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| United States Patent | 5006314 |
| Link to this page | http://www.wikipatents.com/5006314.html |
| Inventor(s) | Gourley; Ted H. (Santa Ana, CA);
Maxwell; Thomas P. (Santa Ana, CA);
Hacker; Thomas G. (Anaheim, CA);
Miller; William W. (Santa Ana, CA);
Yafuso; Masao (El Toro, CA) |
| Abstract | An apparatus for sensing the concentration of a component such as oxygen in
a medium such as blood. The apparatus includes an elongated signal
transmitter and a sensing element at one end thereof. A substantially
rigid sleeve is secured around such end to provide a pocket for the
sensing element. |
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Title Information  |
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Drawing from US Patent 5006314 |
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Sensor and method for sensing the concentration of a component in a
medium |
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| Publication Date |
April 9, 1991 |
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| Filing Date |
June 13, 1988 |
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| Parent Case |
RELATED APPLICATIONS
This application is a continuation in part of U.S. Pat. application Ser.
No. 091,433, filed Aug. 31, 1987 (now abandoned), which in turn is a
continuation-in-part of U.S. Pat. application Ser. No. 853,460, filed Apr.
18, 1986 (now abandoned); U.S. Pat. application Ser. No. 917,913, filed
Oct. 10, 1986 (now U.S. Pat. No. 4,798,738); U.S Pat. application Ser. No.
917,912, filed Oct. 10, 1986 (now U.S. Pat. No. 4,824,789); and U.S. Pat.
application Ser. No. 049,844, filed May 15, 1987 (now U.S. Pat. No.
4,919,891). Each of these applications is incorporated in its entirety by
reference herein.
BACKGROUND OF THE INVENTION
The present invention relates to a sensing or measuring apparatus which
includes a flexible signal transmitter, e.g., an optical fiber, and a
flexible sensing element. More particularly, the invention relates to such
an apparatus and method which involve means to reduce the detrimental
effect of the flexibility of the signal transmitter and sensing element.
Sensors, e.g., optical sensors, are quite useful in systems to measure the
concentration of a component in a medium. For example, optical sensors can
be effectively employed for measuring or monitoring a given component in
blood. Typical components measured by sensors include gases, such as
oxygen and carbon dioxide, hydrogen ions (pH), electrolytes, glucose and
the like.
Such sensors include an indicator, e.g., a fluorescent dye, which interacts
with the component to be sensed or measured. Typically, the indicator,
often in combination with a component permeable matrix, is a sensing
element or sensor means and is placed on or adjacent a surface of a signal
transmitter e.g., an optical fiber. The interaction between the indicator
and the component to be sensed or measured is monitored utilizing signals
carried by the signal transmitter.
The size of such sensors, which in certain instances are sufficiently small
to be employed in vivo in the treatment of a medical patient, often
results in the signal transmitter and sensing element being flexible. As
used herein, an item is "flexible" if the application of a force
perpendicular to the longitudinal axis of the item results in a
displacement of the longitudinal axis. For example, a single optical fiber
made of glass is normally flexible, as is the sensing element.
Although the signal transmitters and the sensing elements are typically
flexible, such flexibility can cause substantial difficulties in obtaining
accurate and consistent measurements. For example, such flexibility can
result in the signal to be transmitted by the signal transmitter becoming
distorted or otherwise not representative of the signal being provided by
the indicator in the sensor. In addition, this flexibility may cause
unwanted relative movement and separation of the signal transmitter and
the indicator, which also may have a detrimental effect on the consistency
and integrity of the signal being transmitted by the signal transmitter.
In view of the size constraints imposed on such sensors, it is often not
possible to avoid using flexible signal transmitters and sensing elements.
However, it would clearly be advantageous to provide such a sensor in
which the adverse effect of such flexibility is reduced. For example, it
would be advantageous to reduce the probability of relative movement
between the signal transmitter and the sensing element.
A number of U.S. Patents and an European Patent Publication have been
considered in preparing this application.
Costello U.S. Pat. No. 4,682,895 discloses a probe which includes a light
sending optical fiber, a light receiving optical fiber, a sample chamber
filled with colorimetric substance, a tip support coating which extends
proximally of the faces of both optical fibers, a protective sheath which
terminates proximally of both of these faces and a semipermeable membrane.
Costello teaches the tip support coating, and not the protective sheath,
as providing a rigid protection for the tip of the probe. Also, Costello's
system which involves two fibers (derived from a doubled-up single optical
fiber) may be too bulky for certain applications.
Gudmunder, et al European Patent Publication No. 0,047,094 discloses an
optical measuring system including a dual channel probe. Light is passed
through the probe by one optical fiber to a fluid-solid interface to be
measured which causes the interface to fluoresce or phosphoresce, and that
resulting light is passed back through the probe by another optical fiber
and analyzed. A plastic sheath surrounds middle portions (neither distal
end nor proximal end) of the optical fibers, and is bonded to a flexible
cable to join the probe to the cable and form a hermetic seal to prevent
the ingress of contaminants. The sheath does not extend beyond either end
of the optical fibers and therefore does not protect or support such ends.
Smolinsky, et al U.S. Pat. No. 3,864,019 discloses an unclad optical fiber
firmly attached to a transparent substrate by photopolymerization of a
transparent filter, e.g., cyclohexyl methacrylate, located between the
unclad fiber and the substrate. Schoch, et al U.S. Pat. No. 4,639,594
discloses a fiberoptic probe which includes two optical fibers, a light
source and two photomultipliers. Lindgren U.S. Pat. No. 4,516,020
discloses a system in which an optical fiber is surrounded by light
transmitting glass or plastic. The system is used to detect undesired,
light-producing events. Peterson, et al U.S. Pat. No. 4,200,100 discloses
a probe including two optical fibers and a flexible protective sheath
which extends well beyond the distal ends of the fibers. Peterson, et al
U.S. Pat. No. 4,476,870 discloses a two optical fiber probe which includes
a dye packing and a hydrophobic gas permeable porous envelope to isolate
the dye packing from contamination. None of these systems is concerned
with reducing the harmful effects of the flexibility of a sensing element
and a signal transmitter, in particular a single optical fiber.
SUMMARY OF THE INVENTION
A new apparatus and method for sensing the presence, or concentration e.g.,
measuring the concentration, of a component in a medium has been
discovered. In one broad aspect, the present system comprises sensor means
including at least one indicator, preferably in a component permeable
matrix; elongated signal means acting to transmit a signal from the sensor
means, and sleeve means secured to the elongated signal means and
extending distally of the distal end of the elongated signal means to at
least partially define a pocket in which the sensor means is located. The
sleeve means acts to reduce the possibility of relative movement between
the sensor means and the distal end of the elongated signal means, i.e.,
relative to the possibility of such movement in a similar apparatus
without the present sleeve means. The sleeve means preferably starts or
commences proximally and terminates distally of the distal end of the
elongated signal means. Further, the sleeve means is preferably more rigid
than the elongated means.
The present apparatus simply and effectively reduces the adverse effect or
effects often caused by the flexibility of the signal transmitter and/or
of the sensor means. Reducing the apparent flexibility, or increasing the
apparent stiffness, of the distal portion of the signal means, and
preferably of the sensor means, reduces unwanted relative movement between
this distal portion and the sensor means. This allows the signal means to
transmit the signal from the sensor means more consistently or more
reproducibly. This also reduces the chances of an undesirable change in
the relative positions of the sensor means and the signal means because of
this unwanted relative movement. More reliable component concentration
measurements result.
The present apparatus may be utilized in an improved method for measuring
the concentration of a component in a medium.
The present sleeve means extends out from the distal end of the signal
means. Preferably, the sleeve means extends out from the distal end of the
signal means a distance in the range of about 0.5 to about 2, more
preferably about 0.8 to about 1.2, times the maximum transverse dimension,
e.g., diameter, of such distal end.
The sleeve means may be of any suitable structure, orientation and
configuration, and may be made of any suitable material of construction
provided that it functions as described herein and has no substantial
adverse effect on the other components of the present system or on the
functioning of these components. The sleeve means preferably substantially
surrounds the distal portion of the elongated signal means. This is
advantageous since the surrounding sleeve conveniently protects the distal
portion of the signal means and/or the sensor means from unwanted movement
regardless of the direction of the force tending to cause this unwanted
movement. Suitable materials from which the sleeve means can be
constructed include, for example, polymeric materials such as polyimides
and the like, and glass, with glass being an especially useful material of
construction.
The sleeve means preferably further acts to increase the apparent stiffness
and/or strength of the distal portion of the signal means and of the
sensor means. That is, with the sleeve means in place, forces acting on
this distal portion and on the sensor means preferably have less harmful
effect, e.g., on the distal portion itself, on the sensor means itself, or
on the relative position of the distal portion of the signal means and the
sensor means, relative to such a system without the present sleeve means.
The presently useful indicators preferably function by modifying a source
signal, e.g., from the signal means, in response to the presence of a
certain component, e.g., oxygen, in medium, e.g., blood. Optical
indicators are preferred for use in the present system. The preferred
optical indicators are selected from the group consisting of luminescence,
e.g., fluorescence indicators, absorbance indicators and mixtures thereof,
with fluorescence indicators being especially preferred. Fluorescence
indicators often include a dye which is sensitive or responsive to a
component of interest. This dye, preferably in the component permeable
matrix, can be placed on or adjacent the distal tip of the signal means,
preferably an optical fiber, and exposed to the medium containing the
component of interest. By monitoring the light signals from the dye tipped
optical fiber, the concentration (partial pressure) of the component in
the medium can be determined. Certain of the above-noted patent
applications disclose various fluorescence indicators useful in the
present invention.
If oxygen is the component of interest, the optical indicator is preferably
selected from the group consisting of polynuclear aromatic compounds,
derivatives of polynuclear aromatic compounds and mixtures thereof. More
preferably, the optical indicator is a mixture of derivatives of
polynuclear aromatic compounds, in particular tertiary butyl derivatives
of decacyclene. Certain of these preferred optical indicators are
described in the above-noted U.S. Pat. application Ser. No. 853,460 (now
abandoned).
In addition to the preferred optical indicator, the sensor means preferably
further includes a component permeable, polymeric matrix. By "component
permeable" is meant that the substance in question, e.g., the polymeric
matrix, is permeable to the component the concentration of which is to be
determined or measured using the sensor. Any suitable polymeric matrix may
be employed. The polymeric matrix should have no substantial adverse
effect of the other components of the present system or on the functioning
of such other components. Certain of the above-noted patent applications
disclose suitable polymeric matrixes. The choice of polymeric matrix is
dependent, for example, on the optical indicator being employed, the
specific component of interest and the specific sensing application
involved. Although various polymers can be employed for the polymeric
matrix, it is important that the polymeric matrix have a high permeability
to the component of interest so that the sensitivity of the optical
indicator to the component of interest is adequate for the sensing
application involved. One particularly useful class of polymeric matrixes
is selected from the group consisting of silicone polymers and mixtures
thereof. For example, the silicone polymer may be a dimethylsiloxane
polymer, a diphenylsiloxane polymer, or a diphenyldimethylsiloxane
copolymer. Of this group, dimethylsiloxane polymers are preferred because
of their high component permeability. Other members of the homologous
series which include the above-mentioned polymers might also be used and
are included within the scope of this invention.
The polymeric matrix is preferably cross-linked to provide improved support
and structure for the optical indicator included in the sensor means. The
term "cross-linking" as used herein refers to a chemical reaction in which
polymeric molecules are reacted with multi-functional, e.g., difunctional,
compounds to join the polymeric molecules together by bridges or
cross-links derived from the multi-functional compounds or cross-linking
agents.
Various cross-linking agents and cross-linking catalysts may be employed to
cross-link the polymeric matrix. Such agents and catalysts should have no
substantial detrimental effect on the components of the present system or
on the functioning of such components. The cross-linking reaction may be
conducted in a conventional manner and, therefore, is not discussed in
detail here.
As noted above, the present elongated signal means acts to transmit signals
from the sensor means. The signals to be transmitted are influenced by or
in response to the presence of the component of interest in the medium.
This signal means is preferably further capable of delivering a source
signal, e.g., excitation light, to the sensor. In one embodiment, the
signal means comprises an optical fiber for (1) delivering excitation
light to the sensor means so that the optical indicator in the sensor
means can provide a signal which is influenced by or is in response to the
component of interest; and (2) transmitting this signal from the sensor
means. A light source, connected to the optical fiber, provides excitation
light of the desired wavelength which is channeled down the fiber toward
the sensor means. In response to this excitation light, the sensor means
emits a light signal, e.g., a fluorescent light signal, which is dependent
on the concentration of the component of interest to which the sensing
means is exposed. This light signal or emission light is then channeled
back up the same optical fiber to a light sensor for electrical readout
and analysis of this light signal. Such analysis results in a
determination of the concentration of the component of interest in the
medium to which the sensing means is exposed. This procedure is similar to
that described in Lubbers et al, U.S. Pat. No. Re. 31,879 and Heitzmann,
U.S. Pat. No. 4,557,900, each of which is incorporated in its entirety
herein by reference.
As noted above, the sleeve means is secured to the distal portion of the
signal means. Preferably, the present apparatus further comprises adhesive
means acting to adhesively secure the sleeve means to the signal means.
For ease and consistency of manufacture, it is preferred that the adhesive
means be curable by exposure to light energy, more preferably ultra-violet
light energy. This feature is particularly useful in applications where
the apparatus is small in size, e.g., sufficiently small to be useful in
vivo in the treatment of a medical patient. The various components can be
carefully situated to be in proper relation and position relative to each
other without being concerned that the adhesive will cure or set up simply
because of the passage of time. Once the components are properly in place,
the adhesive in exposed to the required light energy and the adhesive is
cured.
In one embodiment, the adhesive means is substantially component
impermeable. By "component impermeable" is meant that the substance in
question, e.g., the adhesive means, is impermeable to the component of
interest.
Any suitable adhesive means may be used provided that such adhesive means
function as described herein. This adhesive material should have no
substantial detrimental effect on the other components of the present
system or on the functioning of such components. The specific adhesive
means chosen depends, for example, on the specific application involved.
In one embodiment, the adhesive means includes additional optical
indicator and acts to provide such additional optical indicator to the
sensor means, e.g., over a period of time. The adhesive means is
preferably a polymeric material. More preferably, the adhesive means is
derived from a resin selected from the group consisting of epoxy resins
and mixtures thereof. One particularly useful epoxy resin is sold under
the tradename Dymax 20017 engineering adhesive by American Chemical &
Engineering Company. This particularly useful epoxy resin is curable by
ultra-violet light energy and is substantially impermeable to oxygen.
The present apparatus preferably further comprises an overcoating at least
partially covering, and more preferably acting to protect, the sensor
means. This overcoating preferably comprises a component permeable
material and an effective amount of an opaque agent. The overcoating
should be substantially insoluble in the medium. For example, if blood is
the medium, the overcoating is preferably water insoluble. One
particularly useful component permeable material for use in the
overcoating is cross-linked cellulosic material. Such overcoatings are
more fully described in the above-noted U.S. Pat. application Ser. No.
049,844 (now U.S. Pat. No. 4,919,891).
These and other aspects and advantages of the present invention are set
forth in the following detailed description and claims, particularly when
considered in conjunction with the accompanying drawings in which like
parts bear like reference numerals. |
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Title Information |
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