U.S. patent number 3,630,198 [Application Number 04/835,560] was granted by the patent office on 1971-12-28 for catheter placement device.
Invention is credited to Melvyn L. Henkin.
United States Patent |
3,630,198 |
Henkin |
December 28, 1971 |
CATHETER PLACEMENT DEVICE
Abstract
A catheter placement device including a Teflon catheter with an
imperforate, generally hemispherical tip and two laterally opening
ports adjacent the tip, the catheter being telescoped onto a
cannula which bears against an annular internal shoulder behind the
tip and communicates with the ports. The device is gripped by
handles attached either directly to a hub on the cannula or to an
adapter releasably connected to the hub, and is inserted through a
shallow incision made with a disposable introducer formed in one
piece with a troughlike pointed shank and an integral grip which
centers the thrust of insertion on the shank. A capillary tube and
a syringe are included as alternative sensing devices for
communicating through the cannula with the ports to determine when
a change in condition occurs during placement.
Inventors: |
Henkin; Melvyn L. (Tarzana,
CA) |
Family
ID: |
25269829 |
Appl.
No.: |
04/835,560 |
Filed: |
June 23, 1969 |
Current U.S.
Class: |
604/170.01;
604/523 |
Current CPC
Class: |
A61M
25/065 (20130101) |
Current International
Class: |
A61M
25/06 (20060101); A61m 005/00 () |
Field of
Search: |
;128/215,221,348-350,347 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Trapp; L. W.
Claims
I claim as my invention:
1. A catheter placement device having, in combination:
an elongated resiliently flexible plastic catheter having an
imperforate tip at one end shaped for blunt dissection of tissue, a
central passage extending through said catheter from the opposite
end thereof to said tip, said passage terminating adjacent said tip
in a transverse end wall, and at least one laterally opening port
adjacent said tip communicating with said passage;
an elongated cannula disposed in said catheter in sliding,
telescoped relation therewith and having a transverse end surface
engaging said end wall, the other end portion of said cannula
projecting through said opposite end of the catheter;
means on said other cannula end forming a grip for said placement
device whereby said imperforate tip is pressed through tissue by a
force applied through the cannula against said transverse end wall;
and
said cannula having a longitudinal passage opening through the
transverse end surface thereof toward said end wall, and said port
in said catheter being connected to said cannula passage by means
including a connecting passage opening through the central portion
of said end wall.
2. A catheter placement device having, in combination:
an elongated catheter having an imperforate rounded tip at one end,
a longitudinal passage of preselected diameter extending through
said catheter from the end thereof opposite said tip and
terminating in a transverse end wall adjacent said tip, and a
connecting passage extending from said end wall into said tip and
opening laterally therefrom to form at least one port communicating
through said connecting passage with said longitudinal passage;
an elongated cannula having an outside diameter approximately equal
to said inside diameter, a longitudinal internal passage, and
opposite ends through which the internal passage opens, said
cannula being disposed within said catheter with a sliding fit with
one of its ends abutting against said wall and with said internal
passage communicating with said port through said connecting
passage; and
means on the other end of said cannula forming a grip for said
placement device whereby said tip is pressed through tissue by a
force applied through said cannula and said end wall while said
port remains in communication with said cannula passage.
3. A catheter placement device having, in combination:
an elongated resiliently flexible plastic catheter having an
imperforate tip at one end shaped for blunt dissection of tissue, a
central passage extending through said catheter from the opposite
end thereof to said tip, said passage terminating adjacent said tip
in a transverse end wall;
an elongated cannula disposed in said catheter in sliding,
telescoped relation therewith and having a traverse end surface
engaging said end wall, the other end portion of said cannula
projecting through said opposite end of the catheter;
means on said other cannula end forming a grip for said placement
device whereby said imperforate tip is pressed through tissue by a
force applied through the cannula against said transverse end wall;
and
two laterally opening ports formed on opposite sides of said
catheter adjacent said tip at the opposite ends of a cross-passage
through the catheter between said end wall and said tip, said
cross-passage being connected to said catheter passage by a
connecting port centrally located in said end wall to communicate
with the interior of said cannula through said end surface
thereof.
4. A catheter placement device as defined in claim 3 in which said
tip is generally hemispherical in shape and said cross-passage is
offset from the center of curvature toward said tip, said tip being
thickened longitudinally of said cross-passage to a nearly
rectangular shape to dispose said laterally opening ports in planes
extending substantially longitudinally of said catheter.
Description
BACKGROUND OF THE INVENTION
This invention relates generally to catheters and, more
particularly, to the placement of catheters in body cavities,
passageways and potential spaces for the passage of fluids through
the catheter, either the withdrawal or drainage of fluid from the
body or the administration of fluid to the body.
Heretofore, the placement of catheters typically has been
accomplished with the assistance of a sharply pointed needle for
piercing the body tissue. For some procedures, the needle itself
serves as the catheter through which fluid is passed, while in
other instances, a small-bore internal catheter has been threaded
through the bore of a needle into the body, or a larger-bore
catheter has been externally positioned on a needle for
introduction as an incident to the insertion of the needle. In the
latter type of placement units, the needle point protrudes from the
tapered leading end of the catheter to pierce the body tissue in
advance of the catheter, thereby leading the catheter through the
tissue to the selected body cavity or potential space.
Where a sharply pointed needle leads the catheter through the body
tissue into, or close to, the ultimate position of the inner end or
tip of the catheter, there is a distinct danger of inadvertent
puncturing of delicate tissue and organs disposed in the path of
the needle but beyond the intended area of penetration. For
example, for epidural anethesia, a catheter is inserted into the
spinal structure through the interspinous ligaments and the
bordering ligamentum and into the epidural space, wherein the point
of the needle is very close to the dura. If there is a very slight
misjudgment, a dural puncture can occur, with serious results for
the patient. There are many similar situations, well known to those
skilled in the art, in which the use of sharp needles in the
placement of conventional catheters involves a danger of
inadvertent and harmful punctures.
SUMMARY OF THE INVENTION
The present invention resides in a relatively simple and
inexpensive catheter placement device which eliminates the need for
a needle for leading the catheter into its final position, which
also may be forced with relative ease and control through body
tissue, and which provides a ready indication of the arrival of the
catheter at the desired position before there has been excessive
penetration. More specifically, the preferred embodiment of the
invention includes a disposable catheter that is composed of
low-friction plastic material and is telescoped over a
longitudinally stiff cannula, the catheter being formed with an
imperforate tip that covers the leading end of the cannula and is
shaped for blunt dissection of tissue. The interior of the cannula
communicates through the tip with at least one port that opens
laterally out of the catheter adjacent the tip, and the leading end
of the cannula bears against an end wall of the catheter behind the
tip. For application of the force required to drive the catheter
through the tissue to be penetrated, the trailing end of the
cannula has a hub with means enabling the user to maintain a firm
grip thereon.
To provide a prompt and reliable indication of the entry of the tip
into a body cavity, the hub of the cannula also has a seat for
attachment of a sensing device, e.g., a capillary tube or a
syringe, operable to indicate a change in fluid condition at the
tip of the catheter, and thus to signal the entry of the ported
portion of the catheter into a body cavity. The grip and sensing
device may be mounted directly on the cannula hub, or may be
mounted on a special adapter seated against the hub.
To facilitate initial insertion of the catheter through the skin
and to aid in directing it toward the body cavity, the invention
includes a novel, disposable introducer for making an incision in
the skin and guiding the placement device through the tougher outer
tissue layers into the underlying softer tissue. The introducer is
of simple construction that may be mass produced at relatively low
cost with a sharp and effective point, and has a novel grip for
more effective application of the thrust of insertion so as to
eliminate torque tending to bend the introducer during use.
Accordingly, the introducer is an easily fabricated and inexpensive
tool which is disposable after use, and yet is highly effective for
its intended purpose, as compared with prior instruments designed
for the same general purpose.
Other objects and advantages of the invention will become apparent
from the following detailed description, taken in conjunction with
the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an enlarged side elevational view of a catheter placement
device embodying the novel features of the present invention, with
part of the central portion broken away for compactness and part
shown in cross section for clarity;
FIG. 2 is an enlarged fragmentary cross-sectional view of the tip
and the adjacent portion of the device, taken substantially along
the line 2--2 of FIG. 1;
FIG. 3 is a view similar to FIG. 2 with the cannula removed;
FIG. 4 is an enlarged cross section taken along the line 4--4 of
FIG. 1;
FIG. 5 is a fragmentary perspective view illustrating the insertion
of the introducer through the skin;
FIG. 6 is a view similar to FIG. 5 with the catheter placement
device positioned for insertion along the introducer;
FIG. 7 is a fragmentary sectional view taken in a plane extending
longitudinally of the device and showing the device as it is
inserted along the introducer into a body cavity;
FIG. 8 is an exploded view similar to FIG. 7 after the introducer
and the cannula have been removed from the patient and the
catheter, respectively;
FIG. 9 is an enlarged fragmentary view, partly in cross section and
partly in side elevation, showing a modified form of the invention
with handles and a capillary tube incorporated in the hub of the
cannula;
FIG. 10 is a view similar to FIG. 9 showing a second modified form
with a detachable connector releasably coupled to the hub of the
cannula and to the barrel of a syringe for communicating through
the connector and the cannula with the tip of the catheter;
FIG. 11 is a view similar to FIG. 10 in which a capillary tube has
been applied to a detachable connector;
FIG. 12 is an enlarged perspective view of the introducer;
FIG. 13 is an end view thereof;
FIG. 14 is a side elevation thereof including a fragmentary view of
a grinding wheel for sharpening the point;
FIG. 15 is a plan view;
FIG. 16 is a plan view of a substantially flat blank prior to
bending and sharpening of the blank to form the introducer; and
FIG. 17 is an enlarged cross-sectional view taken substantially
along the line 17--17 of FIG. 16.
DETAILED DESCRIPTION
As shown in the drawings for purposes of illustration, the
invention is embodied in a device, indicated generally by the
number 10, for use in inserting an elongated, tubular catheter 11
through body tissue 12 (FIGS. 5-7) until the inner end portion or
tip 13 of the catheter is disposed within a body cavity 12.sub.a
(FIG. 7) for the eventual passage of fluid through the catheter 11
into or out of the cavity, as determined by the particular medical
treatment being provided for the patient. Examples of the use of
catheters are epidural anesthesia, in which the anesthetic is
passed through the catheter into the epidural space, paracentesis
of pericardial effusion, in which fluid around the heart is
withdrawn through a needle serving as a catheter; and cerebral
ventricular drainage, in which liquid is drained through a catheter
placed in a ventricle of the brain. There are, of course, many
other well-known uses of catheters, and including drainage of the
bladder, the chest, the abdominal cavity, and subcutaneous
wounds.
As previously mentioned, the usual practice has been to use a
sharply pointed needle to pierce or cut through the body tissue
preparatory to insertion of the somewhat flexible catheter through
the tissue, whether the catheter is carried on the outside of the
needle to be left in place after the needle is withdrawn, or is
small enough to be threaded through the needle into place prior to
withdrawal of the needle over the catheter. In some instances, a
pointed, hollow needle is used not only to pierce the tissue but
also to draw fluid from the body cavity. Where the catheter is
externally disposed, it is desirable to use a catheter that is
either composed of or coated with a low-friction material like
tetrafluoroethylene, obtained commercially under the trademark
Teflon of E. I. duPont de Nemours Co., Inc.
In any event, safe placement of a catheter is a body cavity in a
conventional manner with a pointed needle that cuts through the
tissue, requires very careful handling of the needle to avoid
penetration to an excessive depth, beyond the desired end point for
the catheter. The sharp point of such a needle passes through the
body tissue so quickly and smoothly as to give virtually no
indication of the type of tissue being penetrated, and thus can
pass through the wall of a cavity and puncture delicate tissues
beyond the wall before the user realizes the point of the needle
has entered the cavity.
In accordance with a primary aspect of the present invention, the
catheter 11 is formed with an imperforate tip 13 shaped for blunt
dissection of tissue, and is telescoped slidably onto a
longitudinally stiff cannula 14 which has a leading end 15 for
pressing against an inside abutment surface 17 behind, and closely
adjacent, the catheter tip 13, to drive the latter through the body
tissue. At least one port 18 opens laterally out of the catheter
adjacent the tip and communicates reliably with the interior 19 of
the cannula when the latter is in the catheter. A hub 20 is
provided on the outer or trailing end of the cannula with means
thereon for applying the inserting force to the cannula, and thus
to the tip of the catheter, and also for attachment of an
appropriate sensing device or indicator communicating through the
cannula with the port or ports adjacent the tip of the
catheter.
With this arrangement, the resiliently flexible catheter 11 is
driven through the body tissue by the force applied through the
cannula 14 to the abutment surface 17 immediately behind the tip 13
so that the catheter sheaths the cannula, and the blunt tip of the
catheter actually leads the cannula through the tissue and into the
body cavity. Because the tip is blunt, there is sufficient
resistance to movement to provide a perceptible variation as the
tip moves into a cavity, giving the user a "feel" for the progress
of the tip, and the blunt catheter penetrates the tissue
atraumatically, without the cutting action that is characteristic
of a sharpened needle. In addition, no stylet is required to close
the port or ports 18 in the catheter, and the interior of the
catheter thus remains constantly open to the port or ports for
fluid passage through the catheter to the sensing device.
In the present instance, the cannula 14 is simply a flat or blunt
ended, hollow needle (see FIG. 8) having a hub 20 of basically
conventional construction at its outer or trailing end, the lower
end as viewed in FIG. 1 and the right end in FIG. 8. The interior
of the needle forms an internal passage 19 extending from the
leading end completely through the hub. When the placement device
10 is fully assembled, the catheter 11 is telescoped onto the
cannula and covers the latter from the tip to the hub, preferably
having a hub 21 on its trailing end in abutment with the leading
side 22 of the cannula hub 20.
It will be seen in FIGS. 1-4 that the catheter 11 is formed by a
relatively thin-walled tube, preferably of circular cross section,
defining an internal passage 23 which extends from the abutment
surface 17, adjacent the upper end of the catheter in FIGS. 1-3,
through the catheter to the hub 21 thereon. Through the hub, the
passage 23 communicates with a seat 24 in the side of the catheter
hub abutting against the cannula hub 20, the seat being formed in
the trailing side of the catheter hub in relation to the direction
of insertion. This seat preferably is tapered to receive a
conventional tapered fitting (not shown) for connecting an
instrument or conduit to the catheter after it is placed and the
cannula 14 has been removed.
Catheters are made in different sizes, depending upon the
requirements of the particular treatment and ranging, for example
from 1/16 of an inch outside diameter, or smaller, to 1/4 of an
inch or larger. For a general appreciation of the illustrative
embodiment, the outside diameter may be considered as being on the
order of 1/16 of an inch, thus being shown approximately full size
in FIGS. 6-8. The cannula 14 has an outside diameter selected to
fit within the catheter with a snug, sliding fit.
As shown in FIGS. 2 and 3, the tip 13 is disposed across and closes
the leading or upper end of the internal passage 23 of the
catheter, has an imperforate, outer leading side that is shaped for
the blunt dissection of tissue, and has an inner trailing side
extending transversely across the leading end of the passage 23 and
forming the abutment surface 17 for engagement with the transverse
end surface 15 of the cannula. Preferably, the leading side of the
tip is generally hemispherical, and the transverse surfaces 15 and
17 are generally perpendicular to the longitudinal axis of the
catheter.
As shown most clearly in FIG. 1, two laterally opening ports 18
herein are formed on opposite side of the catheter 11, immediately
behind the tip 13, at the opposite ends of a cross-passage 25 in
the tip, and a third port or passage 27 (FIGS. 2 and 3) extends
through the central portion of the abutment surface 17 into the
center of the cross-passage to establish communication between both
ports 18 and the internal passage 19 in the cannula 14 when the
latter is in place in the catheter. The connecting port 27 has
approximately the same diameter as the inside diameter of the
cannula, and is coaxially centered with respect to the cannula and
the catheter.
Thus, the abutment surface 17 is an annular internal shoulder
surrounding the connecting port 27 and having approximately the
same radial width as the radial wall thickness of the cannula. It
will be noted, however, that the end surface area of the cannula
has been utilized advantageously for the application of driving
force through the shoulder 17 to the tip 13, and that the cannula
and the connecting port are maintained positively in full
communication with each other without regard to any changes in the
relative angular positions of the parts.
Although the cross-passage 25 may be made concentric with the
curvature of the leading side of the catheter tip 13, the
cross-passage of the preferred form of the catheter is offset
slightly toward the leading side relative to its center of
curvature, as is most readily seen in FIGS. 2 and 3. This reduces
the amount by which the tip projects beyond the end 15 of the
cannula and correspondingly reduces any tendency the tip may have
to bend over during penetration. In addition, the width of the tip
longitudinally of the cross-passage 25 is increased slightly, as
shown in FIG. 1, to thicken the tip to an almost rectangular cross
section with rounded corners. This strengths the tip and assists in
keeping the ports 18 generally in longitudinal planes nearly
parallel to the longitudinal axis of the catheter 11.
For ease of fabrication, the body of the catheter may be a
shrinkable Teflon tube that is shrunk around a mandrel, and the tip
13 may be meltable Teflon that is fused to the end of the tube and
shaped between the mandrel and a suitable die (not shown). These
and other procedures are within the skill of the art.
It will be seen in FIG. 1 that the trailing end portion of the
catheter 11 is telescoped over a tubular flange 28 of the catheter
hub 21, and is anchored in an annular recess 29 of the hub. This is
merely an illustrative manner of attachment of the catheter to its
hub, and it will be evident that various other mountings may be
used. The catheter hub 21 simply abuts against the cannula hub 20,
and does not interlock therewith. When a nose 30 is formed on the
cannula hub as shown in FIGS. 10 and 11, this nose may fit loosely
into the tapered seat 24 of the catheter hub, but should not be
locked therein.
The means for gripping the placement device 10 and applying the
inserting force through the cannula 14 to the tip 13 of the
catheter 11 herein comprise two winglike handles 31 projecting in
opposite directions from the cannula hub 20 and rigidly secured
thereto. These handles may be grasped between the thumbs and
forefingers of two hands during placement of the catheter, and
provide for convenient application of the force required to insert
the catheter. As shown herein, the handles are the opposite end
portions of a single, elongated plate of metal or suitably rigid
plastic material that is secured to the leading end of the cannula
hub.
To facilitate the proper placement of the catheter 11 in a patient,
the invention contemplates the use of a novel disposable introducer
32 (See FIGS. 5-7) for making an initial incision through the skin
and other outer tissue layers, and guiding the catheter through
these layers into the softer inner layers of flesh. In general, the
introducer comprises an elongated troughlike shank 33 terminating
at one end in a point 34 for making the incision and having a grip
35 on the opposite end portion with which the introducer is held as
the point is pressed through the skin and into the position shown
in FIGS. 5-7.
With the introducer 32 thus inserted, the leading end portion of
the catheter placement device 10 is placed in the upwardly opening
trough or groove defined by the shank 33, and is slid along the
shank through the incision and into the patient. If desired, a
light downward movement of the introducer may be used to open the
incision slightly to admit the catheter.
Initially, the force required to move the placement device 10 will
be slight, because of the preparatory incision made with the
introducer which, it will be seen, is inserted a distance
considerably less than the full depth to which the catheter is to
be driven. After the catheter tip 13 passes the point 34 of the
introducer, the resistance to penetration increases substantially
since the tip then is forced bluntly through the imperforate
tissue.
Although the resulting resistance to penetration is perceptible, it
is not so high as to make the placement difficult, and the use of
Teflon or the like reduces the frictional drag on the catheter to a
negligible amount. Accordingly, relatively firm insertion pressure
is all that is required for the blunt dissection of underlying
tissue, and the variations in resistance in going through different
types of tissue--including muscle, fascia, ligaments and other
connective tissue, and the walls of organs such as the urinary
bladder--are not significant. The tip of the catheter is shown in
FIG. 7 as being disposed just inside the wall 37 of the body cavity
12a.
After serving its purpose of making the initial incision and
directing the catheter 11 into the patient the introducer 32 is
removed as indicated in FIG. 8. When the tip 13 of the catheter 11
has been advanced to its intended final position, the cannula 14
also is withdrawn as shown in FIG. 8, leaving the catheter ready
for connection to a syringe or other instrument for the intended
treatment.
The modified placement devices 10a, 10b and 10c partially shown in
FIGS. 9-11 illustrate various ways in which sensing devices may be
incorporated in, or connected to, the cannula of the placement
device to provide a ready indication of a change in condition at
the tip 13 of the catheter, which is not shown in these views. In
the form shown in FIG. 9, a transparent capillary tube 38 is
secured to the hub 39 of the cannula 14a with the passage 40 in the
capillary tube in communication with the interior 19a of the
cannula and, therefore, arranged for communication with the ports
18 adjacent the tip of the catheter 11, when the latter is in place
on the cannula. Handles 31 are attached to the hub 39, just as in
the first embodiment.
Accordingly, a drop 41 of liquid placed in the capillary tube 38
will remain substantially stationary as the catheter passes through
tissue, but will move in response to a pressure differential within
the tube to indicate exposure of the ports 18 either to an
increased pressure or to a reduced pressure. For example, a reduced
pressure would occur in the epidural space as a result of
deflection or "tenting" of the dura by the blunt tip 13, and this
would cause the drop 41 to move inwardly toward the tip of the
catheter. The opposite result, an outward movement, will be
obtained as the catheter tip enters as cavity filled with fluid,
either liquid or gas, under positive pressure.
It will be seen in FIG. 9 that the handles 31 are attached directly
to the hub 39 of the cannula 14a, as in the first embodiment. The
cannula 14b in the third form 10b, shown in FIG. 10, has a modified
hub 42 without any handle, but combined with an adapter 43 forming
a releasable extension of the hub and having a tapered fitting 44
as its leading end for seating releasably in a tapered socket 45 in
the hub 42. Another tapered socket 47 is formed in the trailing end
of the adapter for receiving the tapered end 48 of a syringe, only
the barrel 49 of which is shown in FIG. 10. A passage 50 in the
adapter connects the socket 47 to the socket 45 to establish
communication between the syringe barrel 49 and the bore 51 of the
cannula 14b.
In this instance, handles 52 are securely attached to the adapter
43 as the opposite end portions of an elongated plate through which
the body of the adapter extends. Accordingly, the handles are
detachable from the cannula 14 with the adapter for possible reuse
if desired.
In FIG. 11, the same concept has been applied to the placement
device 10c to incorporate handles 53 and a capillary tube 54 in an
adapter 55 similar to the adapter 43 of FIG. 10. In this case, the
capillary tube has a tapered end 57 that is seated, either
permanently or detachably, in a tapered socket 58 in the adapter,
and the adapter has a tapered fitting 59 that is releasably engaged
in a tapered seat 60 in the hub 61 of the cannula 14c. Again, this
arrangement permits removal of the adapter, including the handles
53 and the sensing device 54, from the cannula after the latter has
served its purpose.
In addition to the frictional coupling accomplished by the tapered
parts in the various embodiments, conventional, positive interlocks
may be provided on the parts for selective use in the usual manner.
In addition, other well-known features may be incorporated, as
desired, for special purposes, For example, specially shaped
sockets may be provided in the hubs or connectors for connections
to special-purpose instruments or fittings, or a so-called Foley
catheter-type balloon and inflation tube may be incorporated along
the length of the catheter in a well-known manner to aid in
retaining the catheter in a cavity. Moreover, the leading end
portion of the catheter may be trained or prestressed into a
laterally bent shape which it assumes as soon as the cannula is
withdrawn, again in a manner that is known. While the catheter has
been described as having one or two holes adjacent the tip, it will
be apparent that additional holes (not sown) may be spaced along
the catheter from the tip to be opened as the cannula is withdrawn,
thereby to reduce the change of plugging in use and to increase the
flow area where it is desirable to do so. These and other
modifications will suggest themselves readily to those skilled in
the art as being within the spirit and scope of the invention.
The novel introducer 32 is shown most clearly in FIGS. 12-17,
wherein it will be seen that the shank 33 is in the form of an
elongated channel, preferably semicircular in transverse cross
section, and that the grip 35 is formed by two finger pieces
including flaps 62 which extend both above and below the
longitudinal axis of the shank, on opposite side thereof, and have
two opposed, laterally facing holes or recesses 63 for the gripping
thumb and finger of the user. These recesses are centered on the
longitudinal axis of the shank 33, and thus align the thrust of the
user's fingers with the shank to facilitate skin penetration by,
and proper direction of, the shank, without significant danger of
bending as a result of development of torque during insertion.
Each gripping flap 62 preferably is integrally joined to an upper
longitudinal edge 64 of the shank 33, adjacent the end thereof
remote from the point 34, by an inner leg 65 extending upwardly
from the shank and connected by an outwardly and reversely curving
bend 67 to the flap 62, which extends downwardly from the bend to a
level well beyond the shank. The inner legs 65 preferably flare or
diverge upwardly to facilitate the placing of the catheter 11 into
the groove of the shank, and the flaps preferably have slightly
concave outer sides formed with somewhat elongated finger recess 63
which are centered vertically on the shank to receive the tips of
the thumb and finger of the user, as shown in FIG. 5. This assures
the alignment of the thrust with the shank and the point.
This configuration makes it possible to form the introducer 32
inexpensively from a single sheet metal stamping 68 shown in FIG.
16, beginning as a T-shaped blank with a relatively narrow strip 69
for forming the shank, joined at a right angle to the center of a
wider strip 70 for the finger pieces. The finger recesses 63 may be
depressions that are stamped into the opposite end portions of the
wider strip 70 as an incident to the initial stamping operation. As
a first shaping operation, the blank may be curved, longitudinally
of the narrow strip 69, to form the trough of the shank 33, leaving
the opposite end portions of the wide strip 70 in the planes
indicated at 71 in FIG. 13. Then the reverse bends 67 are formed
and the concavity is applied to the flaps 62 to complete the
introducer except for its point 34.
As shown in FIGS. 12, 14 and 15, the point 34 is defined
substantially on the longitudinal centerline of the shank 33 by two
arcuate, upwardly facing edges 72 curving concavely downwardly and
converging to the point. The edges 72 are substantially arcs of a
cylinder that is tangent to the bottom surface of the trough or
channel defined by the shank.
Conventional needle-pointing techniques are not practically
applicable on a mass production basis to a shank that is open sided
and, thus, effectively flat on one side. Moreover, conventional
"flat" grinding of the end of a semicylindrical shank on an angle
with the longitudinal axis of the shank will produce a generally
elliptical cutting edge rather than a point, requiring additional
shaping operations to reduce the edge to a point. As shown in FIG.
14, a grinding wheel 73 rotating about an axis 74 and having a
rounded edge 75 is passed transversely across the end of the shank
33 while the latter is held generally parallel to the axis 74 of
the wheel, and with the centerline of the shank (the bottom of the
trough) generally tangent to the arc of the rounded wheel edge 75.
Of course, a large number of introducers can be clamped in
side-by-side relation to grind points on all the shanks in a single
pass. Thus, the novel introducer may be mass produced at low enough
cost to be disposable, and yet has a sharp, effective and noncoring
point.
It will be evident that the relationship of the radius of curvature
of the rounded edge 75 will determine the sharpness of the point,
the ease of penetration, and the length of the point. In addition,
the point configuration has the advantage of tending to lift the
penetrated wall of a vessel while making a fine, slitlike incision.
Although the one-piece construction of the introducer, including
the integral grip, is preferred for economy of manufacture, it will
be apparent to those skilled in the art that the grip 35 might be
fabricated separately and attached to the shank 33.
From the foregoing, it should be evident that the present invention
provides a catheter placement device 10, and cooperating introducer
32, for safe and convenient placement of a catheter 11 in a body
cavity 12a without need for a sharp needle of the type that has
been used to lead the catheter through the body tissue, with risk
of inadvertent puncture of delicate tissue and organs of the body.
Instead, the novel and disposable introducer 32 is used simply to
open a relatively shallow and fine incision through the tougher
outer layers of tissue, and the blunt-end catheter 11 is placed in
the body through the incision, leading the stiffer cannula through
the tissue and penetrating beyond the depth of the incision by
blunt dissection of tissue.
It has been seen that this is made possible by using a low-friction
resiliently flexible material for the catheter, forming a generally
hemispherical, imperforate tip on the catheter, and applying the
inserting force immediately behind the tip with a longitudinally
stiff, blunt-ended cannula that not only forces the catheter
through the tissue into the desired location, but also communicates
constantly with at least one laterally opening port near the tip of
the catheter. Moreover, the secondary features of the several
modified forms add flexibility to the placement device with regard
to the manner of attachment of the handle and the different
representative sensing devices.
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