U.S. patent application number 15/160903 was filed with the patent office on 2016-11-24 for needle for transcutaneous analyte sensor delivery.
The applicant listed for this patent is DexCom, Inc.. Invention is credited to Jennifer Blackwell, Jonathan Hughes, Ted Tang Lee, Neel Shah, Peter C. Simpson, Shanger Wang.
Application Number | 20160338734 15/160903 |
Document ID | / |
Family ID | 56134579 |
Filed Date | 2016-11-24 |
United States Patent
Application |
20160338734 |
Kind Code |
A1 |
Shah; Neel ; et al. |
November 24, 2016 |
NEEDLE FOR TRANSCUTANEOUS ANALYTE SENSOR DELIVERY
Abstract
The present disclosure relates to a needle including a wall
structure, a cutting edge and a blunt contour. The needle
advantageously can be used to deliver a sensor (such as a glucose
or other analyte sensor) through an outer skin layer and into a
sensor depth in a less invasive way than prior art needles. The
size of the cutting edge is balanced against a portion of the
distal wall structure that has blunt contours. Thus, the needle is
capable of cutting the more durable outer skin layer (first phase)
and then progressively stretching open the cut for further
advancement into the subcutaneous layer (second phase). When the
needle is sufficiently advanced, it is retracted leaving the sensor
in a desired position. Early testing has shown a reduction of "dip
and recover" from glucose sensors delivered using the needle.
Inventors: |
Shah; Neel; (San Diego,
CA) ; Blackwell; Jennifer; (San Diego, CA) ;
Hughes; Jonathan; (Carlsbad, CA) ; Lee; Ted Tang;
(San Diego, CA) ; Simpson; Peter C.; (Cardiff,
CA) ; Wang; Shanger; (Castro Valley, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
DexCom, Inc. |
San Diego |
CA |
US |
|
|
Family ID: |
56134579 |
Appl. No.: |
15/160903 |
Filed: |
May 20, 2016 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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15160516 |
May 20, 2016 |
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15160903 |
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62165837 |
May 22, 2015 |
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62244520 |
Oct 21, 2015 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
A61B 5/14503 20130101;
A61B 2560/063 20130101; A61B 5/14865 20130101; A61B 5/14532
20130101; A61M 5/3286 20130101; A61B 17/3468 20130101; A61B
2017/3456 20130101 |
International
Class: |
A61B 17/34 20060101
A61B017/34; A61B 5/145 20060101 A61B005/145 |
Claims
1. A method of delivering a sensor, the method comprising:
advancing a cutting edge on a wall structure of a needle through an
outer skin layer to cut an opening in the outer skin layer; bluntly
stretching, with a blunt contour extending at least 50% of a cross
dimension of the wall structure viewed along a central axis of the
wall structure, the opening in the outer skin layer; and releasing
the sensor at a sensor depth.
2. The method of claim 1, wherein advancing the cutting edge is
before bluntly stretching.
3. The method of claim 1, including further advancing the cutting
edge until the cutting edge is at the sensor depth.
4. The method of claim 1, wherein releasing the sensor includes
retracting the needle back from the sensor depth and over the
sensor.
5. The method of claim 1, wherein the method reduces wound volume
compared to a straight conventional beveled needle by at least
15%.
6. The method of claim 5, wherein the method reduces wound volume
by at least 35%.
7. The method of claim 1, wherein the method reduces an incidence
of dip and recover to less than 5% of a patient population.
8. The method of claim 1, wherein the method reduces an incidence
of dip and recover to less than 1% of a patient population.
9. The method of claim 1, wherein releasing the sensor includes
laterally sliding the sensor through an elongate window defined in
the wall structure.
Description
INCORPORATION BY REFERENCE TO PRIORITY APPLICATIONS
[0001] Any and all priority claims identified in the Application
Data Sheet, or any correction thereto, are hereby incorporated by
reference under 37 CFR 1.57. This application is a continuation of
U.S. application Ser. No. 15/160,516, filed May 20, 2016, which
claims priority to U.S. Provisional Application No. 62/165,837,
filed May 22, 2015, and U.S. Provisional Application No. 62/244,520
filed Oct. 21, 2015. Each of the aforementioned applications is
incorporated by reference herein in its entirety, and each is
hereby expressly made a part of this specification.
FIELD
[0002] The present disclosure relates to a delivery device for a
sensor, and in particular to a needle for transcutaneous analyte
sensor delivery.
BACKGROUND
[0003] Physicians who understand a patient's glucose level can
better adapt to various treatments, such as the administration of
insulin, to the patient's needs. Most diabetic patients (and many
healthcare institutions) use occasional finger sticks with test
strips to measure patient glucose. Test strips, however, do not
convey the same dynamic information (such as trend information) on
the patient's glucose levels.
[0004] Continuous glucose monitors have the advantage of providing
multiple measurements over short time periods with little
additional labor and less pain. Continuous glucose monitors often
use transcutaneous sensors--sensors positioned through the
patient's skin--to accurately measure glucose values. For example,
the transcutaneous sensors may dwell several layers deep in the
patient's skin and are bathed in interstitial or other fluids. The
sensors often include electrodes that are sensitive to glucose
composition and yield fairly frequent (e.g., every few minutes)
measurements.
[0005] Patients and physicians prefer the glucose sensors to be
small to minimize invasiveness and discomfort. The glucose sensors
therefore tend to be relatively fragile. At the same time, the
patient's skin can be thick and difficult to penetrate. Physicians
and patients therefore often use needles to pierce the skin to its
appropriate layer and depth. The needle houses an electrode portion
of the glucose sensor during insertion and is later withdrawn to
leave the sensor at the appropriate position within the patient's
skin.
[0006] As another example, DexCom, Inc. (applicant on the present
application) owns U.S. Patent Application Publication No.
2011/0077490 which discloses a transcutaneous analyte sensor. The
'490 publication discloses in its FIGS. 1 and 2A, for example, a
transcutaneous sensor device that includes a tissue piercing
element positioned over a sensor body. The piercing element has a
conical shape that enables piercing of the skin for advancement of
the sensor body. The '490 publication also discloses, in FIG. 2B, a
distal tip that is beveled at an angle from about 5.degree. to
60.degree.. The '490 publication also discloses, in FIGS. 2C-2H and
3D, tips with curved surfaces providing greater cutting surface
area for smoother insertion.
SUMMARY
[0007] Despite the improvements disclosed in the '490 publication,
DexCom is continuously improving the delivery of its sensors.
DexCom discloses herein another design of a needle for delivering
sensors that balances invasiveness with other needs of the patient,
physician and sensor.
[0008] The present disclosure in some embodiments relates to a
needle including a wall structure, a cutting edge and a blunt
contour. The needle advantageously can be used to deliver a sensor
(such as a glucose or other analyte sensor) through an outer skin
layer and into a sensor depth in an effective but less invasive way
than prior art needles. The size of the cutting edge is balanced
against a portion of the distal wall structure that has blunt
contours. Thus, the needle is capable of cutting the more durable
outer skin layer (first phase) and then progressively stretching
open the cut for further advancement into the subcutaneous layer
(second phase). When the needle is sufficiently advanced, it is
retracted away from the sensor leaving the sensor in a desired
position. Early testing has shown a reduction of "dip and recover"
from glucose sensors delivered using the needle.
[0009] A needle for delivering a sensor through an outer skin layer
and into a sensor depth is disclosed. The needle includes a wall
structure, at least one cutting edge and at least one blunt
contour. The wall structure has a central axis, at least one cross
dimension and defines at least one inner dimension. The inner
dimension is sized to contain the sensor for delivery. The cutting
edge is on the wall structure and is configured to pierce the outer
skin layer. The blunt contour is also on the wall structure. It is
configured to bluntly dissect tissue as the wall structure advances
to the sensor depth. The projected area of the blunt contour, when
viewed along the central axis of the wall structure, can occupy
more than 50% or 60% of the cross dimension of the wall structure.
The wall structure is also configured for removal from the outer
skin layer to leave the sensor at the sensor depth.
[0010] Beveled edges may be defined on the wall structure. The
cutting edge may be formed on less than 50% of the beveled edge.
Also, the cutting edge (from a view along the central axis) may be
spaced closer to the central axis than an adjacent outer edge of
the blunt contour. And, the central axis may pass through the blunt
contour. The remaining portion of the beveled edge may be smoothed
rather than sharpened.
[0011] The blunt contour in one implementation is at least 2/3 of
an area centered on the central axis and circumscribing an outer
edge of the blunt contour. The area may be, for example, a circular
area having a diameter matching a diameter of the wall
structure.
[0012] The cutting edge may form less than 40% of the beveled edge.
The blunt contour may be sufficiently large in proportion to the
cutting edge to reduce wound volume by at least 15% to 69% or 70%.
Observed incidences of dip and recover in human populations are,
based on early porcine testing, expected to drop to less than 5% or
even less than 1% of the population.
[0013] The needle may be detachable from the sensor to leave the
sensor at the sensor depth.
[0014] In one implementation, the wall structure of the needle has
a cylindrical shape. Also, the cutting edge may be configured to be
sufficiently sharp and large to cut through the outer skin layer
without buckling of the wall structure.
[0015] The beveled edges may be at a range of angles. For example
the beveled edges may be angled at least 7 to 10 degrees. For
example, the wall structure may include a primary bevel that is
angled 7 degrees. The needle may also include a secondary beveled
edge that has two portions angled away from each other and the
central axis.
[0016] The wall structure may further include a bend positioned
proximal and subjacent to the primary bevel, the beveled edge or
the cutting edge. The bend may be 17 degrees or up to 24 degrees.
An inner dimension of the wall structure may be at least 0.0135
inches to afford clearance for the sensor diameter. An outer
dimension of the wall structure may be at least 0.0180 inches. The
inner dimension may be, for example, a diameter of an elongate
cylindrical opening.
[0017] The elongate opening may be configured to retain the sensor
until the wall structure reaches the sensor depth. At the same time
the elongate opening may be configured to allow the sensor to slide
freely therein. The elongate opening may be of sufficient length to
retain the sensor in a recessed position relative to the distal tip
of the wall structure.
[0018] In another embodiment, the wall structure may define a
longitudinal slit connected in communication with the inner
dimension. Also, the wall structure may define an elongate opening.
The inner dimension is a diameter of the elongate opening. The
longitudinal slit is in communication with the elongate opening.
And, the elongate opening is sized to retain the sensor until the
wall structure reaches the sensor depth. The longitudinal slit may
be sized to allow passage of a width of the sensor therethrough.
And the elongate opening may be a cylindrical opening. The elongate
opening and longitudinal slit may extend entirely through a distal
edge of the wall structure to form a C-shape.
[0019] In another aspect, the elongate opening may form a window in
the wall structure. This window can, for example, allow passage
therethrough of connector wires for the sensor.
[0020] Other systems, methods, features and/or advantages will
become apparent to one with skill in the art upon examination of
the following drawings and detailed description. It is intended
that all such additional systems, methods, features and/or
advantages be included within this description and be protected by
the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 shows an elevation view of a needle of one
embodiment;
[0022] FIG. 2 shows a plan view of beveled surfaces of the needle
of FIG. 1;
[0023] FIG. 3 shows an elevation view of tubing being bent to form
a needle of another aspect;
[0024] FIG. 4 shows an elevation view of the tubing of FIG. 3 with
a primary bevel formed thereon;
[0025] FIG. 5 shows an elevation view of the tubing of FIG. 4 with
a secondary bevel formed thereon;
[0026] FIG. 6 shows an enlarged perspective view of the bevels of
FIGS. 4-5;
[0027] FIG. 7 shows a front elevational view (along a central axis)
of the distal end of the bevels of FIGS. 3-5;
[0028] FIG. 8 shows a side elevational view of a needle of another
aspect;
[0029] FIG. 9 shows a side elevational view of a conventional
needle for delivering a sensor;
[0030] FIG. 10 is a cross-sectional view of a conventional needle
track (on the left) next to a track made by a needle with blunt
contours (on the right);
[0031] FIG. 11 is another cross-sectional view of a conventional
needle track (on the left) next to a track made by a needle with
blunt contours (on the right);
[0032] FIG. 12 is a table of test results comparing geometries of
needle holes formed using a needle similar to the ones shown in
FIGS. 1-8 and the needle shown in FIG. 9;
[0033] FIG. 13 is a diagram of a process for creating a coaxial
sensor;
[0034] FIG. 14 shows insertion of the coaxial sensor of FIG. 13 on
a pencil point needle;
[0035] FIG. 15 shows removal of the pencil point needle from the
coaxial sensor of FIG. 13;
[0036] FIG. 16 is a perspective view of a needle of another
embodiment wherein the needle has a slot;
[0037] FIG. 17 is cross-sectional view of the needle of FIG.
16;
[0038] FIG. 18 is a perspective view of another needle with a slot
extending through the distal end of the needle;
[0039] FIG. 19 is a cross-sectional view of the needle of FIG.
18;
[0040] FIG. 20 is a needle of another embodiment;
[0041] FIGS. 21-24 illustrate a needle of another embodiment with a
U-shaped cross-section;
[0042] FIGS. 25-33 show schematics of additional needle
embodiments;
[0043] FIG. 34 shows a schematic of a conventional needle;
[0044] FIG. 35 shows another needle embodiment;
[0045] FIG. 36 shows another needle embodiment; and
[0046] FIGS. 37-38 show a single bevel embodiment of a needle;
[0047] FIG. 39 shows another single bevel embodiment of a needle
with a 13 degree bend angle;
[0048] FIG. 40 shows another single bevel embodiment of a needle
with a 17 degree bend angle;
[0049] FIGS. 41-44 show a single bevel needle having a U-shaped
cross-section;
[0050] FIGS. 45-49 show a single bevel needle having a C-shaped
cross-section;
[0051] FIG. 50 graphically depicts cut area test results for
needles;
[0052] FIG. 51 shows a table of cut area test results for
needles;
[0053] FIG. 52 graphically depicts a part of a process of testing
for dip and recover behavior of a sensor delivered by needles;
[0054] FIG. 53 graphically depicts dip and recover test results for
conventional needles and needles of the embodiments; and
[0055] FIG. 54 shows another needle including a proximal slot to
receive a kink of a sensor.
DETAILED DESCRIPTION
[0056] The following description and examples illustrate some
exemplary embodiments of the disclosed invention in detail. Those
of skill in the art will recognize that there are numerous
variations and modifications of this invention that are encompassed
by its scope. Accordingly, the description of a certain exemplary
embodiment should not be deemed to limit the scope of the present
invention.
[0057] It was determined that that continuous glucose monitoring
(CGM) systems exhibit at times a characteristic called "dip and
recover." The dip and recover phenomenon occurs after initial
placement of the sensor--the signal from that sensor dips from
expected levels and then later recovers to normal behavior. One
drawback of an occurrence of a dip and recover event is lost time
and lost data in what would otherwise have been a robust,
continuous measure of glucose containing dynamic information
desired by physicians.
[0058] Generally, the dip and recover phenomenon was reduced by
developing a needle and sensor insertion system designed
specifically to minimize tissue trauma during sensor insertion.
Minimization of tissue trauma may also advantageously reduce the
likelihood of a dip and recover event during sensor use. The needle
is designed with a tip that pierces the skin, but continues with
blunt dissection through the subcutaneous tissue to the depth of
sensor placement. Blunt dissection occurs without substantial
trauma (breakage of cells) during subcutaneous penetration.
Subsequently, the needle is withdrawn, leaving behind the sensor in
the subcutaneous tissue with minimal trauma to the patient.
Although the needle and sensor insertion does not always completely
eliminate dip and recover, a substantial reduction in the
likelihood of the dip and recover failure mode on day one of sensor
implantation was observed.
[0059] In some embodiments, the needle is specifically designed
with three sometimes competing design criteria: 1) to pierce the
skin, 2) to push through, but not pierce, the cells and tissues
within the subcutaneous space, and 3) to be removable from the host
without causing discernible tissue trauma during the removal
process. Needle removal leaves the sensor in place to function
without substantial interference resulting from wound healing as
seen in prior art devices. Other embodiments are also disclosed
with configurations that help to mediate or address the dip and
recover phenomena. It should be noted that although reduction of
dip and recover occurrences to less than 5% or even 1% is desired,
there are other advantages of the embodiments. Reduced wound trauma
and increased comfort is generally desired from a healing and
patient safety standpoint.
[0060] The needle designs described herein may also extend the
functional life of the sensor. Typically, after sensor insertion, a
foreign body response from the body is triggered which typically
eventually results in encapsulation of the inserted object (e.g.,
an inserted sensor) and biofouling of certain components (e.g., the
membrane) of the inserted object. As more and more amounts of
biomaterial (e.g., proteins) accumulates through encapsulation
and/or biofouling, diffusion of the analyte being measured (e.g.,
glucose) from interstitial fluid through the sensor's membrane
becomes reduced, less and less amounts of analyte are able diffuse
through the membrane, thereby reducing the sensor's
functionality.
[0061] While not wishing to be bound by theory, it is believed that
with a needle design that minimizes tissue trauma during the sensor
insertion process, it may be possible to achieve a delay in the
foreign body response and/or a foreign body response that is less
severe, as compared to one with a conventional needle. In turn, by
achieving a delay and/or a reduced severity in the foreign body
response, the life of the sensor can be extended, as compared to
sensors inserted with a conventional needle.
[0062] With somewhat more specificity for some method embodiments,
the needle is designed to operate in three phases.
[0063] In phase one, the cutting edge (a first zone) of the needle
is designed to cut through the tough part of the skin/dermis only,
not into the subcutaneous tissue. The needle includes a
cutting-edge size and shape design, which, in combination with an
insertion force provided by the system, allows the tip to pierce
the skin to a predetermined depth, while minimizing further cutting
into the soft tissue in the subcutaneous layer.
[0064] In phase two, a portion of the needle is designed with a
non-cutting or blunt surface (a second zone), which pushes through
the subcutaneous tissue, minimizing trauma to, or minimizing the
cutting of, surrounding soft tissue. The system is configured in
such a way that during the second phase of needle insertion, post
skin-piercing, the blunt/non-cutting portion of the needle advances
through the subcutaneous tissue, while the cutting surface of the
needle is substantially prevented from cutting through subcutaneous
tissue. The first sharp zone therefore creates the hole with the
initial penetration and the next layer of tissue is dilated by the
second, non-cutting zone with little further trauma.
[0065] In phase three, the needle is retracted to leave the sensor
in the patient. The needle design may allow the sensor to be
retained in the needle during two phases of needle insertion:
cutting and blunt pushing. At the same time, the needle may still
be easily released (without damaging sensor), leaving the sensor in
the tissue when needle is retracted. For example, the needle may be
designed such that sensor release is independent of the piercing
function by spacing or recessing the sensor from the distal cutting
tip of the needle.
[0066] The above--and below--described aspects and embodiments,
depending upon their configuration, can have advantages over prior
art needle designs--including, for example, reduction in the
occurrence of "dip and recover" events. Prior art needle designs
have extended cutting surfaces that continue cutting through the
subcutaneous tissue after piercing the relatively thick outer
dermis layer. This is believed to cause tissue trauma (such as
breakage of cells) around the sensor. Without being bound by
theory, it is believed that this trauma interferes with sensor
function. In particular, it is believed that cutting through the
subcutaneous tissue with the same cutting surface used to pierce
the skin can cause trauma to the sensor insertion site, which in
turn can affect sensor function. As observed by signal suppression,
this typically occurs during the first 2-24 hours after needle
insertion.
[0067] Prior art sensor deployment needles also include a centrally
located lumen to allow the sensor to extend out of one end of the
needle. A drawback of this design is that the cutting surfaces
typically need to extend around the centrally located lumen to
protect the sensor. Again, as described above, these cutting
surfaces may cause excess damage at the insertion site.
[0068] As shown in FIG. 1, a needle 10 includes a wall structure
12, a cutting edge 14 and a blunt contour 16. The needle 10
advantageously can be used to deliver a sensor 18 (such as an
analyte sensor, for example, a glucose sensor) through an outer
skin layer and into a sensor depth in a less invasive way than when
performed by prior art needles. In the needle design, the size of
the cutting edge 14 is balanced against a portion of the distal
wall structure 12 that has blunt contours 16. Thus, the needle 10
is capable of cutting the more durable outer skin layer (first
phase) and then progressively widening open the cut for further
advancement into the subcutaneous layer (second phase) with minimal
tissue trauma. When the needle is sufficiently advanced with the
sensor therein, the needle and the sensor are then detached, and
the needle is retracted leaving the sensor 18 in a desired
position. Early testing has shown a reduction of "dip and recover"
incidents (and reduction in average duration of an incident) with
glucose sensors delivered using the needles described herein.
[0069] The term "needle" as used herein should be construed to
cover any delivery device that can contain the sensor 18 for
delivery to the appropriate depth. The "needle" can have any of a
variety of shapes with regard to its wall structure 12. For
example, the wall shape can be cylindrical with a circular
cross-section or can have a V-shaped, square or rectangular, or
even some irregular, cross-section. The wall shape also need not be
an extruded shape with the same cross-section along its axis. For
example, the wall shape may start as a cylindrical tube with a
circular cross-section at a proximal end and then change to a
V-shape (in cross section) as it approaches the distal end. The
wall shape may also have defined along its length slots or various
openings--such as a slot that gives it a C-shape in cross-section.
(The open cross-section of the C or V-shapes affords clearance for
attachment of wiring, for example.)
[0070] Generally, however, the wall structure 12 defines some inner
(relative to some outer surface of the wall) dimension (width or
diameter for example) that supports or contains the sensor 18 for
subcutaneous delivery. For example, in a V-shaped cross-section,
the inner part of the V near its base has a diameter that is
occupied by the sensor lodged between the two inner wall surfaces.
Thus, the "dimension" is defined by the position that the sensor
occupies (or would occupy) during delivery in or on the needle wall
structure 12. The term "needle" also covers other devices (with
different names) that share similar wall structures and functions
(e.g., delivery of an implantable device), such as, for example, a
tube, channel, cannula, catheter or blunt dilator with a recess or
opening for deployment of an implantable device (e.g., a
sensor).
[0071] The wall structure 12 of the needle 10 has, in the
embodiment of FIG. 1, a tubular shape defining a central opening 22
with a central axis 20. The wall structure 12 is formed from a tube
by bending, machining and polishing as shown generally by FIGS.
3-5. The proximal end of the wall structure 12 retains its stock
tubular shape and has, for example, an outside diameter of 0.018
plus 0.001 or minus 0.0005 inches. Preferably, the inside diameter
is an inner dimension sized to contain a cross-section of the
sensor 18 for its delivery. The sensor 18 has a smaller cross
sectional diameter than the diameter of the central opening 22. The
size and shape of the central opening 22 may vary though according
to the size and shape of the sensor 18 being delivered. As noted
above, the needle 10 may have a wall structure 12 with a shape that
varies axially and in cross-section. For example, the wall
structure cross-section could have a rectangular, C-shape or
V-shape, as will be discussed in more detail below.
[0072] In some embodiments, the outer diameter of the wall
structure 12 at the proximal end, for example, may be about 0.0135
plus 0.001 or minus 0.0002 inches. The outer diameter and thickness
of the wall structure 12 reflects a balance of columnar stiffness
and minimization of the wound size for clearance of the needle
through the patient's skin. In certain embodiments, the diameter of
the wall structure 12 is minimized, but not to the point where the
needle 10 is susceptible to buckling under the expected axial load
from needle insertion.
[0073] In one aspect, the wall structure 12 has a length configured
to retain and protect the sensor 16. In the case of one type of
subcutaneously delivered glucose sensor, for example, the wall
structure 12 has a length of about 2.31.+-.0.02 inches.
[0074] The strength of the wall structure 12 (e.g., column
strength) is determined in part by its material composition. A
range of materials can be used, for example, steel (e.g., stainless
steel), ceramics, titanium, tantalum, nickel, nickel-titanium,
iridium, silver, palladium, platinum-iridium, iridium, ceramics,
composites, and combinations or alloys thereof, and/or the like.
Polymers that may be used include, but are not limited to,
polycarbonate, polymethacrylic acid, ethylene vinyl acetate,
polyesters, fluoropolymers including polytetrafluorethylene
(TEFLON.RTM.), polyethylene, polypropylene, high density
polyethylene, nylons, polyethylene terephthalate, and polyesters,
combinations thereof, and the like. Stiffer materials like
stainless steel (SS304 with a full hard temper) can store more
deformation energy and have a higher modulus (190-203 GPa Young's
modulus) and elastic limit (205-310 MPa) than many other materials
and thus have good stiffness and resistance to buckling and
permanent (plastic) deformation. This helps to keep the shape of
the needle (and its ability to deliver the sensor) through
penetration of the skin to the sensor depth. Also, steel has the
advantage that it can be machined (formed, filed, ground, etc.) to
create a sharper edge than many other materials. Further, steel
tends to hold its edge well--the aforementioned modulus and energy
storage capability keep the edge sharp through its use.
[0075] The insertion force and buckling strength of the needle 10
has been determined. The needle 10 is inserted at 45 degrees into
10N Syndaver at 1 in/min. Peak insertion force was measured using a
10N load cell. Insertion forces were measured for 8 attempts at an
average of 0.22b lbf with a minimum of 0.156 lbf and a maximum of
0.298 lbf and a standard deviation of 0.0505. Insertion forces were
also measured for conventional needles and averaged 0.191 lbf with
a range of 0.163 lbf and 0.237 lbf and a standard deviation of
0.0239.
[0076] Buckling strength was tested by compressing the needle 10
against a non-pierceable (metal plate) and measuring the axial
force required to buckle the needle using the 10N load cell. The
buckling strength of the needle 10 was (for 8 samples) 2.505 lbf on
average with a minimum of 2.185 lbf and a maximum of 2.280 lbf and
a standard deviation of 0.2189. For conventional needles, 2.458 lbf
on average with a minimum of 2.158 lbf and a maximum of 2.755 lbf
was measured.
[0077] The ratios of buckling strength as a ratio to insertion
force ranged from about 7.3 to 14.6 times the insertion force.
Thus, the needle 10 is capable of withstanding buckling even with
presentation of some relatively high percentage of blunt contour
for dilation of the skin opening.
[0078] The "central axis" is a reference point for an amount and
positioning of the cutting edge 14 and blunt contours relative to
the proximal portion of the sensor 16 (or where the sensor would be
if it were within the needle 10). For example, the central axis of
the wall structure 12 in the implementation of FIG. 1 is defined by
the unbent proximal end of the wall structure. Namely, the center,
elongate axis of the proximal unbent tube of the wall
structure--shown by the intermittently dashed line--is the central
axis 20.
[0079] The central axis 20 is not limited to a linear shape.
Generally, the central axis will be defined by a line through a
series of points wherein the points are the centroids of a series
of cross-sectional slices of the proximal end of the sensor 18.
Thus, as the path of the sensor 18 bends or curves, the central
axis 20 will follow. (The "centroid" is an average position of all
of the points in a shape. For a cylindrical sensor it is the center
of the circular cross-section. However, the sensor need not have
any particular cross-sectional shape to define a central axis--even
an irregular cross-sectional shape has a centroid.) Generally,
then, the central axis defines a central location of the composite
pathway of the sensor 18 proximal the edges and blunt contours as a
reference point for the positioning of the edges and blunt contours
14, 16.
[0080] The central opening 22 is an opening in the center defined
by a closed boundary wall structure--such as the one defined by the
tubular portion of the needle 10 wall structure 12 in FIG. 1. The
central opening 22 is an opening that is configured to receive
(through sizing, finishing, etc.) the major dimensions (e.g.,
diameter or width) of the sensor 18 to be delivered.
[0081] Referring back to FIGS. 1, 2 and 6, the distal end of the
wall structure 12 has formed thereon the cutting edge 14 and blunt
contours 16. The blunt contours 16 may include a bend 30 in the
wall structure 12 of the needle 10. The bend 30 is formed in the
tubing used to create the wall structure 12, as shown in FIG. 3,
prior to application of the bevels and cutting edge 14. The bend
angle can range from about 5 degrees, in increments of one degree,
to about 30 degrees for the cutting edge 14 configurations with
primary bevel angles ranging from 3 to 12 degrees and (optionally)
secondary bevel angles of 8 to 24 degrees.
[0082] The bend may be any of a variety of angles depending on the
desired angle of entry of the tip of the cutting edge. Preferably,
the bevel angle of the cutting edge 14 is balanced to the amount of
blunt contour 16 seen by the skin as it is penetrated. The amount
of blunt contour and cutting edge "seen" by the skin for example is
the projected area occupied by the blunt contour and cutting edge
when viewed along the central axis 20. (This captures a measure of
what proportion of the blunt and cutting edges impacts the skin as
the needle is advanced along the central axis line.) The blunt
surface area is the amount of area occupied by the blunt contours
of the needle from this view and the cutting surface area is the
amount of surface area positioned opposite the blunt contours
starting with the cutting edge, again as viewed along the central
axis 20.
[0083] Generally, a design with a greater bend (and a larger blunt
contour area seen at the insertion site) is more advantageous for
reducing wound size. However, the extent of the bend (and size of
the blunt contour seen at the insertion site) is limited by the
need for some aspect of the cutting edge 14 to be positioned to
penetrate the skin surface and form a hole large enough for
expansion of the hole without further tearing. Thus the bevel angle
or other angle of the cutting edge 14 relative to the central axis
balances the amount of bend 30's angle.
[0084] Lubricants or other materials may be added into the lumen of
the needle 10 to facilitate sensor withdrawal. For example, silane,
silicone, parylene or other material with a low coefficient of
friction may be added to the luminal surface of the needle. Coating
the lumen walls with lubricious fluid improves the ease of release
of the sensor without damaging the sensor membrane or otherwise
inhibiting sensor operation.
[0085] The cutting edge 14 may include several sharpened edges or
portions thereof in composite or a single planar facet forming a
single sharpened edge. In any case, the cutting edge 14 in the
embodiment of FIGS. 1 and 2 is formed on a set of beveled
surfaces.
[0086] The beveled surfaces may include a primary or proximal bevel
24 and a pair of secondary or distal bevels 26, as shown in FIG. 2.
The primary bevel, as shown in FIG. 1, may extend at about a 7
degree angle relative to a line paralleling the central axis and
extending from the outer surface of the wall structure 12 on the
proximal, unbent end of the wall structure. The primary bevel could
be at any of a variety of angles depending upon the desired
proportion and orientation of forward facing cutting edge 14 and
blunt contours 16. For example, the primary bevel 24 could be
within a range of about 3 degrees to about 12 degrees, depending
upon the amount of upstream bend in the wall structure 12.
[0087] In one implementation, the cutting edge 14 could be defined
on a single, primary bevel 24 having an angle in the angle ranges
described above, such as the angle shown in FIG. 4. (FIG. 4 is an
intermediate stage in the process of manufacturing the needle 10 in
FIG. 5, but represents where a single-bevel embodiment would stop
for sharpening.) The distal edges of this primary bevel 24 could
then be sharpened to form the cutting edge 14 sized in some desired
proportion to polished edges and blunt contours to create the
desired two-phase cutting and dilation that reduces invasiveness
and dip and recover. (A more detailed description of how the blunt
dissection and cutting surfaces are balanced in their proportions
is described above and below in more detail.)
[0088] In certain embodiments, such as the one illustrated FIGS. 1,
2 and 5-8, two additional secondary or distal bevels 26 are formed
on the distal tip of the wall structure 12 on the opposite side of
the wall structure from the bend 30. (FIGS. 3 and 4 show the
embodiment of FIG. 5 being formed from stock tubing.) Relative to
the same reference point, the bevels 26 are angled at about 12.4
degrees, as shown in FIG. 1. The two distal bevels 26 may also
define an angle between their proximal edges, as shown in FIGS. 35
and 36. FIG. 35 shows an angle between the proximal bevel edges of
120 degrees. FIG. 36 shows an angle between the proximal bevel
edges of 20 degrees.
[0089] The secondary bevels 26 may be varied in their angle from
the outer surface line. However, a range of about 8 to 24 degrees
balances the proportion of cutting edges 14 and blunt contours 16
for wound reduction. In yet another embodiment, shown in FIG. 20,
the needle has a 17 degree bend 30, 7 degree primary bevel 24 and
16 degree secondary bevel 26.
[0090] In FIG. 2, the distance between the proximal most-tip of the
beveled surfaces (along the central axis 20) to the distal-most tip
of the beveled surfaces is 0.05.+-.0.01 inches. The distance
between the proximal most point of the secondary bevels 16 and the
distal-most tip of the secondary bevels 16 is 0.03.+-.0.006
inches.
[0091] Although the set of bevels 24, 26 form several axially
oriented edges on the distal end of the wall structure 12, not all
of those edges are necessarily sharpened. Instead, the cutting edge
14 is formed only on more distal portions of the secondary bevels
26. In particular, for example, on FIG. 7 a circle centered on the
central axis is shown circumscribed about a bottom edge of the
proximal wall structure 12 and extending over the bevels. In this
implementation, only the portion of the bevels within the circle
are sharpened. Those bevels outside the circle are rounded.
[0092] In the illustrated embodiment of FIG. 7, the circle has a
diameter of 0.018 inches--the same diameter of the tube used to
form the wall structure 12. The sharpened portion of the bevels 26
extends only to the edge of that circle as it maps onto the
secondary bevels 26. Although having the advantage of matching up
with the proximal cross-section of the wall structure 12, the
sharpened portions can be expanded or reduced based on desired
wound size, sensor characteristics, patient variation, etc.
[0093] The remainder of the edges of the bevels 24, 26 may be
rounded into smoothed, non-cutting edges having about 2 to 3
thousandths of an inch radius or greater. For example, the heel and
other edges of the primary bevel 24 may be blasted with media to
smooth them. Blasting the heel of the bevel (the proximal, inner
edge defining the central opening 22) may smooth it to reduce or
eliminate coring, which occurs when the skin is picked up during
needle 10 insertion (also sometimes referred to as "coring").
[0094] As shown in FIG. 7, in some embodiments, the needle design
10 balances the cutting edge 14 and blunt contours 16 to promote
the two-phase cutting and dilation process of sensor 18 insertion.
Various metrics can be used to define and describe the balance in
the needle design between cutting edge 14 and blunt contour 15. For
example, as shown in FIG. 7, in one embodiment, the cutting edge 14
only occupies about 60 degrees (33%) of the 180 degrees of the
outer peripheral edge of the bevels 24, 26. Generally, the smaller
the proportion of the edges of the bevels 24, 26 that are sharpened
to the edges that are unsharpened, the smaller the initial wound
before dilation. Variations are possible from 50% of the total edge
being sharpened down to 20% in increments of 5%.
[0095] In one embodiment, the bend 30 advantageously repositions or
offsets the leading point (and initial contacting cutting feature)
of a conventional needle to the opposite side of the circular
cross-section by 0.0112 inches, as shown by comparison of FIGS. 8
and 9. Thus, the offset of the point pushes it over (0.002 inches,
as shown in FIG. 7) the central axis 20. For example, the point is
about 62% of the way across the diameter to the opposite side of
the circumscribed circle. In this manner, the central axis 20 (as
it would for any offset of greater than 50% of the diameter or
other relevant dimension associated with the position of the
sensor) passes through the blunt contour 16 rather than above the
cutting edge 14.
[0096] It should be noted, however, that an advantage of presenting
a blunt contour 16 starts with any sized bend 30 (or other
structure or modification) that moves the point and other cutting
edges 14 within the outermost periphery of the circumscribed wall
structure 12. Offsetting the cutting edge away from the outermost
periphery and closer to (or past) the central axis than the
adjacent outer edge by even 1% therefore results in some benefit of
reduced invasiveness. Such positioning presents a blunt contour to
the skin during insertion of the needle. Generally, the further the
positioning across the dimension of the needle 10, the larger the
proportion of the area presented to the skin that is made up by a
blunt contour (versus cutting edge). For example, in some
embodiments, the cutting edge can be repositioned across the
dimension from about 5% to about 65% of the dimension in intervals
of 5%. At the same time, some amount of cutting edge must be
presented or no initial opening in the skin will be formed large
enough to be dilated without tearing by the blunt dissection--hence
the concept of "balance" between cutting and blunt dissection
described above.
[0097] Although sometimes referred to as a diameter for the
purposes of the round tubing used for wall structure 12 in the
illustrated embodiments, the relevant "dimension" is any major
dimension across the portion of the wall structure 12--or "cross
dimension"--configured to hold the sensor.
[0098] Another metric that can be used to characterize the
proportion of cutting edge 14 to blunt contour 16 is the projected
area dedicated to blunt contours 16 projected along from a
perspective viewed along the central axis 20. For example, as shown
in a view along the central axis in FIG. 7, about 2/3 of the area
of the circle circumscribing the outer edge of the rounded wall
structure 12 is dedicated to blunt contour 16.
[0099] The various degrees of bend and bevel angles disclosed
herein are not arbitrary. Rather, they impact wound size (and
consequently dip-and-recover and other foreign body responses) and
sensor deployment amongst other things. For example, FIGS. 25-33
and Table 1 below show variations in the bend angle and bevel
angles and the impact on the ratio of blunt area (in grey) to
cutting area (cross-hatched). Ratios run from as low as 0.85 for
FIG. 27--where the blunt area is smaller than the cutting area--to
as high as 2.74 times as much blunt area as cutting area for FIG.
31. Notably, there is an interplay between the bend angle and the
bevel angles that determines the ultimate proportion. If a lower
bend angle is used, then it restricts the amount of primary bevel
angle before the blunt area drops dramatically and may not reduce
wound formation. Eventually, the blunt area is so small as to
approach that of the conventional needle shown in FIG. 34.
Similarly, if a high bend angle is used, the cutting edge may not
be sufficient to pierce the dermis layer during the initial cutting
phase. The bend in the needle can also be limited by other
constraints. If the bend is too severe, then the sensor could get
stuck in the lumen of the needle and may not deploy. Or, the sensor
may be damaged when it is deployed.
TABLE-US-00001 TABLE 1 Cutting Blunt Ratio Bend Primary Secondary
Surface Surface (Blunt SA/ Angle Bevel Bevel Area Area Cutting FIG.
(.degree.) (.degree.) (.degree.) (In{circumflex over ( )}2)
(In{circumflex over ( )}2) SA) 25 10 5 12 0.000096 0.000188 1.96 26
10 7 12 0.000122 0.000151 1.24 27 10 9 12 0.000143 0.000121 0.85 28
17 5 12 0.000079 0.000206 2.61 29 17 7 12 0.000104 0.000168 1.62 30
17 9 12 0.000126 0.000136 1.08 31 20 5 12 0.000076 0.000208 2.74 32
20 7 12 0.000101 0.000171 1.69 33 20 9 12 0.000124 0.000138
1.11
[0100] The relationship of the ratio (blunt surface area/cutting
surface area) versus needle bend and primary bevel angle can be
defined by an equation: Ratio (BSA/CSA)=0.1895+0.2266*(Bend
Angle)-0.004952*(Bend Angle).sup.2 for a primary bevel angle of 5
degrees. The constants change with each of the primary bevel angle
changes. Ratio=0.171+0.1379*Bend Angle)-0.003095*(Bend Angle).sup.2
for a primary bevel angle of 7 degrees. Ratio=0.1329+0.09457*Bend
Angle)-0.002286*(Bend Angle).sup.2 for a primary bevel angle of 9
degrees. The changing constants can be determined via curve fit to
the data above in Table 1 for different bevel angles.
[0101] Preliminary experiments have been conducted to evaluate the
embodiments of FIGS. 1-7 with some favorable findings. Conventional
needles and the above-disclosed needles were fed through clear
silicone material and then removed. Testing was performed to track
the needle's path and determine the cross-sectional area of the of
the initial wound opening (at the surface). Dye was injected in the
simulated wound to measure the volume. The needle tracks in FIG. 10
and FIG. 11 were created by the needle of FIG. 8 and the
conventional needle of FIG. 9. Notably, the proximal ends of the
needles are the same--with the same cylindrical wall shape and
diameter. Only the distal end differs, starting at the bend 30
(e.g., as shown in FIG. 8) while the conventional needle (e.g., as
shown in FIG. 9) continues through to its distal tip with no bend
or repositioning of the leading cutting edge.
[0102] The needles were inserted into approximately 0.020 inch TPE
material at 1 inch/minute using an INSTRON materials testing
machine. The needle cuts were measured using a Keyence microscope.
Notably, the conventional needle made a triangular shaped opening
at the surface of the TPE while the (exemplary) needle made a slit.
Further qualitatively, FIG. 10 shows the conventional needle track
on the left which is larger in cross-section than the needle track
on the right. FIG. 11 again illustrates how one disclosed needle
design that balances the blunt contours 16 with the cutting edge 14
and reduces the degree of tissue trauma caused along the track (on
the right) by needle insertion in comparison to the conventional
needle track (on the left).
[0103] FIG. 12 shows a table comparing the wound diameter
(microns), wound length (microns) and wound volume (square microns)
created by the needle insertion for the best and worst performing
measurements on 5 samples of each needle. The conventional needles
left entry wounds having larger diameters at the surface of the
TPE--for example 47.5 and 81 micrometers compared 34.3 and 45
micrometers respectively. Wound volumes were measured by creating
3D models from the images. The wound volumes in these examples were
reduced about 49% and 69% using a needle 10 with a 17 degree bend
angle and 7 degree primary bevel and 12.4 degree secondary bevel.
Wound volume improvements could also be less depending upon the
balance of blunt to cutting areas, such as a 15% or 35%
reduction.
[0104] Early animal tests were performed using live porcine
specimens with conventional needles next to needles with 10 degree
bend angles and other design characteristics disclosed herein.
Sixty percent of the glucose measurements with the needle showed
some reduction in dip and recover characteristics compared to the
conventional needle adjacent on the same animal.
[0105] FIGS. 3-5 illustrate in part how the needle 10 is
manufactured. Stock tubing is first bent to a predetermined angle
(e.g., about 10 or 17 degrees) to form the bend 30 in wall
structure 12. The primary bevel 24 is then ground or machined to
the first desired angle. Then, the secondary bevels 26 are ground
to the second desired angle. Non-cutting edges are blasted with
material to round them out and remove burrs. The cutting edges 14,
if necessary, are either present from the grinding or generated by
further sharpening on the axially directed bevel edges.
[0106] Referring now to FIGS. 16-17, the needle 10 may be designed
with slot 34 (or slots). These slots may facilitate delivery or
removal of the sensor 18, or aid in reducing wound trauma. FIGS. 16
and 17, for example, illustrate slot 34 formed as a window near the
distal end of the wall structure 12 of the needle 10. The slot 34
is formed by cutting a portion (e.g., about half of the
circumference of the tubular wall structure) away and having ramped
or rounded (radius about 0.5 to about 1 inches) walls near the
proximal and distal ends for a smooth transition. In the particular
embodiment shown, the distal edge of the slot 34 is about 0.8 mm
from the end of the wall structure 12 beginning at the primary
bevel 24. The slot 34 is about 3 mm long. Advantageously, the
sensor (shown in dashed lines) can be inserted through the slot 34
into the distal-most, closed section of the wall structure 12,
allowing it to be more easily freed for delivery. It is
contemplated that the dimensions corresponding to the embodiment
illustrated in FIGS. 16 and 17 can be different depending at least
in part on the dimensions of the sensor to be inserted.
[0107] FIGS. 18-19 illustrate a needle with a slot 34 that extends
to the distal end of the needle 10. In one embodiment, the proximal
closed portion of the needle wall structure 12 is about 8 mm and
the slot extends along 6 mm of the end of the wall structure.
Viewed along the central axis, the slot 34 forms a C-shape at the
distal end of the needle.
[0108] Sensor delivery systems that employ a needle without a slot
are typically unable to deliver a pre-connected sensor (i.e., a
sensor connected to sensor electronics prior to sensor insertion).
With these systems, electrical connection between the sensor and
the sensor electronics occurs after the sensor has been inserted
and often after the needle has been retracted. In some embodiments,
such as the embodiment illustrated in FIGS. 18 and 19, a slot 34
facilitates removal of the needle from a pre-connected sensor which
may be designed to connect to sensor electronics through an
electrical wire that extends through the slot prior to and during
sensor insertion. After sensor insertion, the slot 34 allows for
removal of the needle from the sensor 18 without disturbing the
electrical connection which was already established prior to
insertion.
[0109] In short, the C-shape or V-shape or other shape formed by a
slot 34 extending through the distal end of the needle 10 may
provide for delivery of pre-connected sensors 18. The wires from
the sensor can extend through the slot 34 while the rest of the
sensor is held within the opening 22. More than one slot could be
used, such as for several electrical connectors. In addition, the
slots may vary in size, shape and positioning depending upon the
desired use and/or reduction of invasiveness.
[0110] The windows and slots may be combined with the bend and
other characteristics of the needles illustrated in FIGS. 1-8.
[0111] An example of another slotted needle implementation is shown
in FIGS. 21-24. In particular, as shown by FIG. 24, the needle 10
at its straight, proximal portion has a U-shaped cross-section. The
wall structure 12 includes, in this cross-section, a semi-circular
bottom portion and straight arm portions extending up from the
semi-circular bottom to form the U. The spacing between the arm
portions forms a slot 34. The slot 34 is preferably sized to allow
removal of the sensor 18. In other words, the slot is wider than
the width of the sensor 18. The bend 30 in this implementation has
a 17 degree angle, the primary bevel 24 is 7 degrees and the
secondary bevel is 12 degrees. However, the bends and bevels can
vary as described elsewhere herein.
[0112] FIGS. 14-15 illustrate another embodiment of the needle 10
for delivering a coaxial sensor 18. The sensor 18 is a hollow fiber
sensor mounted on the outside of a conical tipped (pencil point)
needle. That needle is used to pierce the dermal and subdermal
layers, carrying the sensor with it, as shown in FIG. 14. The
needle 10 is then withdrawn, leaving the sensor 18 behind in the
patient. The conical tip needle has a large amount of dilation
contour and therefore reduces wound trauma and the incidence of dip
and recover.
[0113] FIG. 13 illustrates one embodiment of the manufacturing of
the sensor, starting with a polyimide hollow fiber (step 100).
Platinum or other conductive metal is deposited on the hollow
fibers, such as via sputter coating, thermal evaporation,
electroless plating, etc. (step 102). A polymeric layer is applied
using a dip coating process via dip invert and dip method (step
104). A reference coating is applied to one end (step 106). Then
the whole assembly is coated in an interference layer (step 108),
an enzyme layer is applied (step 110), and various RL/biointerface
layers are applied (step 112).
[0114] The hollow fiber need not be retained; it can be removed
from the sensor after forming. Also, rather than a full cylinder,
the sensor 18 could be only half a cylinder to make it more
flexible for tissue compliance. Use of the polymer based structural
support for the sensor 18 allows its mechanical properties to be
tuned. For long term tissue integration, the sensor 18 can have its
stiffness (Young's modulus) matched to that of the surrounding
tissue. Also, the sensor 18 structure can be designed to collapse
on itself after needle withdrawal to increase flexibility. It
should be understood that other variations of sensors may be
inserted with the needles described herein, including the sensors
described in U.S. patent application Ser. No. 12/829,296, filed
Jul. 1, 2010, issued as U.S. Pat. No. 8,828,201 and in U.S. patent
application Ser. No. 14/058,154, filed Oct. 18, 2013, issued as
U.S. Pat. No. 8,954,128, both owned by the assignee of the present
application and herein incorporated by reference in their
entireties.
[0115] Another needle may accomplish the cutting and blunt
dissection phases through uncoupling of the cutting and blunt
dissection structures. The needle includes a cutting surface that
is orthogonal to the axial direction of the needle. For example,
the cutting surface may be shaped like the helical cutting surface
on a drill bit or hand tap. Otherwise, in the linear direction the
needle is relatively blunt at its tip--such as a rounded pencil
point tip. This needle while moving in the linear direction (in and
out of the skin) will not present the cutting surface--it bluntly
dilates the tissue. However, if the needle is rotating on its
longitudinal axis, the cutting surface is presented and a hole is
created. Thus, this "drill bit" style needle can be deployed using
a mechanical system similar to an automatic or hand drill. The
mechanical system will rotate and longitudinally translate the
needle into the skin to puncture the skin surface into the
subcutaneous space of predefined distance. After this initial skin
puncture, the needle will then be pushed longitudinally deeper into
the subcutaneous space without providing cutting action.
[0116] FIGS. 37 and 38 show another embodiment of the needle 10.
The needle 10 includes a single primary bevel 24 having a 13 degree
angle for the bend 30 from the lower horizontal wall line of the
wall structure 12. The point is elevated 0.152 (plus/minus 0.051)
mm from the bottom wall line of the wall structure. The needle 10
has an inner diameter of 0.343 (plus 0.025/minus 0.013) mm and an
outer diameter of 0.457 (plus 0.025/minus 0.013) mm. The primary
bevel has a gentle curvature extending from its tip to the proximal
edge. FIG. # shows a bevel length of 1.270 (plus/minus 0.152) mm.
Shown in cross-hatch is a bead blasted (for burr removal and
anti-coring) proximal length of 0.762 (plus/minus 0.152) mm.
Advantageously, reducing the bend angle from 17 to 13 degrees
reduced the chances of sensor damage during deployment.
[0117] FIG. 39 shows another embodiment of the single-bevel needle
10 with a 13 degree bend 30, but with no gentle curve in its bevel
24. Instead, the primary bevel is straight and at about a 13.5
degree angle with respect to the top outer edge of the wall
structure 12.
[0118] FIG. 40 shows another embodiment of the needle 10 with a
single bevel 24, including a 17 degree bend angle and a 7 degree
bevel angle. The point is elevated 0.012 inches from the bottom
edge of the wall structure 12.
[0119] FIGS. 41-44 show a U-shaped needle 10 including a top slot
34 defined between arms of the U-shape. The bend 30 has a 13 degree
angle and the single primary bevel 24 has an angle of 7 degrees.
The point is elevated 0.011 inches from the bottom edge of the wall
structure 12. The needle 10 has a diameter of 0.013 (plus/minus
0.004) inches and the height of the walls (from the bottom curved
edge of the "U") is 0.017 (plus/minus 0.004) inches. The slot is
0.013 (plus/minus 0.003) inches wide between the top inner edges of
the arms. The needle 10 has a wall thickness of 0.0025 (plus/minus
0.0004) inches. The bevel has a length of 0.05 inches.
[0120] FIGS. 45-49 show tack-slotted needle 10 having slot 34
extending only partially (about 0.60 inches) along a distal length
of the wall structure 12. The needle 10 includes a 17 degree bend
30 and a 12 degree primary bevel 24. The primary bevel 24 has two
primary bevels 24 that are angled away from each other. The use of
two angled primary bevels 24 creates a slight scalloped appearance
when viewed in cross-section, toward the distal tip of the needle
10, as shown in FIG. 49. The distal length of the needle 10
starting at the bend is 0.05 inches and less than the length of the
primary bevel 24. The slot 34 is formed of an axially extending
resection of a top portion of the circular wall structure opposite
the bend 30. FIG. 49 shows the cross-section of the needle 10
having a C-shape with the arms of the C having a height of about
0.012 inches, about 0.003 inches higher than the center axis of the
needle proximal the bend.
[0121] In another embodiment, the needle (or needles) 10 described
herein can be inserted with an automatic inserter, such as the
automatic inserters (applicators) and associated structure
disclosed in U.S. Patent Application Ser. No. 62/244,520 filed Oct.
21, 2015 entitled TRANSCUTANEOUS ANALYTE SENSORS, APPLICATORS
THEREFOR, AND ASSOCIATED METHODS and Ser. No. 13/826,372 filed Mar.
14, 2013 entitled TRANSCUTANEOUS ANALYTE SENSORS, APPLICATORS
THEREFOR, AND ASSOCIATED METHODS both of which are incorporated
herein, by reference, in their entirety.
[0122] Tests were conducted to determine the amount of substrate
cut during penetration of selective needles compared to
conventional needles. The method including deploying the sensor 18
into 1/4 inch thick thermoplastic elastomer. Then, the sensor was
removed right after its deployment. The area of the cut at the
surface was then measured using a KEYENCE software and measurement
system. FIG. 50 shows the comparative results, left-to-right, of
the amount of area cut on the surface of the substrate for A)
manual insertion of a conventional (CONV) needle, 17 degree dual
bevel needle (FIG. 1), and 17 degree single bevel needle (FIG. 39);
and B) auto-insertion of a conventional (CONV) needle, 17 degree
single bevel needle (FIG. 40) and 13 degree single bevel needle
(FIG. 39).
[0123] FIG. 51 shows a table of statistical results of testing of
the six needles graphically illustrated in FIG. 50. Notably, mean
area of cut for manual insertion dropped more than 50% from 31,872
square micrometers for the conventional needle to 14,564 square
micrometers for the dual bevel needle and 11,459 for the 17 degree
single bevel needle. The mean area of cut for auto insertion also
dropped more than 50% from 43,103 square micrometers for the
conventional needle to 17,588 square micrometers for the 17 degree
single bevel needle and 16,846 square micrometers for the 13 degree
single bevel needle.
[0124] The ability of the single-bevel needles to improve the
incidence of dip and recover was assessed. FIG. 52 shows the
testing methodology for a sample subject. Sensor data measuring
mg/dl of blood glucose content was collected (continuous line, top
graph) from the sensor deployed by conventional and needles and
plotted against meter data over time. Then, the mg/dl measurements
were adjusted with a moving average and fit to an expected
sensitivity curve. A threshold for dip and recover of 80% of
expected sensitivity was applied and the dip below and return to
that threshold was defined as the duration and magnitude of the dip
and recover. (A 17% drift from stable sensitivity 48-120 hours from
insertion of the sensor 18 was assumed)
[0125] Three clinical tests (sample size greater than 30) were
conducted comparing conventional needles to various needles. As
shown by FIG. 53, dip and recover was reduced from 64.7% to 35.3%
for manual application of the dual bevel needle 10 (shown in FIG.
1) having a 17 degree bend. Dip and recover was reduced from 50% to
29.4% for manual application of the single bevel needle 10 (shown
in FIG. 39) having a 17 degree bend. Dip and recover was reduced
from 58.8% to 47.1% for insertion by auto applicator of the single
bevel needle 10 (shown in FIG. 40) having a 13 degree bend.
[0126] FIG. 54 shows another embodiment of the needle 10 wherein
the wall structure defines a proximal slot 40. The proximal slot is
scalloped into a portion of the needle on the side of the needle 10
having the point. The sensor 18 includes a kink 42 configured to
seat into the proximal slot 40 so as to maintain the orientation of
the sensor. In particular, the proximal portion of the sensor dips
down into--and optionally somewhat extending out of--the proximal
slot 40, reverses direction and continues distally into alignment
with the needle central opening 22, opposite the proximal slot.
Advantages of the proximal slot 40 include holding the sensor 18 in
a specified position until a pushrod moves it out of position.
Also, needle assembly would be facilitated by holding the sensor 18
in a desired or predictable position. Another advantage is the bend
30 of the needle 10 can be cleared by biasing the sensor 18's
distal end to the opposite side of the wall structure 12. The
sensor 18 would be less likely to run into the bend in the central
opening 22 during deployment.
[0127] While the disclosure has been illustrated and described in
detail in the drawings and foregoing description, such illustration
and description are to be considered illustrative or exemplary and
not restrictive. The disclosure is not limited to the disclosed
embodiments. Variations to the disclosed embodiments can be
understood and effected by those skilled in the art in practicing
the claimed disclosure, from a study of the drawings, the
disclosure and the appended claims.
[0128] All references cited herein are incorporated herein by
reference in their entirety. To the extent publications and patents
or patent applications incorporated by reference contradict the
disclosure contained in the specification, the specification is
intended to supersede and/or take precedence over any such
contradictory material.
[0129] Unless otherwise defined, all terms (including technical and
scientific terms) are to be given their ordinary and customary
meaning to a person of ordinary skill in the art, and are not to be
limited to a special or customized meaning unless expressly so
defined herein. It should be noted that the use of particular
terminology when describing certain features or aspects of the
disclosure should not be taken to imply that the terminology is
being re-defined herein to be restricted to include any specific
characteristics of the features or aspects of the disclosure with
which that terminology is associated. Terms and phrases used in
this application, and variations thereof, especially in the
appended claims, unless otherwise expressly stated, should be
construed as open ended as opposed to limiting. As examples of the
foregoing, the term `including` should be read to mean `including,
without limitation,` `including but not limited to,` or the like;
the term `comprising` as used herein is synonymous with
`including,` `containing,` or `characterized by,` and is inclusive
or open-ended and does not exclude additional, unrecited elements
or method steps; the term `having` should be interpreted as `having
at least;` the term `includes` should be interpreted as `includes
but is not limited to;` the term `example` is used to provide
exemplary instances of the item in discussion, not an exhaustive or
limiting list thereof; adjectives such as `known`, `normal`,
`standard`, and terms of similar meaning should not be construed as
limiting the item described to a given time period or to an item
available as of a given time, but instead should be read to
encompass known, normal, or standard technologies that may be
available or known now or at any time in the future; and use of
terms like `preferably,` `preferred,` `desired,` or `desirable,`
and words of similar meaning should not be understood as implying
that certain features are critical, essential, or even important to
the structure or function of the invention, but instead as merely
intended to highlight alternative or additional features that may
or may not be utilized in a particular embodiment of the invention.
Likewise, a group of items linked with the conjunction `and` should
not be read as requiring that each and every one of those items be
present in the grouping, but rather should be read as `and/or`
unless expressly stated otherwise. Similarly, a group of items
linked with the conjunction `or` should not be read as requiring
mutual exclusivity among that group, but rather should be read as
`and/or` unless expressly stated otherwise.
[0130] Where a range of values is provided, it is understood that
the upper and lower limit, and each intervening value between the
upper and lower limit of the range is encompassed within the
embodiments.
[0131] With respect to the use of substantially any plural and/or
singular terms herein, those having skill in the art can translate
from the plural to the singular and/or from the singular to the
plural as is appropriate to the context and/or application. The
various singular/plural permutations may be expressly set forth
herein for sake of clarity. The indefinite article "a" or "an" does
not exclude a plurality. A single processor or other unit may
fulfill the functions of several items recited in the claims. The
mere fact that certain measures are recited in mutually different
dependent claims does not indicate that a combination of these
measures cannot be used to advantage. Any reference signs in the
claims should not be construed as limiting the scope.
[0132] It will be further understood by those within the art that
if a specific number of an introduced claim recitation is intended,
such an intent will be explicitly recited in the claim, and in the
absence of such recitation no such intent is present. For example,
as an aid to understanding, the following appended claims may
contain usage of the introductory phrases "at least one" and "one
or more" to introduce claim recitations. However, the use of such
phrases should not be construed to imply that the introduction of a
claim recitation by the indefinite articles "a" or "an" limits any
particular claim containing such introduced claim recitation to
embodiments containing only one such recitation, even when the same
claim includes the introductory phrases "one or more" or "at least
one" and indefinite articles such as "a" or "an" (e.g., "a" and/or
"an" should typically be interpreted to mean "at least one" or "one
or more"); the same holds true for the use of definite articles
used to introduce claim recitations. In addition, even if a
specific number of an introduced claim recitation is explicitly
recited, those skilled in the art will recognize that such
recitation should typically be interpreted to mean at least the
recited number (e.g., the bare recitation of "two recitations,"
without other modifiers, typically means at least two recitations,
or two or more recitations). Furthermore, in those instances where
a convention analogous to "at least one of A, B, and C, etc." is
used, in general such a construction is intended in the sense one
having skill in the art would understand the convention (e.g., "a
system having at least one of A, B, and C" would include but not be
limited to systems that have A alone, B alone, C alone, A and B
together, A and C together, B and C together, and/or A, B, and C
together, etc.). In those instances where a convention analogous to
"at least one of A, B, or C, etc." is used, in general such a
construction is intended in the sense one having skill in the art
would understand the convention (e.g., "a system having at least
one of A, B, or C" would include but not be limited to systems that
have A alone, B alone, C alone, A and B together, A and C together,
B and C together, and/or A, B, and C together, etc.). It will be
further understood by those within the art that virtually any
disjunctive word and/or phrase presenting two or more alternative
terms, whether in the description, claims, or drawings, should be
understood to contemplate the possibilities of including one of the
terms, either of the terms, or both terms. For example, the phrase
"A or B" will be understood to include the possibilities of "A" or
"B" or "A and B."
[0133] All numbers expressing quantities of ingredients, reaction
conditions, and so forth used in the specification are to be
understood as being modified in all instances by the term `about.`
Accordingly, unless indicated to the contrary, the numerical
parameters set forth herein are approximations that may vary
depending upon the desired properties sought to be obtained. At the
very least, and not as an attempt to limit the application of the
doctrine of equivalents to the scope of any claims in any
application claiming priority to the present application, each
numerical parameter should be construed in light of the number of
significant digits and ordinary rounding approaches.
[0134] Furthermore, although the foregoing has been described in
some detail by way of illustrations and examples for purposes of
clarity and understanding, it is apparent to those skilled in the
art that certain changes and modifications may be practiced.
Therefore, the description and examples should not be construed as
limiting the scope of the invention to the specific embodiments and
examples described herein, but rather to also cover all
modification and alternatives coming with the true scope and spirit
of the invention.
* * * * *