Catheter-type instrument

June 7, 1949.

2,472,484

L. H. KRIPPENDORF

CATHETER-TYPE INSTRUMENT

Original Filed May 5, 1944

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Patented June 7, 1949

2,472,484

Claims.

.5 .10 .15

UNITED STATES PATENT OFFICE £{472,484

C ATHETER -TYPE INSTRUMENT

Louis H. Krippenfloiff, White IPlains, IN. Y., f»signorto American> Catheter -Corporation, Port Chester, N. Y., a corporation-of New York

Original application May .‘5, 1944, Serial No. 534'207, now -Patent No. 2/37,542, dated March '9 1948. Divided and this -application December 10,1947, -SerialNo. 790)819 (Cl. .138—49) adhered Ίο,-yet the-body portion of the resultant instrument may be -'caused to -embody a flexibility-in the-forward or other section thereof which is to :a -predetermined - extent -appreciably greater ’ or less than-the-flexibility-in an adjacent section.

This new -result -and -its - corresponding advantages -may be .accomplished in the manner illustratively ^exemplified in-the accompanying drawing, inwhich: .

-Figure iJisTaiperspective-view of atypical catneter-type-instrument; .

Figure 2 ds an ^.enlarged fragmentary view of a portion of the instrument -with the outer coating -broken away to -reveal the fabric base in the region-of the line A—A-of-Figure 1; and ,Figure-3.isra-diagrammatic view illustrating the comparative characteristics, as 'far as flexibility is concerned, of a conventional catheter-type instrument-and-one Which has been constructed in accordance -with the present invention.

The features -of the -invention may best be described-by-brief preliminary reference to conventional’practice. „ ...

>A -fabric -base -is -first -created. Usually, this base .assumes the form Of an elongated hollow tube, -but under certain -circumstances it need not -have a .longitudinal -passageway extending through it. This base is -formed of -intertwined threads Of -Silk, cotton, -or -synthetic fibre, and usually the threads are braided -into the -desired relationship. .'Any -.weaving or other procedure may-be resorted to, however,® desired, although braiding machines -have proven to be admirably suited to produce a tubular -or elongated fabric i base of the character-required. This base is initially limp in -character, and .is customarily impregnated with a flexible .-stiffening medium of suitable composition. Where the base is a tube, the impregnation is carried out-while the tube is mounted -upon a .suitable rod or mandrel. After wiping off any excess, the mandrel (if one has been used) is,removed andthe impregnatingmedium is caused to harden or cure,-either by air drying, or by subjection to a bakingprocedure or the like. The reinforced .and strengthened fabric base is then subjected to a series of operations during which -a flexible tough varnish coating is applied to .it, layer .by layer, the successive coatings being cured by baking -of analogous procedures. After the. desired coating -has-been formed, it is burnished -and the .instrument is subjected to -such other -finishing processes as may be deemed desirable.

The .forward tip .of the instrument may -be formed -either prior to .or after the initial impreg-.

This application is a division of my co-pending application, Serial No. 534,207, filed May '5, .1944, nowaPatent:No..2,437.j542.

The invention relates generally to .surgical instruments and has particular reference to catheter-type instruments.

By the term “catheter-type instrument, as used herein-and in the appended claims, I intend to refer to the well-known kind of device which is inserted endwise into and through constricted · body channels for diagnostic, therapeutic and'allied purposes. Illustrative of such .instruments are ureteral and .urethral catheters, bougies, filiforms, and the-like.

A conventional instrument of this type is of elongated -character -and 'has a uniform over-all flexibility coupled with sufficient rigidity to 'permit its endwise advancement. This paradoxical requirement for both flexibility and rigidity has heretofore presented a peculiar problem to the manufacturer. For example, in the case -of -a ureteral catheter, it must be of sufficient flexibility to permit the tip of the instrument to advance harmlessly through the-constricted ureteral canal and readily to ‘follow the curvatures encountered, yet as the flexibility is increased by the manufacturer to meet this requirement, the body portion -loses some of the rigidity .necessary to enable the operator to effect the -desired advancement by endwise pressure exerted upon the rear end of the instrument. Similarly, in the case of bougies or the like, it may under certain circumstances be desirable to increase 'the rigidity of the tip portion, yet the instrument .as a whole may thereby become too inflexible toffol•low an irregularly curvedpath with adequate ease.

The principal -object of my present invention is directed toward a solutionof this -problem, and my invention is predicated upon the -discovery that a catheter-type instrument may be caused 40 to .embody different flexibilities along its .longitudinal axis without materially altering its -basic structural nature or impairing the other inherent qualities which it necessarily must possess. This desirable and advantageous -result is -achieved in an entirely practical and commercially-feasible manner.

Tn accordance with one conventional manufacturing procedure, the -construction .of -a catheter-type instrument involves the formation Pf an initially limp fabric base of intertwined threads, this base being usually first impregnated with a flexible, stiffening medium and then coated with a flexible varnish. Tn the practice of my present invention, this general procedure is 55

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2,472,484 nation of the fabric base, depending upon the nature of the instrument, and the kind and shape of tip which it is intended to have. In the case of catheters, the several openings or eyes which characterize these instruments may be formed at or near the forward tip either during the braiding of the base or during a subsequent stage of treatment.

Depending upon the nature and size of the threads originally employed in forming the fabric base, upon the dimensions of this base and upon the impregnating and coating media which are employed, the resultant instrument will have a size and flexibility of predetermined character. Heretofore, in an instrument in which the body portion is of substantially uniform diameter, the bendability and over-all semi-rigidity has been uniform throughout, being usually determined by a suitable compromise between the flexibility required for any given purpose and the stiffness called for by the well-known method in which the instrument is to be employed.

In accordance with my invention, the essential nature of the manufacturing process remains unchanged, yet varying degrees of flexibility may be imparted to the resultant instrument along its longitudinal axis. For illustrative purposes, I have chosen to describe and illustrate the manner in which a catheter may be caused to have an appreciably increased flexibility in its forward region adjacent to the tip, as compared with the flexibility and rigidity of the remaining main portion thereof.

Thus, in Figure 1,1 have illustrated a catheter 10 in which the region forwardly of the dot-anddash line A has been caused to embody a greater flexibility than the remaining main portion of the catheter.

The procedure followed in accordance with the present invention is illustrated in Figure 2, which shows the structure in the vicinity of the dot-and-dash line A—A. The initially limp fabric base tube is formed of two separate portions 15 and 16 arranged in overlapping nested relationship. These portions may be formed of different materials or may be composed of threads of the same material but having different calibres. Or, if desired, both the material of the threads and their calibres may be different. In any case, the portion 15 is caused to embody an inherent structure which is suitably different from the portion 16 so that after impregnation and curing, these two portions will exhibit appreciably different flexibilities.

Where the instrument has its forward portion more flexible, as indicated in Figure 1, the base tube section in the forward region is of such structure that it has greater flexibility than that of the other section.

The separate parts of the base tube may be brought into the overlapping relationship shown during the course of the braiding procedure. This composite base tube is then impregnated with a flexible stiffening medium which may be, for example, of the general type in which a suitable carrier such as tung oil is associated with a resin or resins of polymerizable type, together with a plasticizer or other customary ingredients. There are numerous resins which can be employed, and among them are, for example, resins of the phenolic type. The plasticizer used may be any of the usual ones, such as castor oil, dibutyl phthallate, tri-cresyl-phosphate, and the like.

In practice, the tube may be mounted on a suitable rod or mandrel (not shown) either be4 fore or after the forward tip is formed, and may then be dipped into the impregnating medium The excess is then wiped off and the impregnated tube may be placed in a suitable oven to bring fi about a curing of the impregnating medium.

At a suitable occasion the mandrel is withdrawn, and subsequently the tube is handled in the usual fashion to form on it the outer coating 14 of flexible varnish, which may be composed, for 10 example, of a tung oil base, a phenolic or other suitable resin, and a plasticizer. This outer coating produces a tough flexible film having a smooth glossy surface and resistant to water, body fluids generally, and standard types of 15 sterilization. The coating of flexible varnish serves to integrate the base tube portions to form a single and unitary body, and in the finished instrument it will be found that the exterior surface is entirely smooth and uniform despite the 20 overlap in the interior, which is shown on an exaggerated scale in Figure 2.

Another way of imparting the desired differences in flexibility to the portions 15 and 16 of the base tube, or of enhancing differences which 25 are otherwise present, is to cause one of the portions 15 and 16 to be more loosely intertwined than the other.

The basic difference between the instrument of Figure 1 and the ordinary type of instrument is 30 indicated diagrammatically in Figure 3. If the ordinary catheter 18 is pressed endwise against an abutment wall 19, by pressure exerted in the direction indicated by the arrow 20, it will buckle throughout its length. On the other hand if 35 the instrument 10 of Figure 1 is similarly pressed against an abutment 19 by a similar pressure exerted along the direction of the arrow 21, it will buckle in the forward region of greater flexibility, but not otherwise. Accordingly, when the instru40 ment 10 is inserted into and advanced through one of the ureters or through any other similar constricted body canal, it will feel its way more easily past the curvatures encountered, and this makes the operation safer and simpler.

While I have illustrated a catheter, it will be understood that the invention is equally applicable to any catheter-type instrument, whether hollow or not; and while I have chosen to illustrate the manner in which the forward region of the 50 instrument may be made more flexible than the balance, it will be understood that other relative flexibilities may be produced, depending upon particular requirements.

In general it will be understood that the details 55 herein described and illustrated to explain the general nature and objective of the invention may readily be modified by those skilled in the art without departing from the spirit and scope of the invention as expressed in the appended 60 claims.