U.S. patent application number 16/551844 was filed with the patent office on 2019-12-19 for methods, devices, systems, and compositions for detecting gases.
The applicant listed for this patent is Respirion, LLC. Invention is credited to Eugene W. Moretti, Allan Bruce Shang, Robert Lavin Wood, Steven S. Yauch.
Application Number | 20190383751 16/551844 |
Document ID | / |
Family ID | 49235310 |
Filed Date | 2019-12-19 |
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United States Patent
Application |
20190383751 |
Kind Code |
A1 |
Moretti; Eugene W. ; et
al. |
December 19, 2019 |
METHODS, DEVICES, SYSTEMS, AND COMPOSITIONS FOR DETECTING GASES
Abstract
A method of monitoring a respiratory stream can be provided by
monitoring color change of a color change material to determine a
CO2 level of the respiratory stream in contact with the color
change material by emitting visible light onto the color change
material. Related devices, systems, and compositions are also
disclosed.
Inventors: |
Moretti; Eugene W.; (Durham,
NC) ; Wood; Robert Lavin; (Cary, NC) ; Shang;
Allan Bruce; (Wake Forest, NC) ; Yauch; Steven
S.; (Clayton, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Respirion, LLC |
Winton Salem |
NC |
US |
|
|
Family ID: |
49235310 |
Appl. No.: |
16/551844 |
Filed: |
August 27, 2019 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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13796593 |
Mar 12, 2013 |
10393666 |
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16551844 |
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13609024 |
Sep 10, 2012 |
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13796593 |
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61609603 |
Mar 12, 2012 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G01N 21/783 20130101;
A61B 5/742 20130101; A61B 5/0836 20130101; Y10T 436/204998
20150115 |
International
Class: |
G01N 21/78 20060101
G01N021/78; A61B 5/00 20060101 A61B005/00; A61B 5/083 20060101
A61B005/083 |
Claims
1-10. (canceled)
11. An apparatus to monitor a respiratory stream comprising: a
breathing circuit adapter configured for coupling to a breathing
circuit to provide the respiratory stream; and a color change
material comprising a reactive portion and an unreactive portion,
the color change material at least partially inside the breathing
circuit adapter positioned for contact with the respiratory
stream.
12. The apparatus of claim 11, wherein the reactive and unreactive
portions are separated from one another, the reactive portion is
configured to provide a first color responsive to a CO.sub.2 level
in the respiratory stream and the unreactive portion is configured
to a second color, different from the first color, that is
irrespective of the CO.sub.2 level in the respiratory stream.
13. The apparatus of claim 12, wherein the color change material is
removably attached to the apparatus.
14. The apparatus of claim 11, wherein the breathing circuit
adapter further comprises an enclosure positioned inside the
breathing circuit adapter proximate to the respiratory stream and
configured to isolate the unreactive portion from the respiratory
stream.
15. The apparatus of claim 11, wherein the breathing circuit
adapter further comprises an opening to the respiratory stream and
configured to provide positioning of the unreactive portion outside
the respiratory stream and to provide positioning of the reactive
portion inside the breathing circuit adapter proximate to the
respiratory stream.
16. The apparatus of claim 11, wherein the color change material
comprises a composition, wherein an alkaline material is present in
an amount of about 0.1% to about 10% by weight of the
composition.
17. The apparatus of claim 12, wherein the unreactive portion
comprises a quenched reactive portion.
18. The apparatus of claim 12, wherein the unreactive portion
comprises an external reactive portion that is outside the
respiratory stream.
19. The apparatus of claim 12, wherein the reactive portion
comprises a catalyst and the unreactive portion is substantially
free of the catalyst.
20. The apparatus of claim 12, wherein the breathing circuit
adapter includes at least one retaining feature configured to hold
the unreactive portion outside the respiratory stream.
21. An apparatus for use in monitoring a respiratory stream
comprising: a color change material having a reactive portion
thereon, wherein the reactive portion is configured to provide a
first color based on exposure to a first CO.sub.2 level and is
configured to change from the first color through a first range of
colors to a second color based on exposure to a second CO.sub.2
level that is greater than the first CO.sub.2 level; and an
unreactive portion, spaced apart from the reactive portion on the
color change material, wherein the unreactive portion is configured
to provide a first color based on exposure to the first CO.sub.2
level and is configured to change from the first color through a
second range of colors that is smaller than the first range of
colors to a third color based on exposure to the second CO.sub.2
level.
22. The apparatus of claim 21, wherein the color change material
comprises a composition, wherein an alkaline material is present in
an amount of about 0.1% to about 10% by weight of the
composition.
23. The apparatus of claim 21, wherein the reactive portion
includes a color change indicator and the unreactive portion is
free of the color change indicator.
24. The apparatus of claim 21, wherein the reactive portion and
unreactive portion each comprise a color change indicator
comprising an alkaline material, wherein the amount of the alkaline
material in the unreactive portion is configured to provide the
unreactive portion with a greater pH than the reactive portion.
25. A carbon dioxide indicator comprising: a color change material,
wherein the color change material is responsive to carbon dioxide;
and a control material, wherein the control material is
substantially non-responsive to carbon dioxide.
26. The carbon dioxide indicator of claim 25, wherein the color
change material comprises a composition, wherein an alkaline
material is present in an amount of about 0.1% to about 10% by
weight of the composition.
27. The carbon dioxide indicator of claim 25, wherein the color
change material and the control material are configured to be
exposed to substantially the same conditions.
28. The carbon dioxide indicator of claim 25, wherein the color
change material is configured to change from a first color to a
second color and return to the first color in response to contact
with at least one carbon dioxide concentration.
29. The carbon dioxide indicator of claim 25, wherein the color
change material is configured to change from a first color to a
second color and return to the first color about 1 to about 60
times per minute in response to contact with at least two
consecutive carbon dioxide concentrations.
30. The carbon dioxide indicator of claim 25, wherein in operation,
the color change material and the control material are
substantially the same color at a first CO.sub.2 concentration
prior to contact with a second CO.sub.2 concentration having a
greater CO.sub.2 concentration.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/796,593, entitled "METHODS, DEVICES,
SYSTEMS, AND COMPOSITIONS FOR DETECTING GASES", filed on Mar. 12,
2013, which claims priority to U.S. patent application Ser. No.
13/609,024, entitled "Methods, Devices, Systems, and Compositions
for Detecting Gases", filed on Sep. 10, 2012, and to U.S.
Provisional Patent Application No. 61/609,603, entitled "Method and
Apparatus for Detecting Carbon Dioxide Levels", filed on Mar. 12,
2012, the disclosures of each of which are entirely incorporated
herein by reference.
FIELD OF INVENTION
[0002] The present invention relates to the measurement of gas
levels, and more specifically, to measuring respiratory gases.
BACKGROUND
[0003] First responders, respiratory therapists and critical care
personnel perform emergency laryngoscopy and intubation under a
variety of conditions and under great duress. Securing a viable and
protected airway is one of the paramount steps of a successful
resuscitation. Often times airway manipulation and instrumentation
are performed in suboptimal conditions by inexperienced or lightly
trained personnel. These procedures have the potential for disaster
if they result in an esophageal intubation, causing hypoxia,
anoxia, and cardiopulmonary arrest if allowed to continue
unrecognized.
[0004] Capnography, the measurement of CO.sub.2 in expired or
respirated gases has been commonly used in the operating room
setting for several years. Capnography readily identifies
situations that can lead to hypoxia if left undetected and dealt
with. For example, one use of a CO.sub.2 measuring device is to
confirm proper endotracheal tube placement during general
anesthesia. By identifying improper placement, the provider can
then rectify potential hypoxic conditions before hypoxia can
actually lead to severe brain damage. Recently the use of
capnography has been extended outside of the operating room arena
to include emergency rooms, intensive care units, endoscopic
suites, radiographic suites and first responders at catastrophic
events (e.g. motor vehicle or industrial accidents).
[0005] The current standard of care for collect endotracheal tube
placement calls for multiple methods of confirmation, one of which
could be a carbon dioxide detector. Typically, however, the method
used to confirm proper placement is a capnographic waveform
monitor. Unfortunately, this monitor may be a complex electronic
device only capable of functioning in highly controlled
environments, such as an operating room. In many cases, these
devices are not available, suited, or adapted for the location in
which these procedures may be necessary.
[0006] Other types of endotrachael tube placement confirmation may
be a disposable colorimetric detector. This type of detector
confirms the presence of CO.sub.2 via a visible color change in
equipment or test strip when exposed to exhaled gases containing
CO.sub.2. This device detects CO.sub.2 via a chemical reaction
which causes a color shift in a reagent containing substrate
contained within the device.
[0007] Colorimetric detectors are generally useful as qualitative
indicators of the presence or absence of CO.sub.2. Various methods
have been disclosed for quantitative detection of CO.sub.2 in
respired gas samples. However limitations of these devices may be
that they may not provide useful feedback during various patient
procedures such as cardiopulmonary resuscitation and/or
ventilation. These simple detectors may not add value to patient
outcomes beyond informing a simple gate decision of whether
CO.sub.2 is present or absent in respiratory gases.
[0008] CO.sub.2 concentration at the end of a breath can represent
the end tidal carbon dioxide concentration (PETCO.sub.2). Decreases
in cardiac output and pulmonary blood flow can result in decreases
in PETCO.sub.2. Correspondingly, increases in cardiac output and
pulmonary blood flow result in better perfusion of the alveoli and
a rise in PETCO.sub.2. The relationship between cardiac output and
PETCO.sub.2 has been determined to be logarithmic. Therefore
capnography can detect the presence of pulmonary blood flow even in
the absence of major pulses, and it can indicate changes in
pulmonary blood flow caused by alterations in cardiac rhythm.
Initial data samples reveal that the PETCO.sub.2 may correlate with
coronary perfusion pressure. This correlation between perfusion
pressure and PETCO.sub.2 is likely to be secondary to the
relationship between PETCO.sub.2 and cardiac output.
[0009] Capnographic measurements have been evaluated to predict
outcomes in cardiac arrest. A study involving 127 patients revealed
that only one patient with a PETCO.sub.2 less than 10 mm Hg during
resuscitation survived to hospital discharge. In another
prospective investigation involving 139 adult victims of
out-of-hospital, non-traumatic cardiac arrest, no patient with an
average PETCO.sub.2 less than 10 mm Hg upon initial resuscitation
survived. The analysis of these studies concluded that PETCO.sub.2
can be correlated with resuscitation and outcome in cardiopulmonary
resuscitation (CPR). Moreover, another application of capnography
in this setting is to provide feedback to optimize chest
compressions during CPR. Monitoring PETCO.sub.2 may detect
inadequate chest compressions secondary to fatigue that could
result in a sub-optimal cardiac output.
[0010] Capnography is gaining increasing acceptance during the
resuscitation of trauma victims. PETCO.sub.2 is a marker of
traumatic physiology, as it reflects changes in cardiac output.
Recently a study involving 191 blunt trauma patients revealed that
PETCO.sub.2 may be of value in predicting outcome from major
trauma. In this investigation only 5% of patients with a
PETCO.sub.2 less than 10 mm Hg survived to hospital discharge.
Other studies have shown capnography to be of value in providing
optimum ventilation in pre-hospital major trauma victims. Patients
monitored using capnography had a statistically significant higher
incidence of normoventilation (normal CO.sub.2 levels in the blood)
compared to those who were not managed with capnography (63.2% vs.
20% p<0.0001).
[0011] Some previous CO.sub.2 detectors make use of an
electrochemical detection device referred to collectively as
"chemiresistors". Such devices respond to the absorption of target
chemical species by undergoing a change in ohmic resistance. In
many chemiresistor designs, the change in ohmic resistance may
provide a quantitative basis for measurement of the absorbed
species. Chemiresistors may generally be comprised of an
electrically insulating substrate, with at least one surface having
two or more conductive electrode layers spaced apart thereon. These
electrodes may comprise a metallic layer, and they may have an
interdigitated geometric form. A chemiresistive layer or "ink" may
cover two or more electrode layers, and act as the "absorber" that
attracts the analyte species of interest. Voltage applied to the
electrodes will induce a current flow within the chemiresistive ink
layer. Measurement of this current may provide a quantitative basis
for detection of absorbed analyte.
[0012] Absorption of a species by a chemiresistive layer results in
changes in the layer's physical and/or chemical properties,
resulting in a change in ohmic resistance. For example, a
chemiresistive ink may comprise finely divided carbon particles in
a polymeric binder. The proportion of binder and particles may be
chosen such that the layer has a first ohmic resistance. Upon
absorption of an organic compound having affinity for the polymeric
binder, the layer may undergo swelling which causes the particles
to generally move out of contact, resulting in high ohmic
resistance. The change in ohmic resistance due to swelling may be
in proportion to the organic compound. Heating of the layer may
desorb the organic compound, regenerating the layer for a new cycle
of measurement.
SUMMARY
[0013] Embodiments according to the invention can provide methods,
devices, systems, and compositions for monitoring gases. In some
embodiments according to the invention, a device can include a
visible light emitter circuit that is configured to provide emitted
visible light into a breathing circuit. A first visible light
sensor circuit can be configured to receive a first portion of the
emitted visible light and a second visible light sensor circuit can
be configured to receive a second portion of the emitted visible
light. A processor circuit can be coupled to the visible light
emitter circuit and to the first and second visible light sensor
circuits, where the processor circuit can be configured to
determine a CO.sub.2 level of a respiratory stream in the breathing
circuit based on the first and second portions of the emitted
visible light.
[0014] In some embodiments according to the invention, the first
visible light sensor circuit can be configured to provide a
reactive signal to the processor circuit as a color indication of
the CO.sub.2 level based on the first portion of the emitted
visible light. In some embodiments according to the invention, the
second visible light sensor circuit can be configured to provide a
control signal to the processor circuit as a color indication
irrespective of the CO.sub.2 level based on the second portion of
the emitted visible light. In some embodiments according to the
invention, the control signal can include an ambient light control
component and color control component.
[0015] In some embodiments according to the invention, the first
visible light sensor circuit can be configured to provide a
reactive signal to the processor circuit as a color indication of
the CO.sub.2 level based on the first portion of the emitted
visible light. The second visible light sensor circuit can be
configured to provide a control signal to the processor circuit as
a color indication irrespective of the CO.sub.2 level based on the
second portion of the emitted visible light.
[0016] In some embodiments according to the invention, a method of
monitoring a respiratory stream can be provided by monitoring color
change of a color change material to determine a CO.sub.2 level of
the respiratory stream in contact with the color change material by
emitting visible light onto the color change material.
[0017] In some embodiments according to the invention, the method
can further include sensing the color change using a sensor to
detect a portion of the emitted visible light reflected from and/or
transmitted through the color change material. As those skilled in
the art will recognize, in some embodiments, a portion of the
emitted visible light may be reflected from the color change
material and a portion of the emitted visible light may be
transmitted through the color change material, and a sensor may be
configured to detect either portion or both portions. An embodiment
describing a sensor detecting a portion of the reflected emitted
visible light can be configured to detect a portion of the
transmitted emitted visible light. In certain embodiments according
to the invention, the method can include using a sensor to detect a
portion of the emitted visible light reflected from and/or
transmitted through a control material, which may not change color
when in contact with CO.sub.2. The method may thus include
comparing a portion of the emitted visible light reflected from
and/or transmitted through the color change material and a portion
of the emitted visible light reflected from and/or transmitted
through a control material.
[0018] In some embodiments according to the invention, the method
can further include determining the CO.sub.2 level based on a
comparison of components of the emitted visible light reflected
from and/or transmitted through the color change material and/or
control material. In some embodiments according to the invention,
the components include at least two color components of the emitted
visible light reflected from and/or transmitted through the color
change material and/or control material. In some embodiments
according to the invention, the at least two color components of
the emitted visible light reflected from and/or transmitted through
the color change material and/or control material comprise red,
green, and blue components.
[0019] In some embodiments according to the invention, the
determining can be provided by determining the CO.sub.2 level based
on a comparison of at least two of a red component, a green
component, and a blue component of the emitted visible light
reflected from and/or transmitted through the color change material
and/or control material.
[0020] In some embodiments according to the invention, an apparatus
to monitor a respiratory stream can include a color change material
and/or control material that can be positioned proximate to the
respiratory stream and an electronic visible light emitter can be
configured to emit visible light onto the color change material
and/or control material.
[0021] In some embodiments according to the invention, the
apparatus can include an electronic visible light sensor, that can
be positioned to receive at least a portion of the emitted visible
light reflected from and/or transmitted through the color change
material and/or control material. An apparatus according to
embodiments of the invention may include two or more electronic
visible light sensors. In certain embodiments according to the
invention the apparatus may comprise at least two electronic
visible light sensors, wherein one sensor may be positioned to
receive at least a portion of the emitted visible light reflected
from and/or transmitted through the color change material and the
other sensor may be positioned to receive at least a portion of the
emitted visible light reflected from and/or transmitted through the
control material.
[0022] In some embodiments according to the invention, the
electronic visible light emitter and the electronic visible light
sensor are remote from the respiratory stream, and the apparatus
can further include an optical transmission medium that extends
from the color change material and/or control material to the
electronic visible light emitter and the electronic visible light
sensor, that can be configured to conduct the emitted visible light
onto the color change material and/or control material and to
conduct the emitted visible light reflected from and/or transmitted
through the color change material and/or control material.
[0023] In some embodiments according to the invention, the
apparatus can further include a breathing circuit adapter having
the color change material and/or control material mounted on an
interior side wall thereof, wherein a major surface of the color
change material and/or control material is parallel to a direction
of the respiratory stream in the adapter.
[0024] In some embodiments according to the invention, a
composition for use in monitoring a respiratory stream, referred to
herein as a color change indicator, can be configured to change
from a first color to a second color in response to an increase in
CO.sub.2 within the respiratory stream, where the first color
includes more of a first component than a second component or more
than a third component and the second color includes less of the
first component than the second component or less than the third
component. In certain embodiments according to the invention, a
color change material, which can include a color change indicator,
can be configured to change from a first color to a second color in
response to an increase in CO.sub.2 within the respiratory stream,
where the first color includes more of a first component than a
second component or more than a third component and the second
color includes less of the first component than the second
component or less than the third component. In certain embodiments
according to the invention, a control composition for use in
monitoring a respiratory stream can include a control material
configured to remain a first color in response to an increase
and/or decrease in CO.sub.2 within the respiratory stream, where
the first color includes more of a first component than a second
component or more than a third component.
[0025] In some embodiments according to the invention, the first
component can be blue and the second and third components can be
red and green, respectively. In some embodiments according to the
invention, the first color includes more of the first component
than both the first and second components and the second color
includes less of the first component than both the second and third
components.
[0026] In some embodiments according to the invention, a
composition comprising: a dye present in an amount of about 0.001%
to about 0.1% by weight of the composition; a buffer present in an
amount of about 0.5% to about 10% by weight of the composition; an
alkaline material present in an amount of about 0.1% to about 10%
by weight of the composition; and a nitrogen containing compound
present in an amount of about 0.01% to about 2% by weight of the
composition may be provided. The nitrogen containing compound may
be configured to provide an increase in a colorific response.
According to some embodiments, the composition may be used to
determine a CO.sub.2 concentration, such as, but not limited to, a
CO.sub.2 concentration in a respiratory stream.
[0027] In some embodiments according to the invention, a color
change material may be provided. The color change material may
comprise a substrate; and a color change composition according to
embodiments described herein, and the color change composition may
be in contact with at least a portion of the said substrate.
According to some embodiments, the substrate is optically
transmissive.
[0028] In some embodiments according to the invention, a carbon
dioxide indicator may be provided. The carbon dioxide indicator may
comprise a color change material, wherein said color change
material is responsive to carbon dioxide; and a control material,
wherein said control material is substantially non-responsive to
carbon dioxide.
[0029] In some embodiments according to the invention, a kit may be
provided. The kit may comprise a carbon dioxide indicator, wherein
at least a portion of said carbon dioxide indicator is responsive
to carbon dioxide; a support member, wherein said carbon dioxide
indicator is attached to said support member; and a storage bag
configured to isolate said carbon dioxide indicator from external
carbon dioxide.
[0030] In some embodiments according to the invention, a method of
determining a carbon dioxide level in a subject's respiratory
stream is provided. The method may comprise contacting said
respiratory stream to a color change material according to
embodiments described herein; and monitoring color change of the
color change material by emitting visible light onto the color
change material, thereby determining a carbon dioxide level of the
respiratory stream in contact with said color change material.
BRIEF DESCRIPTION OF THE DRAWINGS
[0031] FIG. 1 is a schematic illustration of a color change
material configured for placement within a breathing circuit for
contact with CO.sub.2 in some embodiments according to the
invention.
[0032] FIG. 2 is a schematic representation illustrating a chemical
reaction between a color change indicator included in the color
change material and CO.sub.2 in contact therewith as part of the
breathing cycle in some embodiments according to the invention.
[0033] FIGS. 3-6 are schematic representations illustrating
different configurations of color change materials in some
embodiments according to the invention.
[0034] FIG. 7A is a schematic representation of a color change
material included in a breathing circuit and exposed to
electronically generated visible light and electronic sensing
thereof in some embodiments according to the invention.
[0035] FIG. 7B is a schematic representation of a color change
material included in a breathing circuit and exposed to
electronically generated visible light and electronic sensing
thereof in some embodiments according to the invention.
[0036] FIG. 8 is a schematic representation of a CO.sub.2 detection
system in some embodiments according to the invention.
[0037] FIG. 9 is a schematic representation of a CO.sub.2 detection
system in some embodiments according to the invention.
[0038] FIG. 10 is a schematic representation of a CO.sub.2
detection system in some embodiments according to the
invention.
[0039] FIG. 11 is a schematic representation of a CO.sub.2
detection system in some embodiments according to the
invention.
[0040] FIG. 12 is a schematic illustration of a display configured
to provide information regarding CO.sub.2 provided by the CO.sub.2
system in some embodiments according to the invention.
[0041] FIG. 13 is a schematic illustration of a mask incorporating
a display configured to provide CO.sub.2 information provided by
the CO.sub.2 system in some embodiments according to the
invention.
[0042] FIG. 14 is a schematic illustration of a CO.sub.2 detection
system utilized in an open breathing environment in some
embodiments according to the present invention.
[0043] FIG. 15A is a greater detail schematic illustration of the
CO.sub.2 detection system shown in FIG. 14 in some embodiments
according to the invention.
[0044] FIG. 15B is a greater detail schematic illustration of the
CO.sub.2 detection system shown in FIG. 14 in some embodiments
according to the invention.
[0045] FIG. 16 is a schematic illustration of the CO.sub.2
detection system including optical components in some embodiments
according to the invention.
[0046] FIG. 17 is a schematic illustration of test setup for a
CO.sub.2 detection system in some embodiments according to the
invention.
[0047] FIG. 18 is a graph illustrating CO.sub.2 information
generated by the CO.sub.2 detection system operating in the test
setup shown in FIG. 17.
[0048] FIG. 19 is a 1931 CIE chromaticity diagram.
[0049] FIG. 20 is a schematic representation of a color change
material included in a breathing circuit and exposed to
electronically generated visible light and electronic sensing
thereof in some embodiments according to the invention.
[0050] FIG. 21 is a schematic representation of a color change
material included in a breathing circuit and exposed to
electronically generated visible light and electronic sensing
thereof in some embodiments according to the invention.
[0051] FIG. 22 is a flowchart illustrating operations of a CO.sub.2
detection system including a color change material operatively
coupled to a visible light emitter circuit and visible light sensor
circuits in some embodiments according to the invention.
[0052] FIG. 23 is a schematic representation of a color change
material included in a breathing circuit and exposed to
electronically generated visible light and electronic sensing
thereof in some embodiments according to the invention.
[0053] FIG. 24 is a schematic representation of a color change
material included in a breathing circuit and exposed to
electronically generated visible light and electronic sensing
thereof in some embodiments according to the invention.
[0054] FIG. 25 is a schematic representation of a CO.sub.2
detection system including a color change material in a breathing
circuit and exposed to electronically generated visible light and
electronic sensing thereof in a side stream configuration in some
embodiments according to the invention.
[0055] FIG. 26 is a schematic illustration of a CO.sub.2 detection
system including a color change material exposed to electronically
generated visible light and electronic sensing thereof in an open
breathing environment in some embodiments according to the present
invention.
[0056] FIGS. 27-31 are schematic representations of various
configurations of color change materials at least partially
included in a breathing circuit in some embodiments according to
the invention.
DESCRIPTION OF EMBODIMENTS ACCORDING TO THE INVENTION
[0057] Embodiments of the present inventive subject matter are
described hereinafter with reference to the accompanying drawings,
in which embodiments of the present inventive subject matter are
shown. This present inventive subject matter may, however, be
embodied in many different forms and should not be construed as
limited to the embodiments set forth herein. Rather, these
embodiments are provided so that this disclosure will be thorough
and complete, and will fully convey the scope of the present
inventive subject matter to those skilled in the art. Like numbers
refer to like elements throughout.
[0058] It will be understood that in the embodiments discussed
herein, the respiratory gasses can be those inhaled/exhaled by any
living organism, such as a human, an animal, etc. Accordingly, the
respiratory gas is referred to as being inhaled/exhaled by a
subject, which can refer to any living organism.
[0059] In still further embodiments according to the invention, it
will be understood that the use of the systems for the detection of
CO.sub.2 can be implemented in any environment where the
measurement of CO.sub.2 may be desirable. For example, in some
embodiments according to the invention, systems, etc. for the
detection of CO.sub.2 as described herein may be implemented as
part of mass transit systems (such as trains, airplanes, buses,
etc.), places where large crowds congregate, such as stadiums etc.,
environments where the level of CO.sub.2 in a subject undergoing
physical exercise may be monitored, such as during running,
training, or other physical exertion with a level of CO.sub.2
expired by the subject may be relevant. In still other embodiments
according to the invention, systems as described herein may be
utilized to detect the level of CO.sub.2 in closed breathing
systems other than those normally associated with medical
procedures, such as use with fire fighting breathing apparatus,
mining environments, underwater breathing equipment (i.e., scuba),
space applications, and military applications, etc.
[0060] In other embodiments according to the invention, the level
of CO.sub.2 associated with a subject may be provided in
environments such as emergency situations wherein CO.sub.2 levels
may be determined by first responders, where such first responders
would utilize what is commonly referred to as an emergency CO.sub.2
detector in connection with an endotracheal tube. In still other
embodiments according to the invention, the level of CO.sub.2
described herein may be determined in association with the
administration of IV sedation, such as that used during dentistry
or other medical procedures where full anesthesia is not required
or used.
[0061] It will be understood that the levels of CO.sub.2 using
systems, devices, methods, etc. as described herein can be utilized
in any system that employs a breathing circuit. Such environments
may include a ventilator, a respirator, etc., which may be used in
conjunction with the administration of anesthesia in an operating
room, emergency room, etc. where a level of CO.sub.2 may provide an
accurate and relatively quick indication of heart/lung function and
otherwise provide medical professionals with an indication of the
patient's stability.
[0062] In some embodiments according to the invention, the CO.sub.2
detection systems may be utilized in what is referred to as an open
breathing environment, where the color change material included in
the system is not housed within a tube or other full enclosure
through which the respiratory gas stream flows. Other types of
environments and applications are also described herein.
[0063] Further, it will be understood that although many
embodiments are described herein as using visible light from an
electronic emitter, other types of light many be used to determine
levels of CO.sub.2 consistent with the inventive concepts described
herein.
[0064] As appreciated by the present inventors, various existing
CO.sub.2 detection schemes may rely on a visual color change in a
detector configured with colored paper responsive to CO.sub.2
absorption. Such detectors can indicate the presence or absence of
CO.sub.2 in a respiratory stream, and are commonly used in
emergency medical settings. However, these detectors generally do
not provide sufficient accuracy to guide clinical decisions
regarding effectiveness of emergency procedures such as ventilation
and/or CPR. As further appreciated by the present inventors,
conventional devices may have limitations which may include lack of
quantifiable results, relative insensitivity, time dependent and
temperature sensitive decay of reagents, and poor visibility in
less than optimal light conditions.
[0065] Moreover, such devices may have limitations with respect to
working life once activated, since CO.sub.2 absorption from the
atmosphere or from the respiratory gas stream eventually exhausts
the capacity of the absorber in the detector.
[0066] Embodiments according to the invention can provide for
colorimetric detection of CO.sub.2 in a stream of respiratory gases
using electronically generated visible light and electronic
detection of the colorimetric change. Accordingly, in some
embodiments according to the present invention, a color change
material can be placed in contact with the respiratory stream, such
as when located on the interior wall of a portion of breathing
circuit. A control material, according to some embodiments of the
present invention, may also be placed in contact with the
respiratory stream, such as when located on the interior wall of a
portion of breathing circuit, or may be not be in contact with the
respiratory stream. A first surface of the color change material
and/or control material can be in contact-with the interior wall
while a second surface can be in contact with at least a portion of
the respiratory stream. In certain embodiments, a color change
material (sometimes referred to herein as a reactive portion)
and/or control material (sometimes referred to herein as an
unreactive portion) may be configured to be removably attached to a
portion of a CO.sub.2 detection system and/or device. A control
material may be a portion of a color change material or may be
separate from a color change material. When a control material is a
portion of a color change material there optionally may be a
delineation or mark to separate and/or indicate the color change
material and the control material.
[0067] Carbon dioxide gas within the respiratory stream may diffuse
partially into the color change material (which includes a
composition referred to as a color change indicator), where it may
undergo absorption and/or reaction with components within the
layer. Absorption and/or reaction within the layer may result in a
color change of the indicator within the layer that is indicative
of the amount of CO.sub.2 absorbed by the layer and thereby may
provide an indication of CO.sub.2 in the respiratory stream. The
color change material may be configured to permit rapid absorption
and desorption of CO.sub.2 in order to facilitate sensing of a
time-varying level of CO.sub.2 in the respiratory stream and may be
reversible in that variation of the CO.sub.2 is indicated as the
gas is exhaled/inhaled. Exemplary materials or substrates for the
color change material and/or control material include, but are not
limited to, a cellulosic material such as paper (e.g., filter
paper, ink jet paper, and chromatography paper), woven, and
non-woven materials, a clay material, a mineral material, and any
combination thereof.
[0068] In some embodiments, a substrate for a color change material
and/or control material is optically transmissive. "Optically
transmissive," as used herein, refers to the ability of a substrate
to allow for light in a region of the light spectrum in a range of
about 300 nm to about 900 nm, or any range and/or individual value
therein such as, for example, light in the visible region of the
light spectrum of about 400 nm to about 700 nm, to pass through the
substrate. Accordingly, the optically transmissive substrate does
not reflect all (100%) light in a range of about 300 nm to about
900 nm. In certain embodiments, an optically transmissive substrate
reflects about 98% or less, about 97% or less, about 95% or less,
about 90% or less, about 85% or less, about 80% or less, or about
70% or less of light in a range of about 300 nm to about 900 nm or
about 400 nm to about 700 nm.
[0069] Carbon dioxide gas within the respiratory stream may also
diffuse partially into the control material (which may include a
control composition). In some embodiments according to the
invention, the CO.sub.2 may undergo absorption and/or reaction with
components within at least one layer of the control material, but
the color of the control material in operation remains
substantially the same. Thus, the control material may act as a
color standard or reference that may be compared with one or more
colors of the color change material. In certain embodiments, a
control material may be indicative of the shelf life of the system
and/or device. For example, a change in the color of the control
material may indicate that the system and/or device is no longer
suitable for use. In some embodiments, a control material indicates
that the system and/or device is no longer suitable for use when
the color of control material in operation does not remain
substantially the same.
[0070] A color change material, system, and/or device according to
embodiments of the present invention may have a shelf life of at
least about 3 months, 6 months, 9 months, 1 year, 2 years, 3 years,
4 years, 5 years, or more. "Shelf life," as used herein, refers to
the length of time the color change material, system, and/or device
maintains the ability to respond to CO.sub.2 in an unopened package
stored under recommended storage conditions, such as, but not
limited to, stored at about 15.degree. C. to about 30.degree. C. or
about room temperature (i.e., about 20.degree. C.). The shelf life
may, for example, be evidenced by a "use by" or "best if used by"
date for the color change material, system, and/or device; the
manufacturer's expiration date of the color change material,
system, and/or device; and/or the actual characteristics of the
color change material, system, and/or device after a specified
period of time. Accordingly, the term "shelf life" as used herein
should be construed as including both an "actual" shelf life of the
color change material, system, and/or device and a "predicted"
shelf life of the color change material, system, and/or device
unless stated otherwise.
[0071] A color change material and/or control material may be dry,
partially hydrated, or hydrated. The term "dry" as used herein
means that the color change material and/or control material has a
moisture content of less than about 5% by weight of the color
change material and/or control material compared to the moisture
content at full hydration as measured after 24 hours in an aqueous
solution at ambient conditions. The term "partially hydrated" as
used herein means that the color change material and/or control
material has a moisture content that is 50% or less by weight of
the color change material and/or control material, typically less
than about 75% of the color change material and/or control
material, compared to the moisture content at full hydration as
measured after 24 hours in an aqueous solution at ambient
conditions. "Hydrated," as used herein means that the color change
material and/or control material has a moisture content that is
about 51% or greater by weight of the color change material and/or
control material compared to the moisture content at full hydration
(i.e., 100% hydrated) as measured after 24 hours in an aqueous
solution at ambient conditions.
[0072] In some embodiments, a color change material and/or control
material may be dry prior to use and/or dry in a kit according to
embodiments of the present invention. In other embodiments, a color
change material and/or control material may be partially hydrated
or hydrated prior to use and/or partially hydrated or hydrated in a
kit according to embodiments of the present invention. In
operation, the moisture content of the color change material and/or
control material may increase. Thus, in some embodiments, a color
change material and/or control material that is dry prior to use
may become partially hydrated or hydrated in operation upon contact
with moisture present in a respiratory stream and/or ambient
air.
[0073] Respiratory gas flow may be confined within, for example, a
tube that makes up part of the breathing circuit. The color change
material and/or control material can be located in any portion of
the interior of the tube and oriented to allow the respiratory
stream to flow across the major surface of the material.
Alternatively or in addition, the control material may be
configured to be not in contact with the respiratory stream, such
as outside the tube interior. An electronic emitter (sometimes
referred to as a visible light emitter circuit) can provide a
visible light source with suitable color output and may be
positioned outside the tube, such that a portion of emitted light
is projected through the wall of the tube to illuminate the color
change material and/or control material. An electronic sensor
(sometimes referred to herein as a visible light sensor circuit)
can detect the color change exhibited by the color change material,
which can then be used to indicate the level of CO.sub.2 in the
respiratory stream. Another electronic sensor can detect the color
of the control material, which may be compared to the color
exhibited by the color change material.
[0074] FIG. 1 is a schematic illustration of a color change
material 100 that is configured for inclusion within a breathing
circuit in some embodiments according to the invention. According
to FIG. 1, the color change material 100 is configured for contact
with a subject's respiratory stream. The color change material 100
is positioned within the stream so that when the subject exhales,
exhaled gas contacts the major surface of the color change material
100 in the first direction 105. When the subject inhales,
inhalation gas is drawn across the major surface of the color
change material 100 in the direction 110 which is generally
opposite to the direction 105.
[0075] It will be understood that the generation of the exhalation
gas in the direction 105 and the inhalation gas in the direction
110 is generally referred to herein as a cycle of breathing (i.e.,
cycle) and further that the exhalation 105 and the inhalation 110
are referred to together as a respiratory gas. It will be further
understood that portions of the respiratory gas can flow in other
directions which are not parallel to the major surface of the color
change material 100. It will be further understood that the color
change material 100 is positioned within the breathing circuit so
that the respiratory gas is drawn across the major surface of the
color change material 100 during the breathing cycle in a
repeatable and consistent fashion. Accordingly, the orientation of
the color change material 100 within the breathing circuit can
reduce obstruction to the respiratory gas. For example, such
configurations of the color change material 100 within the
breathing circuit can be provided when, for example, the color
change material 100 is placed "in-line" in an endotracheal tube or
near an exit port of a face mask (such as a mask used for the
administration of anesthesia), or in-line with a spirometer,
etc.
[0076] The color change material 100 shown in FIG. 1 can include a
color change indicator configured for detection and measurement of
the level of carbon dioxide in the respiratory stream using a
reversible color change in response to the presence of carbon
dioxide. It will be understood that the color change indicator can
be a composition that is impregnated or otherwise included in
and/or on the color change material 100. In some embodiments, at
least a portion of the color change material 100 is contacted with
a color change indicator such as by impregnating, immersing,
painting, soaking, submerging, dipping, and the like.
[0077] In some embodiments according to the invention, the color
change indicator can include an alkaline material. An alkaline
material present in a color change indicator may be reactive to
gaseous carbon dioxide and may thereby change the pH of a portion
of the color-change layer in contact with a respiratory stream
containing carbon dioxide. Exemplary alkaline materials may include
sodium carbonate, potassium carbonate, calcium carbonate, magnesium
carbonate, sodium hydroxide, potassium hydroxide, primary,
secondary, or tertiary amines, or combinations thereof. In some
embodiments according to the invention, an alkaline material is
present in the color change indicator in an amount of about 0.1% to
about 20% by weight of the composition, or any range and/or
individual value therein, such as about 0.1% to about 10% or about
1% to about 5% by weight of the composition. In certain
embodiments, an alkaline material is present in the color change
indicator in an amount of about 0.1%, 0.25%, 0.5%, 0.75%, 1%,
1.25%, 1.5%, 1.75%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%,
13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20% or any range and/or
individual value therein. In some embodiments according to the
invention, the color change indicator comprises sodium carbonate in
an amount of about 0.5% to about 2% by weight of the composition,
and in certain embodiments, in an amount of about 1.25% by weight
of the composition.
[0078] In some embodiments according to the invention, the color
change indicator can include a dye or pigment. A dye or pigment
present in a color change indicator may undergo reversible color
change in response to change in pH. Exemplary dyes or pigments may
include metacresol purple, thymol blue, and phenol red, and
combinations thereof. In some embodiments according to the
invention, the color change indicator may include two or more dyes
or pigments. In some embodiments according to the invention, a dye
or pigment is present in the color change indicator in an amount of
about 0.001% to about 2% by weight of the composition, or any range
and/or individual value therein, such as about 0.001% to about 1%
or about 0.01% to about 1% by weight of the composition. In certain
embodiments, a dye or pigment is present in the color change
indicator in an amount of about 0.001%, 0.0025%, 0.005%, 0.0075%,
0.01%, 0.025%, 0.075%, 0.1%, 0.25%, 0.5%, 0.75%, 1%, 1.25%, 1.5%,
1.75%, or 2%, or any range and/or individual value therein. In some
embodiments according to the invention, the color change indicator
comprises metacresol purple in an amount of about 0.001% to about
0.05% by weight of the composition, and in certain embodiments, in
an amount of about 0.015% by weight of the composition.
[0079] In some embodiments according to the invention, the color
change indicator can include one or more buffers. One or more
buffers present in a color change indicator may modify the pH of
the color-change layer and/or aid in maintaining a particular pH or
pH range. Buffers may also be selected to provide a faster response
time, better reversibility, and longer life. Exemplary buffers
include aqueous solutions of sodium bisulfate, sodium carbonate,
and mixtures thereof. In some embodiments according to the
invention, the color change indicator can be configured to undergo
a change in color and/or color saturation in the presence of a
metabolically relevant carbon dioxide concentration. In some
embodiments according to the invention, a buffer is present in the
color change indicator in an amount of about 0.1% to about 20% by
weight of the composition, or any range and/or individual value
therein, such as about 0.1% to about 10% or about 1% to about 5% by
weight of the composition. In certain embodiments, a buffer is
present in the color change indicator in an amount of about 0.1%,
0.25%, 0.5%, 0.75%, 1%, 1.25%, 1.5%, 1.75%, 2%, 3%, 4%, 5%, 6%, 7%,
8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, or 20% or
any range and/or individual value therein. In some embodiments
according to the invention, the color change indicator comprises
sodium bisulfate in an amount of about 1% to about 5% by weight of
the composition, and in certain embodiments, in an amount of about
2% by weight of the composition. In some embodiments according to
the invention, the color change indicator comprises an alkaline
material, a dye or pigment, and one or more buffers.
[0080] In some embodiments according to the invention, the color
change indicator can include a water-attractive component. A
water-attractive component present in a color change indicator may
facilitate hydration of a color-change layer in the presence of
vapor-phase moisture in the respiratory stream. Exemplary
water-attractive components may include glycerol, propylene glycol
and mixtures thereof. In some embodiments according to the
invention, a water-attractive component is present in the color
change indicator in an amount of about 1% to about 75% by weight of
the composition, or any range and/or individual value therein, such
as about 5% to about 50% or about 10% to about 30% by weight of the
composition. In certain embodiments, a water-attractive component
is present in the color change indicator in an amount of about 1%,
5%, 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%,
70%, or 75% or any range and/or individual value therein. In some
embodiments according to the invention, the color change indicator
comprises glycerin in an amount of about 5% to about 45% by weight
of the composition, and in certain embodiments, in an amount of
about 25% by weight of the composition. In some embodiments
according to the invention, the color change indicator comprises an
alkaline material, a dye or pigment, one or more buffers, and a
water-attractive component.
[0081] In some embodiments according to the invention, the color
change indicator can include surface modifying additives including
ionic and nonionic surfactants. Exemplary surfactants include, but
are not limited to, amines, such as mono-, di-, and
trimethanolamine, and quaternary ammonium compounds, such as
benzalkonium chloride, benzethonium chloride, methylbenzethonium
chloride, cetalkonium chloride, cetylpyridinium chloride,
cetrimonium, cetrimide, dofanium chloride, tetraethylammonium
bromide, didecyldimethylammonium chloride and domiphen bromide. In
some embodiments according to the invention, a surface modifying
additive is present in the color change indicator in an amount of
about 0.1% to about 10% by weight of the composition, or any range
and/or individual value therein, such as about 0.1% to about 5% or
about 0.1% to about 1% by weight of the composition. In certain
embodiments, a surface modifying additive is present in the color
change indicator in an amount of about 0.1%, 0.25%, 0.5%, 0.75%,
1%, 1.25%, 1.5%, 1.75%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, or 10% or
any range and/or individual value therein. In some embodiments
according to the invention, the color change indicator comprises
sodium lauryl sulfate in an amount of about 0.1% to about 1% by
weight of the composition, and in certain embodiments, in an amount
of about 0.2% by weight of the composition.
[0082] In some embodiments according to the invention, the color
change indicator can include an antimicrobial additive. An
antimicrobial additive present in a color change indicator may
inhibit growth of bacteria, molds, funguses or other microbes.
Exemplary antimicrobial additives include, but are not limited to,
hexachlorophene; cationic biguanides such as chlorhexidine and
cyclohexidine; iodine and iodophores such as povidone-iodine;
halo-substituted phenolic compounds such as PCMX (i.e.,
p-chloro-m-xylenol), triclocarban, and triclosan (i.e.,
5-chloro-2-(2,4-dichlorophenoxy)phenol); furan medical preparations
such as nitrofurantoin and nitrofurazone; methenamine; aldehydes
such as glutaraldehyde and formaldehyde; alcohols; metal-containing
therapeutics such as silver-containing therapeutics or
zinc-containing therapeutics; and any combination thereof. In some
embodiments according to the invention, an antimicrobial additive
is present in the color change indicator in an amount of about 1
part per million (ppm) to about 1000 ppm, or any range and/or
individual value therein, such as about 5 ppm to about 500 ppm or
about 10 ppm to about 50 ppm. In certain embodiments, an
antimicrobial additive is present in the color change indicator in
an amount of about 1, 5, 10, 20, 30, 40, 50, 60, 70, 80, 90, 100,
150, 200, 300, 400, 500, 600, 700, 800, 900, or 1000 ppm or any
range and/or individual value therein. In some embodiments
according to the invention, the color change indicator comprises
triclosan in an amount of about 1 ppm to about 50 ppm, and in
certain embodiments, in an amount of about 20 ppm.
[0083] According to some embodiments, a color change material
and/or color change indicator may be configured to provide an
increase in a colorific response. "Colorific response," as used
herein, refers to the magnitude of the color change and/or color
saturation in the color change material and/or color change
indicator when in the presence of a metabolically relevant carbon
dioxide concentration and/or the rate at which the color change
material and/or color change indicator responds between
metabolically relevant carbon dioxide concentrations. In some
embodiments, a color change material and/or color change indicator
may comprise means for catalyzing an increase in a colorific
response, such as, but not limited to, a catalyst configured to
provide an increase in a colorific response. Means for catalyzing
an increase in a colorific response may increase the magnitude of
the color change and/or color saturation in the color change
material and/or color change indicator when in the presence of a
metabolically relevant carbon dioxide concentration and/or the
color change rate between metabolically relevant carbon dioxide
concentrations compared to the colorific response in the absence of
the means for catalyzing an increase in a colorific response. Thus,
means for catalyzing an increase in a colorific response may
increase the sensitivity of the color change indicator, color
change material, and/or CO.sub.2 detection system and/or device
when present in a color change material and/or color change
indicator. "Color change rate," as used herein, refers to the rate
at which the color change material and/or color change indicator
changes from a first color to a second color and/or the rate at
which the color change material and/or color change indicator
changes from the second color to the first color. Thus, the color
change rate may refer to the rate at which the color change
material and/or color change indicator reversibly changes.
[0084] In particular embodiments, means for catalyzing an increase
in a colorific response may be present in the color change material
and/or color change indicator in an amount sufficient to increase
the sensitivity of the color change indicator, color change
material, and/or CO.sub.2 detection system and/or device. Means for
catalyzing an increase in a colorific response may be present in
the color change material and/or color change indicator in an
amount sufficient to increase the sensitivity of the color change
indicator, color change material, and/or CO.sub.2 detection system
and/or device by at least about 5%, 10%, 20%, 30%, 40%, 50%, 60%,
70%, 80%, 90%, 100%, 125%, 150%, 200%, 300% or more, or any range
and/or individual value therein compared to the sensitivity of the
color change and/or color saturation in the absence of a means for
catalyzing an increase in a colorific response in the color change
material and/or color change indicator.
[0085] In certain embodiments, the presence of a means for
catalyzing an increase in a colorific response in the color change
material and/or color change indicator may increase the magnitude
of the color change and/or color saturation by a factor of about
1.2 to about 20 or more, or any range and/or individual value
therein, compared to the magnitude of the color change and/or color
saturation in the absence of a means for catalyzing an increase in
a colorific response in the color change material and/or color
change indicator. For example, in certain embodiments, the presence
of a means for catalyzing an increase in a colorific response in
the color change material and/or color change indicator may
increase the magnitude of the color change and/or color saturation
by a factor of about 1.5, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13,
14, 15, 16, 17, 18, 19, 20, or more, or any range therein, compared
to the magnitude of the color change and/or color saturation in the
absence of a means for catalyzing an increase in a colorific
response in the color change material and/or color change
indicator.
[0086] According to some embodiments, the presence of a means for
catalyzing an increase in a colorific response in a color change
material and/or color change indicator may increase the rate at
which the color change material and/or color change indicator
responds between metabolically relevant carbon dioxide
concentrations compared to the rate at which the color change
material and/or color change indicator responds between
metabolically relevant carbon dioxide concentrations in the absence
of a means for catalyzing an increase in a colorific response.
Means for catalyzing an increase in a colorific response of the
color change material and/or color change indicator may thus
increase the color change rate.
[0087] A color change material and/or color change indicator may
respond to a subject's breathing cycle. In certain embodiments, a
color change material and/or color change indicator is configured
to provide a color change rate that provides a reversible color
change to occur between consecutive breaths. Thus, a color change
material and/or color change indicator may be configured to change
from a first color to a second color in response to a first
metabolically relevant carbon dioxide concentration (e.g., the
CO.sub.2 concentration in a subject's exhale) and return to the
first color before a second metabolically relevant carbon dioxide
concentration (e.g., the CO.sub.2 concentration in the subject's
subsequent exhale) occurs. In particular embodiments, a color
change material and/or color change indicator is configured to
provide a color change rate that provides for the color change
material and/or color change indicator to change from a first color
to a second color and return to the first color between about 0 to
about 60 times per minute, or any range and/or individual value
therein. In certain embodiments, a color change material and/or
color change indicator is configured to provide a color change rate
that provides for the color change material and/or color change
indicator to change from a first color to a second color and return
to the first color about 0, 5, 10, 15, 20, 25, 30, 35, 40, 45, 50,
55, 60 or more times per minute, or any range therein.
[0088] In certain embodiments, a color change material and/or color
change indicator comprises means for catalyzing an increase in a
colorific response and the means for catalyzing an increase in a
colorific response is configured to increase the color change rate
by about 5% or more, such as, but not limited to, about 10%, 20%,
30%, 40%, 50%, 60%, 70%, 80%, 90%, 100%, 150%, 200%, or more or any
range and/or individual value therein. In this manner, the means
for catalyzing an increase in a colorific response may increase the
sensitivity of the color change indicator, color change material,
and/or CO.sub.2 detection system and/or device when present in a
color change material and/or color change indicator.
[0089] A color change material and/or color change indicator may be
configured to have a desired responsiveness to changes in carbon
dioxide concentration. The responsiveness of a color change
material and/or color change indicator may be measured by the color
change rate. In some embodiments, a color change material and/or
color change indicator is configured to have a fast color change
rate in reference to a control material and/or control composition,
which may be configured to have a slow color change rate or no
color change. According to some embodiments, a system and/or device
may comprise a first color change material that is configured to
have a fast responsiveness to changes in carbon dioxide
concentration and a second color change material that is configured
to have a slower responsiveness to changes in carbon dioxide
compared to the responsiveness of the first color change material.
The composition of the color change material and/or color change
indicator may provide for differences in the color change rate. In
some embodiments, a nitrogen containing compound is configured to
provide the desired responsiveness to changes in carbon dioxide
concentration. In some embodiments, by increasing the concentration
of a nitrogen containing compound in the color change material
and/or color change indicator the color change rate may be
increased.
[0090] As appreciated by the present inventors, in some
embodiments, a nitrogen containing compound is configured to
provide an increase in a colorific response. A nitrogen containing
compound may be a catalyst. In some embodiments, a nitrogen
containing compound may be present in an amount sufficient to
provide an increase in a colorific response and/or configured to
provide an increase in a colorific response. The nitrogen
containing compound may comprise an amine and/or ammonium moiety.
Exemplary nitrogen containing compounds include, but are not
limited to, an amine, a quaternary ammonium compound, an amino
acid, an amino acid derivative, and any combination thereof "Amino
acid derivative," as used herein, refers to an amino acid
substituted with one or more substituents. Exemplary substituents
include, but are not limited to, alkyl, lower alkyl, halo,
haloalkyl, alkenyl, alkynyl, cycloalkyl, cycloalkylalkyl,
heterocyclo, heterocycloalkyl, aryl, arylalkyl, lower alkoxy,
thioalkyl, hydroxyl, thio, mercapto, amino, imino, halo, cyano,
nitro, nitroso, azido, carboxy, sulfide, sulfone, sulfoxy,
phosphoryl, silyl, silylalkyl, silyloxy, boronyl, and modified
lower alkyl. Further exemplary nitrogen containing compounds
include, but are not limited to, an amine, such as mono-, di-, and
trimethanolamine; a quaternary ammonium compound, such as
benzalkonium chloride, benzethonium chloride,
n-alkyl-n-(2-aminoethyl)piperidine, methylbenzethonium chloride,
cetalkonium chloride, cetylpyridinium chloride, cetrimonium,
cetrimide, dofanium chloride, tetraethylammonium bromide,
didecyldimethylammonium chloride, and domiphen bromide; an amino
acid, such as lysine, histidine, arginine, aspartic acid, serine,
asparagine, glutamine, cysteine, glycine, alanine, leucine,
tryptophan, and proline; an amino acid derivative, such as alanine
methyl ester, nitroarginine, acetyllysine, and acetylphenylalanine;
and any combination thereof In some embodiments, means for
catalyzing an increase in a colorific response comprises an amine,
a quaternary ammonium compound, an amino acid, an amino acid
derivative, and any combination thereof. In some embodiments, a
color change material and/or color change indicator may comprise
monoethanolamine.
[0091] In some embodiments according to the invention, means for
catalyzing an increase in a colorific response is present in the
color change material and/or color change indicator in an amount of
about 0.01% to about 5% by weight of the composition, or any range
and/or individual value therein, such as about 0.1% to about 3% or
about 0.1% to about 1% by weight of the composition. In certain
embodiments, means for catalyzing a colorific response is present
in the color change material and/or color change indicator in an
amount of about 0.01%, 0.025%, 0.05%, 0.075%, 0.1%, 0.25%, 0.5%,
0.75%, 1%, 1.25%, 1.5%, 1.75%, 2%, 2.5%, 3%, 3.5, 4%, 4.5%, or 5%,
or any range and/or individual value therein. In some embodiments
according to the invention, the color change material and/or color
change indicator comprises triethanolamine in an amount of about
0.01% to about 1.5% by weight of the composition, and in certain
embodiments, in an amount of about 0.2% by weight of the
composition.
[0092] FIG. 2 is a schematic representation of operation of the
color change indicator in the color change material 100 responsive
to respiratory gas during a breathing cycle in some embodiments
according to the invention. According to FIG. 2, respiratory gas
including about 5% CO.sub.2 contacts the color change material 100.
It will be understood that in some embodiments according to the
invention, the color change material 100 includes a buffer as well
as the color change indicator described herein. According to FIG.
2, the buffer can include Na.sub.2CO.sub.3 and NaHSO.sub.4 together
which operate to stabilize the pH of the color change material 100.
Water (H.sub.2O) can also be introduced into the color change
material 100 via moisture carrier in the respiratory gas during the
exhalation portion of the cycle. It will be understood that the pH
exhibited by the color change indicator in an initial condition
(i.e., prior to the exhalation cycle and the absorption of
CO.sub.2) can be at a pH from about 7 to about 14, or any range
therein, such as, from about 7 to about 12, or from about 8 to
about 10. In some embodiments according to the invention, the color
change indicator can be at a pH of about 9 or about 8.7.
[0093] During the exhale cycle, a portion of the CO.sub.2 is
absorbed into the color change material 100, whereupon the carbon
dioxide and water react to create H.sub.2CO.sub.3 whereupon a
hydrogen ion (H+) becomes disassociated therewith and also
generates the byproducts shown. Because the CO.sub.2 is in a
gaseous form, the carbon dioxide can diffuse into the color change
material 100 faster than the buffer may be able to stabilize the pH
so that the hydrogen ions lower the pH of the color change material
100, such that the color exhibited by the color change indicator
shifts.
[0094] As shown in FIG. 2, during the inhale portion of the
breathing cycle, time elapses where no CO.sub.2 is introduced into
the color change material 100 so the time is provided for the
hydrogen ions to combine with the base portion of the buffer to
again raise the pH of the color change material 100 to the static
condition (e.g., about a pH of 9). It will be understood that the
above described breathing cycle is then repeated as the subject
continues to breathe. It will be further understood that the amount
of the buffer introduced into the color change material 100 can be
configured to allow the color change material 100 to exhibit the
color change for the desired period of time whereupon the buffer
may be replenished for further operation.
[0095] According to some embodiments of the invention, a control
material may be dyed and/or printed a particular color. A control
material may comprise a control composition that may comprise one
or more of the same and/or different components as the color change
indicator and/or color change material. In certain embodiments, a
control composition and/or control material comprises the same dye
and optionally one or more of the same buffers as the color change
indicator and/or color change material. In particular embodiments,
a control composition and/or control material may be configured to
provide the control material with a color that is substantially the
same color as the color of the color change material in the absence
of CO.sub.2. Thus, in operation, at the initial time point prior to
exposure to a change in CO.sub.2 concentration, the control
material and color change material may be substantially the same
color. Two colors that are substantially the same color have a hue
and a value that are substantially the same.
[0096] In some embodiments according to the invention, a control
composition and/or control material may be configured so that in
operation, the control material is not responsive to a change in
CO.sub.2 concentration, such as, for example, respiratory gas
during a breathing cycle. A control composition and/or control
material may not be responsive to a change in CO.sub.2
concentration by not changing to a color having a hue and value
that indicate a change in CO.sub.2 concentration. For example, a
dye or pigment in the control material and/or control composition
may be quenched and/or the pH of the control composition and/or
control material may be configured to prevent or minimize a color
change and/or a component, such as an alkaline material, may be
added in excess to prevent or minimize a color change.
Alternatively or in addition, a control material may be configured
to be non-responsive to a change in CO.sub.2, such as respiratory
gas during a breathing cycle, by coating the control material with
a coating such as, but not limited to a wax, a film such as a
polymeric film, a plastic, and the like. In some embodiments, the
coating may be substantially impermeable to vapor and/or
respiratory gases.
[0097] A control composition and/or control material may be
configured to indicate the shelf life of the system and/or device
and may according to some embodiments change color after a
prolonged period of time, such as for example after about 3 or more
months, such as after about 3 months, 6 months, 9 months, 1 year, 2
years, 3 years or more. Thus, the control composition and/or
control material may be configured to be responsive to CO.sub.2,
such as after a particular period of time, and may indicate that
the shelf life of the system and/or device has expired.
[0098] A control material may be a material that is separate from
the color change material. Alternatively or in addition, a control
material may be part of the color change material and may
optionally be partitioned from the color change material with means
for separating the two, such as with a barrier material (e.g., a
wax or plastic). In some embodiments, a control material and a
color change material may be in close proximity to one another in a
device and/or system and/or in a configuration such that the
control material and color change material are exposed to
substantially the same conditions (e.g., light gas, humidity,
etc.). The signal to noise ratio may be used to determine if the
control material and the color change material are exposed to
substantially the same conditions. In some embodiments, a color
change larger than the signal to noise ratio may indicate that the
conditions are not substantially the same. In certain embodiments,
a color change that is 10% or more above the signal to noise ratio
may indicate that the conditions are not substantially the
same.
[0099] FIGS. 3-6 are schematic illustrations of different
configurations of a color change material 100 allowing for
different applications in some embodiments according to the
invention. In particular, in some configurations the color change
material can include a thin material, such as paper, having the
color change indicator infused therein. In other embodiments, a
separate substrate may be provided to which the color change
material is attached. In still other embodiments, the color change
material can be supported by what is referred to a mineral support,
which can allow the color change indicator to be applied in the
form of a composition onto to a surface of the breathing circuit in
some embodiments according to the invention.
[0100] In some embodiments according to the invention, the color
change material 100 can be provided in the form of a unitary
format, such as a liquid including color change indicator (which
may be, for example sprayed or painted onto a surface) or the color
change indicator impregnated into a substrate such as a thin paper.
Accordingly, in these embodiments according to the invention, the
color change material 100 can be painted or coated onto an interior
surface of the breathing circuit. Accordingly, the color change
material 100 can include unitary layer with high specific surface
area. The unitary layer may be impregnated with chemical species
that bring about a reversible color change in response to carbon
dioxide in the respiratory stream. The unitary layer may be porous
or microporous. Exemplary unitary layers include cellulosic paper,
microporous olefinic synthetic paper, and various coatings based on
particulates such as clay and/or silica and/or ground limestone
and/or purlite and/or talc or other mineral-based materials. Other
coatings may contain finely divided cellulose and/or other finely
divided organic materials or combinations thereof.
[0101] In some embodiments according to the invention, the color
change material 100 is a multilayer construction comprising a
substrate, a bonding layer, and a color-change layer (including the
color change indicator). See, for example, FIGS. 4-6. The substrate
may be selected from a variety of thin, rigid or flexible materials
such as paper, glass, or plastic films or sheets, or molded plastic
articles. Substrate materials may be-optically transparent,
reflective, or opaque, or some combination thereof. The substrate
material may be selected in order to provide mechanical support for
a color-change layer, and also may be selected to have desirable
optical properties such as transmission, reflectance, or opacity,
to facilitate photometric measurement of the color-change layer. A
bonding layer may be applied to the substrate to adhesively attach
the color-change layer. The bonding layer may be selected for good
mechanical bonding between the color-change layer and the
substrate. The bonding layer may further be selected to provide a
source of chemical agents that facilitate the color-change
chemistry by migration of said agents from the bonding layer into
the color-change layer. A color-change layer may be included that
has a high specific surface area to facilitate interaction with a
respiratory stream. The color change layer may be porous or
microporous. The color-change layer may be impregnated with
chemical species that bring about a reversible color change in
response to carbon dioxide or other exhaled gases in the
respiratory stream.
[0102] In some embodiments according to the invention, the color
change material 100 can be provided as shown for example in FIG. 5,
wherein the color change material 100 is a multilayer construction
comprising a substrate, a bonding layer, and a color-change layer
(including the color change indicator). In this embodiment, the
substrate may be a portion of the airway circuit containing at
least a portion of a respiratory stream. A bonding layer may be
applied to the substrate to adhesively attach the color-change
layer. The bonding layer may be selected for good mechanical
bonding between the color-change layer and the substrate. The
bonding layer may further be selected to provide a source of
chemical agents that facilitate the color-change chemistry by
migration of said agents from the bonding layer into the
color-change layer. A color-change layer may be included that has a
high specific surface area to facilitate interaction with a
respiratory stream. The color change layer may be porous or
microporous. The color-change layer may be impregnated with
chemical species that bring about a reversible color change in
response to carbon dioxide in the respiratory stream.
[0103] In some embodiments according to the invention, as shown for
example in FIG. 6, the color change material 100 is a substantially
transparent article, such as a planar waveguide, with a
color-change layer adhesively attached to at least one edge of the
waveguide, and wherein the portion of the waveguide having a
color-layer attached thereto is projected into a portion of a
respiratory stream.
[0104] As described herein, the color change material 100 can
include a color change indicator, which may be incorporated into
the color change material 100 structures shown in FIGS. 4-6, for
example, as a color change layer. The color change indicator can
provide for the colorimetric response in the presence of CO.sub.2.
The following examples describe exemplary color change indicators
that were fabricated:
EXAMPLE 1
[0105] A color change indicator according to the present invention
was fabricated using 0.4 grams of anhydrous sodium bisulfate
dissolved in 9.6 grams of water. 5.0 grams of glycerin was added
and mixed to dissolve. 1.0 gram of a 0.1% w/w aqueous solution of
metacresol purple dye was added and stirred to mix, resulting in a
red colored solution. A 10% w/w aqueous solution of anhydrous
sodium carbonate was added drop-wise until the color of the
solution permanently changed to purple, occurring at a pH of
approximately 9.0.
EXAMPLE 2
[0106] Another color change indicator according to the present
invention was fabricated using 0.5 grams of anhydrous sodium
bisulfate were dissolved in 9.5 grams of water. 5.0 grams of
glycerin was added and mixed to dissolve. 1.0 gram of a 0.1% w/w
aqueous solution of metacresol purple dye was added and stirred to
mix, resulting in a red colored solution. A 10% w/w aqueous
solution of anhydrous sodium carbonate was added drop-wise until
the color of the solution permanently changed to purple, occurring
at a pH of approximately 9.0.
EXAMPLE 3
[0107] A mineral support embodiment as an alternative to the
impregnation of paper with the color change indicator was
fabricated using 4.0 grams of kaolin clay combined with 2.0 grams
of diatomaceous earth (Celite 535), 3.0 grams water, and 1.0 gram
of Neocryl A-614 acrylic latex resin (DSM Neoresins) to form a
stiff paste. A layer approximately 3 mils in thickness was
doctor-bladed onto a heavy poster-paper support and baked in an
oven for 5 minutes at 150.degree. C. The resulting layer was nearly
white in color, adherent, and had a matte finish.
EXAMPLE 4
[0108] A mineral support was fabricated using 1.0 grams of kaolin
clay combined with 5.0 grams of calcium carbonate, 3.0 grams of
water, and 1.0 gram of Neocryl A-614 acrylic latex resin (DSM
Neoresins) to form a stiff paste. A layer approximately 3 mils in
thickness was doctor-bladed onto a heavy poster-paper support and
baked in an oven for 5 minutes at 150.degree. C. The resulting
layer was nearly white in color, opaque, adherent, with a matte
finish.
EXAMPLE 5
[0109] An embodiment of the color change material 100 shown in FIG.
6 was fabricated using a sheet of polycarbonate plastic
approximately 30 mils in thickness laminated to a sheet of white
paper having a basis weight of approximately 270 g/square meter
using an adhesive layer consisting of 3.0 grams of a 10% (w/w)
solution of monoethanolamine in methanol and 5.0 grams of Neocryl
A-614 acrylic latex resin (DSM Neoresins). The laminated
construction was baked in an oven at 100.degree. C. for 5 minutes.
The resulting construction had an adherent white paper layer firmly
attached to a transparent polycarbonate support layer.
EXAMPLE 6
[0110] A change color material 100 shown in the embodiment
illustrated in FIG. 3 was fabricated using strips of conventional
ink jet printer paper approximately 1 inch wide and 2 inches long
were soaked in the color change of examples 1 or 2 indicator for
5-10 seconds, drained on absorbent toweling, and baked at about
100.degree. C. for 60 sec. The resulting paper strips had an
intense purple color on both sides, were dry to the touch, and
spontaneously and reversibly changed in color shade when exposed to
physiologically relevant levels of carbon dioxide, e.g. 1-10% (v/v)
in air at approximately one atmosphere pressure. Color shade
variation in response to carbon dioxide was discernible from either
side of the strip.
EXAMPLE 7
[0111] A color change material 100 according to the embodiment
illustrated in FIG. 3 was fabricated using strips of mineral
support of examples 3 and 4 approximately 1 inch wide and 2 inches
long were soaked for 5-10 seconds in Color Change Indicator 2, and
baked in an oven at 100.degree. C. for 60 sec. The resulting strips
were opaque, had an intense purple color on the mineral-coated
side, were dry to the touch, and spontaneously and reversibly
changed in color shade when exposed to physiologically relevant
levels of carbon dioxide, e.g. 1-10% v/v in air at approximately
one atmosphere pressure.
EXAMPLE 8
[0112] A color change material 100 illustrated in FIG. 6 are
fabricated using strips of the plastic support of example 5 1
approximately 1 inch wide and 2 inches long were soaked for 5-10
seconds in color change Indicator of examples 1 or 2, and baked in
an oven at 100.degree. C. for 60 sec. The resulting strips had an
intense purple color, were partially transparent, were dry to the
touch, and spontaneously and reversibly changed in color shade when
exposed to physiologically relevant levels of carbon dioxide, e.g.
1-10% v/v in air at approximately one atmosphere pressure. The
color shade variation was discernible from either side of the
plastic support.
EXAMPLE 9
[0113] A color change indicator according to embodiments of the
present invention was prepared by dissolving 0.44 gram of anhydrous
sodium bisulfate in 9.0 grams of water, adding 5.0 grams of
glycerol, stirring to mix, then adding 1.0 gram of an aqueous 0.1%
(w/w) solution of metacresol purple. The solution was titrated to a
permanent grape-purple color with approximately 1.67 grams of an
aqueous 20% (w/w) solution of sodium carbonate monohydrate. Twenty
parts by volume of the resulting solution were combined with 2
parts by volume of a solution of benzalkonium chloride (Andwin
Scientific part number 190009) and 3 parts by volume of a 10% (w/w)
solution of monoethanolamine in methyl alcohol. The resulting
solution was brushed onto strips of white paper having a basis
weight of approximately 320 grams per square meter, then baked in
an oven for 60 seconds at approximately 100 degrees C. The
resulting strips had a uniform sky-blue color, were dry to the
touch, and spontaneously and reversibly changed in color shade when
exposed to physiologically relevant levels of carbon dioxide, e.g.
1-10% v/v in air at approximately one atmosphere pressure. The
color shade variation was discernible from either side of the
strip.
EXAMPLE 10
[0114] A color change indicator according to embodiments of the
present invention was prepared by combining 31.8 g of water, 93.6 g
of a 5% of sodium bisulfate solution, 58.2 g of glycerin, 3.6 g of
a 1% solution of metacresol purple, 4.8 g of a 10% solution of
methanolamine, and 12.6 g of a solution comprising 10% by weight
sodium lauryl sulfate and 0.4% by weight triclosan. Then, the
composition was titrated with a 10% solution of sodium carbonate to
a final pH of 8.7.
[0115] According to some embodiments of the present invention, an
apparatus for use in monitoring a respiratory stream may be
provided. The apparatus may comprise a color change material and at
least one part of the color change material may comprise a reactive
portion. At least one part of the reactive portion may be
configured to be in contact with a respiratory stream. At least one
part of the reactive portion is configured to provide a first color
based on exposure to a first CO.sub.2 level and is configured to
change from the first color through a first range of colors to a
second color based on exposure to a second CO.sub.2 level that is
greater than the first CO.sub.2 level. In some embodiments, the
reactive portion comprises a color change indicator.
[0116] The apparatus may also comprise an unreactive portion. The
unreactive portion may be spaced apart from the reactive portion of
the color change material. In some embodiments, the unreactive
portion is separate from the reactive portion. In other
embodiments, the unreactive portion comprises at least one part of
the color change material. At least one part of the unreactive
portion is configured to provide a first color based on exposure to
the first CO.sub.2 level and is configured to change from the first
color through a second range of colors that is smaller than the
first range of colors to a third color based on exposure to the
second CO.sub.2 level. The third color may comprise a hue and value
that may not be indicative of a CO.sub.2 level. The first color of
the reactive portion and the first color of the unreactive portion
may be substantially the same color. In some embodiments, if the
first color of the reactive portion and unreactive portion are not
substantially the same color prior to exposure to the second
CO.sub.2 level, then the apparatus may be expired and/or past the
recommended shelf life. Alternatively or in addition, if the third
color of the unreactive portion comprises a hue and value that is
indicative of a CO.sub.2 level, then the apparatus may be expired
and/or past the recommended shelf life.
[0117] In some embodiments, the reactive portion and unreactive
portion may each comprise a color change indicator comprising a dye
and/or an alkaline material. The amount of the alkaline material in
the unreactive portion may be configured to provide the unreactive
portion with a greater pH than the reactive portion. The higher pH
of the unreactive portion may cause a dye present in the unreactive
portion to be quenched and/or may cause the color change indicator
to be non-responsive to changes in CO.sub.2 concentration, while
the lower pH of the reactive portion may allow for a dye to be
active, such as by absorbing a different wavelength of light,
and/or may cause the color change indicator to be responsive to
changes in CO.sub.2 concentration. In other embodiments, the
unreactive portion is free of the color change indicator.
[0118] In further embodiments, a carbon dioxide indicator may be
provided. A carbon dioxide indicator may comprise a color change
material as described herein and a control material as described
herein. The color change material may be responsive to carbon
dioxide and the control material may be substantially
non-responsive to carbon dioxide. The color change material and
control material of a carbon dioxide indicator may-be configured to
be exposed to substantially the same conditions. In some
embodiments, the color change material and the control material are
in close proximity to one another and/or are in the same
orientation in relation to a respiratory stream.
[0119] A color change material may be responsive to carbon dioxide
by changing color in response to changes in the concentration of
carbon dioxide. Thus, a control material may be substantially
non-responsive to carbon dioxide by not changing color in response
to changes in the concentration of carbon dioxide and/or by not
changing to a color that is indicative of a change in CO.sub.2
concentration. In some embodiments, the control material comprises
a dye and is configured to be non-responsive to carbon dioxide by
quenching the dye. In other embodiments, a control material is
printed to have a color that is substantially the same value and
hue as the color of the color change material.
[0120] The color change material and control material may be
substantially the same color at a first CO.sub.2 concentration
prior to contact with a second CO.sub.2 concentration having a
greater CO.sub.2 concentration. When the carbon dioxide indicator
is in operation, this may allow for the color of the color change
material to be compared to the color of the control material and
may aid in determining the value and/or extent of the change in
CO.sub.2 concentration. The color change material may be configured
to change from a first color to a second color and return to said
first color in response to contact with at least one carbon dioxide
concentration. In some embodiments, the color change material is
configured to change from a first color to a second color and
return to said first color about 1 to about 60 times per minute in
response to contact with at least two consecutive carbon dioxide
concentrations. Thus, the color of the color change material may be
reversible in response to a change in CO.sub.2 concentration and
may reversibly change color at a rate that is responsive to a
breathing cycle of a subject. For example, after a first exhale in
a breathing cycle, the color change material may return to the
first color prior to exposure to an immediately subsequent second
exhale in the breathing cycle.
[0121] According to some embodiments a kit may be provided. A kit
of the present invention may comprise a color change material as
described herein or a carbon dioxide indicator as described herein,
a support member, and a storage bag. The color change material or
carbon dioxide indicator may be attached to the support member. In
some embodiments, the color change material or carbon dioxide
indicator may be removably attached to the support member. The kit
may also comprise a control material as described herein that may
optionally be attached, such as removably attached, to the support
member. In certain embodiments, the support member comprises a
breathing circuit adapter.
[0122] The storage bag may be configured to isolate the color
change material or carbon dioxide indicator from external carbon
dioxide and may be substantially impermeable to carbon dioxide. The
storage bag may comprise a polymer such as thermoplastic polymers
(e.g., metallic polyethylene terephthalate (METPET)); a metallic
foil such as aluminum foil, tin foil, and/or nickel foil; a metal
film such as aluminum-evaporated film and/or tin-evaporated film;
and any combination thereof. In some embodiments, the storage bag
is substantially impermeable to moisture and/or water vapor. The
kit may comprise a moisture desiccant, oxygen scavenger (e.g.,
metal oxygen scavengers), carbon dioxide scavengers, and any
combination thereof. Exemplary moisture desiccants include, but are
not limited to, silica gel, molecular sieves, calcium chloride, and
the like. The kit may comprise a sachet having at least one of a
moisture desiccant, oxygen scavenger, and carbon dioxide scavenger.
Exemplary carbon dioxide scavengers include, but are not limited
to, a metal oxide (e.g., calcium oxide), a metal hydroxide (e.g.,
calcium hydroxide), silica gel, and any combination thereof. In
some embodiments, storage of a color change material or a carbon
dioxide indicator in a storage bag, optionally with at least one of
a moisture desiccant, oxygen scavenger, and carbon dioxide
scavenger, may increase the shelf life of the kit. In certain
embodiments, the kit may have a shelf life of at least about 1
year, 2 years, 3 years, or more.
[0123] FIGS. 7A and 7B are schematic illustrations of a CO.sub.2
detection system in some embodiments according to the invention. In
particular, FIG. 7A illustrates operation of the CO.sub.2 detection
system 700 where the color change material 100 is exposed to a
relatively low concentration of CO.sub.2, such as when a subject
inhales as part of the breathing cycle. The electronic light
emitter 705 emits visible light to illuminate the color change
material 100 which is detected by an electronic light sensor 710,
both of which can operate under the control of a processor 720. In
some embodiments according to the invention, visible light includes
light that falls within a range of wavelengths of about 400 nm to
about 700 nm, so that at least some of this range may not be
perceptible to a human observer without the assistance of
embodiments according to the invention.
[0124] As described herein, during the inhale portion of the
breathing cycle, the relatively low concentration of CO.sub.2 in
the respiratory stream causes little or no change in the pH of the
color change indicator 100 and pH remains generally constant at
approximately pH 9. No color shift occurs in the indicator 100 and
the reflected light detected by the electronic sensor 710 has a
particular value similar in magnitude to the initial color of the
color indicator. For example, in some embodiments according to the
invention, the value of the reflected light detected by the
electronic sensor 710 can be separated into its color components,
such as red, green and blue components of the visible light, each
of which may be characterized by a particular value, such as an
intensity, color value, color temperature etc. In other embodiments
according to the invention, the components of the visible light may
represent a single color temperature value, which can be
represented using, for example, the 1931 CIE chart shown in FIG.
19. The value of the light reflected from the color change
indicator 100 and detected by the electronic sensor 710 can
indicate the level of CO.sub.2 that contacts the color change
indicator 100, which can be determined by the processor 720.
[0125] FIG. 7B illustrates the same CO.sub.2 detector system 700
operating during the exhale portion of the breathing cycle.
According to FIG. 7B, the electronic emitter 705 emits visible
light to illuminate the color change indicator 100 that is exposed
to a relatively high concentration of CO.sub.2 during the exhale
portion of the breathing cycle. Accordingly, the increased
concentration of CO.sub.2 in contact with the color change
indicator 100 can cause the pH of the color change indicator 100 to
decrease (therefore becoming more acidic) which may, in turn, be
reflected by a change in color of the color change indicator 100.
This change in color can be detected by the electronic sensor 710
which can be represented using the same approach described above in
reference to FIG. 7A. Therefore, as the breathing cycle proceeds,
the change in the pH of the color change indicator 100 (due to the
varying levels of CO.sub.2 exposed thereto) can be determined by
the electronic sensor 710 analyzing the values of the reflected
light.
[0126] In some embodiments according to the invention, "white"
light can be used as the visible light, which includes components
of red, green, and blue. Further, a ratio of the red component to
the blue component (in the reflected light) may yield a first value
of red-to-blue ratio when the color change indicator 100 is exposed
to a relatively low concentration of CO.sub.2. As further shown in
FIG. 7A, the ratio of the green component to the blue component may
also yield an initial first value of green-to-blue ratio in the
same situation. It will be further understood that other types of
visible light and components thereof may also be utilized.
[0127] In contrast, as shown in FIG. 7B, when the color change
indicator 100 is exposed to the relatively high concentration of
CO.sub.2, the ratio of the red component to the blue component may
yield a second value that is greater than the first value. As
further shown in FIG. 7B, a ratio of the green component to the
blue component is also greater than the first value. As appreciated
by the present inventors, in some embodiments according to the
invention, the green to blue ratio may be less susceptible to noise
and to other external factors which can provide a more stable
indication of color values detected in the environments illustrated
by FIGS. 7A and 7B.
[0128] According to FIGS. 7A and 7B, the ratio of one component to
another can increase in presence of increased levels of CO2. For
example, in FIG. 7A, a relatively low level of CO2 can be evidenced
by red, green, and blue color components 80, 50, and 70,
respectively. When, however, the level of CO2 increases, as
illustrated in FIG. 7B, the color component values can change to,
for example, 83, 55, and 71, respectively (where the component
values are expressed as values/100). Therefore, a change in the
ratio of selected components to one another can indicate the change
in CO2.
[0129] In some embodiments according to the present invention, a
comparison between multiple component values can provide the
indication of CO2 levels. In some embodiments according to the
invention, a change in a single component value can indicate a
change in the CO2 level.
[0130] In some embodiments according to the invention, the color
change material can be analyzed by selecting a first color or group
of colors that become more saturated in the presence of CO2, a
second color or group of colors that become less saturated in the
presence of CO2, and a third color or group of colors whose
saturation is insensitive to the presence of CO2. A scaling factor
can be determined for each of the first, second, and third colors
and a computational method can be applied to combine the first,
second, and third colors and/or their respective scaling factors in
order to compute a value representative of the CO2 concentration in
the colorimetric sensor, such that the CO2 concentration thereby
calculated is relatively insensitive to interference effects from
moisture, condensation, or long-term color drift caused by
depletion of buffer in the colorimetric sensor material.
[0131] In some embodiments according to the invention, the first
color or group of colors may be selected to coincide with one or
more absorption maxima in the absorption spectra of the at least
partially deprotonated indicator dye. In some embodiments according
to the invention, the second color or group of colors may be
selected to coincide with one or more absorption minima in the
absorption spectra of the at least partially protonated indicator
dye.
[0132] In some embodiments according to the invention, the third
color or group of colors may be selected to coincide with one or
more isobestic points in the absorption spectrum of the color
indicating dye. In some embodiments according to the-invention, the
first and second colors or groups of colors may be selected on the
basis of computing a maximum signal level in the detector response,
regardless of where the colors may fall in the absorption spectrum.
In some embodiments according to the invention, an instant ratio of
color saturation of colors from the first and second color groups
is compared with a time-weighted and/or running average of the
color saturation of the first and second color groups. The
electronic emitter 705 can be a light emitting device, such as a
light emitting diode, along with other support electronics used to
operate the LED using the processor 720, such as a driver circuit
to provide biasing and current to the LED(s).
[0133] A representative example of a white LED lamp includes a
package of a blue light emitting diode chip, made of gallium
nitride (GaN), coated with a phosphor such as YAG In such an LED
lamp, the blue light emitting diode chip produces a blue emission
and the phosphor produces yellow fluorescence on receiving that
emission, which is sometimes referred to as blue-shifted-yellow
(BSY). For instance, white light emitting diodes can be fabricated
by forming a ceramic phosphor layer on the output surface of a blue
light-emitting semiconductor light emitting diode. Part of the blue
ray emitted from the light emitting diode chip passes through the
phosphor, while part of the blue ray emitted from the light
emitting diode chip is absorbed by the phosphor, which becomes
excited and emits a yellow ray. The part of the blue light emitted
by the light emitting diode which is transmitted through the
phosphor is mixed with the yellow light emitted by the
phosphor.
[0134] More specifically, a "BSY LED" refers to a blue LED and an
associated recipient luminophoric medium that together emit light
having a color point that falls within a trapezoidal "BSY region"
on the 1931 CIE Chromaticity Diagram (FIG. 19) defined by the
following x, y chromaticity coordinates: (0.32, 0.40), (0.36,
0.48), (0.43, 0.45), (0.42, 0.42), (0.36, 0.38), (0.32, 0.40),
which is generally within the yellow color range, see for example,
FIG. 5. A "BSG LED" refers to a blue LED and an associated
recipient luminophoric medium that together emit light having a
color point that falls within a trapezoidal "BSG region" on the
1931 CIE Chromaticity Diagram defined by the following x, y
chromaticity coordinates: (0.35, 0.48), (0.26, 0.50), (0.13, 0.26),
(0.15, 0.20), (0.26, 0.28), (0.35, 0.48), which is generally within
the green color range. A "BSR LED" refers to a blue LED that
includes a recipient luminophoric medium that emits light having a
dominant wavelength between 600 and 720 nm in response to the light
emitted by the blue LED. A BSR LED will typically have two distinct
spectral peaks on a plot of light output versus wavelength, namely
a first peak at the peak wavelength of the blue LED in the blue
color range and a second peak at the peak wavelength of the
luminescent materials in the recipient luminophoric medium when
excited by the light from the blue LED, which is within the red
color range. Typically, the red LEDs and/or BSR LEDs will have a
dominant wavelength between 600 and 660 nm, and in most cases
between 600 and 640 nm.
[0135] As shown in FIG. 19, colors on the 1931 CIE Chromaticity
Diagram are defined by x and y coordinates (i.e., chromaticity
coordinates, or color points) that fall within a generally U-shaped
area. Colors on or near the outside of the area are saturated
colors composed of light having a single wavelength, or a very
small wavelength distribution. Colors on the interior of the area
are unsaturated colors that are composed of a mixture of different
wavelengths. White light, which can be a mixture of many different
wavelengths, is generally found near the middle of the diagram, in
the region labeled 106 in FIG. 19. There are many different hues of
light that may be considered "white," as evidenced by the size of
the region 106. For example, some "white" light, such as light
generated by sodium vapor lighting devices, may appear yellowish in
color, while other "white" light, such as light generated by some
fluorescent lighting devices, may appear more bluish in color.
[0136] Light that generally appears green is plotted in the regions
101, 102 and 103 that are above the white region 106, while light
below the white region 106 generally appears pink, purple or
magenta. For example, light plotted in regions 104 and 105 of FIG.
5 generally appears magenta (i.e., red-purple or purplish red).
[0137] Also illustrated in FIG. 19 is the planckian locus 106,
which corresponds to the location of color points of light emitted
by a black-body radiator that is heated to various temperatures. In
particular, FIG. 19 includes temperature listings along the
black-body locus. These temperature listings show the color path of
light emitted by a black-body radiator that is heated to such
temperatures. As a heated object becomes incandescent, it first
glows reddish, then yellowish, then white, and finally bluish, as
the wavelength associated with the peak radiation of the black-body
radiator becomes progressively shorter with increased temperature.
Illuminants which produce light which is on or near the black-body
locus can thus be described in terms of their correlated color
temperature (CCT).
[0138] The chromaticity of a particular light source may be
referred to as the "color point" of the source. For a white light
source, the chromaticity may be referred to as the "white point" of
the source. As noted above, the white point of a white light source
may fall along the planckian locus. Accordingly, a white point may
be identified by a correlated color temperature (CCT) of the light
source. White light typically has a CCT of between about 2000 K and
8000 K. White light with a CCT of 4000 may appear yellowish in
color, while light with a CCT of 8000 K may appear more bluish in
color. Color coordinates that lie on or near the black-body locus
at a color temperature between about 2500 K and 6000 K may yield
pleasing white light to a human observer.
[0139] "White" light also includes light that is near, but not
directly on the planckian locus. A Macadam ellipse can be used on a
1931 CIE Chromaticity Diagram to identify color points that are so
closely related that they appear the same, or substantially
similar, to a human observer. A Macadam ellipse is a closed region
around a center point in a two-dimensional chromaticity space, such
as the 1931 CIE Chromaticity Diagram, that encompasses all points
that are visually indistinguishable from the center point. A
seven-step Macadam ellipse captures points that are
indistinguishable to an ordinary observer within seven standard
deviations, a ten step Macadam ellipse captures points that are
indistinguishable to an ordinary observer within ten standard
deviations, and so on. Accordingly, light having a color point that
is within about a ten step Macadam ellipse of a point on the
planckian locus may be considered to have the same color as the
point on the planckian locus.
[0140] The use of these types (and other) LEDs can promote truer
color reproduction, which is typically measured using the Color
Rendering Index (CRI). CRI is a relative measurement of how the
color rendition of an illumination system compares to that of a
blackbody radiator, i.e., it is a relative measure of the shift in
surface color of an object when lit by a particular lamp. The CRI
equals 100 if the color coordinates of a set of test colors being
illuminated by the illumination system are the same as the
coordinates of the same test colors being irradiated by the
blackbody radiator. Daylight has the highest CRI (of 100), with
incandescent bulbs being relatively close (about 95), and
fluorescent lighting being less accurate (70-85). Certain types of
specialized lighting have relatively low CRI's (e.g., mercury vapor
or sodium, both as low as about 40 or even lower). Sodium lights
are used, e.g., to light highways. Driver response time, however,
significantly decreases with lower CRI values (for any given
brightness, legibility decreases with lower CRI). Accordingly, the
processor 720 can utilize, for example, CRI, color temperature,
color values, CCT, etc. to determine values associated with the
reflected light received by the electronic sensor 710, which can in
turn be used to determine a CO.sub.2 level. It will be understood
that the CO.sub.2 level can be determined by any approach, such as
an equation or lookup table.
[0141] FIG. 8 is a schematic representation of a CO.sub.2 detection
system in some embodiments according to the invention. As shown in
FIG. 8, the color change material 100 is located on an interior
sidewall 801 of an adapter 807 configured to be removably coupled
to a breathing circuit. For example, the adapter 807 is configured
to be removably coupled to standard form-factor tubing typically
used in systems such as ventilators, respirators, and other
equipment used for medical procedures such as in operating rooms,
emergency rooms, etc. The adapter 807 is further configured to
allow the respiratory stream to flow longitudinally so that at
least a portion of the respiratory gas conducted through the
adapter 807 comes into contact with the surface of the color change
material 100. It will be understood that due to the orientation and
location of the color change material 100, the flow of respiratory
gas is substantially unobstructed. Although the color change
material 100 is shown attached to the sidewall 801, it will be
understood that the color change material 100 can be located at any
position within the interior of the adapter 807 while being
longitudinally oriented as shown relative to the respiratory gas
flow so as not to substantially impede the flow thereof.
[0142] An electronic emitter 805 is located outside the adapter 807
and is configured to emit visible light into the adapter 807 to
illuminate the color change material 100 located on the adapter
807. An electronic sensor 810 is also located outside the adapter
807 and is configured to receive a portion of the light reflected
by the color change material 100. As described herein, the change
in the amount of CO.sub.2 in the respiratory gases can cause a
change in the pH of the color change material 100 thereby causing a
shift in the color which can be detected using the electronic
sensor 810 to determine the level of various light components of
the visible light reflected by the color change material 100.
[0143] FIG. 9 is a schematic illustration of a CO.sub.2 detection
system in some embodiments according to the invention. According to
FIG. 9, the color change material 100 is located on an interior
surface 901 of an adapter 907. An electronic emitter 905 is located
outside the adapter 907 opposite the color change material 100. The
adapter 907 is configured to allow the respiratory gases to be
conducted in a longitudinal direction while coming into contact
with the surface of the color change material 100.
[0144] An electronic sensor 910 is located outside the adapter 907
behind the color change material 100 relative to the position of
the electronic emitter 905. The electronic sensor 910 can be spaced
apart from the outside surface of the adapter 907 by a spacer 912,
which creates a space between a mounting for the sensor 910 and the
surface: The space can be utilized to also accommodate filters
(such as red, green, and blue filters) on the sensor 910, which can
be used to promote the detection of those light components.
[0145] Accordingly, when the electronic emitter 905 emits visible
light, the visible light impacts the color change material 100 but
rather than reflecting from the surface to the sensor as described
above in reference to, for example, FIG. 8, the visible light is
detected by the electronic sensor 910 located on the opposing side
of the color change material 100 on the outside of the adapter 907.
It will be understood that the electronic sensor 910 can be used to
determine the relative levels of CO.sub.2 in the respiratory stream
as described herein.
[0146] FIG. 10 is a schematic illustration of a CO.sub.2 detection
system in some embodiments according to the invention. According to
FIG. 10, the color change material 100 is located on an interior
surface 1001 of an adapter 1007 and is configured to allow the
respiratory stream of gases to come into contact therewith without
substantially restricting the flow thereof As further shown in FIG.
10, a reflector 1011 is located outside the adapter 1007 on an
opposing side thereof relative to the color change material 1100.
An electronic emitter 1005 located outside the adapter 1007 and
emits visible light to impact the reflector 1011 which is reflected
onto the color change material 1100 as shown. The visible light
reflected onto the color change material 100 is detected using an
electronic sensor 1010 located outside the adapter 1007 on an
opposing side thereof relative to the reflector 1011. It will be
understood that the relative levels of CO.sub.2 in the respiratory
gas stream can be determined as described herein.
[0147] FIG. 11 is a schematic illustration of a CO.sub.2 detection
system in some embodiments according to the invention. According to
FIG. 11, a color change material 100 is located on an interior
surface 1101 of an adapter 1107. The color change material 100 is
configured within the adapter 1107 to allow the respiratory gas
stream conducted therein to come into contact therewith while not
substantially obstructing the flow of respiratory gases. As further
shown in FIG. 11, the sidewall of the adapter 1107 includes an
optical path configured to refract visible light emitted by an
electronic emitter 1105 onto the surface of the color change
material 100. The visible light reflected onto the color change
material 100 can be detected by an electronic sensor 1110. It will
be understood that the relative levels of CO.sub.2 in the
respiratory gas stream can be determined based on the approaches
described herein.
[0148] FIG. 12 is a schematic representation of an exemplary
display included in a CO.sub.2 detection system in some embodiments
according to the invention. According to FIG. 12, a CO.sub.2 level
portion of the display 1205 indicates the level of CO.sub.2 in the
respiratory stream based on the electronic sensors processing of
the color components included in the reflected visible light. An
auxiliary portion of display 1210 can include other information
regarding the status of the subject. For example, auxiliary
information 1210 may include a read out RR which indicates
respiration rate, an indicator light signaling an apnea condition,
and a battery level indicator.
[0149] FIG. 13 is a schematic representation of a mask configured
for placement over a subject's mouth and nose and including the
display 1200 shown in FIG. 12. Although the display 1200 is shown
located at a bridge portion of the mask, it will be understood that
the display 1200 can be located in any orientation or location of
the mask which facilitates its use in a particular environment. In
particular, for example, in some embodiments according to the
invention, the display 1200 may be located on a side portion of the
mask.
[0150] FIG. 14 is a schematic representation of a CO.sub.2
detection system configured for operation in an open breathing
environment in some embodiments according to the invention.
According to FIG. 14, the color change material 100 along with the
electronic emitter and a sensor as described herein can be located
in an open environment. For example, adjacent to a subject's nose
and/or mouth and not enclosed within, for example, the adapter
shown in FIG. 8. According to FIG. 14, an open environment CO.sub.2
detection system 1400 includes a sensor portion 1405 that can
include the color change material 100 described herein. The sensor
portion can also include a transmit/receive system which allows for
the transmission of visible light from an emitter that is located
remote from the sensor portion 1405. The transmit/receive system
can also include a receiver that provides for the reflected visible
light to be provided to an electronic sensor that is remote from
the sensor portion 1405.
[0151] The CO.sub.2 detection system 1400 also includes an
electronic portion 1410 that can include the electronic emitter and
electronic sensor in communication with the sensor portion 1405 via
a transmission medium 1415 located therebetween. It will be
understood that the electronics portion 1410 can also include a
display such as that shown in FIG. 12 in some embodiments according
to the invention. In operation, when the subject breathes in the
open environment, sufficient CO.sub.2 may be brought into contact
with the color change material located in the sensor portion 1405
despite the fact that it is not enclosed within a breathing circuit
as described herein. The remote electronics portion 1410 can be in
communication with the sensor portion 1405 via the transmission
media 1415 to provide the same determination of CO.sub.2 levels
included in the respiratory stream in the open environment.
[0152] FIGS. 15A and 15B are different views of the CO.sub.2
detection system 1400 shown in FIG. 14. According to FIG. 15A, the
sensor portion 1405 can include ports that allow for the exhaled
CO.sub.2 to be in contact with the color change material located
within. In addition, the sensor portion 1405 can include other
features, such as, a microphone, oxygen ports, and other modalities
and/or sensors. As shown in FIG. 15B, the color change material 100
may be included as part of an apparatus that is removably coupled
to the sensor portion 1405. For example, the color change material
100 may be included as part of a cartridge that is inserted into
the rear of the sensor portion 1405 so that the CO.sub.2 detection
system 1400 is not required to be removed from the subject for
replacement of the color change material 100 such as when the
buffer included in the color change indicator is depleted to the
point where inaccurate CO.sub.2 levels may be reported.
Accordingly, other services to the subject, such as oxygen and
other features may be uninterrupted while the CO.sub.2 sensor color
change material 100 is replaced.
[0153] FIG. 16 is a schematic representation of an optical
implementation of the CO.sub.2 detection system 1400 shown in FIG.
14. According to FIG. 16, the color change material 100 can be
located proximate to the respiratory stream as shown, for example,
in FIG. 14 within the sensor portion 1405. The transmission medium
1415 can be provided by an optical cable that allows for the
electronic emitter to provide the visible light to the color change
material 100 via a first channel of the transmission medium, the
first optical channel 1605 whereas the electronic sensor is
provided with the reflected visible light via a second optical
channel 1610. It will be understood that other types of
transmission mediums may also be used.
[0154] It is also noted that circuitry designed for detecting
CO.sub.2 levels or other types of compounds may be small enough to
be housed in a portable unit operating under battery power. The
advantages of having a portable unit are numerous but may include
availability in remote locations under in-the-field conditions.
This may allow the detector to be provided to all EMT's, first
responders, military units, police personnel and the like. Various
types of batteries may be used to generate sufficient power to
detect the presence of CO.sub.2 as well as operate any type of
display or data transmission. Other power sources can also be
used.
[0155] Furthermore, the CO.sub.2 detection system can be designed
to be an all-in-one unit designed to display data or measurements
at the actual point of measurement, which would be a display
incorporated as part of the device that attaches to the
endotrachael tube, ventilating mask, or source of the exhaled gases
intended to be tested for the presence of CO.sub.2. An alternative
method would allow for remote monitoring of the collected data or
measurements, via wireless connection to either a specifically
designed, purpose built base unit which could either be hand held
or bench top in nature, or via a specific application/app written
to be used on a smart phone platform.
[0156] FIG. 17 is a schematic illustration of test setup for a
CO.sub.2 detection system in some embodiments according to the
invention. FIG. 18 in a graph illustrating CO.sub.2 information
generated by the CO.sub.2 detection system operating in the test
setup of FIG. 17.
[0157] Carbon dioxide detector 1 was configured inside of a 21 mm
adapter tube commonly used as a connector fitting in medical airway
circuits. The color change material was mounted such that air flow
within the tube was substantially parallel to the surface of the
color change material, and the color change material was at a
position approximately equatorial within the tube. The
colorimetrically active surface of the color change material was
illuminated from outside of the tube using a multicolor LED device
containing a red, a green, and a blue LED in a surface mount
package. A color sensing device was mounted adjacent the LED
outside of the tube. The color sensing device was aimed at the
surface of the color change material to intercept a portion of
light reflected from its surface. The color sensing device was
electronically configured to provide digital signals representative
of the relative portions of red, green, and blue light in the
reflected light.
[0158] Gas within the tube comprised a mixture of air and carbon
dioxide, the relative proportions of which could be varied. The
breathing circuit was connected to a respirator to simulate human
breathing at 10 breaths per minute and a volume flow of 4 liters
per minute. The gas circuit was configured to route gases through a
"polysorb" carbon dioxide scrubber during the exhalation portion of
the breathing cycle. This removed all CO.sub.2 in the gas stream.
CO.sub.2 was mixed in a portion of the circuit to mimic production
of CO.sub.2 during an exhalation cycle. The "exhaled" breath was
passed through the tube containing the color change material, and
then routed to the scrubber. While breathing various mixtures of
carbon dioxide that were intentionally varied from below normal
physiological levels to above normal levels, data were recorded
from the digital outputs of the color sensor device and plotted
over time, as shown in FIG. 18. The plot showed that the average
ratio of red color to blue color varied in proportion to the carbon
dioxide content in the breath stream. The plot also showed that
breath-to-breath differences in carbon dioxide could be recorded.
Data was found to provide an accurate calibration of carbon dioxide
content and respiratory rate.
[0159] In further embodiments according to the invention, the color
change material 100 can include at least two portions where at
least one portion is reactive to CO.sub.2 exposure whereas another
portion is unreactive to the CO.sub.2. Accordingly, the reactive
portion can be configured to change color responsive to the
CO.sub.2 level in the respiratory stream. The unreactive portion,
however, may not change color (or may exhibit a lesser change in
color compared to the reactive portion) so that the unreactive
portion can be used to provide a control signal to the processor
circuit. The control signal can be used, for example, to monitor
the functionality of the color change material 100 over time.
[0160] As the color change material 100 is repeatedly exposed to
the respiratory stream over time, the color change exhibited by the
reactive portion can be reduced despite being exposed to the same
level of CO.sub.2 in the respiratory stream. Accordingly, the
reactive portion of the color change material 100 may provide a
less accurate indication of the CO.sub.2 level. As appreciated by
the present inventors, the color exhibited by the unreactive
portion can be compared to the color change exhibited by the
reactive portion in response to the CO.sub.2 level in the
respiratory stream. If the difference between the colors is less
than a predetermined threshold, a signal can be generated to
indicate that the functionality of the color change material 100
may be ineffective.
[0161] In some embodiments according to the invention, the circuits
operatively coupled to the color change material 100 can include
multiple visible light sensor circuits. For example, in some
embodiments according to the invention, the visible light can be
emitted into the breathing circuit to impinge upon the reactive and
unreactive portions of the color change material. A first visible
light sensor circuit can be operatively coupled to the reactive
portion of the color change material 100, whereas a second visible
light sensor circuit can be operatively coupled to the unreactive
portion of the color change material 100. This type of arrangement
can allow the monitoring of the color change exhibited by the
reactive portion over time as described above. In some embodiments
according to the invention, the first and second visible light
sensor circuits are separately controlled by the processor
circuit.
[0162] The color change material 100 can be separated into
different-portions so that the emitted visible light impinging on
the reactive portion does not affect the second visible light
sensor circuit and the visible light impinging on the unreactive
portion does not affect the first visible light sensor circuit. In
other words, the configuration of the color change material 100 may
shield each of the respective sensor circuits from unwanted
portions of the emitted visible light.
[0163] In still further embodiments according to the invention, one
of the visible light sensor circuits may be utilized to detect an
ambient light level in the breathing circuit. In operation, the
processor circuit may receive the ambient light component from one
of the visible light sensor circuits as a control signal, which may
be utilized to compensate for the ambient light component detected
by the other visible light sensor circuit.
[0164] FIG. 20 is a schematic representation of a color change
material 100 included in a breathing circuit and exposed to
electrically generated visible light and electronic sensing thereof
in some embodiments according to the invention. Specifically, FIG.
20 illustrates that the color change material 100 is exposed to a
relatively low CO.sub.2 level in the respiratory stream conducted
by the breathing circuit. A first visible light sensor circuit 2015
is operatively coupled to a reactive portion 2005 of the color
change material 100, whereas a second visible light sensor circuit
2020 is operatively coupled to an unreactive portion 2010 of the
color change material 100. In operation, when the visible light
emitter circuit 705 emits visible light onto the color change
material 100, the first visible light sensor circuit 2015 detects a
first portion of the emitted visible light that passes through the
reactive portion 2005, whereas the second visible light sensor
circuit 2020 detects a second portion of the emitted visible light
that passes through the unreactive portion 2010.
[0165] Because the relatively low level of CO.sub.2 elicits a
particular color response from the reactive portion 2005, the
visible light sensor circuit 2015 provides a reactive signal to the
processor circuit 720. In contrast, the second visible light sensor
circuit 2020 generates a control signal to the processor circuit
that represents little (or at least reduced) color change relative
to that provided by the reactive portion 2005 when exposed to the
relatively low level of CO.sub.2.
[0166] As further shown in FIG. 20, the components of the color
indication 2030 are associated with the reactive signal generated
by the first visible light sensor circuit 2015 whereas the
components of the color control indication 2025 show the color
components included in the control signal generated by the second
visible light sensor circuit 2020. It will be understood that
because of the relatively low CO.sub.2 level shown in FIG. 20, the
color indication 2030 and the color control indication 2025 may be
substantially identical to each other.
[0167] As further shown in FIG. 20, the second visible light sensor
circuit 2020 can also be utilized to determine an ambient light
control component 2035. In operation, the processor circuit 720 may
provide the ambient light control component 2035 by summing the
individual components of the color control indication 2025. In
other embodiments according to the invention, the processor circuit
720 may access a separate portion of the sensor circuit 2020, such
as a clear channel, to provide the ambient light control component
2035. The processor circuit 720 can compensate the color indication
2030 using the ambient light control component 2035. In some
embodiments according to the invention, the ambient light control
component 2035 may be subtracted from the color indication 2030 to
provide a more accurate indication of only the portion of the
emitted visible light detected by the first visible light sensor
circuit 2015 (by reducing the influence of the ambient light on the
color indication 2030). It will be understood that in some
embodiments according to the invention, the ambient component 2035
can be provided using either of the sensor circuits or by another
sensor circuit.
[0168] FIG. 21 is a schematic representation of a color change
material included in a breathing circuit and exposed to
electronically generated visible light and electronic sensing
thereof in some embodiments according to the invention. According
to FIG. 21, the color change material 100 is exposed to a
relatively high CO.sub.2 level in the respiratory stream conducted
by the breathing circuit as a part of a respiratory cycle. As
further illustrated in FIG. 21, because of the increase in the
CO.sub.2 level detected by the color change material 100, the color
indication 2030 changes from that shown in FIG. 20, whereas the
color control indication 2025 provided by the unreactive portion
2010 may remain the same as that shown in FIG. 20 (i.e., the
relatively low CO.sub.2 level environment).
[0169] In operation, the processor circuit 720 can compare the
color control indication 2025 provided by the unreactive portion
2010 to the color indication 2030 provided by the reactive portion
2005. If the processor circuit 720 determines that the color
indication 2030 is exhibiting less color change than expected in a
high CO.sub.2 level environment, the, processor circuit can provide
a signal that maintenance of the color change material 100 should
be performed. For example, the processor circuit 720 may indicate
that the color change material 100 should be changed.
[0170] As appreciated by the present inventors, as the color change
material 100 is repeatedly utilized, the reactive nature of the
color change material may be depleted due to repeated exposure to
the respiratory stream. Therefore, and in order to provide more
accurate results over time, the color change material 100 may be
replaced with a fresh color change material 100 if a predetermined
threshold is reached. As further appreciated by the present
inventors, the color control indication 2025 can be utilized as a
"base line" to indicate the color that exhibited by the reactive
portion 2005 in a functional (or original) state. In other words,
the color control indication 2025 can correspond to a known good
color that reactive portion 2005 should exhibit when in the
breathing circuit. Over time, as the color change material 100 is
exposed to the CO.sub.2 in the respiratory stream, the color change
exhibited by the reactive portion 2005 may be reduced, and
therefore, may more closely resemble the color control indication
2025 associated with the unreactive portion 2010.
[0171] As further shown in FIG. 21, the processor circuit 720 can
utilize the second visible light sensor circuit 2020 to provide the
ambient light control component 2035 which may be used to adjust
the color indication 2030 provided by the first visible light
sensor circuit 2015, so that the processor circuit 720 may
determine a more accurate indication of the CO.sub.2 level to which
the color change material 100 is exposed by reducing the
contribution from ambient light. Other circuits can also be used to
provide the ambient light component.
[0172] FIG. 22 is a flowchart that illustrates operations of a
CO.sub.2 level detection system in some embodiments according to
the invention. According to FIG. 22, the processor circuit 720
controls the visible light emitter circuit to emit visible light
into the breathing circuit into the respiratory stream and through
the color change material to impinge on the first and second
visible light sensor circuits 2015 and 2020 (block 2200). The first
and second visible light sensor circuits 2015 and 2020 detect the
respective colors generated by the reactive portion 2005 and the
unreactive portion 2010 (blocks 2205). It will be further
understood that the reactive portion 2005 can change color in
response to exposure to the CO.sub.2 in the respiratory stream
whereas the unreactive portion 2010 exhibits less color change.
[0173] The processor circuit 720 can access the data generated by
the first and second visible light sensor circuits 2015 and 2020.
In particular, the processor circuit 720 can receive color
indications in the form of color components from each of the first
and second visible light sensor circuits 2015 and 2020. For
example, the processor circuit 720 can access the first visible
light sensor circuit 2015 to retrieve red, green, and blue color
components for the color exhibited by the reactive portion 2005.
Similarly, the processor circuit 720 can retrieve red, green, and
blue color components from the second visible light sensor circuit
2020 with the indication of the color generated by the unreactive
portion 2010.
[0174] The processor circuit 720 can also utilize the color
components to compensate for adverse artifacts that may otherwise
impact the determination of the CO.sub.2 level exhibited by the
color change material 100 (block 2210). For example, the processor
circuit 720 can compare the color components associated with the
reactive portion 2005 to the color components associated with the
unreactive portion 2010 (block 2215). If the difference between
these two sets of color components is less than a predetermined
threshold the processor circuit 720 may determine that the reactive
portion 2005 is, for example, beyond its useful life and should be
replaced. In particular, the reactive portion 2005 may be saturated
with CO.sub.2 due to prolonged exposure to the respiratory stream
and therefore should be replaced. In still other embodiments
according to the invention, the processor circuit 720 can use the
comparison of color components as described herein to provide an
initial indication of whether the reactive portion 2005 is adequate
for an accurate determination of the CO.sub.2 level. Still further,
over time the processor circuit 720 can use the comparison of the
color components associated with the reactive and unreactive
portions 2005 and 2010, to monitor the "wear" on the color change
material 100.
[0175] If the processor circuit 720 determines that the reactive
portion 2005 is past its useful lifetime (Block 2215) the processor
circuit 720 can generate a maintenance indicator signaling that the
color change material (or at least the reactive portion 2005)
should be replaced. Still further, operations of the CO.sub.2 level
detection system in some embodiments according to the invention may
cease until a functional color change material 100 is provided and
tested by the processor circuit 720 during initialization. If,
however, the processor circuit 720 determines that the
functionality of the reactive portion 2005 is adequate (Block
2215), the processor circuit 720 may also compensate for ambient
light detected within the breathing circuit (block 2217). For
example, the processor circuit 720 may determine the ambient light
control component 2035 by accessing a clear channel associated with
the second visible light sensor circuit 2020. In other embodiments
according to the invention, the processor circuit 720 may combine
the color control components 2025 to provide an indication of the
ambient light. The processor circuit 720 may then compensate for
the ambient light to reduce any adverse artifacts associated with
ambient light in the breathing circuit to provide a more accurate
indication of the true color generated by the reactive portion 2005
and thereby a more accurate indication of the CO.sub.2 level in the
respiratory stream.
[0176] The processor circuit 720 can then determine ratios of
components in the color indication 2030 to one another and ratios
of components in the color control indication 2025 to one another.
For example, in some embodiments according to the invention, the
processor circuit 720 may provide a ratio of the red component
divided by the green component for each of the color control
indications 2025 and the color indications 2030 collected over time
(block 2220).
[0177] It will be understood that the processor circuit 720 can be
configured to sample the color control indication 2025 and the
color indication 2030 at least ten times per second in order to
determine a respiration rate based on the ratios generated by the
processor circuit 720 (Block 2225). For example, the processor
circuit 720 can repeatedly sample the data provided by the first
and second visible light sensor circuits 2015 and 2020 until an
adequate data set is generated where the data set includes the
ratios described above. The value of the ratios can then be
examined over time to determine the respiration rate of the
respiratory stream. In particular, the processor circuit 720 can be
configured to locate three directly adjacent minimum or maximum
values for the ratios to identify at least one cycle of respiration
within the respiratory stream. The timing between the minimum or
maximum ratio values can be used to determine the respiration
rate.
[0178] The processor circuit 720 is configured to determine the
CO.sub.2 level in the respiratory stream using the data set
including the ratio values described above (block 2230). For
example, in some embodiments according to the invention, the
processor circuit 720 may examine the data set to calculate the
peak-to-peak value that represents the difference between the
minimum ratio value within the cycle and the maximum ratio value
within the cycle. In some embodiments according to the invention,
the processor circuit 720 is configured to determine the CO.sub.2
level based on the ratio values associated with the first visible
light sensor circuit 2015 (having been compensated with the ambient
light control component). In still other embodiments according to
the invention, the processor circuit 720 is configured to determine
the CO.sub.2 level based on a combination of the peak-to-peak ratio
value and the minimum value of the ratio associated with the first
visible light sensor circuit 2015. In still further embodiments
according to the invention, the processor circuit 720 is configured
to determine the CO.sub.2 level utilizing the peak-to-peak value
approach more heavily during relatively low respiratory rates,
whereas the minimum ratio value may be more heavily weighted during
periods of higher respiratory rates. Operations can continue as
described above as long as the respiratory stream is supplied to
the breathing-circuit and/or at least the reactive portion 2005 is
deemed functional by the processor circuit 720 (block 2235).
[0179] FIG. 23 is a schematic representation of the color change
material 100 included in a breathing circuit and exposed to
electronically generated visible light and electronic sensing
thereof in some embodiments according to the invention. According
to FIG. 23, the processor circuit 720 controls the visible light
emitter circuit 905 to emit visible light into the breathing
circuit 907 that conducts the respiratory stream. The emitted
visible light passes through the respiratory stream and impinges on
the color change material 100.
[0180] The color change material 100 includes the reactive portion
2005 and the unreactive portion 2010 that is spaced apart from the
reactive portion 2005. The first visible light sensor circuit 2015
is positioned proximate to the reactive portion 2005 and the second
visible light sensor circuit 2020 is positioned proximate to the
unreactive portion 2010. In operation, a first portion of the
emitted visible light passes through the reactive portion 2005 and
impinges on the first visible light sensor circuit 2015. In
contrast, a second portion of the emitted visible light passes
through the unreactive portion 2010 and impinges on the second
visible light sensor circuit 2020.
[0181] It will be understood that the first and second visible
light sensor circuits 2015 and 2020 are positioned relative to the
reactive and unreactive portions 2005 and 2010 to reduce artifacts
attributable to that portion of the emitted visible light which is
provided to the other sensor circuit. For example, the first
visible light sensor circuit 2015 can be shielded from receiving
any of the second portion of visible emitted light passing through
the unreactive portion 2010. Similarly, the second visible light
sensor circuit 2020 can be shielded from receiving any of the first
portion of the emitted visible light passing through the reactive
portion 2005. Accordingly, the signals provided by the first and
second visible light sensor circuits 2015 and 2020 may be more
attributable to only that portion of the emitted visible light
which passes through the associated portion of the color change
material 100. The processor circuit 720 can access the first and
second visible light sensor circuits 2015 and 2020 to provide the
data set described herein with which the CO.sub.2 level can be
determined in some embodiments according to the invention. The
embodiments illustrated by FIG. 23 can include various elements as
described, for example, in FIG. 9 and can operate with any of the
color change material 100 configurations and compositions described
herein.
[0182] FIG. 24 is a schematic representation of a color change
material included in a breathing circuit and exposed to
electronically generated visible light and electronic sensing
thereof in some embodiments according to the invention. According
to FIG. 24, the processor circuit 720 operates the visible light
emitter circuit 705 to provide emitted visible light to the
reflector 1011 which reflects the visible emitted light onto the
reactive and unreactive portions 2005 and 2010. The first portion
of the emitted visible light passes through the reactive portion
2005 to impact the first visible light sensor circuit 2015. In
contrast, the second portion of the visible emitted light passes
through the unreactive portion 2010 to impact the second visible
light sensor circuit 2020. As described above, the first and second
visible light sensor circuits 2015 and 2020 are shielded from
receiving any unintended portion of the emitted visible light. In
operation, the processor circuit 720 can access the first and
second visible light sensor circuits 2015 and 2020 to provide the
data set upon which the CO.sub.2 level can be determined in some
embodiments according to the invention. The embodiments illustrated
by FIG. 24 can include various elements as described, for example,
in FIG. 8 and can operate with any of the color change material 100
configurations and compositions described herein.
[0183] FIG. 25 is a schematic representation of a CO.sub.2
detection system 2500 including a color change material in a
breathing circuit and exposed to electronically generated visible
light and electronic sensing thereof in a side stream configuration
in some embodiments according to the invention. According to FIG.
25, the system 2500 can include a processor circuit, visible light
emitter circuit, color change material 100, and visible light
sensor circuits as described herein. It will be further understood
that although FIG. 25 illustrates the visible light emitter circuit
and visible light sensor circuits on opposing sides of the
breathing circuit, any configuration of visible light emitter
circuits, visible light sensor circuits and color change material
can be utilized in association with the side stream configuration
shown in FIG. 25.
[0184] As further shown in FIG. 25, a pump 2505 is configured for
coupling to the CO.sub.2 detection system 2500 to provide the
respiratory stream