U.S. patent number 3,877,429 [Application Number 05/420,635] was granted by the patent office on 1975-04-15 for catheter placement device.
Invention is credited to David L. Rasumoff.
United States Patent |
3,877,429 |
Rasumoff |
April 15, 1975 |
Catheter placement device
Abstract
The invention is a flexible cannula for introducing a catheter
into a vein during a surgical cutdown procedure. The cannula
includes a hollow plastic member having aa cylindrical portion and
an integral conical portion with a truncated tip and two pairs of
longitudinal slits one of which pairs extends nearly to the
truncated tip so that the conical portion is split open when a
catheter is moved through the cannula toward its tip.
Inventors: |
Rasumoff; David L. (Woodland
Hills, CA) |
Family
ID: |
23667250 |
Appl.
No.: |
05/420,635 |
Filed: |
November 30, 1973 |
Current U.S.
Class: |
604/158;
606/108 |
Current CPC
Class: |
A61M
25/0668 (20130101) |
Current International
Class: |
A61M
25/06 (20060101); A61m 005/14 () |
Field of
Search: |
;128/214.4,221,215,343,345,DIG.16 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Truluck; Dalton L.
Attorney, Agent or Firm: Johansen; W. Edward
Claims
What I claim is:
1. A catheter placement device for introducing a catheter into a
vein of a patient during a surgical cutdown procedure,
comprising:
a hollow plastic member including a conical portion having a base
and a truncated distal end, said conical portion also including a
first set of longitudinally disposed slits extending from said base
axially along said conical portion to a point substantially
adjacent said distal end but spaced inwardly therefrom and adapted
to split thereat when a catheter is moved through said hollow
plastic member toward said distal end the unsplit portion of said
distal end initially retaining rigidity enough to dilate a
collapsed vein.
2. The catheter placement device according to claim 1, also
comprising a second set of slits in said conical portion extending
from said base to a point intermediate said distal end, and wherein
each of said sets of slits include two essentially oppositely
disposed slits.
3. The catheter placement device according to claim 1 wherein said
hollow, plastic member has a cylindrical portion coaxially
contiguous to said base of said conical portion.
4. The catheter placement device according to claim 3 wherein the
taper of said conical portion relative to said cylindrical portion
is in the range of 10.degree. to 20.degree..
5. The catheter placement device as in claim 4 wherein said first
set of slits includes two slits, and a second set of slits includes
two longitudinally disposed slits along said conical portion
extending from said base to a point intermediate to said distal end
and said base.
6. The catheter placement device according to claim 5, wherein said
device includes a tab extending from the open end of said
cylindrical portion.
7. The catheter placement device according to claim 6 wherein one
of said first set of slits extends from the base of said conical
portion to the open end of said cylindrical portion of said hollow,
plastic member.
8. The catheter placement device according to claim 1, wherein said
hollow plastic member is of polyethylene plastic material in tubing
form, said conical portion being a heated and drawn portion forming
a gradual longitudinal taper.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to improvements in a catheter placement
device, and more particularly to an intravenous catheter placement
device for introducing a catheter into a vein during a surgical
cutdown procedure.
2. Statement of the Prior Art
One prior art device for placing a catheter percutaneously is
taught by Douglas MacGregor in his U.S. Pat. No. 3,550,591,
entitled "Intravenous Catheter Unit", issued Dec. 29, 1970. This
unit provides a cannulated needle about the outer surface of the
catheter, which needle is split longitudinally such that when the
needle is removed from the patient, the needle can be peeled back,
removed from the catheter, and discarded. This unit has eliminated
the problem of protecting the catheter from the needle once the
needle is removed from the patient, but the difficulty in finding
materials stiff enough for use as a needle and still pliable enough
to be removed from the catheter as intended has been a problem.
This problem of finding such a material has been mentioned by Ralph
D. Alley and Davis S. Sheridan in their U.S. Pat. No. 3,633,579
entitled "Catheter Placement Device and Method", issued to them on
Jan. 11, 1972. Their solution to this problem is to use a flexible
cannula having a needle or stylet through the center bore thereof
with the point extending beyond the exposed end of the cannula. The
combined unit, cannula and needle, is inserted through the skin and
into the vein of a patient. The needle is then withdrawn and the
cannula permitted to maintain its position in through the skin and
into the vein of the patient. A long flexible catheter of matching
size or of a smaller diameter is then inserted into the flexible
cannula and is threaded through the cannula into the vein of the
patient an appropriate distance.
The above prior art devices are percutaneous catheter placement
units, which cannot always be used in an emergency where a
patient's vein has collapsed. In such an emergency, a doctor will
make a surgical incision or cutdown in the skin and vein so that
the distal end of a catheter can be inserted directly into the vein
and threaded a desired distance into the vein. The requisite skill
for threading a catheter into a collapsed vein is similar to that
required for sticking one's finger into a collapsed balloon, the
neck of which is comparable in its diameter to the diameter of
one's finger. Usually the doctor will insert a catheter of a
smaller diameter than that of the inner diameter of the vein. This
is not the best possible solution because the larger the catheter
is, the more vital fluids are received by the patient at the time
when he needs them.
SUMMARY OF THE INVENTION
In view of the foregoing factors and conditions characteristic of
the prior art, it is a primary object of the present invention to
provide a flexible cannula which will give sufficient structural
support to a collapsed vein during a surgical cutdown of the vein
so that the largest possible catheter may be used.
It is another object of the invention to provide a flexible cannula
which can be split longitudinally such that, after the catheter has
been placed inside the vein, it can be withdrawn easily from the
vein and removed from the catheter.
It is still another object of the invention to provide a catheter
placement device consisting of a single plastic component which is
of such simple design that it is inexpensive to fabricate.
In accordance with an embodiment of the present invention, a
catheter placement device for introducing a catheter into a vein of
a patient during a surgical cutdown procedure includes a hollow
plastic member having a conical portion with a base and a truncated
distal end, the conical portion also including a first set of
longitudinally disposed slits extending to a point substantially
adjacent to the distal end and adapted to split apart thereat when
a catheter is moved through the plastic member toward the distal
end.
The features of the present invention which are believed to be
novel are set forth with particularity in the appended claims.
Other objects and many of the attendant advantages of this
invention will be more readily appreciated as the same becomes
better understood by reference to the following detailed
description and considered in connection with the accompanying
drawing in which like reference symbols designate like parts
throughout the figures.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is a longitudinal cross-sectional view of a cannula
constructed in accordance with the principles of the invention.
FIG. 2 is a cross-sectional view taken along the lines 2--2 of FIG.
1.
FIG. 3 is a cross-sectional view taken along the lines 3--3 of FIG.
1.
FIG. 4 is a partial cross-sectional view of the cannula into which
a catheter has been inserted.
FIG. 5 is a cross-sectional view taken along the lines 5--5 of FIG.
4.
FIG. 6 is a partial cross-sectional view of the cannula through
which the catheter has passed.
FIG. 7 is a cross-sectional view taken along the lines 7--7 of FIG.
6.
FIG. 8 is a schematic drawing of the preferred embodiment as it is
being used in accordance with the principles of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Briefly, the present invention is a catheter placement device for
introducing a catheter into a vein during a surgical cutdown of the
skin and vein of a patient. The catheter placement device is a
flexible cannula which is stiff enough to provide structural
support to a collapsed vein during the introduction of a catheter
therein. The stiffness of the cannula is derived from the use of
polyethylene plastic tubing which is heated, drawn, and cooled to
form a conical section of tubing. It is the original inner diameter
of the tubing that determines the outer diameter of the catheter
which can be placed in the vein. The much narrower conical section
expands to allow the catheter to pass through it, because there is
a plurality of longitudinal slits disposed along the conical
section of the tubing. By cutting these slits, as described
hereinafter sufficient structural stiffness is retained to enable
the flexible cannula to support a collapsed vein during the
introduction of a catheter therein.
The invention can best be understood by reference to FIG. 1 wherein
a hollow, flexible cannula 10 of polyethylene plastic has a
cylindrical portion 11 of a uniform inner diameter and a conical
portion 12 coaxially contiguous to the cylindrical portion 11. The
cannula 10 has a proximal end 13 at the end of the cylindrical
portion 11. The inner and outer diameters of the cylindrical
portion 11 are shown in FIG. 2 as one looks through the flexible
cannula 10 at the proximal end 13 thereof. With reference to FIG.
3, a cross-sectional view of the cannula 10 near the middle of its
conical portion 12 shows the inner and outer diameters as one looks
through the cannula 10 toward the proximal end 13 thereof. The
cannula 10 has a distal end 15 opposite the proximal end 13 and the
conical portion 12 is truncated near the distal end 15 to provide a
narrower tip for inserting the cannula 10 into the vein.
Structural stiffness of the flexible cannula 10 is obtained by
using a polyethylene plastic tubing having a wall thickness (which
is defined to be outer diameter minus inner diameter, divided by
two) such that after it has been heated, drawn to form a gradual
longitudinal taper 16, and quenched in water, it retains a wall
thickness sufficient to withstand the compressive force placed on
the cannula 10 as it is pressed into the vein. In the prototype
model of the invention, polyethylene plastic tubing was used having
an outer diameter of one-quarter of an inch and an inner diameter
of five thirty-seconds of an inch, i.e., the tubing had a wall
thickness of three sixty-fourths of an inch.
It has been determined by the inventor that different sizes of
polyethylene plastic tubing may be used to provide catheter
placement devices for placing catheters of varying sizes. It should
also be noted that tubing of other plastic materials may be used to
form alternative embodiments of the invention. It should further be
noted that the taper 16 must be gradual enough to allow an even and
easy expansion of a collapsed vein so that the vein will not be
torn. However, if the taper 16 is too gradual then the cannula 10
will lose necessary structural stiffness. The most advantageous
result has been obtained when the taper 16 was in the range of
10.degree. to 20.degree. measured by the longitudinal slope of the
conical portion 12 of the cannula 10 relative to the cylindrical
portion 11 thereof. Although larger and smaller tapers will work,
they may not be as suitable as those in the above range.
The flexible cannula 10 has two pairs of longitudinal slits 17 and
18 disposed along its conical portion 12. One pair of slits 17,
shown in FIG. 1 extends from the base of the conical portion 12 to
a point substantially adjacent the distal end 15 of the cannula 10
(where substantially adjacent is defined to be approximately
two-tenths of a millimeter). It has been determined that the point
substantially adjacent the distal end 15 must be close enough so
that when a catheter is pushed through the cannula 10, it will
split open the first pair of slits 17.
The second pair of slits 18 is best illustrated in FIG. 4. This
pair of slits 18 extends from the base of the conical portion 12 to
about the middle of the conical portion. It has been found that by
not extending this second pair of slits 18 to the same point as the
first pair of slits 17, virtually all of the structural stiffness
that the flexible cannula 10 would have without the slits may be
maintained.
In accordance with the presently preferred embodiment of the
invention, the two pairs of slits 17 and 18, orthogonally disposed
to each other, are advantageous because they enable a catheter
having a uniform inner diameter, such as shown in FIG. 5, to slide
freely within the cylindrical portion 11 of the cannula 10 and to
still be able to be pushed easily through the conical portion 12
thereof. Referring again to FIG. 4, one can see that as the
catheter is pushed forward into the conical portion 12 of the
cannula 10 the pairs 17 and 18 of slits enable the wall 19 of the
cannula 10 to expand.
It has been found that only the first pair of slits 17 is required
for the advantageous operation of the invention, however, the
second pair of slits 18 increases the effectiveness of the
invention because the catheter may be more evenly and easily
threaded into the vein.
Referring now to FIG. 6, the catheter has split open the cannula 10
by breaking apart the first pair of longitudinal slits 17 and has
pushed through into the vein. The catheter has the same outer
diameter in the vein as it does in the cylindrical portion 11 of
the cannula 10 as shown in FIG. 7.
Referring now to FIG. 8, the presently preferred embodiment of the
invention also has a tab 20 contiguous to the proximal end 13
thereof which a doctor grasps in order to withdraw the cannula 10
from the patient's vein. The tab 20 is not a necessary feature of
the invention, but it is very useful in removing the cannula 10
from the vein. The inclusion of the tab 20 allows the doctor
holding the catheter in place with one hand to withdraw the cannula
10 by grasping the tab 20 in his other hand and pulling the cannula
10 out of the vein. It is advantageous that the doctor need not
change his hands in order to withdraw the cannula 10 because it is
awkward to do so.
One slit 21 of the pair of longitudinal slits 17 may advantageously
be extended to the proximal end 13 of the cannula 10 so that the
cannula 10 can be forced apart and removed from the catheter after
it has been withdrawn from the vein.
Referring again to FIG. 8, after a surgical cutdown of the skin and
vein of a patient has been performed, the cannula 10 has been
inserted into the vein. A catheter is inserted into the cannula 10
(as shown in FIG. 4), expanding the wall 19 of the conical portion
12 thereof. As the catheter is pressed further into the cannula it
splits open the first pair of slits 17 of cannula 10 at the distal
end, expands the inner diameter of the conical portion 12, and is
threaded an appropriate distance into the vein. A doctor may then
grasp the tab 20 and withdraw the cannula 10 from the vein, and
leaving the catheter in place by sliding the cannula 10 back along
the catheter at which time he may remove the cannula 10 from the
catheter by prying apart the cannula 10 along the extended
longitudinal slit 21.
From the foregoing it can be seen that a flexible cannula has been
described. The cannula is of sufficient stiffness to provide
structural support to a collapsed vein. Additionally, it has been
noted that the flexible cannula may be longitudinally split so that
after it has been withdrawn from the vein it may be removed from
the catheter. Furthermore, it should be noted that the sketches are
not drawn to scale and that the thicknesses and distances of and
between various figures are not to be considered significant.
Accordingly, it is intended that the foregoing disclosure and
showings made in the drawing shall be considered only as
illustrations of the principles of the invention.
* * * * *