Method for the production of a medical instrument

The invention relates to a method for the production of a medical instrument, in particular a tube or catheter, with a balloon made of an elastomeric and/or thermoplastic material, comprising the steps of providing an inflation line for the balloon on or in one hose section and applying thereafter the cuff-shaped balloon with its two ends closely fitting and overlapping one outlet of the said inflation line. To render the production economical, a coat (3) of a parting compound is applied to the hose section (1) in the area where the balloon (10) is to be formed, whereafter the hose is sheathed by extrusion with a sheathing coat (5) of a thermoplastic or elastomeric material.

The present invention relates to a method for the production of a medical 
instrument, in particular a tube or catheter, with a balloon made of an 
elastomeric and/or thermoplastic material, comprising the steps of 
providing an inflation line for the balloon on or in one hose section and 
applying thereafter the balloon with its two ends closely fitting and 
overlapping one outlet of the said inflation line. 
Certain known methods for the production of a medical instrument equipped 
with a balloon consist in that initially a hose or hose section with a 
lumen extending in its longitudinal direction is produced into which an 
inflation line consisting of a thin hose is inserted which in turn has its 
end connected to a device for inflating or deflating the balloon, such as 
a syringe. Or else one produces, for instance by extrusion, a hose having 
two lumens extending along its longitudinal direction, with the second 
lumen, which serves as the inflation line and which has a very small 
cross-section being embedded in the hose wall defining the large lumen. If 
the hose consists of an appropriate material or was produced 
appropriately, the balloon may then be applied by dipping. To this end, a 
parting compound is applied to the balloon area, whereafter the hose is 
dipped until the skin applied by such dipping exhibits the required 
thickness. However, when the hose section is produced for instance by 
die-pressing or extruding, the long hose thus produced is cut into shorter 
sections onto which the balloon forming the cuff is mechanically fitted; 
tight fastening of the cuff is then achieved either by serving, if the 
hose section is for instance made of rubber or a similar material, or by 
heat-sealing or gluing of the balloon ends. 
However, both methods for producing medical instruments comprising a 
balloon, such as tubes and catheters, are extremely complicated because 
they require numerous operations to be carried out separately. 
Now, it is the object of the present invention to provide a production 
method permitting the low-cost and still reliable production of medical 
instruments of this type. 
According to the invention, this object is achieved in that initially a 
coat of a parting compound is applied to the hose section in the area of 
the balloon to be applied and that then the hose is sheathed with a coat 
of a thermoplastic or elastomeric material which is applied in one single 
operation by extrusion. 
It is a particular advantage of the method of the invention that it permits 
the very reliable and at the same time low-cost production of tubes, 
catheters and the like with a single or multiple balloons and that it 
permits the hose and the sheathing coat to be of different materials. It 
is of course possible also to make the hose walls and the sheathing coat 
of the same material, but in many cases it is preferred to employ a 
combination of two or even more materials to give the medical instruments 
produced in this manner certain desired properties which hitherto could 
not be achieved. For instance, it is now possible to make the hose walls 
and/or the sheathing coat of PVC or its copolymer, with the addition of a 
plastisizer. Or else, the hose wall and/or the sheathing coat may be made 
of a polyolefin. Likewise, the combination of PVC with plastisizer and 
polyurethane, in particular a thermoplastic polyurethane, may be used for 
the production of both hose walls and sheathing. This combination offers 
the advantage that the balloon is free from any plastisizer so that no 
plastisizer may penetrate from the packaged inflated balloon into the 
packaging material. Thus, the very expensive protection of the packing 
from such plastisizer which was hitherto necessary (multi-layer packing) 
is no longer needed. Further, this method prevents any migration of 
plastisizer from the balloon into the shaft which would render the latter 
excessively soft for practical use. 
Finally, the hose wall and/or the sheathing coat may also be made of 
caoutchouc and/or silicone caoutchouc. 
In order to permit the determination of the location of the medical 
instrument in the patient's body, preferred embodiments of the method of 
the invention use a material for the hose wall and/or the sheathing coat 
which is opaque to X-rays. Or else, the end of the inflation lumen is 
closed at the tip of the instrument with a plastic compound opaque to 
X-rays, or a metal pin is inserted into the tip of the inflation lumen. 
Finally, it is also possible to coat the tip area of the instrument with a 
varnish compound which is opaque to X-rays. 
When extruding the sheathing coat upon the hose section, which may 
initially have any desired length, the thickness of the sheathing coat may 
be freely selected within very broad limits, depending on the particular 
requirements. According to a preferred embodiment of the invention, the 
sheating coat may also be produced by applying to the hose section 
different successive layers of the same or else of different materials. In 
this arrangement, the last layer forms the balloon, while the layers 
previously applied form a sheathing about the hose section. 
In certain preferred embodiments of the invention, the surface to be 
coated, with the exception of the area to which the parting compound has 
been applied, is treated with a bonding agent or activated in any other 
manner, for instance by ionizing radiation or by flames, prior to applying 
the sheathing coat or--in the case of multilayer sheathings--prior to 
applying a layer of the sheathing coat. This activation may be achieved 
either by heating the surface areas in question in order to improve the 
bonding properties or else by the application in any form whatever of a 
chemical bonding agent, preferably in liquid form. When a bonding agent is 
used, it is finally also possible to produce the balloon by the fact that 
no bonding agent is applied in the area where the balloon is to be formed. 
As a result, no bond will be achieved between the hose section and the 
sheathing layer in this area, and in many cases it will not even be 
necessary to use a parting compound in this area. 
When the hose including the main lumen and the inflation lumen is produced 
by extrusion so that the hose is produced and the inflation lumen formed 
by one single operation, the method of the invention may immediately 
follow the production of the hose. In this case, a continuous production 
line may have the hose production immediately followed by a store, in 
particular a roll store, followed in turn by a marking device for applying 
the print. This in turn may be followed by devices for applying the 
parting compound and/or devices for activating the surface of the hose so 
that the latter will readily bond to the sheathing coat applied 
thereafter. In this area, means are also provided for opening the 
inflation lumen from the outside, for instance by cutting, milling or 
boring, in the area where the balloon is to be subsequently formed. 
This device is in turn followed, if necessary via an additional store--by 
an extruder with crosshead which applies to the hose the sheathing forming 
also the balloon. However, the method of the invention also lends itself 
to the processing of hoses purchased as semi-finished product. While the 
mehtod described first is mainly suited for larger production series, the 
latter permits the low-cost production of medical instruments with balloon 
also in medium and small series. 
Medical instruments produced in accordance with the invention offer the 
advantage that the material of the hose section may be selected along 
criteria different from those used for the selection of the sheathing 
material, so that optimum properties of the instrument as a whole and 
especially of the sheathing coat may be achieved, depending on the 
particular application of the instrument. In particular, the material used 
for the sheathing coat will be selected on the one hand to be well 
tolerated by the body and, on the other hand, to give the balloon the 
desired properties.

The hose section 1 is produced by die-pressing or extrusion. 
During this process, an inflation lumen 2 extending over the whole length 
of the hose is formed in the wall of the hose section. Following the 
production of the hose, the desired prints are applied to the hose. In the 
areas were the hose is to be provided with balloons, a ring of parting 
compound 3 is applied to the hose. If the inflation lumen 2 is to open 
outwardly, corresponding openings are milled, cut or provided in any other 
manner in the corresponding areas. In this operation, the tools are 
approached to the hose mainly in the tangential direction so as to produce 
a relatively large cut which will be easily found during the finishing 
processes. 
Thereafter, the hose or hose section 1 is transferred to the crosshead of 
an extruder for the application of a sheathing coat 5. While passing the 
crosshead, the hose section is sheathed with a thin coat 5. In order to 
increase the rigidity of the hose during this operation, an internal 
pressure may be generated within the hose in a conventional manner. The 
thin sheathing coat 5 applied bonds firmly to all areas of the hose 
section 1 where no parting compound 3 has been previously applied or where 
the surface had not been activated, and forms a balloon 10 in the areas 
overlying the parting compound 3, and this area also exhibits one opening 
6 leading from the inflation lumen 2 to a point below the sheathing coat 
5. 
In the area opposite the balloon 10, an opening 7 is provided to which an 
inflation hose 4 is fastened. The opening 6 forming the desired connection 
between the inflation lumen and the interior of the balloon is provided in 
the inflation lumen, which was produced in one operation with the 
production of the hose section, prior to the application of the coat or 
coats forming the balloon. 
The forward end of the catheter adjacent the balloon is heated whereby the 
edges melt together and the end of the inflation lumen is closed. Instead, 
however, a PVC tip closing simultaneously the inflation lumen may be fixed 
by gelling For this purpose, a PVC mixture which is opaque to X-rays may 
be used. Or else, the inflation lumen may be closed by a plug made of 
plastic material or metal which is opaque to X-rays and which may be fixed 
by gluing or else inserted and thereafter fixed by gelling (In the case of 
the instrument shown in the drawing, this operation was not yet carried 
out, and the front end of the instrument is still sharp-edged). PG,10