U.S. patent application number 10/881955 was filed with the patent office on 2004-11-25 for sensing apparatus and process.
This patent application is currently assigned to MEDTRONIC MINIMED, INC.. Invention is credited to Chernoff, Edward, Lebel, Ronald J., Montalvo, Rudolph A., Shah, Rajiv, Zhang, Yanan.
Application Number | 20040236201 10/881955 |
Document ID | / |
Family ID | 26712780 |
Filed Date | 2004-11-25 |
United States Patent
Application |
20040236201 |
Kind Code |
A1 |
Lebel, Ronald J. ; et
al. |
November 25, 2004 |
Sensing apparatus and process
Abstract
A sensing apparatus with a connector, a sensor lead and a sensor
module with a spacer placed over electrodes that have been
deposited on a substrate. The spacer may have a space for receiving
an enzyme. End portions of the sensor module may be encapsulated,
such as with molded beads. A sensor lead may attach to the sensor
module and may have an outer tubing that passes over the module and
attaches to the beads at the end of the sensor module. The sensor
lead may also attach to the connector such that the sensing
apparatus may be electrically coupled to a pump, electronics or
other devices. The sensing apparatus may be implanted into a vein
or artery.
Inventors: |
Lebel, Ronald J.; (Sherman
Oaks, CA) ; Shah, Rajiv; (Rancho Palos Verdes,
CA) ; Zhang, Yanan; (Valencia, CA) ; Chernoff,
Edward; (Frazier Park, CA) ; Montalvo, Rudolph
A.; (Woodland Hills, CA) |
Correspondence
Address: |
FOLEY & LARDNER
2029 CENTURY PARK EAST
SUITE 3500
LOS ANGELES
CA
90067
|
Assignee: |
MEDTRONIC MINIMED, INC.
|
Family ID: |
26712780 |
Appl. No.: |
10/881955 |
Filed: |
June 29, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10881955 |
Jun 29, 2004 |
|
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|
10036093 |
Dec 28, 2001 |
|
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60318060 |
Sep 7, 2001 |
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Current U.S.
Class: |
600/345 ;
600/347; 600/365 |
Current CPC
Class: |
A61B 5/14532 20130101;
A61N 1/05 20130101; A61B 5/145 20130101; Y10T 29/49204 20150115;
A61B 5/14865 20130101; A61B 5/1473 20130101 |
Class at
Publication: |
600/345 ;
600/347; 600/365 |
International
Class: |
A61B 005/00 |
Claims
1. A sensing apparatus comprising: a cable having a first end, a
second end and a core, wherein the core extends from the first end
of the cable to the second end of the cable and wherein the core
defines an outer diameter within which no electrical conduction
occurs; a connector residing at the first end of the cable; a
sensor module residing at the second end of the cable; a conductive
element extending from the connector to the sensor module and
electrically coupled to at least one of said connector and sensor
module, wherein the conductive element is helically wrapped around
at least a substantial length of the outer diameter of the core
between the connector and the sensor.
2. A sensing apparatus according to claim 1, wherein the cable, and
the sensor module are unidiametrical; and wherein the diameter of
the connector is no greater than the diameter of the cable and
sensor module.
3. A sensing apparatus according to claim 1, wherein the cable
comprises a first tubing covering the core and the conductive
element.
4. sensing apparatus according to claim 3, wherein the core is
polyester.
5. A sensing apparatus according to claim 3, wherein the conductive
element is a ribbon cable.
6. A sensing apparatus according to claim 3, wherein the conductive
element includes wires.
7. A sensing apparatus according to claim 6, wherein the wires are
welded to the connector and the sensor module.
8. A sensing apparatus according to claim 6, wherein the wires are
crimped to the connector.
9. A sensing apparatus according to claim 6, wherein the wires are
platinum.
10. A sensing apparatus according to claim 3, wherein the first
tubing is radio opaque.
11. A sensing apparatus according to claim 3, further comprising a
second tubing covering the first tubing.
12. A sensing apparatus according to claim 11, wherein a window is
cut into the second tubing.
13. A sensing apparatus according to claim 1, wherein the sensor
module comprises a first end and a second end.
14-16. (Cancelled)
17. A sensing apparatus according to claim 1, further comprising an
enzyme within the sensor module.
18. A sensing apparatus according to claim 17, wherein the enzyme
is glucose oxidase.
19. A sensing apparatus according to claim 17, wherein the enzyme
is human serum albumin.
20. A sensing apparatus according to claim 17, wherein the enzyme
is a protein matrix.
21. A method of making a sensing apparatus comprising obtaining a
connector; obtaining a cable, wherein the cable has a core;
obtaining a sensor module; attaching a first end of the cable to
the connector; attaching a second end of the cable to the sensor
modules; extending a conductive element from the connector to the
sensor module, wherein the conductive element is electrically
coupled to at least one of said connector and sensor module; and
helically wrapping the conductive element around a substantial
lenth of the outer diameter of the core between the connector and
the sensor module, wherein the core extends from the first end of
the cable to the second end of the cable, and wherein the core
defines an outer diameter within which no electrical conduction
occurs.
22-23. (Cancelled)
24. A sensing apparatus according to claim 1, wherein the core is
made from shock absorptive material.
25. A sensing apparatus according to claim 24, wherein the shock
absorptive material is selected from the following group:
Kevlar.RTM., Dacron.RTM. and polyester.
26. A sensing apparatus according to claim 1, wherein the at least
a substantial length of the core is the entire length of the
core.
27. A sensing apparatus according to claim 1, wherein the sensor
module further comprises a spacing element.
28. A sensing apparatus according to claim 1, wherein the sensor
module further comprises a first spacing element and a second
spacing element, the first spacing element being configured to
couple with the second spacing element; and wherein the first
spacing element comprises a floor, the floor of the first spacing
element being configured to allow the passage of oxygen.
29. A sensing apparatus according to claim 1, wherein the core
further comprises an insulating material.
30. A sensing apparatus according to claim 1, wherein said core is
solid.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] Embodiments of the present invention claim priority from a
U.S. Provisional Application entitled "Sensing Apparatus and
process," Serial No. 60/318,060 filed Sep. 7, 2001, the contents of
which are incorporated by reference herein.
BACKGROUND
[0002] 1. Field of the Invention
[0003] The present invention relates to the field of sensor
technology and, in particular, to implantable, in-vivo sensing
systems used for sensing a variety of parameters, including
physiological parameters.
[0004] 2. Description of Related Art
[0005] The combination of biosensors and microelectronics has
resulted in the availability of portable diagnostic medical
equipment that has improved the quality of life for countless
people. Many people suffering from disease or disability who, in
the past, were forced to make routine visits to a hospital or
doctor's office for diagnostic testing currently perform diagnostic
testing on themselves in the comfort of their own homes using
equipment with accuracy to rival laboratory equipment.
[0006] Nonetheless, challenges in the biosensing field have
remained. For example, although many diabetics currently utilize
diagnostic medical equipment in the comfort of their own homes, the
vast majority of such devices still require diabetics to draw their
own blood and inject their own insulin. Drawing blood typically
requires pricking a finger. For someone who is diagnosed with
diabetes at an early age, the number of self-induced finger pricks
over the course of a lifetime could easily reach into the tens of
thousands. In addition, the number of insulin injections may also
reach into tens of thousands. Under any circumstances, drawing
blood and injecting insulin thousands of times is overly invasive
and inconvenient at best and most likely painful and emotionally
debilitating.
[0007] Some medical conditions have been amenable to automated,
implantable sensing. For example, thousands of people with heart
conditions have had pacemakers or defibrillators implanted into
their bodies that utilize sensors for monitoring the oxygen content
of their blood. Ideally, these sensors should be able to determine
whether, for example, a person's heart is running very efficiently
at a high heart rate or whether a person's heart has entered
defibrillation. In order to effectively make this determination, an
accurate sensor must be employed. Unfortunately, oxygen sensors
implanted into the body have, thus far, typically required frequent
and periodic checking and recalibration. In fact, one of the "holy
grails" of the pacemaker industry has been an accurate, no drift,
no calibration oxygen sensor. Up until now, such a sensor has been
unavailable.
[0008] An ideal solution to the diagnostic requirements of those
with disease or disability, absent an outright cure, is a sensing
apparatus that may be implanted into the body and that may remain
in the body for extended periods of time without the need to reset
or recalibrate the sensor. Regardless of the particular application
for such a sensor system, in order to effect such a system, the
associated sensor must remain accurate, exhibit low drift and
require no recalibration for extended periods of time.
[0009] Thus, an ideal implantable sensing apparatus would provide
for a sensing apparatus that may be inserted into a vein, artery or
other part of a body while being unobtrusive, easy to insert and
remove, yet accurate and reliable. Embodiments of the present
invention provides such a system.
SUMMARY OF THE DISCLOSURE
[0010] Embodiments of the present invention relate to a sensing
apparatus. A sensing apparatus includes a cable having a first end
and a second end, a connector residing at the first end of the
cable and a sensor module residing at the second end of the cable.
The cable, the connector and the sensor module may be
unidiametrical.
[0011] The cable may comprise a core, a conductive element wrapped
around the core, and a first tubing covering the core and the
conductive element. The core may be polyester. The conductive
element may be a ribbon cable. The conductive element may include
wires. The wires may be platinum. The wires may be welded to the
connector and the sensor module. Alternatively, the wires may be
crimped to the connector. The first tubing of the cable may be
radio opaque. A second tubing may cover the first tubing. A window
may be cut into the second tubing.
[0012] The sensor module may have a first end and a second end.
Beads may encapsulate the first end and the second end. The sensor
module may also have a spacing element. A height of the spacing
element may be greater than a height of the beads.
[0013] The sensing apparatus may also include an enzyme. The enzyme
may be glucose oxidase or human serum albumin. The enzyme may be a
protein matrix. The enzyme may be hydrated.
[0014] A method of making a sensing apparatus may comprise
obtaining a connector; obtaining a cable; obtaining a sensor
module; attaching a first end of the cable to the connector; and
attaching a second end of the cable to the sensor module. The
method may further include forming beads over ends of the sensor
module; inserting a spacing element between the beads; covering the
sensor module with a tubing of the cable; cutting a window in the
tubing of the cable; and inserting an enzyme in the sensor
module.
[0015] These and other objects, features, and advantages of
embodiments of the invention will be apparent to those skilled in
the art from the following detailed description of embodiments of
the invention when read with the drawings and appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIG. 1 is a perspective view of a generalized sensing
apparatus configuration according to an embodiment of the present
invention.
[0017] FIG. 2A is a perspective view of an electrode side of a
generalized sensor module configuration according to an embodiment
of the present invention.
[0018] FIG. 2B is a perspective view of an electronics side of a
generalized sensor module configuration according to an embodiment
of the present invention.
[0019] FIG. 3A is a perspective view of an electrode side of a
generalized sensor module configuration with encapsulated ends
according to an embodiment of the present invention.
[0020] FIG. 3B is a perspective view of an electronics side of a
generalized sensor module configuration with encapsulated ends
according to an embodiment of the present invention.
[0021] FIG. 4 is a perspective view of a sensor module
configuration wherein two sensor modules are connected together in
a "daisy-chain" fashion according to an embodiment of the present
invention.
[0022] FIG. 5 is a perspective view of a sensor module with spacers
according to an embodiment of the present invention.
[0023] FIG. 6A is a perspective view of a generalized sensor lead
according to an embodiment of the present invention.
[0024] FIG. 6B is a perspective view of a conductor element
according to an embodiment of the present invention.
[0025] FIG. 7 is a process for making a sensing apparatus according
to an embodiment of the present invention.
[0026] FIG. 8 is a side showing a window cut into an outer tubing
of the sensor lead according to an embodiment of the present
invention.
[0027] FIG. 9 is a process for removing or replacing a sensing
apparatus according to an embodiment of the present invention.
DETAILED DESCRIPTION
[0028] In the following description of preferred embodiments,
reference is made to the accompanying drawings which form a part
hereof, and in which are shown by way of illustration specific
embodiments in which the invention may be practiced. It is to be
understood that other embodiments may be utilized and structural
changes may be made without departing from the scope of the
preferred embodiments of the present invention.
[0029] Embodiments of the present invention comprise a sensing
apparatus including, without limitation, a sensor module, a sensor
lead and a connector. As will be explained below in greater detail,
the sensor module may comprise, without limitation, an enzyme and
one or more spacers. The lead may comprise, without limitation, a
core, a conductor, a first tubing and a second tubing. In
embodiments of the sensing apparatus, each element of the sensing
apparatus may be modified separately or in conjunction with another
element according to the application or environment in which
sensing apparatus is used. Thus, the sensing apparatus may be seen
as a plurality of modular, individual elements, each of which may
be modified and combined with one another to provide a sensing
apparatus that may be used in a variety of applications, in a
variety of environments, and implanted in a variety of
locations.
[0030] FIG. 1 shows a generalized sensing apparatus configuration
according to an embodiment of the present invention. A sensing
apparatus 10 includes a sensor lead 12, a first end 14 comprising a
connector 16 and a second end 18 comprising a sensor module 20.
Molded onto each end of the sensor module 20 are beads 22. An
ogive, or bullet shaped, tip 24 attaches to a bead 22 that is
opposite the sensor lead 12 such that the entire assembly is
streamlined in a fluidic environment, such as a bloodstream. The
sensor lead 12 comprises tubing that attaches to the ogive tip 24.
The entire sensing apparatus 10 may be placed in a vein or other
area within a human body using a process according to an embodiment
of the present invention to be discussed below.
[0031] The connector 16 may be a male, female or other type
connector. The connector 16 may provide for multiple conductive
paths, thereby accommodating a variety of sensor lead 12
configurations. Also, the connector 16 may be made from a variety
of materials. For example, the connector 16 may be made from any
material that is electrically conductive yet chemically inert.
[0032] FIGS. 2A and 2B show a generalized sensor configuration
according to an embodiment of the present invention. A sensor
module 20 may include a substrate 30 having a sensing element side
32 and an electronics side 34. The substrate 30 may be made from
ceramic or other materials. As can be seen in FIG. 2A, electrodes
36 may be deposited onto the sensing element side 32 of the
substrate 30. The electrodes 36 may interface with a sensing
element (not shown) which will be described below. As can be seen
in FIG. 2B, the electronics side 34 of the substrate 30 may include
a lid 38 that covers a variety of electronics, such as, for
example, an integrated circuit 40 and a capacitor 42. The
electronics side 34 of the substrate 30 may also include welding
pads 44 to which wire leads may be welded as well as other types of
pads and traces common to electronic circuitry. The electrodes 36
and the electronics on the electronics side 34 of the substrate 30
provide the basis for electrochemical measurement. According to one
embodiment of the invention, the sensor module 20 may be utilized
for oxygen sensing. However, the sensor module is not limited to
this application and may also be utilized in other applications
such as, for example, for ion, neurotransmitter or nitric oxide
sensing.
[0033] FIGS. 3A and 3B show further details of a generalized sensor
configuration according to an embodiment of the present invention.
In FIG. 3A, a portion of the electrode pattern may be encapsulated
by the beads 22. In FIG. 3B, beads 22 may be molded over the ends
of the substrate 30 such that the welding pads 44 and any wires
welded to the welding pads 44 are encapsulated within the beads 22.
In addition, the beads 22 may also encapsulate a core of the sensor
lead 12, thereby giving the core an anchor. The beads 22 may be
formed over the ends of the substrate 30 using a mold. The
substrate 30 may be placed into the mold and the ends of the
substrate 30 subsequently covered with an epoxy or other
encapsulating material.
[0034] FIG. 4 shows a sensor configuration wherein two sensor
modules 20 are connected together in a "daisy-chain" fashion. In
this configuration, the welding pads 44 may be straight-through
pads, such that electrical continuity exists between corresponding
welding pads 44 on opposite sides of each sensor module 20. Thus,
by serially connecting a welding pad 44 of one sensor module 20 to
a corresponding welding pad 44 of another sensing module 20, the
sensing modules 20 may be individually addressed using a two-wire
line and unique addresses.
[0035] FIG. 5 shows a sensor module with spacers according to an
embodiment of the present invention. A first spacing element 50 may
be placed over the electrodes 36, fitting into a recess between the
beads 22. The first spacing element 50 may be thought of as a
spacer shim because it has the function of maintaining a certain
distance or space between the electrodes 36 and an enzyme which may
eventually be placed within the sensor module 20. The floor 52 of
the first spacing element 50 may be such that it allows the passage
of oxygen. If, for example, the first spacing element is made from
silicone or polydimethylsiloxane, the floor 52 of the first spacing
element 50 will pass oxygen but will not pass other compounds found
in the bloodstream, such as glucose.
[0036] An enzyme and space may be used to fine tune sensor
performance. The size and configuration of the enzyme and spacer
may be modified to effect of variety of sensing characteristics.
For example, the enzyme and spacer size and configuration may be
modified to improve dynamic range, reduce noise due to oxygen
transients, and increase sensing apparatus lifetime. The
configuration of the enzyme and spacer may be driven by a variety
of factors including, without limitation, the need to measure a
physiological parameter, such as, for example, blood glucose, and
the need to keep membranes of the sensor module 20 in compression
during the lifetime of the device.
[0037] A second spacing element 54 fits within the first spacing
element 50 and provides support for a window that may be cut into
tubing that covers the sensor module 20 and attaches to the ogive
tip 24. After the window has been cut, as will be explained below,
the second spacing element 54 may be discarded and an enzyme or
other sensing catalyst may be disposed in its place.
[0038] An outer tubing of the sensor lead 12 may be pulled over the
first spacing element 50. The outer diameter of the first spacing
element 50 may be such that it is greater than the inner diameter
of the outer tubing of the sensor lead 12. Thus, when the outer
tubing of the sensor lead 12 is pulled over the first spacing
element 50 the first spacing element 50 may be forced against the
electrodes 36 on the substrate 30 by the contraction force of the
outer tubing.
[0039] The spacing elements may be made from the same mold used to
form the beads 22. If the same mold that was used to form the beads
22 is used to form the spacing elements 50, 54, the spacing
elements 50, 54 will form a precise fit with the beads 22. The
spacing elements 50, 54 may be made from silicon or other suitable
material.
[0040] In addition, the height of the first spacing element 50 may
extend beyond the height of the beads 22. When the height of the
first spacing element 50 and the beads 22 are offset, any
compression upon the first spacing element 50, such as that that
might be applied when the outer tubing of the sensor lead 12 is
slipped over the sensor module 20, tends to stabilize the
dimensions of the elements of the apparatus, such as membranes that
may exist above the electrodes 36, that may change through chemical
reaction.
[0041] FIG. 6A shows a generalized sensor lead 12 according to an
embodiment of the present invention. At the center of the sensor
lead 12 may be a core 60. The core 60 may be a material such as,
for example, polyester or other material, or a commercially
available material such as, for example, DACRON OR KEVLAR, that
provides shock absorption and strength to the sensor lead 12.
According to one embodiment of the present invention, a polyester
core may provide as much as 18-20 lbs. of tensile strength to the
sensor lead 20. In addition, the core 60 limits sensor lead 12
elongation. Thus, if the sensing apparatus 10 has been implanted
into a vein in a human body, a doctor or other medical professional
who needs to remove the sensing apparatus 10 from the vein may pull
on the sensor lead 12 without fear of excessively stretching it or
breaking it. Various factors may influence the size of the core 60
and the material used for the core 60 such as, for example, the
overall diameter, device stiffness, and sensor lead 12 attachment
scheme.
[0042] Wrapped around the core 60 in a helical fashion is a
conductive element 62. The conductive element 62 may be a flat
cable or ribbon cable having multiple conductor wires. The
conductive element 62 may also be a laminate structure conducive to
being wrapped around the core 60 with a pitch in between the
windings such that the conductive element 62 has enough flexibility
to move with the core 60 if the core 60 is stretched. The helical
nature of the winding also contributes to the flexibility of the
conductive element 62 if the core 60 is stretched or otherwise
moved. The conductive element 62 may include only a few wires, such
as, for example, three wires or four wires. Alternatively, if the
application requires a large number of data channels or high
current carrying capacitor, the conductive element 62 may include a
larger number of wires, such as, for example, five wires, ten wires
or more. The size of the conductive element 62, the number of wires
in the conductive element 62, and the materials used as the
conductive element 62 may be influenced by a variety of factors
including, without limitation, sensing apparatus application and
signal transmission requirements. For example, the size of the
conductive element 62, the number of wires in the conductive
element 62, and the materials used as the conductive element 62 may
be chosen depending on whether the sensing apparatus is used in
digital or analog applications or depending on a particular
communications protocol. The strength of the conductive element 62
needed for a particular application may be a factor in determining
wire size. In addition, the wires used in the conductive element 62
may be, for example, platinum, iridium, MP35, gold or silver, or
other conductive material.
[0043] A first tubing 64 may be slid around the core 60 wrapped
with the conductive element 60. The first tubing 64 may be made
from a radio opaque material such as silicone or may be made from
other materials such as, for example, radio opaque polyurethane.
The size and dimensions of the first tubing 64 and the materials
used for the first tubing 64 may be influenced by a variety of
factors including, without limitation, the overall stiffness
requirements of the sensor lead 12 according to the application of
the sensing apparatus 10.
[0044] A second tubing 66 may be slid around the first tubing 64.
The second tubing 66 may be made from silicone or other material.
The second tubing 66 may be used to provide oxygen transport and
mechanical compression. Depending on the application, the surface
of the second tubing 66 may be treated for biocompatibility,
lubricity and stiffness.
[0045] According to an embodiment of the present invention the
conductive element 62 may be a flat cable having four wires 68 as
shown in FIG. 6B. The wires 68 may be platinum or another type of
conductor, such as, for example, a noble metal. The diameter of
each wire 68 may be as thin as one one-thousandth of an inch or
thinner and the entire cable may be molded with TEFLON or another
insulator such that the wires are insulated from one another.
Because much of the strength of the sensor lead 12 may be derived
from the core 60, the wires themselves need not be chosen for
strength. Thus, the wires need a diameter only as large as
necessary to carry the currents being generated by the devices to
which the sensor lead 12 is attached. For example, in the case
where the sensor module 20 employs an electrochemical sensing
element, the currents generated may be on the order of hundreds of
nanoamps or tens of microamps. The type of wire used in the sensor
lead 12 may be chosen accordingly. In the case where the sensor
lead 12 is attached to a pacemaker, the wires may be chosen such
that they can accommodate a current of a few milliamps, a typical
value for heart stimulating pulses used in pacemakers. Thus, in the
case where the sensor lead 12 is inserted into a vein, a metal such
as platinum may be used as the wire. Platinum, although very
fragile at the small diameters required for carrying the electrical
currents just mentioned, such as, for example, one one-thousandth
of an inch, is chemically inert and corrosion resistant and, thus,
desirable in a fluidic environment, such as blood. However, because
the wires are so thin, they may be generally less intrusive to the
environment in which they are placed than larger diameter wires
typically used in an in-vivo application. Thus, according to
embodiments of the present invention, a thin, fragile wire may be
used where, traditionally, larger diameter, strong wires have been
used. Thus, a wire made from a metal such as platinum may be
employed.
[0046] In order to connect the wires to the relevant portions of
the connector 16 and the sensor module 20 the cable may be stripped
and the wires connected together in groups of two. Once connected
together, the wires may be viewed as two wires having two strands
each. Thus, the wires are redundant and should one break, another
is available to maintain electrical continuity. One of the wire
pairs may then be crimped and welded to the connector 16 and the
other wire pair may be spot welded to the wire pads 44 on the
sensor module 20
[0047] A completed sensor lead 12 may be labeled for identification
or other purposes. A variety of labeling materials may be used for
labeling. According to one embodiment of the present invention, any
labeling material may be used so long as the material chosen
remains visible after sterilization of the sensing apparatus
10.
[0048] Also, the label may be placed in a variety of positions on
the sensor lead 12. For example, according to one embodiment of the
present invention, the label may be placed on the outer surface of
the first tubing 64 in between the first tubing 64 and the second
tubing 66 using an green-colored, epoxy based ink that is
biocompatible and that does not leach toxic materials into or out
of the sensor lead 12.
[0049] FIG. 7 shows a process for making a sensing apparatus
according to an embodiment of the present invention. At step 70 ,
the connector 16, the sensor lead 12 and the sensor module 20 are
obtained. At step 72 the wires in the conductive element of the
sensor lead 12 are attached to the pads 44 on the substrate 30 of
the sensor module 20 and to the connector 16 The wires in the
conductive element may be welded or otherwise attached to the pads
44 and crimped or otherwise attached to the connector.
[0050] At step 74, beads 22 are formed over the ends of the
substrate 30 such that the welding pads, a portion of the
electrodes 36 and the core 60 are encapsulated within the beads 22.
In addition, an ogive tip 24 may be glued or otherwise attached to
a bead 22 opposite the sensor lead 12.
[0051] At step 76 spacing elements may be inserted in between the
beads 22. The spacers may comprise a first spacing element 50 and a
second spacing element 54 At step 78, an outer tubing of the sensor
lead 12 may be pulled over the sensor module 20 and attached to the
ogive tip 24 attached to the bead 22 opposite the sensor lead
12.
[0052] At step 80, a window may be cut in the outer tubing of the
sensor lead 12 over the second spacing element 54. The window may
be cut and placed in a manner suitable for the application of the
sensing apparatus 10 and such that the sensitivity of the apparatus
is advantageous. For example, if the sensing apparatus is to be
used in a glucose monitoring application, such as might be used in
the case of a diabetic, the window may be cut with a particular
width and at such a place on the outer tubing of the sensor lead 12
such that oxygen influx into the enzyme is aided. In glucose
sensing applications, a typical window width may be five
thousandths of an inch, or may be ten to twenty thousandths of an
inch. In addition, window depth may be anywhere from about four
thousandths of an inch to ten thousandths of an inch. The response
time of the device may also be adjusted by the cut and placement of
the window. A window 94 cut into an outer tubing of the sensor lead
12 may be seen in FIG. 8.
[0053] The second spacing element 54 may be removed at step 82 and
the entire sensing apparatus 10 may be sterilized. The
sterilization step 84 may be implemented using a variety of
sterilization techniques. For example, the entire sensing apparatus
10 (which may or may not include an enzyme, protein, or other
physiological parameter sensor) may be put into an ethylene oxide
(ETO) gas such that the ETO gas permeates all of the elements of
the sensing apparatus 10. After sterilization, the sensing
apparatus may be stored until it is ready for use.
[0054] If desired, an enzyme may be put in the place of the second
spacing element 54 through the window at step 86. The enzyme may be
any of a variety of enzymes that may be employed for sensing. For
example, if physiological parameter sensing is desired, one or more
proteins may be used as the enzyme. According to one embodiment of
the present invention, a combination of glucose oxidase and human
serum albumin may be used concurrently in a solid matrix form to
form a sensor matrix protein (SMP). The SMP may be cross-linked
together or glymerized using glutaraldehyde or other suitable
chemical such that a three-dimensional structure is created.
[0055] The enzyme may be hydrated at step 88 such that it expands
to form a tight fit and to fill the area left by the removal of the
second spacing element 54 . The enzyme may initially be in a
slightly desiccated state when placed into the area vacated by the
second spacing element 54. Although such a desiccated state
facilitates placement, space may exist between the enzyme and the
surround area of the sensor module 20. Thus, the surrounding area
and the enzyme may be hydrated with a sterile buffer, thereby
swelling the enzyme and forming a compression fit with the first
spacing element 50. Any cavity left in surrounding area after the
enzyme has been hydrated may be filled at step 90 with, for
example, a hydrogel, such as, for example, methacrylate or other
hydrophilic acrylic, that is permeable to the sterilant.
Subsequently, the hydrogel may be polymerized using a UV
polymerization process.
[0056] At step 92, the window may be closed and the sensing
apparatus 10 may be sterilized again in a manner that is not
damaging to the enzyme. For example, a more dilute form of the
glutaraldehyde may be used to sterilize the sensing apparatus 10
after the enzyme has been place in the first spacing element 50.
The sensing apparatus 10 may then be used as necessary.
[0057] FIG. 9 shows a process for removing or replacing a sensing
apparatus from a vein or artery. The vein or artery may belong to a
human being or other animal. At step 100, a connector 16 that has
been implanted into a vein along with the rest of the sensing
apparatus is found by locating it under the skin by touch and feel
in the general area that the connector 16 should be residing. At
step 102, an incision is made into the skin and the connector 16
may be brought out of the skin.
[0058] At step 104, a tool with clamping fingers is placed over the
connector 16 such that the fingers close onto the connector 16 and
form a secure connection with the connector 16. A canula/introducer
is then slid over the tool and the connector at step 106 into the
vein at the location of the incision. Fabricating the connector 16,
the sensor lead 12, and the sensor module 20 to be unidiametrical
facilitates sliding the canula/introducer over them. While the
canula/introducer remains in the vein, the tool, connector 16,
sensor lead 12 and sensor module 20 may be pulled through the
canula/introducer at step 108, thereby removing the sensing
apparatus 10 from the vein.
[0059] At step 110, a new sensing apparatus may be inserted into
the vein. Once the new sensing apparatus is inserted into the vein,
the canula/introducer may be removed at step 112 and the incision
may be sewn up.
[0060] While particular embodiments of the present invention have
been shown and described, it will be obvious to those skilled in
the art that the invention is not limited to the particular
embodiments shown and described and that changes and modifications
may be made without departing from the spirit and scope of the
appended claims.
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