Simple double lumen catheter

A double lumen catheter comprising an elongated cylindrical tube enclosing first and second lumens separated by an internal divider, the proximal end of the elongated tube connecting to two separate connecting tubes communicating with the respective first and second lumens for the injection and removal of blood, the first lumen extending from the proximal end of the elongated tube to a first opening formed in the side wall of the tube and at the distal end of the elongated tube, and the second lumen extending from the proximal end of the elongated tube to a second opening spaced a sufficient distance away from the first opening, in the longitudinal direction, to prevent mixing of the returned blood with the blood taken in, the distal end portion of the tube beyond the distal end of the second lumen continuing the cylindrical configuration of the tube to the distal end of the first lumen so as to form a blunt circular end on the tube to prevent the end of the catheter from traumatizing or becoming caught in the walls of a blood vessel into which the catheter is inserted.

BACKGROUND OF THE INVENTION 
1. Field of Invention 
The present invention relates to surgical instruments for withdrawing 
fluids from or introducing fluids into a cavity of the body. 
2. Description of the Related Art (Information Disclosure Statement 
Incorporated Into The Specification per 37 C.F.R. .sctn.1.97(a)) 
As is well known, a catheter is a tubular, flexible, surgical instrument 
for withdrawing fluids from (or introducing fluids into) a cavity of the 
body. A double-current catheter is a catheter having two channels; one for 
injection and one for removal of fluid. Dorlan's Illustrated Medical 
Dictionary, Twenty Fifth-Edition (W. B. Saunders, Philadelphia 1974), p. 
274. As is well known, a double-current catheter is used for removing 
blood from a fistula or vein for processing in a dialysis machine and 
returning the processed blood back to the fistula or vein. A 
double-current catheter suitable for this purpose is disclosed in 
Mahurkar, U.S. Pat. No. 4,134,402 issued Jan. 16, 1979. Mahurkar U.S. Pat. 
No. 4,134,402 discloses a double lumen continuous flow hemodialysis needle 
and cannula having contiguous lumens of different lengths formed by 
dividing a unitary straight tube, the shorter lumen acting as a blood 
intake lumen and the longer acting as a blood return lumen. A sharp 
penetrating bevel is provided on the distal tip for percutaneous entry 
into a fistula. Semi-circular lumens provide a minimal resistance to blood 
flow resulting in a smaller but highly efficient catheter in comparison to 
a coaxial double-current catheter. Hemodialysis requires, for example, a 
blood flow rate of about 200 ml/min or more and flow resistance less than 
about 100 mm of mercury. 
There are numerous other United States Patents disclosing double-current 
catheters for hemodialysis and evidencing a long-felt need for a small, 
functionally efficient catheter having a minimum of insertion trauma and 
potential for clotting. McLaughlin, U.S. Pat. No. 4,096,860 issued Jun. 
27, 1978 discloses a coaxial hemodialysis catheter said to allow a step 
enlargement of the opening of a blood vessel to avoid tearing and rupture 
of the side walls. A simultaneous flow device incorporates a hub with an 
extension conduit and a valve therein for receipt of a needle 
therethrough. The extension conduit is of sufficient size to allow the 
passage of the needle therethrough adjacent the interior side walls 
thereof with an attendant extension thereof from its opening. The needle 
with the extension conduit is adapted for combined insertion within a 
blood vessel, after which it can be withdrawn while the valve prevents the 
backflow of blood through the axial passage of the hub. A coaxial flow 
device can then be inserted within the hub conduit. 
Sorensen et al., U.S. Pat. No. 4,099,528 issued Jul. 11, 1978 discloses a 
coaxial double lumen cannula mounted upon a hub and having a central 
stylet needle for penetrating a patient's vein and which is retractable 
after penetration. 
Grimsrud, U.S. Pat. No. 4,203,436 issued May 20, 1980 discloses a hollow 
hypodermic needle with a divider for providing a first channel for removal 
of blood for treatment from a punctured blood vessel and a second channel 
for returning the treated blood to the blood vessel. 
Uthmann, U.S. Pat. No. 4,385,631 issued May 31, 1983 discloses a 
hemodialysis catheter for puncturing blood vessels which includes a 
section insertable through a puncture opening into a blood vessel and a 
hose line following thereafter. This catheter has two circular lumens 
arranged side by side. One of the circular lumens has a sloping bevel 
while the other circular lumen passes slidably through a sheath integral 
with the first lumen. This device requires a large puncture opening and 
produces an inefficient relationship of flow rate to puncture area. 
Jacobson et al., U.S. Pat. No. 4,180,068 issued Dec. 25, 1979 discloses a 
double-current hemodialysis catheter comprising a primary tube and an 
internal divider which also functions as a trocar and valve. The primary 
tube has a side opening for receiving blood and a central opening at the 
distal end of the primary tube. The internal divider includes a cutting 
end which protrudes from the distal opening when the divider is 
longitudinally moved to an insert position. In the insert position, blood 
flow is blocked. 
Mahurkar, Design U.S. Pat. No. 272,651 issued Feb. 14, 1984 discloses a 
double lumen catheter having an outlet lumen which has an opening at the 
tip of the catheter and a shorter inlet lumen which terminates in a bevel 
substantially displaced from the tip. 
Uldall U.S. Pat. No. 4,493,696 issued Jan. 15, 1985 describes a coaxial 
double lumen catheter in which the outer lumen is constricted at its 
distal end, and the tip of the inner lumen rests against the beginning of 
this constriction. Blood is withdrawn for processing through the outer 
lumen via multiple openings in the outer wall; the processed blood is 
returned through the inner lumen. 
SUMMARY OF THE INVENTION 
The primary object of the invention is to provide a simple and efficient 
double lumen catheter of small size which will not traumatize or become 
caught in the walls of a blood vessel into which the catheter is inserted, 
and yet is relatively easy to insert into the blood vessel. 
A further object of this invention is to provide a double lumen catheter 
which is easy and inexpensive to manufacture. 
Other objects and advantages of the invention will become apparent from the 
following detailed description and the accompanying drawings.

While the invention will be described in connection with a certain 
preferred embodiment, it will be understood that it is not intended to 
limit the invention to that particular embodiment. On the contrary, it is 
intended to cover all alternatives, modifications, and equivalents as may 
be included within the spirit and scope of the invention as defined by the 
appended claims. 
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
Turning now to the drawings, FIGS. 1, 2, 3 and 6 show various external 
views of a simple double lumen catheter, generally designated 10, in 
accordance with the present invention. As is conventional for a catheter, 
the double lumen catheter 10 has an elongated unitary hollow tube 11 which 
is inserted into a body cavity such as a vein. The major portion of the 
tube 11 is circular in cross section, as shown in FIG. 5, and has an 
internal planar axial divider or septum 12 defining a return lumen 13 and 
an inlet lumen 14 within the interior of the hollow tube 11. This divider 
12 is preferably of unitary or one-piece construction with the tube 11, 
bisecting the tube into the two lumens 13 and 14. The transverse 
cross-sections of the lumens 13 and 14 are semicircular or "D" shaped (see 
FIG. 5) which minimizes resistance to fluid flow. 
As is conventional for this type of dual lumen construction, the divider 12 
extends axially along the interior of the tube 11 from a branching 
connector 15. The branching connector 15 connects the proximal ends of the 
return lumen 13 and the inlet lumen 14 to respective fluid return and 
inlet lines 16 and 17 which are, for example, respective venous and 
arterial lines of a dialysis or plasmapheresis circuit. The preferred 
direction of fluid circulation is indicated by dashed arrows in FIG. 1. 
The hollow tube 11 includes openings or apertures at the distal end 
portions of the lumens 13 and 14 to permit the flow of the fluid between a 
body cavity (not shown) and the lumens. The return lumen 13 extends along 
the entire length of the tube 11 to an aperture or opening 18 at the 
distal end of the tube 11 as is more clearly shown in FIG. 4. The inlet 
lumen 14 is shorter than the return lumen 13 and terminates at a pair of 
apertures or openings 19 in the side wall of the tube 11. The openings are 
substantially displaced, in the longitudinal direction from the return 
aperture 18 to prevent mixing of the returned blood with the blood taken 
in. 
In accordance with the invention, the tube 11 terminates with a blunt 
distal end 21 which is normal to the axis of the catheter 10. It does not 
have the conical tip or taper that is characteristic of other catheters. 
The absence of the conical tip avoids trauma and migration of the catheter 
into the tributaries of the veins, e.g., the blunt end prevents the end of 
the catheter from traumatizing or becoming caught in the walls of a blood 
vessel into which the catheter is inserted. 
To continue the cylindrical configuration of the tube 11 all the way to the 
blunt distal end 21, the half of the tube which forms the intake lumen 14 
forms a solid portion 20 which extends from the distal end of the lumen 14 
to the blunt distal end 21 of the tube. This provides the blunt distal end 
21 of the tube with a circular configuration, as can be seen in FIGS. 3 
and 6, with the semi-circular cavity of the return lumen 13 opening 
through one half of the circle. To facilitate the flow of blood into the 
intake lumen 14, the solid distal end portion of the tube 11 forms a 
curved surface rising at its proximal end from the planar divider 12 and 
terminating at its distal end on the edge of the distal opening 19 in the 
side wall of the tube. 
The dual lumen tube 11 can be formed by molding a polymeric material. 
Alternatively, the dual-lumen tube can be extruded with the two 
semi-circular lumens extending through the full length of the tube, and 
then the distal end of one of the lumens filled with a polymeric material 
to form the shorter intake lumen 14. The openings 19 can be cut in the 
side wall of the tube to provide the requisite access to the intake lumen. 
For use in hemodialysis, the double lumen catheter 10 is introduced in the 
direction of blood flow in a large vein by surgically exposing the vein 
or, over a Seldinger's guide wire through a sheath as is conventional. The 
inlet opening 19 on the blood inlet lumen 14 draws the blood for 
processing and the processed blood is returned through the return lumen 13 
and out through the hole to return the blood upstream into circulation.