Abstract:
A flexible tip dilator is disclosed. The flexible tip dilator includes a hollow elongated tubular member with a proximal region and a tapered distal region. The tapered distal region has three regions with a first region made from at least a first material but not a second material and a third region made from at least the second material but not the first material. The second region is includes both the first and second materials overlapping one another.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to U.S. Provisional Patent App. No. 62/111,664, filed Feb. 4, 2015, the disclosure of which is hereby incorporated by reference in its entirety. 
    
    
     FIELD OF THE DISCLOSURE 
     The disclosure generally relates to a dilator. Specifically, the disclosure relates to a dilator having a flexible tip. 
     BACKGROUND 
     Dilators are generally used to stretch a channel created by a needle through the skin and subcutaneous tissue in a procedure to gain vascular access. In Internal Jugular insertions, dilators are inserted over a guidewire and, therefore, have a tip that tapers from a small diameter that is slightly greater than the diameter of the guidewire to the widest diameter of the dilator. 
     Dilators are traditionally made of polyethylene to achieve optimal product performance. The distal tips of the dilators are typically made of the same material as the rest of the dilator and are, therefore, stiff and sharp. Due to manufacturing variations and the need for minimized drag along the guidewire, dilator tips are usually loose around the guidewire, causing the dilator tip to catch tissue or damage vessel walls during dilation. In addition, due to their stiffness, the dilator tips cannot flex enough when there is tight bend over a short distance, causing a kink in the guidewire. Furthermore, dilator tips typically flare when the dilator hits an object like skin, subcutaneous tissue, or a vessel wall, causing sharp edges at the distal tip that can prevent insertion of the dilator or can damage a vessel during insertion. 
     Accordingly, there is a need for a dilator having a flexible tip such that risk of injury to vessels is reduced. 
     SUMMARY OF THE DISCLOSURE 
     The foregoing needs are met, to a great extent, by a flexible tip dilator. In one or more aspects, the flexible tip dilator is made of at least a first material and a second material. The flexible tip dilator includes a hollow elongated tubular member having a proximal region and a tapered distal region. The tapered distal region includes a first region, a second region distal to the first region, and a third region distal to the second region. The first region of the tapered distal region is made of at least the first material but not the second material. The second region of the tapered distal region includes the first material and a second material overlapping one another. The third region of the tapered distal region is made of at least the second material but not the first material. The second material is different from and more flexible relative to the first material. 
     In some aspects, the first region can have a first taper angle and the second region can have a second taper angle continuous with the first taper angle. In some aspects, the first material can be adhered over the second material in the second region, while in other aspects, the second material can be adhered over the first material in the second region. The first material can be polyethylene, polypropylene, polymethylpentene, fluoropolymer, polybutene-1, or a copolymer thereof. The second material can be ethyl-vinyl acetate, styrenic block co-polymers, or other thermoplastic elastomers. The second material can preferably be ethyl-vinyl acetate. 
     In some aspects, the elongated tubular member can have an inner diameter larger than an outer diameter of a guidewire. The proximal region of the hollow elongated tubular member can include a hollow hub. 
     Certain aspects of the flexible tip dilator have thus been outlined in order that the detailed description may be better understood. There are, of course, additional aspects of the disclosure that will be described below and which will form the subject matter of the claims. 
     In this respect, before explaining at least one aspect of the disclosure in detail, it is to be understood that the disclosure is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The disclosure is capable of aspects in addition to those described and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the Abstract, are for the purpose of description and should not be regarded as limiting. 
     As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods, and systems for carrying out the several purposes of the disclosure. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the disclosure may be readily understood, aspects of the disclosure are illustrated by way of examples in the accompanying drawings. 
         FIG. 1  is a perspective view of a dilator and sheath assembly. 
         FIG. 2  is a side view of a distal region of one aspect of a flexible tip dilator. 
         FIG. 3 a    is a first partial cross-sectional view of the distal region of one aspect of a flexible tip dilator. 
         FIG. 3 b    is a second partial cross-sectional view of the distal region of another aspect of a flexible tip dilator. 
         FIG. 3 c    is a third partial cross-sectional view of the distal region of yet another aspect of a flexible tip dilator. 
     
    
    
     Aspects of the flexible tip dilator are described with reference to the drawings, in which like reference numerals refer to like parts throughout. 
     DETAILED DESCRIPTION 
     The flexible tip dilator disclosed herein minimizes vessel damage due to its tapered tip made from a flexible material, and provides improved tracking over the guidewire. In addition, insertion forces required to introduce the dilator into the vessel can be reduced. 
     Referring to  FIG. 1 , a dilator assembly  2  is illustrated. The dilator assembly  2  includes a dilator  4  and an introducer  10 . The introducer  10  may be a cylindrical shaft with an end that may be tapered. An introducer hub  6  is located at the proximal end of the introducer. The dilator assembly  2  includes lumens  12  for injection and aspiration and hubs  13  at the proximal ends of the lumens  12 . 
     The dilator  4  is an elongated tubular shaft having a hollow inner portion. The dilator  4  has a tapered distal end and a dilator hub  8  at its proximal end. The dilator  4  has an outer diameter smaller than an inner diameter of the introducer  10 , such that the dilator  4  may be inserted into the proximal end of the introducer through the introducer hub  6 . The dilator  4  and the dilator hub  8  may be fixed securely to one another in a manner that prevents axial and rotational movement of the dilator relative to the dilator hub  8 . 
     One aspect of the distal region of the dilator  4  is illustrated in  FIG. 2 . The distal region of the dilator  4  includes two sections. A first region  14  includes a first material and the second region  16  includes a different second material more materially flexible than the first material. The first region  14  of the dilator  4  proximal of the tapered region  18  does not include the second material. The second region  16  of the dilator  4  does not include the first material. The dilator  4  may also begin tapering at a tapered region  18  of the first region  14  and continue tapering through the second region  16 . The tapered region  18  may begin at any point along the length of the dilator  4 . Alternatively, the tapered region  18  may also extend along the full length of the dilator  4 . The inner diameter of the dilator  4  may be large enough to accommodate a guidewire having a diameter between, for example, 0.01 to 0.05 inches. 
     In some aspects, the first region  14  may be made from a polyolefin, such as high density polyethylene (HDPE) or low density polyethylene (LDPE). The first region  14  may alternatively be made of polypropylene, fluoropolymer, polymethylpentene, polybutene-1, or a copolymer thereof, or another polymer having similar stiffness properties. The selected polymer may exhibit crazing as opposed to cracking when reaching material yield. The first region  14  may have a low coefficient of friction, be hydrophobic, and/or have low surface energy. 
     In some aspects, the second region  16  may be made of ethylene-vinyl acetate (EVA) or another elastomeric polymer such as styrenic block copolymers, or other thermoplastic elastomers. The second region  16  may have a Shore durometer measurement less than a Shore durometer measurement of the first region  14  and have a high strain before failure and/or relatively high tear resistance. The material of the second region  16  may adhere to the material of the first region  14  during a melting process. 
       FIGS. 3 a -3 c    describe different aspects of the distal tip of the dilator  4 . In  FIG. 3 a   , the first region  14  may contact the second region  16  along an even seam  20  at an annular cross-section. The first region  14  may adhere to the second region  16  at seam  20  after a melting process or using an adhesive. Alternatively, as shown in  FIG. 3 b   , the second region  16  may adhere over the first region  14  in an overlap region  22 . Due to the increased surface area of contact between the first region  14  and the second region  16  relative to the aspect shown in  FIG. 3 a   , there may be improved adhesion between the first region  14  and the second region  16  in the aspect shown in  FIG. 3 b   . In addition, because the second region  16  may adhere over the first region  14 , there may be a less likelihood that a corner of the first region  14  catches onto a vessel during insertion of the dilator  4 . 
     In yet another aspect, as shown in  FIG. 3 c   , the first region  14  may adhere over the second region  16  in an overlap region  22 . Due to the increased surface area of contact between the first region  14  and the second region  16  relative to the aspect shown in  FIG. 3 a   , there may also be improvement in adhesion between the first region  14  and the second region  16  in the aspect shown in  FIG. 3 c   . Because of the material and structural properties of the first region  14  and the second region  16 , this configuration may provide improved mechanical support for material adhesion between the two regions through a friction fit or an interference fit. 
     The many features and advantages of the flexible tip dilator  4  are apparent from the detailed specification, and thus, the claims cover all such features and advantages within the scope of this application. Further, numerous modifications and variations are possible. As such, it is not desired to limit the flexible tip dilator  4  to the exact construction and operation described and illustrated and, accordingly, all suitable modifications and equivalents may fall within the scope of the claims.