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BACKGROUND OF THE INVENTION
Intravenous catheters are well-known medical devices that are used for
obtaining blood samples or injecting fluids, such as blood, medication,
intravenous liquids, water, and the like, into a patient's bloodstream.
Throughout the years, many varieties of intravenous catheters have been
developed and used, some having more success than others. Most prior art
intravenous catheters require a cutting means, usually a needle, which is
used to insert an elongated, hollow tube into the vein of the patient. The
needle first penetrates through the skin of the patient and then pierces
the vein to allow the hollow catheter tube to be inserted into the vein.
After the catheter tube is inserted, the needle is removed leaving only
the flexible catheter tube in place. Depending upon the desired use, the
catheter tube can remain in the vein for a relatively short period of time
or can remain for days or weeks at a time.
One of the more widely used intravenous catheter devices utilizes a hollow
needle that has a flexible catheter tube fitted axially on the outside of
the needle. The needle penetrates the skin and the wall of the vein
creating a small opening for the catheter tube to pass through. However,
since the outer diameter of the needle is smaller than the outer diameter
of the catheter tube, the catheter tube must be forced into a smaller
opening causing considerable pain and discomfort to the patient. Also, it
is possible for the vein to become perforated due to the additional force
needed to push the catheter tube through the smaller size opening in the
vein. As a result, both the needle and the catheter tube can possibly pass
entirely through the vein, rather than being inserted into the lumen of
the vein. If this occurs, the vein usually becomes collapsed or ripped and
cannot be used for intravenous purposes until fully healed. As a result,
the catheter tube must be placed in another location in a different vein.
Another popular intravenous catheter device also utilizes a large, hollow
needle which has the catheter tube placed axially within the hollow
channel formed in the needle. The needle first penetrates the skin and the
wall of the vein to place the catheter tube within the vein. Since the
needle has a larger outer diameter than the catheter tube, an excessively
larger opening is made in the wall of the vein that cannot be fully
occupied by the smaller catheter tube once the needle is removed. As a
result excess bleeding that can last hours and sometimes days may occur
around the opening until the vein can properly heal itself around the tube
to prevent further bleeding. The opening could be possibly further
enlarged by the movement of the catheter tube during the changing of the
dressing surrounding the catheter tube which inhibits the healing process.
A solution to the bleeding problem caused by an over-size or under-size
needle is to simply utilize a needle that has the same outer diameter as
the catheter tube. However, from a physical standpoint, such a catheter
system could not be created using prior art needles and tubing since the
insertion needle has always been removed from the vein once the catheter
tube has been inserted As a result, a larger or smaller size opening would
have to be formed in the patient's vein.
Therefore, there is a need for an intravenous catheter that utilizes a
cutting system which creates an opening that is the same size as the outer
diameter of the catheter tube. Such an intravenous catheter system would
eliminate excess bleeding and should alleviate some pain since the
catheter tube would not be forced into a smaller opening in the vein. To
be effective, such an intravenous catheter should be easy to insert into a
vein and should also be easy to manufacture.
A partial solution to this problem was developed and disclosed in my U.S.
Pat. No. 3,584,624 issued June 15, 1971 and now expired. This invention
utilized a flexible tubular portion that was affixed to a cutting tip by
permanent adhesive. While the structure was effective, one of the major
problems encountered in manufacturing this device was the enormous amount
of time and effort that was needed to properly glue or adhesively affix
the cutting tip to the catheter tube. This problem prevented the device
from being mass produced since the bonding of the cutting tip to the
tubing is so critical. The cutting tip cannot become unattached from the
tubing while in the vein since the tip would enter the bloodstream and
cause imminent death to the patient. Therefore, there is a need for an
improved structure and method for permanently affixing the cutting tip to
the catheter tube which does not require great effort yet achieves a solid
and dependable bond.
SUMMARY OF THE INVENTION
The purpose of the present invention is to provide an intravenous catheter
with a built-in cutting tip which is designed to remain permanently with
the catheter tube once inserted into the vein of a patient. The present
invention provides an advantageous design and method over my previous
catheter device since less effort is required to permanently affix the
cutting tip to the catheter tube resulting in a unit that is more
dependable and can be more easily mass produced.
The present invention utilizes a flexible catheter tube or tubular member
that is made from a material which can be shrinkably affixed to a portion
of a cutting tip to form an integral unit. A portion of the catheter tube
is placed over a specially designed portion of the cutting tip to allow
the tube to be shrinkably affixed to the tip upon the application of an
external shrinking source. This external shrinking source can be one of
many sources that will allow at least part of the tubing material to be
shrunk onto the cutting tip. The selection of tubing material will depend
upon which external shrinking source is used.
The cutting tip includes holding means that can take the form of outwardly
extending, angular serrations that point outward towards the distal end of
the cutting tip. This particular orientation helps maintain the catheter
tube on the cutting tip after the tube is shrunk in place. These angular
serrations also form cavities which receive the tube material that flows
once the catheter tube is shrunk onto the cutting tip. This particular
structure enhances the ability of the cutting tip to remain affixed to the
catheter tube.
An alternative embodiment of the intravenous catheter includes a similar
cutting tip, conventional catheter tubing, and a layer of shrinkable
material that surrounds portions of both the cutting tip and the catheter
tubing to hold the elements together. This shrinkable material is placed
on the outer surface of the cutting tip and catheter tube and is
shrinkably affixed to these elements after being subjected to the external
shrinking source. The layer of material, usually a thermoplastic material,
forms an extremely tight bond with the surface of cutting tip and catheter
tubing resulting in the cutting tip being permanently affixed to the
catheter tubing.
Another embodiment includes the placement of a catheter tube over the
holding portion of a cutting tip. A similar layer of shrinkable material
can be placed and shrunk over the outer surface of the tube. This layer of
shrinkable material acts somewhat like a "clamp" to maintain the catheter
tube on the cutting tip.
These other embodiments of the present invention can also include holding
means located on the cutting tip in the form of angular serrations which
also help promote affixation of the shrinkable material or catheter tube
to the cutting tip. In each embodiment of the present invention, a stylet,
usually a needle such as a spinal needle, can be inserted into the
proximal end of the catheter tube and into the cutting tip to temporarily
stiffen the flexible catheter tube. This stylet merely provides rigidity
to the flexible catheter tube during insertion and can be easily removed
once the catheter tube is in place in the vein of the patient.
Other features and advantages of the present invention will become apparent
from the following detailed description, taken in conjunction with the
accompanying drawings, which illustrate by way of example, the principles
of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view of the intravenous catheter with a built-in
cutting tip made in accordance with the present invention.
FIG. 2 is a cross-sectional, side elevational view of the structure taken
along line 2--2 of FIG. 1.
FIG. 3 is a partial perspective view showing another embodiment of an
intravenous catheter with a built-in cutting tip built in accordance with
the present invention.
FIG. 4 is a cross-sectional side view of the structure taken along line
4--4 of FIG. 3.
FIG. 5 is a cross-sectional side view showing the improved cutting tip and
a stylet as the stylet strikes abutting means located within the cutting
tip.
FIG. 6 is a partial cross-sectional view showing
the stylet within the catheter tube taken along line 6--6 of FIG. 5.
FIG. 7 is a perspective view of one embodiment of an improved cutting tip
made in accordance with the present invention.
FIG. 8 is a perspective view showing another embodiment of an improved
cutting tip made in accordance with the present invention.
FIG. 9 is a cross-sectional view of another embodiment of an intravenous
catheter with a built-in cutting tip made in accordance with the present
invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The present invention provides an intravenous catheter with a built-in
cutting tip which has a continuous external diameter from cutting tip to
the proximal end of the catheter tubing. The cutting tip produces an
opening in a blood vessel of a patient which is the same size as the outer
diameter of the catheter tubing, thus, self-sealing the blood vessel with
respect to the catheter tube to minimize blood leakage.
With reference to FIG. 1, an improved intravenous catheter system 10
includes an elongated, flexible catheter tube or tubular member 12 having
cutting means in the form of a cutting tip 14 located at the distal end 16
of the member 12. A conventional medical connector 18 is permanently
attached to a proximal end 20 of the tubular member 12 and functions as an
independent source for introducing medication, blood, transfusion liquids,
and the like, into the intravenous tubular, once it is placed in the blood
vessel of a patient. It should be appreciated that the connector 18 can be
any one of a number of commercially available connectors such as a "L" or
"T" connector or other connectors which are readily available depending
upon the particular use of the catheter system.
Referring now to FIG. 2, a cross-sectional view of the cutting tip 14 and
tubular member 12 is shown in greater detail to show the interconnection
between these two elements The cutting tip 14 has a general cylindrical
shape and includes a distal end 22 which includes a cutting edge 24 to be
used in penetrating the skin and wall of the blood vessel of the patient
during insertion. The cutting tip 14 also includes a proximal end portion
26 which receives the distal end 16 of the tubular member 12. As is seen
in FIG. 2, the distal end 22 of the cutting tip 14 has the same outer
diameter as the tubular member 12 in order to create a continuous, smooth
outer surface 27. In order to achieve this structure, the proximal end
portion 26 of the cutting tip must be somewhat recessed from the rest of
the outer surface of the cutting tip to allow at least a portion of the
tubular member 12 to fit over that portion. The tubular member 12 must be
made from a material which is capable of shrinkage when subjected to an
external shrinkage source to allow the tubular member 12 to be shrinkably
affixed to the cutting tip.
The proximal end portion 26 includes holding means usually in the form of
angular serrations 28 (see FIG. 7) which extend from the outer surface 30
and extend outward towards the distal end 22 of the cutting tip. These
angular serrations 28 are generally rows of outwardly projecting ridges
that can be arranged in parallel rows with occasional intermediate spaces
32 (shown in FIG. 7) that help hold the tubular member to the cutting tip
and prevent the cutting tip from turning with the tubular member. Spaces
33 between the rows of angular serrations allow the tubing material to
flow into them during the shrinking process. Once the tubing material
cools down, the material is formed around the ridges and remains within
the spaces 33 to help hold the tubular member to the cutting tip.
Another form of holding means located on the cutting tip are shown in FIG.
8 as upwardly extending fingers 34 which provide additional surface area
that can be encapsulated by the flowing tubing during the shrinking
procedure. These upwardly extending fingers 34 can also be oriented
towards the distal end of the cutting tip to help prevent the tubular
member from becoming separated from the cutting tip when the catheter unit
is being inserted into the patient or when the catheter tubing remains in
the blood vessel of the patient.
FIGS. 3 and 4 show another embodiment of the present invention used to
maintain the cutting tip 114 and tubular member 12 together to form an
integral structure. This embodiment includes many similar elements found
in the embodiment shown in FIGS. 1 and 2. Like elements in FIGS. 3 and 4
will be designated by the addition of a prefix "1" for clarity. FIG. 3
shows a middle portion 140 formed around the cutting tip 114 and tubular
member 112. This middle portion 140 is made from a layer of shrinkable
material 142 such as thermoplastic or similar material which is shrinkable
by thermal, irradiation, or other shrinking methods. The middle portion
140 provides an advantageous means for maintaining the cutting tip
together with the tubular member.
Referring now specifically to FIG. 4, the cutting tip 114 used in this
embodiment can be similar to the cutting tips shown in FIGS. 2, 7, and 8,
except that the proximal end portion 126 formed on this cutting tip does
not usually need as deep a recess as the cutting tips shown in these other
figures. This is due to the fact that the middle portion 140 is formed
with a very thin layer of shrinkable material 142 which provides a
sufficient connection to maintain the cutting tip with the tubular member.
As is shown in FIG. 4, the distal end 116 of the tubular member 112 may
also have a slight formed recessed portion 144 for receiving the layer of
shrinkable material 142. However, this recessed portion 144 may not be
necessary if the layer of shrinkable material is thin and does not inverse
the outer diameter of the tubular member. The cutting tip 114 can also
include holding means such as the angular serrations or upwardly extending
fingers similar to those shown in FIGS. 7 and 8.
The intravenous catheter shown in FIGS. 3 and 4 is formed by first aligning
and abutting the proximal edge 146 of the cutting tip 114 with the distal
edge 148 of the tubular member 112. Once these two members are properly
aligned with one another, a single layer or several layers of the
shrinkable material can be placed around the recessed portions of the
cutting tip and tubular member to form the middle portion 140. They layer
or layers of shrinkable material at first may be placed slightly above the
outer surfaces of the cutting tip and tubular member to allow the material
to shrink flush with these surfaces after being subjected to the external
shrinking source. After the material is in place, it can then be subjected
to an appropriate amount of hat, irradiation or other source necessary to
shrink the material over the outer surfaces of the cutting tip and tubular
member to provide an extremely strong bond. The result is a single
continuous outer surface extending from the cutting tip to the proximal
end of the tubular member.
It should be appreciated that the tubular member used in the embodiment
shown in FIGS. 3 and 4 has to be somewhat stiffer than the tubing used in
the other embodiment of the invention. This additional rigidity is needed
to enable the tubular member to remain properly affixed to the layer of
shrinkable material. If the tubing is too soft, it is possible for the
tubing to collapse and become loosened from the material. To alleviate
this problem it is possible to utilize tubing that has more rigidity to
retain the layer of shrinkable material.
During the manufacture of the catheter unit shown in FIGS. 3 and 4, a
stylet or mandrel could first be inserted into the tubular member to
provide additional rigidity. After the cutting tip is aligned with the
tubular member, the layer of shrinkable material can be placed and shrunk
over the recessed end of the tubular member. During the shrinking process,
an adhesive-type bond may form between the outer surface of the tubular
member and the shrinkable material due to the source that shrinks or
"melts" the material in place. Preferably, the materials making up the
tubular member and shrinkable layer of the embodiment should be chosen to
create this additional intermeshing of materials since an even stronger
bond will be achieved.
An additional embodiment of the present invention is also shown in FIG. 9.
Again, this figure includes using similar elements as found in FIGS. 1 and
2. Like elements will be designated by similar reference characters with a
prefix "2" in FIG. 9. This figure shows a cutting tip 214 having a similar
proximal end portion 226 as shown in the other embodiments. In this
embodiment, the tubular member 212 is placed over the proximal end portion
226 as was done in the embodiment shown in FIGS. 1 and 2. However, a layer
of shrinkable material 250 is place over the outer surface of the tubular
member to create a shrinkable bank which helps maintain the tubular member
on the cutting tip. This layer of shrinkable material 250 acts somewhat
like a "clamp" to help maintain the two elements together. Again, the
tubular member 212 may have a recess 252 for receiving the layer of
shrinkable material. This recess 252 may be actually preformed into the
tubular member if needed. Again, the shrinkable material is designed to be
shrunk flush with the outer surfaces of the cutting tip and flexible
tubular member to create a continuous outer surface. It is possible for
the shrinkable material to compress the tubular member 212 once it is
shrunk in place. If the layer of shrinkable material is sufficiently thin,
than the formed recess on the outer surface of the tubular member may not
be necessary. This embodiment also includes holding means in the form of
angular serrations 228 which are similar to those shown in FIGS. 7 and 8.
The present invention also utilizes force transmitting means in the form of
an internal stylet which can be placed within the tubular and cutting tip
to provide rigidity to the structure when it is being inserted into the
patient. This same stylet can be used with each embodiment of the present
invention. Turning now to FIGS. 5 and 6, the stylet 60 is usually a hollow
tube or needle which is slidable within the tubular member 12 and cutting
tip 14. Usually, a spinal needle can be used and inserted in the tubular
member 12 and cutting tip 14 to provide added rigidity to the structure.
The cutting tip 14 may further include abutting means shown in FIGS. 5 and
6 as a pair of upper and lower abutments 62 and 64 are located within the
internal opening 66 formed in the cutting tip. These abutments are
integral with the cutting tip and provide a bearing surface 68 for the tip
70 of the stylet 60 to contact during insertion. Preferably, the abutments
are small projecting extensions that do not interfere with the size of the
inner diameter of the cutting tip. If the abutment is too large or is a
continuous projection formed in the cutting tip, then it is possible that
the flow rate of the fluid through the tip could change. For this reason,
the abutments should not be too pronounced to prevent possible adverse
flow changes past the cutting tip.
The stylet 60 is capable of transmitting a force to the cutting tip 14 that
allows the cutting edge of the tip to penetrate through the skin and
through the wall of the blood vessel. Once the cutting tip 14 has
penetrated into the blood vessel and the tubular member has been properly
placed within the blood vessel, then the stylet can be removed through the
opening in the proximal end of the catheter tube. The tubular member will
remain flexible to prevent any discomfort while remaining in the patient.
It is preferable to place the abutting means within the cutting tip rather
than at the proximal edge of the tip since a sizeable amount of force is
usually required to enable the cutting tip to penetrate both through the
skin and wall of the blood vessel of the patient. If the force is directed
right behind the cutting tip, it is possible for the tip of the stylet to
misdirect the transmitted force at an angle offset from the centerline of
the cutting tip, which can cause a wobbly cutting action (called "coring")
to occur. This cutting action is undesirable since it creates a larger
opening both in the skin and blood vessel which defeats the self-sealing
feature of the present invention.
The cutting tip may be made from metal such as stainless steel or from a
hard cutting plastic material such as methyl methacrylate which is a known
and widely used material in the medical profession. The cutting tip can be
machined or created by using injection molding techniques. The manner in
which the cutting tip is made does not depart from the spirit and scope of
the invention.
The shrinking method used in accordance with the present invention can be
any one of a number of shrinking techniques well-known in the art. For
example, thermal sealing or bonding can be used in which direct
application of heat is used to join the cutting tip with the tubular
member. For example, in the embodiment shown in FIGS. 1 and 2, the tubular
member would have to be made from a material which would at least
partially shrink once subjected to the application of direct heat. Also,
pressure is sometimes simultaneously added to aid in the thermal bonding.
The material would have to be shrinkable but yet retain its strength in
order to prevent possible breakage at the point of attachment to the
cutting tip. The tubular member could be made from a teflon-type material
which is manufactured and sold by the Dupont Company of the United States.
Any other similar material which achieves the desired results could also
be used.
Another external shrinking source used to shrink the tubular member onto
the cutting tip could utilize irradiation shrinking techniques. In this
type of shrinkage, the tubular member is made from a material that shrinks
when exposed to some form of irradiation, usually ultraviolet rays or
lights. The irradiation may cause the material to melt which again causes
shrinkage to occur which can create a tight bond needed between the
tubular member and the cutting tip. Such irradiation techniques are
already commercially used in other shrinking, applications, for example,
for shrinking thermal plastic over objects for storage. The tubular member
can again be made from a teflon-type material that is manufactured and
sold by the Dupont Company of the United States.
The embodiments shown in FIGS. 3, 4, and 9 can use a similar material or
hard plastic cutting tip with a flexible tubular member made from a
material such as nylon or teflon that is commercially available and
manufactured by a number of companies worldwide. The layer of shrinkable
material used with these embodiments can be made from a thermo plastic
material such as Silastic which is also manufactured by the Dupont Company
of the United States. However, any material which can be shrunk by any
external source can be used in these embodiments.
Preferably, the materials used to form the cutting tip, tubular member, and
layer of shrinkable material should be of a type that is medically
approved by the United States Food and Drug Administration. The use of
pre-approved materials will prevent the possibility of possible delays due
to obtaining approval before the unit can be sold or used in the United
States.
The embodiment of the intravenous catheter shown in FIGS. 1 and 2 can be
made by first placing at least a portion of the tubular member over the
proximal end portion of the cutting tip. This step may result in the
tubing bulging somewhat outward due to the angular serrations or upraised
fingers located on the proximal end portion. However, this bulge will
dissipate once the material is subjected to the external shrinking source.
The next step is to subject at least this overlapping portion of the tubing
and cutting tip to the respective shrinking source, depending upon the
material characteristics of the tubing material. Once the material starts
to shrink, it will "flow" between the spaces located between the angular
serrations on the cutting tip, thus reducing the bulge that first results
when the tube is placed on the cutting tip. The result is an intravenous
catheter which incorporates a flexible tubular member with a built-in
cutting tip that are shrinkably affixed together to form an integral unit
having a continuous outer diameter.
From the above it may be seen that the present invention represents a
simple and elegant solution to the problems associated in prior art
intravenous catheters. The built-in cutting tip is permanently affixed to
the tubular member and remains within the patient during usage, thereby
eliminating the need to create a larger or smaller opening in the vein for
the catheter tube to fit through. As a result, there is a minimal loss of
blood and similar loss of discomfort to the patient when the present
invention is placed in the blood vessel of a patient.
While particular forms of the invention have been illustrated and
described, it will be apparent to those skilled in the art that various
modifications can be made without departing from the spirit and scope of
the invention. Accordingly, it is not intended that the invention be
limited except by the appended claims.
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