating mass of the
aerosolized particles to the number of scattering particles. The
coefficient .gamma. has units of L/.mu.Lm.sup.3.
[0033] To solve for .mu..sub.m,
mu..sub.m=(-Q/.alpha..gamma.)[ln(I.sub.0+-I.sub.DC-I.sub.m)-ln(I.sub.0)].
This equation provides a nominal functional relation between
aerosol mass flow, airflow, and measured intensity. In practice, of
course, embodiments of the system exhibit non-ideal and non-linear
behavior. These behaviors can be based on (i) a non-zero width of
the laser beam; (ii) a non-constant velocity profile of the airflow
and aerosol distribution; (iii) a polydispersed aerosol; and (iv)
volatility of the aerosol.
[0034] Thus, the volume flow rate of the aerosolized particles may
retain the form
.mu.m=f(Q{ln(I.sub.0+I.sub.DC-I.sub.m)-ln(I.sub.0)}). To
accommodate for non-linearities, the following cubic approximation
to the true functional relation may be used: 1 m=i=1 3 a i{Q[ln(I
0+I DC-I m)-ln(I 0)]}.
[0035] This relation and its coefficients absorb the product
.alpha..gamma..
[0036] The coefficients a.sub.i can be determined in a number of
ways, including through the use of a standard least-squares
algorithm to minimize the difference between predicted mass flow
and mass flow measured from a calibrated aerosol or a test strip
with a calibration scattering coefficient
[0037] In one embodiment, light source 201 can be modulated with an
on-off square beam to improve the signal to noise ratio. In this
embodiment, the detector signal is integrated during the on period)
S.sub.1, and separately during the off period, S.sub.0. The signal
used to calculate aerosol volume is thus the difference,
S.sub.1-S.sub.0. To implement this embodiment, the system is
configured such that the baseline noise from the detector and any
ambient light are likely captured by the off-period signal. In
other embodiments of the invention, other modulation techniques can
be used to improve the signal to noise ratio.
[0038] FIG. 2A is a block diagram of a light scatter detector
including a beam dump according to an embodiment of the invention.
In this embodiment, light source 201a emits light into scatter
chamber 202a. Detector 203a contains an aperture (not numbered), so
that when light from light source 201a exits the aperture, it
illuminates beam dump 204a. Beam dump 204a is in the direct path of
the light beam, and is configured to absorb or contain light that
is not scattered by the aerosol. In one embodiment, beam dump 204a
is simply a hole allowing the light beam to exit the system.
[0039] FIG. 3 is a schematic diagram of a system for delivering an
aerosol according to an embodiment of the invention. The context
for the embodiment displayed in this figure is a device capable of
delivering doses of aerosolized drugs. In this embodiment,
reservoir 301 is coupled to dose controller 302 via flow channel
304. Dose controller 302, including valve 303, is configured to
deliver a metered amount of the compound to atomizer 305 via flow
channel 306. Atomizer 305, upon receiving the compound, can create
an aerosol of the compound and deliver it to flow path 306, which
can be a user interface, or it can be any type of conduit for the
aerosol.
[0040] In one embodiment, aerosol flow path 306 includes light
source 307 and light detector 308. Light source 307 is configured
to send light across aerosol flow path 306, either directly or in
combination with mirrors and collimators, or in any practicable way
such that scattered light can be detected by light detector 308.
Light detector 308 is placed in such a way that it can detect light
from light source 307, including light that has scattered from an
aerosol present in aerosol pathway 306. Processor 309, coupled to
light detector 308, is further coupled to dose controller 302 and
can provide a signal to dose controller 302 that is associated with
the light detected at light detector 308.
[0041] In one embodiment, aerosol flow path 306 includes pressure
sensor 311 for detecting pressure inside aerosol flow path 306.
Pressure sensor 311 can be coupled to processor 309. In this
embodiment, processor 309 can use information received from
pressure sensor 311 in providing an output signal for feedback to
dose controller 302.
[0042] In one embodiment, person 310 can receive the aerosol by
inserting the distal end of aerosol flow path 306 into an orifice,
and inhaling the aerosol. After delivering the aerosol to person
310, processor 309 is configured to receive a signal from light
detector 310 and send an output signal to dose controller 302. The
output signal can include information for metering a subsequent
dose or doses.
[0043] In another embodiment of the invention, processor 309 is
configured to receive a signal from light detector 308 that is
associated with person 310 exhaling after inhaling the aerosol.
Using the signal associated with inhaling and the signal associated
with exhaling, processor 309 is configured to calculate a
comparison of the two signals, and send an output signal associated
with this comparison to dose controller 302. The output signal can
include information for metering a subsequent dose or doses.
[0044] FIG. 4 is a block-diagram overview of a method according to
an embodiment of the invention. One skilled in the art will
recognize that the steps described in FIG. 4 need not necessarily
be performed in the order displayed; the steps may be performed in
any order practicable.
[0045] At step 401, a first aerosol enters a flow path under a
first pressure. The first pressure can be caused by, for example,
inhalation, exhalation, or any other practicable source for
creating pressure appropriate for a given context. At step 402, a
light source activates and light from the light source scatters
from a first aerosol. One skilled in the art would understand that
the light source may not be a single light source, but can be any
appropriate combination of light sources.
[0046] At step 403, a light detector detects the scattered light,
and sends a light-detection signal to a processor to process the
signal. At step 404, the processor receives the light-detection
signal.
[0047] At step 405, the processor receives from a pressure sensor a
signal associated with the airflow, or any general fluid flow, in
the flow path. The processor, at step 406, can use the received
signals to calculate the amount of the first aerosol that traverses
the flow path.
[0048] At step 407, a second aerosol enters the flow path under a
second pressure. The second pressure can be caused by, for example,
inhalation, exhalation, or any other practicable source for
creating a pressure appropriate for a given context. The light
source is activated at step 408, and light from the light source is
scattered from the second aerosol.
[0049] Next, at step 409, the scattered light is detected by the
light detector, and a detection signal is sent to the processor for
processing. The signal is received by the processor at step 410,
and at step 411, the processor receives a signal from the pressure
sensor associated with the aerosol flow in the flow path.
[0050] The processor, at step 412, can use the received signals to
calculate the amount of the second aerosol that traverses the flow
path. At step 413, the processor compares the amount of the first
aerosol detected with the amount of the second aerosol detected,
and outputs a signal associated with the difference between the two
at step 414.
[0051] FIG. 5 is a block diagram of a method according to an
embodiment of the invention. This method is presented in the
context of a person inhaling and exhaling an aerosolized drug. One
skilled in the art will recognize, however, that the method is
equally applicable in any situation in which a compound is metered,
aerosolized and dispensed under pressure. One skilled in the art
will further recognize that the steps described in FIG. 4 need not
necessarily be performed in the order displayed; the steps may be
performed in any order practicable.
[0052] At step 501, initial conditions for depositing the aerosol
are set up. In these initial conditions, the compound to be
aerosolized exists in a reservoir chamber. At this point, the
system metering valve is closed, and the light source and light
detector for measuring the deposited dose are dormant.
[0053] At step 502, a person's lungs expand, thereby creating a
pressure region in the aerosol flow path. A pressure sensor changes
in response to this change in pressure.
[0054] At step 503, the person holds his breath and the drug is
metered by a dose controller. At this point, a valve opens,
delivering the drug to an atomizer. At step 504, the person
exhales, and the pressure sensor reflects this change in pressure.
At this point, light source is active. One skilled in the art will
appreciate that steps 502 and 503 can be used to calibrate the
system by creating a baseline measurement that can be subtracted
out of subsequent aerosol measurements.
[0055] Possible methods of metering include, but are not limited
to, using a piston or syringe device, a peristaltic pump. Other
possible methods include using acoustic volume sensing (AVS)
techniques as described in U.S. Pat. No. 5,575,310, incorporated
herein in its entirety, and fluid management system (FMS)
techniques as described in U.S. Pat. No. 5,193,990, incorporated
herein in its entirety.
[0056] The aerosol is delivered to the person in step 505. In this
step, the person inhales. The change in pressure is noted by the
pressure sensor, and an air valve opens. In this step, the target
volume is atomized at an atomizer, and the aerosol flows into an
aerosol flow path for measurement and delivery to the person. The
light source is active in this step, the pressure sensor indicates
pressure, and the aerosol volume of the inhaled aerosol is
calculated. In one embodiment, the aerosol is delivered at room
temperature. In this step, the person can hold his breath to
maximize aerosol deposition in the lungs.
[0057] At step 507, the person exhales, causing the pressure sensor
to indicate airflow. At this step, the light source is activated
and the aerosol volume of the exhaled aerosol is calculated. Using
the calculations performed during inhalation and exhalation, at
step 508, the target volume of the aerosol is adjusted. At step
509, the sequence is repeated.
[0058] In one embodiment of the invention, the method steps of FIG.
5 are embodied as a computer program on a processor readable medium
that stores instructions to cause a processor to perform the steps
of the method.
[0059] The foregoing description of the embodiments of the
invention has been presented only for the purpose of illustration
and description and is not intended to be exhaustive or to limit
the invention to the precise forms disclosed. Numerous
modifications and adaptations thereof will be apparent to those
skilled in the art without departing from the spirit and scope of
the present invention.
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