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BACKGROUND OF THE INVENTION
The present invention relates to catheter designs. In particular, it
relates to a radiopaque indicator which may also be used as a plug in the
lumen of a multi-lumen catheter.
Catheters are used in medical applications to introduce or extract fluids
from the body. A variety of catheter designs have been used and are well
known. Typically, catheters are flexible, plastic tubular structures
having single or multiple openings called lumens. Many multiple lumen
("multi-lumen") catheters require plugging devices to terminate lumens at
some opening along the catheter length.
The standard technology used for plugging lumens involves bonding a
flexible plastic plug (using an adhesive or a solvent) into the lumen
requiring the plug. The plastics used are normally soft, flexible,
biomedically safe, radiopaque, and compatible with parent catheter
materials. The limitation associated with using a plastic plugging
material is principally one of radiopacity.
Radiopacity is important because it allows the physician to follow the
catheter tip using a fluoroscope when the catheter is inserted into a
patient. Accordingly, injury to the patient can be avoided. The degree of
radiopacity of a plastic plug is determined by the amount of plastic
filler, such as barium or bismuth, which the plastic contains. Typically,
the filler concentration ranges from about 9% to about 24%. Although
higher concentrations of radiopaque fillers are desirable, using existing
technology, the filler percentage cannot be increased without losing the
parent material's desirable properties, such as flexibility and strength.
Heretofore, metal radiopaque indicators, comprising solid metal bands
formed around the exterior of a catheter, have been used. However, such
exterior bands have the disadvantage of interrupting the smooth outer
surface of the catheter as they may encourage thrombosis.
SUMMARY OF THE INVENTION
In accordance with the present invention a radiopaque indicator which may
also be used as a plug for a lumen of a multi-lumen catheter is
constructed from a finely coiled metal spring.
BRIEF DESCRIPTION OF THE DRAWING
In the Drawing:
FIG. 1 is a side, partial cross-sectional view of a multi-lumen catheter
using the present invention;
FIG. 2 is a cross-sectional view of the multi-lumen catheter taken along
the lines 2--2 of FIG; 1; and
FIG. 3 is a cross-sectional view of the stainless steel spring plug of the
preferred embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring generally to FIG. 1, a multi-lumen catheter 10 having three
lumens 12, 14, 16 is shown. One of the lumens 16 extends through the end
18 of the catheter 10. The other lumens 12, 14 have openings 20, 22,
respectively, through the wall 24 of the catheter 10.
In view of the fact that the catheter 10 is initially formed as a single
extrusion, each of the lumens 12, 14, 16, initially extends along the
entire length of the extrusion. Accordingly, in the course of manufacture,
the end 18 of the catheter 10 is formed by inserting a wire (not shown)
into each lumen which is to remain open to the end 18, i.e., the lumen 16
in the preferred embodiment shown in FIG. 2. The lumens which are to
terminate before the end 18, i.e., the lumens 12, 14 in the catheter 10,
are sealed at the end 18, and it is reformed by heating, which seals the
ends of the lumens 12, 14. Side holes 20, 22 which are remote from the end
18, are formed to provide access to the terminated lumens 12, 14. The
procedure just described would leave "dead end" portions of the lumens 12,
14 between the side holes 20, 22 and the end 18. As is well known, any
blood which got into those "dead ends" could coagulate, resulting in
problems. Accordingly, it is necessary to insert plugs between the side
holes 20, 22 and the end 18 of the catheter 10 in the terminated lumens
12, 14.
In accordance with the present invention, lumen plugs 26, 28, respectively,
comprised of coiled metal springs 30 having rounded ends 32 attached to
either end of the coiled spring 30 (See FIG. 3) are used to plug the
lumens 12, 14 before the end 18 is reformed. The lumens plugs 26, 28 are
inserted into the lumens 12, 14 and are bonded just downstream of the side
holes 20, 22. In the preferred embodiment of the invention, the springs
are made of stainless steel. However, other radiopaque materials, such as
platinum or gold, could also be used. In the preferred embodiment, the
bonding is accomplished using a cyanoacrylate adhesive, such as Permabond
which is manufactured by Permabond in Englewood, N.Y.
In order to manufacture the preferred embodiment of the invention, the
rounded ends 32 are made by melting the ends of the coiled springs 30 to
form them into hemispheres. This may be accomplished by a resistance
welding process. The stainless steel plugs 26, 28 are extremely flexible.
Accordingly, they do not restrict the flexibility of the catheter 10. The
balled ends 32, when formed by resistance welding, will be fully radiused
balls, i.e. as hemispheres, on either end of the spring 30 which serve to
prevent the plugs 26, 26 from cutting through the side wall 24 of the
catheter 10 and to seal the lumens 12, 14.
Advantages of the present invention are that the coiled metal plugs 30 can
be made with variations in metal type, coil wire diameter, metal grade,
and method of attachment. As will be obvious to those skilled in the art,
while the present invention illustrates the use of the stainless steel
coiled spring plug as both a lumen plug and as a radiopaque indicator, an
unplugged coiled spring, in accordance with the invention, could also be
used as a radiopaque indicator within a lumen which was intended to remain
open without departing from the spirit or scope of the present invention.
In such application, the coiled spring would still provide a superior
radiopaque indicator, when compared to the prior plastic plugs, without
affecting the flexibility of the catheter 10. By way of example, an open
coiled spring plug could be used in a balloon catheter in which air is to
be blown through the open coiled spring.
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