Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to catheters made of plastic material
or gaining temporary vascular access to the circulatory system of a
patient requiring hemodialysis.
This application is a divisional of Canadian Patent Applique-
lion Serial No. 459,487, filed July 23, 1984.
More specifically, such a catheter is designed to catheterize
a predetermined blood vessel of a patient by a single puncture. The
catheter is inserted into the blood vessel so that untreated blood is
withdrawn continuously from that vessel and passed to a dialysis
apparatus. Processed blood is returned from the apparatus to the same
blood Yess~l.
2. Description of the Prior Art
It is well accepted medical practice in the performance of
both emergency and chronic hemodialysis to use a double lumen
catheter of concentrically disposed tubular construction. See, for
example, Fig. 5 in Raulerson, US. Patent 4,037,599, and Figs. 3, 4
and 5 in Allentown Limited, Canadian Patent 1,092,927.
The placement of catheters of this type is
accomplished commonly by the "Seldinger" technique. this
technique involves the puncture of a vein with a hollow
needle. A flexible stainless steel wire is then threaded
through the needle and into the vein. The needle is with-
drawn over the wire and the flexible plastic catheter
slipped down over the wire, as a guide for proper place-
mint of the distal end of the catheter inside the blood
vessel. A typical subclavian application of a double
lumen catheter is shown in Canadian Patent 1,092,927.
It can be seen that once the catheter is
inserted into the vein of a patient. it serves as a
linkage between the blood stream and an extra corporeal
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hemodialysis circuit. The arterial lumen of the catheter
captures, from the vein, the arterial blood to be treated
and the venous lumen returns fresh or processed blood
(venous flow) into the same vein downstream of the blood
flow. This arrangement makes the extra corporeal hero-
dialysis circuit, including the catheter, in effect, an
extension of the patient's vein.
There must be an opening at the distal tip of
the catheter large enough to receive a Goodyear The
surface surrounding this opening must be rounded and
smooth and the diameter of the body of the catheter must
increase gradually and smoothly to ease its insertion.
Even though dialysis may only be performed inter-
mittently, it is common to leave the catheter in the
patient's vein for some time, say up to about two weeks,
and between dialysis to inject into the catheter a drug
to prevent blood clotting, for instance heparin It is
desirable that the drum remain in the catheter for as long
as possible.
A major problem in catheterizing is kinking of
the catheter during insertion. One attempt to overcome
this has been to employ, in the outer tube of a concern-
trig double lumen catheter, relatively heavy tubing, for
exemplify Teflon and to rely on the wall thickness to
prevent kinking. While the thicker tubing impedes insert
lion, it has not been altogether effective to prevent
kinking and a proportion of catheters made in this way
still kink.
Another problem with the concentric tubular
construction is that, despite the size of the tubing, the
lumen does not allow adequate blood flow, because of the
significant thickness of the wall compared to the overall
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diameter and the significant cross-sectional area of the
inner tubing.
A still further problem is that there is dead
space in the Y-adapter commonly forming a part of the
catheter causing disorder of the blood flow. Blood
clotting also takes place more frequently with double
lumen catheters than with single lumen catheters.
An aim of the present invention is to provide
catheters and methods of making them which overcome these
lo problems and which provide positive advantages as will be
apparent from the detailed description to follow.
SUMMARY OF THE INVENTION
Irving regard to what has been said, a double
lumen catheter, according to one preferred form of the
invention, comprises a thin septum-walled double lumen
plastic tubing body and a removable obturator extending
within each lumen when the catheter is inserted.
the use of obturators, extending within both
lumens of a suitably constructed catheter, provides lateral
support to the wall of the tubing throughout its length.
This prevents it from buckling inward and kinking under
the eccentric axial load encountered during the insertion
into the body.
The catheter is constructed to facilitate the
insertion and removal of obturators and, at the same time,
obviate the problem of oversized tubing, restricted
patency, dead space, and blood clotting.
The invention also contemplates novel septum-
walled double lumen tubing having unique cross-sections
and novel branched adapters.
A preferred catheter is made up of an elongated
integral flexible plastic thin-walled tubular body extend-
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in from a proximal end part, through an intermediate part,
to a distal end part, terminating in a tip. The inter-
mediate part has an outer wall and an internal septum wall
containing juxtaposed arterial and venous lumens. The
proximal end part is a continuation of the intermediate
part and either continues in juxtaposed lumens or, prefer-
ably, is branched to provide diverging lumens. The end of
each lumen, in the proximal part, is adaptedforconnection
to an access tube, leading to hemodialysis apparatus. At
the junction of the intermediate part and the distal part,
the arterial lumen is terminated and the venous lumen
continued at least part way to the tip of the distal part.
The cross-section of the lumens in the intermediate part
is uniform throughout, although the cross-section of the
lumens in the proximal part may be the same or slightly
larger than in the intermediate part. m e venous lumen
continues at the same cross-section, or slightly less,
throughout at least an obturator-receiving length of the
distal part.
The outside surface of the outer walls are
continuous and smooth so as to offer minimum resistance
to insertion into the body of a patient. The walls are
also relatively thin to provide for lumens of relatively
large cross-section compared to the total cross-section
of the catheter body. This particular form of the device
employs removable obturators to prevent the catheter from
buckling while it is being inserted. The overall con-
struction of the body is designed to receive an obturator
in each lumen and to facilitate their insertion and with-
drawl. So, the inner surface of the outer wall and the
surfaces of the septum walls are continuous and smooth
and any change of direction, for example, between the
sag
intermediate and proximal or distal end parts in the lumen,
as in some embodiments, is a gradual curve to accommodate
its negotiation by a flexible obturator.
The obturator for the arterial lumen is solid and
that for the venous lumen has a passage extending through
it to accommodate a wire used with a needle to insert the
catheter into the body of the patient.
The ability to fashion an effective thin-walled
body is facilitated by the use, in preferred embodiments, of
plastic tubing having a special cross-sectional shape. This
cross-sectional shape may be symmetrical, for example, some-
what oval with a long and short axis, the septum wall being
in the short axis and the lumens being of the same cross-
section. Variations of this shape are shown in the drawings.
Or, the shape may be non-symmetrical, with the respective
lumens of the same cross-sectional area, but of different
shape. One of the lumens could be larger than the other, if
desired, but the septum wall should be parallel to the short
ax s .
The proximal end of the catheter may also assume
different forms, for example, it may be straight or branched,
the proximal end of the body diverges into branches, each
enclosing the continuation of a lumen from the intermediate
part. Desirably, the branched proximal end of a catheter is
contained in and firmly fixed to a branched adapter. In one
version, the adapter is molded integrally with the proximal
end of the tubing. In another form, the branched adapter
and the proximal end are formed separately, but later per-
manently connected by welding.
The distal end part of the catheter may vary in
different respects. In all forms, there is a narrow lead-
in end part, extending from the intermediate part to a
tip, which accommodates part of the venous lumen. In one
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case, this leading end part is connected to the inter-
mediate part by a tubular extension of the intermediate
part which is of large enough cross-section to receive
the venous lumen obturator. This extension may be aligned
with the venous lumen in the intermediate part or may be
smoothly offset inwards to be axially aligned with the
intermediate part. Another construction lacks the narrow
leading end part and the distal part terminates with the
extension, which is itself provided with a tip opening of
the same diameter as that of the venous lumen so as to
allow the venous lumen obturator to protrude in an
insertable tip.
In still further forms of distal part, the lead-
in end part is made up of an extension of the same die-
meter as the intermediate part which ultimately tapers
symmetrically to provide the leading end part. In this
- case, the arterial lumen extends part way into the distal
end part and the extension is filled with a plug so as to
terminate the effective length of the arterial lumen near
the beginning of the distal part. In all cases, there is
a blood-conducting orifice through the outside wall of the
catheter in the distal end part, leading to the arterial
lumen.
The invention also contemplates special forms of
obturators as will be apparent from the description to
follow.
The invention also contemplates other ways of
making -the catheter body rigid enough to insert into the
body of a patient without the use of obturators. One way
of doing this is by employing unique tubing made up of a
series of alternating hard and soft plastic rings welded
together. The hard plastic rings should be at least twice
-- 7
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the length ox the soft plastic rings. The septum wall is
welded within the tubing to divide it into respective
lumens.
Another form of special tubing which may be
employed is wire-reinforced. One embodiment has a con-
tenuous wire as a spiral within the wall of the tubing
and looping back at the distal end.
Another type of tubing has a septum wall, incur-
porting length-stabilizing means, for example, the septum
wall has a central part of hard, but flexible plastic, and
side parts of soft elastic plastic welded to the central
part and to the outer wall.
In still another form, the length of the tubing
is stabilized by providing a septum wall of soft elastic
plastic with a wire extending through it in both directions
and looping back at the distal end.
While certain forms of catheter have been desk
cried as not needing obturators, obturators could be
employed with these catheters as well, if desired.
The catheters described are fashioned by the use
of particular welding and molding techniques, described
herein in detail and which form part of the invention.
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BRIEF DESCRIPTION OF THE DRAWINGS
Having thus generally described the invention, it
will be referred to more specifically by reference to thy
accompanying drawings, which illustrate preferred enbodi-
mints, and in which:
Fig. 1 is-a general view in side elevation of a
catheter, according to the invention;
Figs. lo to to are enlarged longitudinal frog-
- Monterey cross-sectional views of the
distal end parts of several different
catheters of the general structure
illustrated in Fig. 1,
Fig. if is a fragmentary transverse cross section
on the scale of Figs. lo to to of the part
of the catheter shown in Fig, to at right
angles to the view of those Figs.,
Figs. pa to of are transverse cross-sections on
a still further enlarged scale through
several different types of tubing suitable
for use in a catheter body of the type
shown in the previous Figs.,
Figs. 2g to us are transverse cross-sections on
the scale of Figs. pa to of through
obturators for use in the lumens of
catheter bodies shown beside them in
the drawings;
Figs, pa to pharaoh transverse cross-sections on
the scale of Figs. pa to of through a
distal part of various catheters as shown
in Figs. pa to of with obturator and
Goodyear in place,
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Fig. pa is a longitudinal cross-section through
a proximal end part of a catheter showing
the branched body of the catheter within
a Y-adapter;
Figs 4b, I and 4j show three alternate forms
of proximal end part of a catheter
according to the invention,
Fig. 4c is a further alternate form of proximal
end of a catheter, according to the
invention,
Figs. Ed to oh and ok to on are transverse cross-
sections along the lines shown in Figs. pa,
4b, 4c, 41 and 4j (Figs. Ed, ye and of
appear on the sheet with Fig. pa and Figs.
4g and oh are on the sheet with Figs. 4b
and 4c);
Fig. 5 illustrates a step in the manufacture of
an obturator, according to the invention,
Figs. pa to Ed are enlarged fragmentary longitu-
dial cross-sections through different
forms of obturator,
Figs. ye to oh are transverse cross-sections
through the obturators of Figs. pa to Ed;
Figs. 7 to 10 are fragmentary longitudinal cross-
sectional views illustrating steps in the
fashioning of the proximal end of the tubing,
Fig. if is a fragmentary longitudinal cross-
section through tubing resulting from the
procedure of Figs. 7 to 10;
Figs. 12 and 13 are longitudinal fragmentary
cross-sectional views illustrating a way
of connecting the tubing to a Y-adapter;
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us
Fig. 14 is a fragmentary longitudinal cross-
section showing another way of fashioning
the proximal end of tubing at the same
time as forming a Y-adapter;
Figs. 15, aye, 15b, 16, aye to 17d and 18 are
fragmentary cross-sectional views showing
different ways of fashioning the distal
end of the catheter as shown in Foxily to to,
Fig. 19 is a general view in side elevation of a
further form of catheter, according to
the invention,
Fig. lea is an enlarged fragmentary longitudinal
cross-section through-the distal end of
the catheter of Fig. 19,
Fig. 20 is a side elevation of the septum wall
of the tubing shown in cross-section in
Figs 27 and 28;
Figs. aye to 20d are transverse cross-sections
through different types of septum wall of
the general type shown in Fig. 20,
Fig. 21 is a side elevation of a ring of soft
plastic used as a component in making
multi-ring tubing;
Fig. aye is a side elevation of a ring of hard
plastic used in combination with the soft
plastic ring of Fig. 21 to make the tubing,
Fix. 21b is a transverse cross-section of the
rings of Figs. 21 and aye;
Figs. 21c and 21d show alternative cross-sectional
shapes for the wall of the ring shown in
Fig. 21b;
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Fig. 22 is a side elevation of another form of
tubing made of soft plastic shown in
cross-section in' Figs. aye and 22b,
Fig. aye is a cross-section through the tubing
of Fig. 22;
Fig. 22b is a cross-section through another kind
of tubing similar to that of Fig. 22;
Fig. 23 is a longitudinal cross-section thus-
treating an assembly in the manufacture of
multi-ring tubing, according to the
invention;
Figs. aye and 23b are transverse cross-sections
through the assembly of Fig. 23;
Fig. aye is a side elevation of a spring used
for manufacturing metal spring-plastic
tubing;
Fig. 24b is a side elevation of another form of
spring
Fig. 24c shows a reinforcing wire for making the
septum wall as shown in Fig. 20b, used in
another form of plastic tubing;
Fig. 25 is a longitudinal cross-section thus-
treating an assembly in the manufacture
of metal-spring tubing, according to the
invention;
Fig. aye is a cross-section as along the line
aye of Figs 25 and 26,
Fig. 25b is a cross-section as along the line
25b-25b of Figs. 25 and 26,
Fig. 25c is a cross-section as along the line
25b-25b of Figs. 25 and 26 through another
type of tubing, the septum wall differing
from that of Fig. 25b;
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~;~ZS29~
Fig. 25d is a cross-section as along the line
25b-25b of another form of catheter
body in which the septum wall differs
from that of Figs. 25b and 25c;
Fig. 26 is a longitudinal eross-section thus-
treating another assembly in manufacturing
metal-spring plastic tubing,
Fig. 27 is a longitudinal cross-section through
multi-ring tubing made by the method
illustrated in Fig. 23,
Fig. aye is a transverse cross-seetion through
the tubing of Fig. 27,
Fig. 27b is- a transverse cross-seetion through
slightly modified forms of tubing from
that of Fig. 27,
Fig. 28 is a longitudinal eross-section through
double lumen tubing having a metal spring
embedded in its wall;
Fog. aye is a transverse cross-section through
tubing having the general form of that
of Fig. 28;
Fig. 28h is a transverse eross-section through
a slightly modified form of tubing to
that of Fig. aye,
DESCRIPTION OF THE PREFERRED EMBODIMENTS
General Construction
Fig. 1 is a side elevation of a catheter, accord-
in to the invention, with obturators and Goodyear in
place, in a condition ready for insertion into a vein of a
patient once the lure locks 33, 29 are closed.
The catheter is made up of an integral elongated
septum-walled double-lumen body A of thin tubular plastic
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I 99
material having outer walls and a Sutton wall providing a
venous lumen 18 and an arterial lumen 16 juxtaposed to it.
The cross-section of the body A may be circular
(Fig. pa), flat circular (Fig. 2b), elliptical (Figs. 2c
and Ed), rhomboid with arcuate sides (Fig. ye) or oval
(Fig. of),
The body A extends from a distal end part 15,
through an intermediate part 17, to a proximal end part.
At the distal end part 15, there is only one lumen 18 (a
venous lumen) whose cross-section is shown, in alternative'
form it may take in Figs. pa, 3b, 3c, Ed, ye and of with a
tapered tip 9 and an end hole 7.
There are also two groups of side holes (pro-
fireball .040 inches to .045 inches in diameter). These
holes are preferably arranged spirally. One group 12 of
side holes is on the end of the lumen 16 as a blood inlet.
Another group 13 is on the end of the lumen 18 as a blood
outlet.
Modifications of the distal end part 15 are shown
in Figs. lay lb, to, id and le. At the proximal end part,
two lumens of the body A are separated into two branches
19 and 21, the branches and part of the body A being con-
twined and fixed within a branched adapter B, in this case
a Y-adapter. The intennediate part 17 is curved to match
the shape of the vein so that after the catheter is in-
sorted there is almost no bending stress on the body of
the catheter.
The body A is invade up of tubing D which will be
described below under "Manufacturing Procedure".
A tube 23 of silicon elastomers surrounds the
proximal end of the body A and the end of the Y-adapter B.
A silicon elastomers tube 27 connected to the end
- 14 -
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of each branch of the Y-adapter B to a female lure lock 29
which, in turn, engages a male lure lock having a body 34
and a cap 33. The body 34 of one male lure lock engages
an obturator 31, the other an obturator 32 (the end of an
obturator is thus fixed inside of each body I and the
obturator extends to the distal end of the catheter). The
cap 33 of each mule lure lock freely embraces each body 34
and is screwed on the female lure lock 29.
The female and male lure locks and Y-adapter are
molded from a hard commercially available plastic. The
Y-adapter is preferably weldable to the material of the
tubing D.
The obturators 31 and 32 are elongated lengths
of plastic, preferably Teflon (trade mark) or polyurethane.
The plastic is flexible and has a higher modulus of eras-
Taoist than the material of the tubing D and his a glossy
surface
One obturator 31 extends to the distal end of
the venous lumen 18 and has the same cross-sectional shape
(shown in Figs. em through us) as the lumen 18 and is
hollow. The obturator 31 has an opening and a stainless
steel Goodyear 41 extends through it. Zoo other obtur-
atop 32 is unperforated (solid) and extends down to the
end of the arterial lumen 16 and has the same cross-
sectional shape (shown in Figs. 2g through Al) as the
lumen 16. m e distal end of each obturator is shaped and
polished to fit the end of the lumen.
As explained above, the proximal end of each
obturator is fixed inside the body of a male lure lock 34.
The cap ofithe male lure lock 33 must be screwed tightly
onto the female lure lock 29 so that preferably the sift-
con elastomers tubing 27 is stretched to a certain extent,
- 15 -
to create a certain pressure Betty the ends of the lumen
and the obturator and there is a certain prestressed pros-
sure in the obturator itself and thus prestressed tension
in the wall of the tubing body A.
After both the obturators and Goodyear are
assembled within the lumens, there is preferably sub Stan-
tidally no empty space in the catheter body A throughout its
length and the body A cannot be squashed by pinching or
kneading between the thumb and index finger.
At the proximal end, the relative position of the
lumen 16 and the obturator 32 and the lumen 18 and the
obturator 31 may be exchanged with each other in the Y-
adapter, i.e. the lumen 18 and the obturator 31 may be
placed in the straight channel of the Y-adapter and the
lumen 16 and obturator 32 in the other channel. The
obturators should be pulled out as soon as possible after
the catheter is inserted in the body. Blood clotting may
take place if the obturator is left in place too long.
Among the important features of the construction
described are the following: ,
a) An obturator extends within each lumen of the
catheter A. This effectively prevents the catheter from
kinking when inserted into the body of a patient. After
insertion, the obturators and Goodyear are withdrawn so
that the catheter provides for the greatest possible
blood flow.
b) The way in which a smooth bib ranched tubular
construction is formed at the proximal end of the tubing
body A and is fixed inside the branched adapter, e.g. the
Y-adapter, or a auditor to be described. The branched
adapter can have one arcuate deviating channel which makes
it possible for an obturator to be readily inserted and
- - 16 -
Sue
pulled out through each lumen. This does away with a dead
end in the Y-adapter normally present in other catheters.
this eliminates interference with the blood flow.
I The way in which a single venous lumen construe-
lion is formed at the distal end of the tubing body A. It
has the same cross-section as that of the venous lumen in
the body of the catheter. This allows the obturator to
work efficiently in preventing the body of the catheter
from kinking.
d) The construction lends itself to several different
novel cross-sectional shapes for the body of the catheter,
namely flat circular or flat sided circular, elliptical,
rhombic with arcuate sides and oval. These shapes are
shown in Figs. 2b to of. These shapes are preferred to
the conventional circular shape shown in Fig. pa. The aim
is to provide the optimal cross-section of a septum walled
double lumen tubing. It is desirable that the lumen cross-
sectional area be substantially the maximum for the total
cross-sectional area of the tubing. Calculations show
that, when the ratio between the long and short axis,
alpha of the flat-circle cross-section which consists of
two half circles and a rectangle between it 1 . 5, i.e. the
long axis should be 1.5 times the short axis, but the
ratio alpha in a circle is 1Ø On the other hand, the
best ratio beta of the elliptic cross-section is 1.637
(1 pow ) but the ratio beta in a circle is 1.0 also. For
a rhombic cross-section it would be higher.
Second, in a circular cross-section tubing, the
septum wall is longer than the others. But, the shorter
it is, the more rigid and, the stronger it is as a lateral
support to the wall of the tubing. This means that the
body of the tubing in other shapes is stronger than that
~2~;~g~
of the circular one and the wall of the tubing can be
thinner, i.e. the lumens may be larger.
Laredo, the size of the Y-adapter may be smaller
and the shape of the distal part of the single lumen part
is better than that of the circular tubing because the
septum wall is shorter.
All things considered, the ratio between the
long and the short axis, 1.5 may be too high for the cross-
section, and a lower one of 1.1, 1.2, 1.3 etc. could be
selected rather than a circle.
Manufacturing Procedures
Preferred manufacturing procedures, according to
- the invention are as follows.
Part i Figs. lo to 18 - Materials and Equipment
The raw materials and equipment required, which
are commercially available, are as follows:
1) Raw tubing D and 14 for the body of the catheter.
The material of both must be uniform, weldable.
glossy smooth, and non-thrombogenic polyurethane or polyp
ethylene. It is preferably transparent. D is -a septum
walled double lumen tubing and has arterial and venous
lumens 16 and 18 respectively. 14 is an extension of the
lumen 18 in the tubing D. The cross-sections of tubing D
are shown in Figs. pa, 2b, 2c, Ed, ye and of, and tubing
14 in Figs. pa, 3b, 3c, Ed, end of. Tubing 14 may be
omitted, as will be explained later.
The cross-sectional dimensions of the tubing D may
be as follows (for subclavian veins only). The diameter of
the catheter tube having a circular cross-section, as shown
in Fig. pa, is preferably about 10 French (0.131 inches)
and could range from 9 to 11 French. For the non-circular
tubing shown in Figs. 2b to of, the short axis of the
- 18 -
~225~g9
cross-section is about 8 to 10 French (0.104 to 0.131
inches). The long axis of the cross-section is about 10
French to 12 French (0.131 to 0.157 inches). The thickness
of the wall in any of these embodiments should preferably
be about 0.10 inches and could range from about 0.009
inches to about 0.011 inches. m e septum wall may be
slightly thicker than the wall of the tubing. It should
be understood that for other veins than subclavian, these
dimensions may vary.
2) Plastic rods 31, 32 for the body of the obturators.
32 is solid. 31 icily to accommodate a
stainless steel Goodyear. m e material of the rods 31,32
may be polyurethane weldable to the male lure lock) or
Teflon (unweldable) and must be harder than that of the
tubing D, 14. The modulus of elasticity (or deformation)
is higher, and the surfaces of the rods must be smooth and
glossy. These cross-sections are shown in Figs. 2g, oh,
I, 2j, ok, 21, em, on, up, 2q, or and us relative to the
tubing D.
I Rods 20,22,48,49 for welding.
The material of these rods may be Teflon (flex-
isle) or steel (rigid or a combination of Teflon and
steel. Teflon is better than steel. m e rigid part of
the rods 48 and 49 may consist of a Teflon sheath and a
steel core. m e surface of these rods must be very smooth
and glossy. Their cross-section is such that they fit
tightly in the lumens of the tubing D. m e rods 48,49
and 20,22 are slightly larger in cross-sectional area than
the rod 32 or at least the same size.
4) Silicon elastomers sleeve for welding 24,25,26,28,30.
The inside shape and size of the cross-section
are the same as the outside shape and size of the tubing D,
- 19 -
~25~99
14, Y-adapter or the body of the male lure lock, respect
lively. In case it is not a circle, there should be two
or more bright, straight dotted index lines on the inside
or outside surface of the sleeve. For example. if the
cross-section is an ellipse, there must be at least two
dotted index lines to indicate both ends of the short axis
in the ellipse throughout the length of the silicon
sleeve. one thickness of the wall of the silicon- sleeve
is about half of the average of the inside diameter.
5) m e Y-adapter B or auditor and the male-female
lure locks 29, 33, 34 and the silicon elastomers
tubing 23, 27 which fit the ends of the Y-adapter
and the lure locks for assembly.
Roy material of the Y-adapter and lure locks is
inflexible and transparent, e.g. a polycarbona-te. And,
the material of the Y-adapter is preferably selected so as
to be weldable to that of limbs 21 and 19.
6) Soldering irons E and H with a temperature control
device.
These have iron blocks E and H with four or more
channels which fit the outside shapes and sizes of the
silicon tubing G (Fig. 10). The thickness of the iron
blocks or the width of the working edge of the channel in
the block H is typically 3 to 4 mm and in E typically 6
to 7 mm.
7) Ultrasonic heating apparatus.
This may be employed.
8) Liquid freon.
9) Alcohol.
- 20 -
3LZ~
Part i, Figs. pa to on and Figs. 7 to 14 -
Fashioning the Proximal End
1) An assembly is made as shown in Figs. 7, 8 and
9 proceeding through the following steps:
i) At the proximal end of the tubing D, part of the
lumen 18 is removed, for example, by cutting with a blade,
leaving the single lumen 16 alone protruding from the
proximal end (see Fig. 7).
ii) A length of tubing 14 is cut to provide a limb 11,
and one end of the limb 11 is sanded to provide an outside
taper on its end as at tic (see Fig. 7). The sanded end
is then cleaned with alcohol.
iii) The ends of rod 20 and 22 are sanded and polished
to be round and shiny smooth and are then inserted into
the proximal ends of the lumens 16 and 18 respectively
(see Fig. I
iv) The lumen 11 is then pushed onto the rod 22 until
its tapered end enters the end of the lumen 18. The end
of the lumen 18 is stretched and enlarged by the entry of
the limb 11. The width of the overlap 88 is 1 to 3 mm
(see Fig. 7).
m e following should be noted.
In the case of a circular or flat circular,
elliptical or arcuate sides rhombus tubing D, the tubing 14
may be omitted and the limb 11 provided by cutting off a
length of a single lumen 16 which is left protruding from
the proximal end.
Or, the step (i) may be omitted and the tubing 14
cut to provide two limbs 11 which are sanded and then
pushed onto the rods 20 and 22 (see Fig. 8).
Because both lumens of the circular, flat air-
cuter or elliptical or arcuate sided rhombus tubing D are
- 21 -
US
the same shape, the rods 20 and 22 may be the same.
v) A length of silicon elastomers tubing 24 is cut
off to provide a sleeve 24. The sleeve 24 is first dipped
into liquid Freon, which causes its enlargement and
lubrication. m en, the sleeve 24 is put on the assembly.
See Figs. 9 and 10. Preferably one hundred or more asset-
bites are prepared to be ready for the next step
I After the Freon has dried thoroughly, the assembly
is placed in a channel on the iron E. For productivity
there should be four or more assemblies handled at the same
time.
m e heating elements E are first activated to
preheat the adjoining part of the assembly to a temperature
higher than 100C, but lower than the melting (fusion) point
of the tubing material (Figs. 9 and 10).
3) Then, one of the assemblies which is preheated
sufficiently, usually 30 to 50 seconds, is removed from
the preheating iron E to the welding iron H (Figs. 9 and
10) .
For productivity, the number of the assemblies
in the iron E should be more than three, i.e. before the
next one is taken away, a cold assembly should be placed
in the iron where the last one was. In other words, the
number of vacant channels in the iron E should not be
more than one.
m e welding iron H is activated to heat a narrow
band of the assembly so that the tube material in the
vicinity of the overlap 88 of the limb 11 with the end of
the lumen is melted enough so that the material flows
smoothly, leaving an imperceptible joint in which the
respective parts are to all intents and purposes integral.
m e heating should not be for long enough to degrade the
tubing material.
22 -
~225~
The temperature of the iron H must be higher than
the melting point of the tube material (the higher the
better), but must be lower than the burning point, i.e.
carbonizing point of the tube material and lower than the
melting point of the rods 20 and 22 material.
The following should be noted. The temperature
of the welding iron can be conveniently controlled occur-
lately and steadily. Step 2 may be omitted. Steps 2 and 3
can be changed as follows. The temperature of the iron H
is properly adjusted to be higher than the melting point of
the tube material and the temperature is kept substantially
constant. Four or more assemblies are placed in the iron H
at the same time (see Figs. 9 and 10). A narrow band of
the assembly is heated by the iron H. So after a couple
of minutes the tube material in the vicinity of the overlap
of the limb with the end of the lumen is melted so that the
material flows smoothly leaving an imperceptible joint in
which the respective parts are to all intents and purposes
integral.
When one of the assemblies is heated sufficiently
as above, it is removed from the heater and a cold assembly
placed in the heater. When observation shows that it is
heated sufficiently, it is removed and another cold assembly
placed in the heater, and so on.
Step 3 may be improved by using ultrasonic appear-
anus. In that case; the width of the narrow band of the
assembly, which is subjected to heating should be con-
trolled quite accurately and steadily.
Steps 2 and 3 may be carried out at a rate of 60
to 100 assemblies or more per hour per operator.
I Toe assembly is removed from the heater and air-
cooled. Then, the silicon sleeve 24 and the Teflon rods
20, 22 are removed. The branched tubular construction is
formed at the proximal end of the tubing D (as shown in
Fig. 11). Two limbs 19, 21 deviate at 89 to folk two
extensions, one for each lumen.
5) The branched construction is then fixed inside
the Y-adapter or auditor.
A new Y-adapter and Taipei adapter are designed
as shown in Figs. pa, 4b, 4c, I and 4j.
In a Y-adapter there is an arcuate deviating
channel 79. wafter the Y-adapter is molded, the inner mold
in this channel can be removed with a circular withdrawal
motion. The arcuate channel 79 is better adapted for the
obturators than a straight deviating channel. The branches
19, 21 are inserted through the single channel of the Y-
adapter into its deviating channels 78, 79. m e ends of
the branches 19, 21 are then welded inside the ends of the
channels 78, 79 at point 81.
One welding method is shown in Fig 12. A sift-
con sleeve 25 is put on each end of the channel 78, 79
and a rod 20 or 22 inserted into each end of the branches
19, 21. The assembly is then heated in the iron H. After
the ends of the channel and branch have been melted and
flowed together, the assembly is removed and air cooled
After it is cooled, the sleeve 25 and the rods 20, 22 are
removed. Then, the end which is melted is cut straight
and rounded by sanding.
Another method is shown in Fig. 13. A thin-
walled Teflon sleeve 37 is inserted with a tight fit into
the branch 19 or 21. A steel rod 38 which fits the inside
of the sleeve 37 is heated in the iron H and then inserted
into the sleeve 37, heating the end of the branch 19 or 21
through the Teflon sleeve 37.
- 24 -
I
In the meantime, the end of the channel 78 or 79
is also heated. After the end of the branch lo or 21 and
the inside of the channel 78 or 79 are melted so that the
material flows together, the Y-adapter with the sleeve 37
is removed and air-cooled. After cooling, the sleeve 37 is
removed. No cutting nor sanding is required. For this
reason, the method just described is faster than the first
method. The result of both is shown in Fig. pa.
In another method, the deviating channels 78, 79
lo are short, say 6 to lo mm in length, leaving the branches
19, 21 protruding, with the ends of branches 19, 21 flared
and perforated. Then, a compression molded end, which
will be integrated with the end of each branch (lo or 21)
is molded and integrated with each end of the channels
78, 79. The resulting product is as shown in Fig. pa.
A modified type of branched adapter C is shown
in Fig. 4c. A connector 39 is molded on the end of each
branch 78, 79). Then, the catheter is inserted through
the modified Y-adapter C and the connectors 39 are held in
place by a plastic block 40 and a screw 50.
Anther of making the proximal end part is
as follows. See Fig. 14.
The adapter C is molded at the proximal
end of the tubing D. At the same time, the end of tubing
D is welded integrally to the adapter forming a branched
tubular construction inside the adapter.
The prerequisites are the following. The mater-
tat of the adapter is weldable to the tubing D and is in-
flexible, and as hard as possible.
A straight rod US is selected of the same cross-
section as the rod 20, i.e. it fits tightly into the
arterial lumen 16. The rod 48 must be rigid and inflexible.
- 25 -
So
It may ye made of pure steel or of a Teflon sheath 47 with
a steel rod 46 as a rigid core. This is in effect a steel
rod 46 with a Teflon sheath 47 which may be quite thin, as
shown in Fig. 14.
An arcuate rod 49 is selected to have the same
cross-section as the rod 22, i.e. it fits tightly in the
venous lumen 18. The straight part of the rod 49 should
be flexible, but its arcuate part should be relatively
rigid, for example, Teflon sheath 45 with a steel core 44.
The straight part has a flexible Teflon core 43.
The rods 48 and 49 form the inner molds. Their
size may be progressively larger from the point aye, aye
- to the end 48b, 49b, as shown in Fig. 14.
A mold 42 is selected to form the outside shape
and size of the Adapter
At the proximal end of the tubing D, part of the
lumen 18 is removed, leaving the lumen 16 protruding.
Toe rods 48, 49 are inserted into the correspond-
in lumens respectively.
lye assembly is placed in the mold 42, leaving the
rods 48, 49 protruding. A length of silicon sleeve 24 is
put on the outside of the tubing D as shown in Fig. 14.
According to one method, the melted plastic to
form the Y-adapter is injected into the mold 42. The mold
42 is then heated until the tubing is melted sufficiently
to weld the Y-adapter to the tubing, specially in the
vicinity of the points aye and aye.
m e mold 42 is then cooled. After it is cooled,
the mold 42 and the rods 48, 49 are removed. The resulting
product is shown in Fig. 4b.
According to another method, the end of the
lumen 16 is flared, the lumen 16 is perforated near the
- - 26 -
~z~s;~9
end and then the Y-adapter is molded on the proximal end of
the tubing and cooled, the outside mold 42 of the Y-adapter
is removed, but the rods 48, 49 remain in the inner mold.
Then, melting is effected in the vicinity of thy point aye,
by a welding iron H and a length of silicon sleeve is put
onto the Y-adapter. After the Y-adapter is melted and
cooled, the rods 48, 49 and the silicon sleeve are
finally removed. The resulting product is shown in Fig
According to a still further method the end of
both lumens are first flared and both lumens perforated
near their ends. Then, the Y-adapted is molded. em e
resulting product is shown in Fig. 4j.
Part llC) Figs. 15 to 18 - Fashioning the Distal End
The distal end of the catheter A is manufactured
as follows.
1) An assembly is made up, as shown in Fig. 15, by
the following steps:
(i) The lumen 16 is slit lengthwise to a predator-
mined leIlgth at the distal end part of the
2 I:) tubing A;
(ii) A length of Teflon rod 22, sanded and polished
on its ends, is inserted into the lumen 18 and
protrudes beyond it,
(iii) A length of silicon tubing F is cut off to
provide a sleeve 26 (about SO mm in length).
e sleeve 26 is first dipped into liquid
Freon which causes it to enlarge and also
lubricates it. Then, the sleeve 26 is put
on the assembly (see Fig. 15).
Preferably, a large number, say, one hundred or
more, assemblies are jade up at the same time for the next
step.
- 27 -
12~g~
2) After the Freon has dried thoroughly, the welding
iron H is activated to heat the side of the assembly on
which the lumen 16 is slitted and the assembly is moved
relative to the iron to make sure the heated zone is moved
from a point 82 to the tip of the tubing A. The welding
temperature should be high enough and the speed of the
assembly slow enough to cause fusion of the overlapping
part of the slit portion of the lumen 16. The elasticity
of the silicon sleeve 26 will cause the molten material
to flow against the wall of the lumen 18 and will become
integral with it when it solidifies.
3) After it is melted sufficiently, the assembly is
removed from the iron and air-cooled. When it has cooled
sufficiently, -the silicon sleeve 26 and the Teflon rod 22
are removed. The result is shown in Fig. lo or to.
Part i - Making the Distal End (Alternative)
An alternative way of making the distal end is as
follows.
1) An assembly is made up, as shown in Fig. 16 by
the following steps:
(i) A length of raw plastic tubing is cut to
provide an extension 14. The extension
14 is sanded to provide an outside taper
on its end as at 14c, like limb 11 (Fig. 7).
- The sanded end is then cleaned with alcohol.
(ii) The rod 22, sanded and polished on its ends,
is inserted into the lumen 13 and protrudes
beyond it.
(iii) The extension 14 is then pushed into the
rod 22 until its tapered end enters the
end of the lumen 18. The end of the lumen
18 is stretched and enlarged by the entry
- 28 -
go
of the extension 14. The width of the over-
lap is preferably 1 to 3 mm.
(iv) A length of silicon elastomers tubing 26
is cut off to provide a sleeve 26 (about
20 mm in length). The sleeve 26 is first
dipped in liquid Freon which causes it to
enlarge and lubricates it. Then, the
sleeve 26 is put on the assembly (see Fig.
16).
Preferably, a number of assemblies, say one
hundred or more, are made up at the same time for the next
step.
2) After the Freon has dried thoroughly, the assembly
is placed in a channel on the iron E. For productivity,
there should be four or more assemblies placed in the
channel at the same time.
m e heating elements E are first activated to
preheat the adjoining part of the assembly to a temperature
higher than Luke, but lower than the melting (fusion)
point of the tubing material.
3) Then, one of the assemblies, which is preheated
sufficiently, is taken away from the preheating iron E to
be placed on the welding iron H.
The welding iron H is activated to heat a band,
which may be wider than that at the proximal end of the
assembly, so that, the tube material in the vicinity of the
overlap of the extension 14 with the end of the tubing D
is melted sufficiently so that the material flows smoothly
and the elasticity of the silicon sleeve 26 will cause
the molten material of the wall at the end of the lumen 16
to flow against the wall of the lumen 18, leaving an
imperceptible joint. The end of the extension 14 and the
- 29 -
1;~25i~9~
lumen 18, the wall at the end of the lumen 16, are to all
intents and purposes, integral, as shown in Fig. lo or to.
The speed of the steps (2), (3) should preferably
be, for example, 60 to 100 assemblies per hour per operator.
Using a special silicon elasiomer sleeve 30,
having the longitudinal section as shown in Fig. aye, and
the cross-section at an end aye, the same as silicon
tubing 24, and this cross-section (Fig. 17d), the other
end 30b is the same as that of the silicon tubing 26
(Fig. 17), and which is commercially available, the
assembly could be changed as follows.
The extension 14 is the same as described above.
A rod 20a,-rounded at the end by sanding and
polishing, is inserted in the lumen 16 to the extent shown
in Fig. 17b.
A rod aye consists of a Teflon sheath 45 and a
steel core aye which is curved at the predetermined points
as shown in Fig. 17b. The rod aye, which is rigid and
curved, is inserted in the lumen 18, as shown in Fig. 17b.
A pellet 56, of the same plastic material as that of the
tubing D, is placed in the lumen 16 just ahead of the
rod aye.
m en, the sleeve 30 is dipped in liquid Freon and
put on the assembly, as shown in Fig. 17b.
There should be a dotted bright line in the wall
of the silicon sleeve 30, as a visual index to show the
changing cross-section, i.e. so as to indicate the relative
positions of the rods aye, and -tubing 14, D and
sleeve 30.
After the Freon has dried thoroughly, the
assembly is preheated and welded as above. The width of
the molten zone is wider than in tune form of the invention
- 30 -
2529~
shown in Fig. 9 so that the iron block H must be wider.
The result is shown in Fig. lb. It is superior
to that in Fig. lay because there is no sharp corner at
the end of the lumen 16.
Another way of fashioning the distal end part is
as follows.
1) A length of rod 61 is selected of polyurethane
or polyethylene which is flexible and harder than the
material of tubing D and is readily weldable to it. The
cross-section of the rod 61 is the same as that of the
arterial lumen 16 of the tubing D, i.e. the rod 61 tightly
fits the lumen 16.
2) The distal end of the tubing D is tapered as
shown in Fig. 18.
3) An assembly is made up of the following steps,
shown in Fig. 18:
(i) An end aye of the rod 61 is sanded and
polished to fit the end of the arterial
lumen 16. The other end of the rod 61 is
cut as shown in Figs. lo and to and if.
(ii) A length of Teflon rod 20 is cut to fit
the cut end of the rod 61.
(iii) The rods 61 and 20 are inserted into the
arterial lumen 16. A length of Teflon 22
is inserted into the venous lumen 18. The
silicon sleeve 24 is then put on.
4) m e assembly is then placed in the iron H. The
end part 68 of the rod 61 is heated. After the end part
68 of the rod 61 is melted and welded with the wall of the
tubing D, the assembly is removed and air-cooled. Then
the rods 20, 22 and silicon sleeve 34 are removed.
- 31 -
lZ25Z951
The result is shown in Figs. id and to (after the
tip is sanded).
Part i Figs. 5 and pa to oh - Making the Obturators
The obturators must fulfill the quality require-
mints described. The body of the obturator is custom
ordered.
The distal end of the solid obturator 32 is
merely sanded and polished to fit the end of the lumen 16.
The distal end of the hollow obturator 31 should
be flared first to enlarge the end hole in order to receive
the Goodyear. Then, the outside of the end is sanded and
polished to fit the end of the lumen 18.
The proximal end of the obturator may be welded
inside of the body of the male lure lock 34 as shown in
Fig. 5. H is a melting iron, 28 a length of silicon
elastomers sleeve, 10 a steel rod within the hollow
obturator 31. The resulting product is shown in Figs.
6c and Ed.
When the obturators are made from Teflon and not
weldable to the body I the proximal end of the obturators
must be indented (for the solid obturator 32) or perforated
(for the hollow one 31) or flared at the tip. Then, the
body 34 of the male lure lock is molded on the end, as
shown in Figs. pa and 6b. If the body 34 of the male lure
lock is custom ordered, then a part of the body 34 is
melted on the indented or perforated or flared end of the
obturators, as shown in Fig. 5. The result is similar to
what is shown in Figs. pa and 6b.
The body of the male lure lock 34 must be par-
tidally closed at the end tip leaving a small hole for
receiving the Goodyear, bordered by an annular flange,
which is to prevent the hollow obturator 31 coming out at
1" ''I ~9g
this end. This end should not be melted, so as to avoid
the extra step of finishing it.
The length of the obturator must be predetermined.
If the material of the obturator is too hard to
make it flexible, some longitudinal straight discontinuous
slits may be cut along the length of the body of the
obturator to reduce the bend-resisting rigidity but, at
the same time, to retain rigidity against lateral pressure.
Alternative Forms of Tubing
Figs. 19 to 28
Another way to overcome the problem of kinking is
by manufacturing a special tubing, which inherently pro-
vents kinking. Up to now, the raw tubing for manufacturing
various catheters is made from uniform isotropic plastic.
Because a double lumen catheter is much larger than a
single one and the kinking, i.e. local buckling, occurs
much more easily, a non-uniform material is better than a
uniform material.
In the field of plastic engineering, varieties
of non-uniform, non-isotropic or combinative plastic pro-
ducts can be tailored to improve their mechanical behavior
under different loading and working conditions.
The invention contemplates special tubing desk
cried below for making the catheter.
One is a "multi-ring link" tubing. It is made
from two types of plastic. One plastic is very hard and
almost inflexible, ire. its modulus of elasticity (of
deformation) is substantially as high as possible. Another
is a soft stretch elastomers i.e. its modulus of eras-
I Taoist is quite low. The tensional strength of both are
almost equal. A prerequisite is that they are readily
weldable to each other.
Two kinds of rings, inflexible rings and elastic
~2;~S2S~
rings made from these two types of plastic are welded to-
getter one after another to form tubing. The inflexible
hard rings resist squashing (lateral stress). The elastic
soft rings make the tubing easily bent. And, the septum
wall prevents the tubing from changing in length, i.e.
stretching or compressing so the tubing may be bent with-
out kinking.
Another is a "metal spring" plastic tubing and
is a combination of a metal spring and soft elastic plastic.
m e metal spring resists squashing (lateral stress). The
plastic wall is easily bent. And, the septum wall keeps
the tubing constant in length. m e tubing may be bent
without kinking.
The distal end of the spring is looped, i.e.
doubled back as shown in Figs. aback, so that it will
not present a sharp end which might injure the vein of
the patient. The length of the spring is such that the
two opened free ends of the wire are located inside the
Adapter and thus away from the body of the patient.
A double lumen catheter formed from either of
these two types of tubing does not require obturators.
Alternate Embodiment
Fig. 19 is a side elevation of another form of
catheter, according to the invention.
The catheter is made up of a special septum walled
double lumen body M having an arterial lumen 16 and a venous
lumen 18. m e cross-section of the body M may be circular.
The body M extends from the distal end part 55
through an intermediate part 57 to a proximal end part.
At the distal end part 55 (the longitudinal section is
shown in Fig. lea), the lumen 16 is plugged by welding at
point 62. Then, there is a tapered tip 9, an end hole 7
- 34 -
I 39
and two groups of side holes 12, 13 as inlet and outlet
of the blood flow. At -the proximal end part, there is a
flexible tube 23 of silicon elastomers an inflexible
Y-adapter B and a flexible tube I of silicon elastomers
which connects the end of each branch of the Y-adapter
to a female lure lock 29.
This particular construction has the following
features:
a the body M of the catheter is made up of
a special septum walled double lumen
tubing which is made up of a combination
of two or three different materials so that
it is inherently capable of preventing
kinking,
b) the way in which the tubing is manufactured;
c3 the way in which a smooth branched tubular
construction is formed at the proximal end
of the body M in the same way as described
in Procedure Part I, or, at the same time
of manufacturing the tubing; and
d) the way in which the lumen 16 is plugged
at the distal end part.
m e way in which these alternative embodiments
of tubing are manufactured will be described in the
Manufacturing Procedure Part II.
Manufacturing Procedure Part II
Figs. 19 to 28
A) m e raw materials and equipment, which are
commercially available are the following.
1) A plastic which is hard, almost inflexible, e.g.
with very high modulus of elasticity. A plastic which is
soft elastic, e.g. with quite low modulus of elasticity.
m e materials are readily weldable to each other.
- 35 -
~L2~5~
2) The septum walls 74, 75, 76 and 77 are molded as
shown in Fig 20. In the wall 74, the area aye is hard
plastic, the area 74b, 75, 76, 77 are of soft plastic and
both 74 and 74b are molded (welded) integrally. The
thickness of the wall 76 is half of 74, 75 and 77.
3) The hard rings 63 made from hard plastic and
soft rings 65 made from soft plastic are molded as shown
in Figs. 21 and aye. The thickness of the ring should be
the same as that of the septum walls 74, 75, 77. The
width of the ring 63 is wider than twice that of 65.
4) Tubing 69 and 67, molded from the soft plastic,
is shown in Fig. 22.
5) The metal spring 70 or 90 for the walls of the
tubing and the straight wire 60 for the septum wall 75,
as shown in Figs. aye, 24b and 24c, are made from stain-
less steel or copper. The distal ends aye, aye, aye are
looped back, i.e. are continuous and smoothly curved.
one proximal ends 70b, 90b, 60b are free. A straight part
92 and the spring 90 is at the center of the cross-section
(see Fig. 25c). The diameter ox their wires is half the
thickness of the tubing wall, or slightly more.
6) A silicon elastomers sleeve 94, as shown in Fig. 23.
7) Two rigid straight rods 84, 85 or 86. 84 is made
of steel or of a Teflon sheath with a steel core. The
cross-section of the rods are shown in Figs. aye and 25b,
cud.
8) A steel outer mold 98 or aye, as shown in Figs.
25 or 26.
9) Heat treating equipment with temperature control
device, e.g. an oven. It should be noted that if the
pitch in the spring is less than the diameter of the side
holes, the special wire of the spring must be curved for
- 36 -
~L~ZS~
each side hole and when the spring is put on the retaining
rods, the location of two groups of side holes must be
carefully noted.
B) Manufacturing the multi-ring link tubing is as
follows. See Figs. 20 to 23 and 27, aye, 27b.
1) An assembly is made up, as shown in Fig. 23.
A septum wall 74 (or 75) is clipped (inserted) between
two rods 84 (or 85). See Figs. 23b or 25d. The rings
63 and 65 are put on one after another. The half circle
tubing 67 is put on the proximal end. At the proximal end
part there is a piece of aluminum foil 93 inserted between
the tubing 67. m en, the silicon sleeve 94 is dipped
into liquid Freon and put on the assembly.
2) After the Freon has dried thoroughly, the asset-
lo bites are placed in a preheating oven to be heated above
100C, but below the melting point of the hard and soft
plastics, i.e. not melted.
3) The preheated assembly is then placed in the
melting oven to melt the rings 63, 65, the septum wall 74
(or 75) and the tubing 67.
4) The assembly is finally taken out and cooled.
Then the sleeves 94 and the rods 84 (or 86) are removed.
The resulting product is shown in Fig. 27.
5) Fashioning the proximal end as described in Part
I, the foil 93 is inserted in the assembly, the steps (1),
to), (3), (4) in Part IT may be omitted.
6) Fashioning the distal end part, the lumen 16 is
plugged as described in Part ID. The rod 61 may be
shorter, as shown in Fig. lea.
C) Manufacturing the metal spring plastic tubing is
as follows. See Figs. aye, 20b, 20c, aye to 26 and 28.
1) A mold is formed as shown in Fig. aye. 98 is an
~zz~ g
outer mold of which the inner surface may be a Teflon
tubing, but the Cody of the mold must be steel. 97 is a
steel fixer to fix each end of the rods 84, 85 or 86. The
rods 84 or 85 or 86 must match the septum wall 74 or 76
with 92 or 75, respectively (see Figs. 25~, 25c, 25d).
Pieces of film 87 which are very thin and made from soft
plastic are inserted between the rods and the spring 70
(or 90~.
2) Molten plastic is injected into the mold 98
through the inlet 51 and the air is expelled by the outlet
53. m e whole mold is placed in an oven to keep it
slightly hotter than the melting point of the plastic.
3) After the plastic fills the inside of the mold
98, the mold is removed from the oven and cooled.
4) After the mold has cooled sufficiently, the
outer mold 98, the fixer 97 and the rods 84 (or 85, 86)
are removed. The tubing is then obtained. Steps (5) and
(6) are the same as that in B above. m e resulting pro-
duct is shown in Fig. 28.
D) A continuous manufacturing procedure is shown
in Fig. 26.
m e outer mold aye is much longer than 98 (in
Fig. 25) and with an open entrance 104 and an open exit
106.
The inner mold is the same as that in Fig. 25 and
consists of rod 84 (or 85, spurring 70 (or 90), septum
walls 74, 75 or 76 and fixers 97.
The container 101 is filled with molten plastic.
A small pipe 102 is an outlet for air. 107 is a heating
area, where the temperature is kept higher than the melt-
in point of the plastic. 109 is a cooling area where
the temperature is dropped from the melting point of the
- 38 -
:~22S~
of the plastic down to the normal temperature for example
20C at the exit 106.
Lowe inner molds 97, 84 go one by one into the
outer mold aye through the entrance 104 and leave the
exit 106 with the metal spring plastic tubing. See Fig.
28. The inner mold is taken apart to obtain the tubing
and assembled to be reinserted into the outer mold 98
through the entrance 104.
Advantages
Among the advantages of catheters, according to
the invention, are the following:
1. Effectiveness. During insertion of the
catheter into the body of a patient, there
is no kinking.
2. Size. The body of the catheter is 20 to 30%
smaller in cross-sectional area than existing
catheters.
3. Blood flow patency. The catheter, despite its
smaller size, increases the blood flow potent
trial by 10 to 20% or more over existing
products.
4. Blood flow quality. There is no dead space
in the branched adapter into which the blood
flow can be diverted.
5. Drug retention. When the catheter is left in
the body of a patient it effectively retains
the drug Heparin. This hinders blood clotting
as well as does a single lumen catheter.
6. Manufacture. The catheters of the invention can
be made at least as economically as existing
products because of their machinability.
- 39 -
Sag
7. The body of the catheter with the obturators
could be more flexible and pliable than the
existing product and could be stiffer, if
desired.
- - 40 -
