URINARY CATHETER HAVING A SOFT TIP

Abstract

A urinary catheter is disclosed, comprising a tubular shaft extending between an insertable end and a discharge end, and a tip fixedly connected to said insertable end of the tubular shaft. The tip has an outer diameter which at all places is equal to or lower than the outer diameter of the tubular shaft, and is very soft, so that the hardness of the tip is equal to or lower than 60 micro Shore A. It has been found that such a soft tip provides a catheter which is easier to insert into the urethra, in particular in urethras providing various types of obstacles. A corresponding method of manufacturing is also disclosed.

Claims

1-26. (canceled)

27. A urinary catheter comprising a tubular shaft extending between an insertable end and a discharge end, and a tip fixedly connected to said insertable end of the tubular shaft, wherein said tip is solid and has an outer diameter which at all places is equal to or smaller than the outer diameter of the tubular shaft, and comprises a part tapering in a direction away from the tubular shaft, and a rounded end part, and wherein a hardness of the tip is within the range 20-60 micro Shore A and the tip has a micro Shore A hardness which is lower than the micro Shore A hardness of the tubular shaft, wherein the urinary catheter is a hydrophilic urinary catheter with a single lumen.

28. The urinary catheter of claim 27, wherein the tip is curved and angled upwards.

29. The urinary catheter of claim 27, wherein the hardness of the tip is equal to or lower than 50 micro Shore A.

30. The urinary catheter of claim 27, wherein the hardness of the tip is equal to or lower than 45 micro Shore A.

31. The urinary catheter of claim 27, wherein the hydrophilic urinary catheter is at least partly provided with a hydrophilic surface coating, said hydrophilic surface coating exhibiting a reduced friction when wetted

32. The urinary catheter of claim 27, wherein the hydrophilic urinary catheter is made of a hydrophilic material.

33. The urinary catheter of claim 27, wherein the tip has a micro Shore A hardness that has at least 10% lower than a micro Shore A hardness of the tubular shaft.

34. The urinary catheter of claim 27, wherein the tip has a micro Shore A hardness that is at least 30% lower than a micro Shore A hardness of the tubular shaft.

35. The urinary catheter of claim 27, wherein the tip has a micro Shore A hardness that is at least 50% lower than a micro Shore A hardness of the tubular shaft.

36. The urinary catheter of claim 27, wherein the tubular shaft has a micro Shore A hardness within the range 75-95 micro Shore A.

37. The urinary catheter of claim 27, wherein the tip is continuously tapering in a direction away from the tubular shaft.

38. The urinary catheter of claim 27, wherein the tip has an E-modulus which is lower than the E-modulus of the tubular shaft.

39. The urinary catheter of claim 27, wherein the tip has an E-modulus which is 10-30% lower than the E-modulus of the tubular shaft.

40. The urinary catheter of claim 27, wherein the E-modulus of the tip is within the range 6-16 MPa.

41. The urinary catheter of claim 27, wherein the E-modulus of the tip is within the range 9-13 MPa.

42. The urinary catheter of claim 27, wherein the tip is integrally and monolithically formed with the tubular shaft.

43. The urinary catheter of claim 27, wherein the tip is partly inserted into a lumen opening of the tubular shaft.

44. The urinary catheter of claim 27, wherein the tip is connected to the tubular shaft by at least one of welding, adhesion or injection molding.

45. The urinary catheter of claim 43, wherein the contacting surfaces of the tip and the tubular shaft are extending at least partly in a longitudinal direction of the catheter.

46. The urinary catheter of claim 45, wherein the contacting surfaces of the tip and the tubular shaft form at least one of a finger joint or a splice joint.

47. The urinary catheter of claim 27, wherein the tip and the tubular shaft are formed of different materials.

48. The urinary catheter of claim 28, wherein the tip has a height in a lateral direction which is higher than the diameter of the tubular shaft.

49. The urinary catheter of claim 48, wherein a relation K/d is in the range 1.5 to 2, where K is the height of the tip and d is the diameter of the tubular shaft.

50. The urinary catheter of claim 27, wherein the end part forms a ball-shaped head portion.

51. A urinary catheter comprising a tubular shaft extending between an insertable end and a discharge end, and a tip fixedly connected to said insertable end of the tubular shaft, wherein said tip is solid and has an outer diameter which at all places is equal to or smaller than the outer diameter of the tubular shaft, and comprises a part tapering in a direction away from the tubular shaft, and wherein a hardness of the tip is within the range 10-50 micro Shore A, an E-modulus of the tip is within the range 6-16 MPa, and a hardness of the tubular shaft is within the range 75-95 micro Shore A, and wherein the urinary catheter is a hydrophilic urinary catheter with a single lumen.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0060] By way of example embodiments of the invention will now be described with reference to the accompanying drawings in which:

[0061] FIG. 1 illustrates an embodiment of a catheter according to the invention;

[0062] FIG. 2 is a more detailed cross-sectional view of the catheter tip in the catheter of FIG. 1;

[0063] FIG. 3 is a cross-sectional view of a curved tip configuration, in accordance with another embodiment of the present invention; and

[0064] FIGS. 4a-f are cross-sectional views of various tips in accordance with embodiments of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0065] In the following detailed description preferred embodiments of the invention will be described. However, it is to be understood that features of the different embodiments are exchangeable between the embodiments and may be combined in different ways, unless anything else is specifically indicated. It may also be noted that, for the sake of clarity, the dimensions of certain components illustrated in the drawings may differ from the corresponding dimensions in real-life implementations. Even though in the following description, numerous specific details are set forth to provide a more thorough understanding of the present invention, it will be apparent to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well known constructions or functions are not described in detail, so as not to obscure the present invention.

[0066] The following discussion is in particular concerned with hydrophilic urinary catheters for intermittent use. However, the invention can also be used in relation to other types of urinary catheters.

[0067] A catheter 1 as illustrated in FIG. 1, comprises a flared rearward portion 2 and an elongate shaft or tube 3 projecting forwardly from the rearward portion 2. An open-ended internal lumen extends from the rear end of the rearward portion 2 to one or more drainage apertures 4 in a forward end of the catheter. At the forward end of the elongate shaft 3, a tapering tip 5 is arranged, having a rounded tip end. The rearward portion 2 may function as a connector of the catheter 1, being connectable to other devices, such as a urine collection bag, a drainage tube or the like.

[0068] The drainage openings may be arranged in the forward end of the tubular shaft, in which case the lumen does not need to continue into the tip, which may as a consequence be solid. Alternatively, the eyes may be arranged in the tip, in which case the lumen at least partly continues into the tip.

[0069] At least a part of the elongate tube 3 forms an insertable length to be inserted through a body opening of the user, such as the urethra in case of a urinary catheter. By insertable length is normally meant that length of the elongate tube 2 which is insertable into the urethra of the patient during ordinary use. In case a hydrophilic catheter is used, the insertable length is coated with a hydrophilic material, for example PVP, or is made of hydrophilic material. Typically, the insertable length is 80-140 mm for a female patient and 200-350 mm for a male patient.

[0070] The tip may be straight, extending in the same direction as the tubular shaft and forming a rounded forward end, thereby forming a Nelaton type catheter. Such an embodiment is illustrated in FIGS. 1 and 2. The tip has an outer diameter dT which at all places is equal to or lower than the outer diameter d of the tubular shaft. The tip is preferably arranged conically tapering in the forward direction, to end in a rounded tip. However, alternative configurations are also feasible. For example, the tip may over part of its extension have a cylindrical configuration with the same diameter, may be arranged in a stepwise reduced diameter, may have parts being slightly enlarged, such as a ball shaped forward end, or the like. For example, the end may be provided with a slightly enlarged rounded or ball-shaped head portion, which, however, has at least a slightly smaller diameter than the diameter of the tube.

[0071] The tip may also be curved, forming a Tiemann or Coudé type catheter. Such a tip is illustrated in FIG. 3. The curved tip also has a diameter dT which at all places is equal to or lower than the outer diameter d of the tubular shaft. The curved tip preferably has a height K in a lateral direction which is higher than the diameter d of the tube, and preferably the relation K/d is in the range 1.5-2.

[0072] The tips may be designed and connected to the tubular shaft in various ways, and some exemplary embodiments of this will now be discussed with reference to FIGS. 4a-e. The tip preferably connects with the same outer diameter to the tube, thereby providing an outer transition area without steps, edges or the like.

[0073] The tip of the catheter forms a free forward end which presents the free forward end of the catheter body, which is spaced apart from the forward end portion of the tubular shaft. Thus, the shaft extends rearwardly from the rear end of the tip portion. A lumen extends through the tubular shaft, from the discharge end to the forward end of the catheter. The lumen ends in drainage openings, so-called eyes, These eyes may be arranged in the forward end of the tubular shaft, in which case the lumen does not need to continue into the tip, which may as a consequence be solid. Examples of such tip configurations are illustrated in FIGS. 4a, 4b, 4d and 4f. Alternatively, the eyes may be arranged in the tip, in which case the lumen at least partly continues into the tip, as in FIG. 4c. It is also possible to use a lumen partly extending into the tip, even though the drainage eyes are provided in the tubular shaft, as illustrated in the embodiment of FIG. 4e. Hereby, the tip can be made more flexible, and less material is needed for producing the tip.

[0074] The tip may be integrally and monolithically formed with the tubular shaft. In this case the tip may be partly inserted into a lumen opening of the tubular shaft. Such an embodiment is illustrated in FIG. 4a. The tip and tubular shaft may also be produced simultaneously, e.g. by two-component injection molding.

[0075] The connector, i.e. the flared rearward portion 2 is optional, and catheters without any flared rearward portion may also be used. In case a flared connector is used, this may be formed integrally and monolithically at the rearward end of the tubular shaft. However, it may also be formed as a separate component, being connected to the tubular shaft by means of welding, adhesion or the like. It may also be inject molded directly in place. In this case, the inject molding of the tip at the forward end of the tubular shaft and the connector at the rearward end of the tubular shaft can be performed simultaneously.

[0076] In order to provide a stronger connection between the tip and the tubular shaft, the outer surface of the inserted tip, and/or the corresponding inner surface of the tubular shaft, may be provided with a surface texture or surface features, and preferably a texture/feature matching each other to form a mechanical engagement. For example, the tip may be provided with outwardly protruding elements, such as a dent, bump, ridge or the like, and the tubular shaft may be provided with corresponding indent elements, such as holes, grooves or the like. However, naturally the protruding elements can be arranged on the tubular shaft instead, or a combination of protruding and indent elements be provided on both parts. Such an embodiment is schematically illustrated in FIG. 4f.

[0077] Alternatively, the tip may be connected to the tubular shaft by at least one of welding, adhesion and inject molding. In the embodiment of FIG. 4d, the connection is made on surfaces extending entirely perpendicular to the longitudinal direction of the catheter.

[0078] However, in order to increase the strength of the joint, the contacting surfaces of the tip and the tubular shaft may also extend at least partly in a longitudinal direction of the catheter, thereby e.g. forming a finger joint, as illustrated schematically in FIG. 4c, or a splice joint, as illustrated schematically in FIGS. 4b and 4e.

[0079] The catheter can be un-coated, and can e.g. be used together with a gel lubricant or the like for insertion. The catheter may also be formed by a material having low friction, and can e.g. be made by a hydrophilic material. However, the catheter is preferably coated, as have been discussed in the foregoing. In particular, for catheters, it is preferred to coat the outer surface, at least of the insertable part, with a hydrophilic coating. Many different types of well-known hydrophilic surfaces can be used.

[0080] Some preferred examples of methods for applying a hydrophilic surface coating to the tubular shaft and/or the tip will now be discussed in greater detail. However, it is to be noted that the many other methods for obtaining a hydrophilic surface coating can also be used.

[0081] In one embodiment, the entire or part of the outer surface of the catheter is coated with a stable hydrophilic coating by applying sequentially to the surface of the substrate first a solution comprising between 0.05 to 40% (weight to volume) of an isocyanate compound and thereafter a solution containing between 0.5 and 50% (weight to volume) of polyvinylpyrrolidone and curing at an elevated temperature. The isocyanate solution may advantageously contain between 0.5 to 10% (weight to volume) of the isocyanate compound, and may preferably contain between 1 to 6% (weight to volume) of the isocyanate compound. Generally, the isocyanate solution only needs to be in contact with the surface briefly, for example 5 to 60 sec.

[0082] Application of the isocyanate solution to the catheter surface results in a coating having unreacted isocyanate groups being formed on the substrate surface. Application of the polyvinylpyrrolidone solution to the catheter surface then results in a hydrophilic polyvinylpyrrolidone-polyurea interpolymer coating being formed. Curing of this hydrophilic coating binds the isocyanate compounds together to form a stable non-reactive network that binds the hydrophilic polyvinylpyrrolidone. To advantage, curing takes place in the presence of a water-containing gas, for example ambient air, to enable the isocyanate groups to react with the water to yield an amine which rapidly reacts with other isocyanate groups to form a urea cross-link. Further, the method may comprise the steps of evaporating the solvent of the isocyanate solution prior to application of the polyvinylpyrrolidone solution and evaporating the solvent of the polyvinylpyrrolidone solution prior to curing of the hydrophilic coating. This may for example be done by air drying.

[0083] The isocyanate compound preferably comprises at least two unreacted isocyanate groups per molecule. The isocyanate may be selected from 2,4-toluene diisocyanate and 4,4′-diphenylmethane diisocyanate, or a pentamer of hexamethylene diisocyanate and toluene diisocyanate of cyanurate type, or trimerized hexamethylene diisocyanate biuret or mixtures thereof.

[0084] The solvent for the isocyanate compound is preferably one which does not react with isocyanate groups. A suitable solvent is methylene chloride but it is also possible to use ethyl acetate, acetone, chloroform, methyl ethyl ketone and ethylene dichloride, for example.

[0085] In order to shorten the necessary reaction times and curing times suitable catalysts for isocyanate curing may be added. These catalysts may be dissolved in either the isocyanate solution or the polyvinylpyrrolidone solution but are preferably dissolved in the latter. Different types of amines are especially useful, for example diamines, but also for example triethylenediamine. Preferably, an aliphatic amine is employed which is volatisable at the drying and curing temperatures used for the coating, and which furthermore is non-toxic. Examples of suitable amines are N,N′diethylethylendiamine, hexamethylendiamine, ethylendiamine, paradiaminobenzene, 1,3-propandiol-para-aminobenzoic acid diester and diaminobicyclo-octane.

[0086] The polyvinylpyrrolidone used preferably has a mean molecular weight of between 104 to 107 with the most preferred mean molecular weight being about 105. Polyvinylpyrrolidone having such a molecular weight is commercially available, for example under the trademark Kollidon® (BASF). Examples of suitable solvents for polyvinylpyrrolidone that may be used are methylene chloride, ethyl acetate, acetone, chloroform, methyl ethyl ketone and ethylene dichloride. The proportion of polyvinylpyrrolidone in the solution is preferably between 0.5 to 10% (weight to volume) and most preferred between 2 to 8% (weight to volume). The polyvinylpyrrolidone in the solvent is applied by dipping, spraying or the like for a short period of time, e.g. during 5 to 50 sec.

[0087] Curing of the coating is preferably performed at a temperature of 50 to 130 deg. C., in for example an oven, for a duration of between 5 to 300 min.

[0088] In a preferred embodiment the hydrophilic coating contains an osmolality-increasing compound, for instance an inorganic salt selected from sodium and potassium chlorides, iodides, citrates and benzoates. The osmolality-increasing compound may be applied in the manner detailed in EP 0 217 771 by the same applicant.

[0089] In case a hydrophilic coating is used, it is preferred that both the tip and an insertable part of the tubular shaft are provided with said coating. The coating may be applied after joining of the tip and the tubular shaft, but may alternatively be provided separately to the tip and the tubular shaft, prior to joining.

[0090] Upon use, the catheter, when being provided with a hydrophilic coating, or being made by a hydrophilic material, is wetted by a wetting fluid, whereby the hydrophilic surface becomes slippery and easy to insert into e.g. the urethra of the patient, i.e. to provide a low-friction character of the surface. The wetting fluid is preferably a water-based liquid, i.e. using water as a solvent.

[0091] Experiments

[0092] In the catheters used for the experimental tests relating to embodiments of the present invention, the tubular shafts were made by a material commercially available under the trade name Meliflex M6504 by Melitek, and which is a polyolefin thermoplastic elastomer, with a composition generally in accordance with the previously discussed polyolefin based materials. This material is in the following referred to as material A. The catheter tubes were of 40 cm length, and had a size of Ch 12.

[0093] The tips for these catheters were made of four different materials. The tips all had the same conically tapering geometry, in accordance with the discussion above.

[0094] The tips were made by the following materials, respectively: [0095] Material B, which is a commercially available thermoplastic elastomeric material sold under the trade name Dryflex 500400S by Elasto. This material is primarily based on SEBS. [0096] Material C, which is a commercially available thermoplastic elastomeric material sold under the trade name Meliflex M7940 by Melitek, and which is a soft TPE with good moulding properties. [0097] Material D, which is a commercially available thermoplastic elastomeric material sold under the trade name Dryflex 500122 by Elasto. This material is primarily based on TPS-SEBS.

[0098] As a comparative example, a commercially available catheter from Manfred Sauer, sold under the trade name IQ-Cath, was used. This is a PVC-based catheter, having an enlarged, ball-shaped tip, in accordance with the disclosure in the above-discussed patent application US 2004/193143. These catheters were also of the size Ch 12.

[0099] In one line of experimental tests, the E-modulus of the tubular shafts and tips were determined. To this end, measurements were made generally in accordance with the standard ASTM D 638. However, since this standard requires relatively long samples, the test was slightly modified to make it possible to measure on short samples, such as the tips of the catheters. The tips here had a length in the range 30-50 mm. The sample was clamped between two clamping jaws. The clamping jaws were initially separated by 2 mm. After initial clamping, the samples were maintained in this position for a minute, for conditioning and relaxation of the material.

[0100] Thereafter, the measurement parameters were reset, and measurements were made by pulling the clamping jaws apart. The pulling speed was set to 10 mm/min, and pulling was continued until the jaws were stretched apart by 5 mm. The pulling force was measured after 0.05 mm and 0.25 mm. The E-modulus was then calculated in accordance with the following formula:

E=[4*L.sub.0*(X.sub.H−X.sub.L)]/[π*(d.sub.a.sup.2−d.sub.i.sup.2)*(L.sub.H−L.sub.L)]

where E is the tensile modulus (also known as Young's modulus) in kN/mm.sup.2, L.sub.0 is the initial gage length in mm, X.sub.H is the end of tensile in kN, X.sub.L is the being of tensile in kN, π is a constant (3.14159), d.sub.a is the outer diameter in mm, d.sub.i is the inner diameter in mm, L.sub.H is the strain in mm at X.sub.H, and L.sub.L is the strain in mm at X.sub.L.

[0101] Further, the hardness was measured. Due to the limited size of the samples, the hardness was measured in micro Shore A (μShA). The measurements were made with a commercially available measurement device, the Bareiss Shore meter Digitest II, provided with a micro Shore A tip. The measurements were made in accordance with the standard ASTM D 2240. Measurements were made at different positions along the samples. The tips were solid, and could be measured directly. The tubular shafts were provided with a steel rod in the lumen, and a cut open second tube was arranged on top of the first tube, in order to obtain sufficient thickness.

[0102] Still further, insertion of the catheters into an artificial urethra, having an artificial sphincter was tested. The artificial urethra comprised a large container, simulating the bladder, a tube connected to an inlet of the container, simulating the urethra, and a porous member with a through bore having 4 mm in diameter arranged in the inlet of the bladder, simulating the sphincter. The porous member was made by using conventional foam ear plugs.

[0103] The results of the E-modulus measurements are presented in the following table 1:

TABLE-US-00001 TABLE 1 E modulus [MPa] for different materials, and for tip and shaft Mat. B Mat. C Mat. D IQ-Cath Mat. A IQ-Cath tip tip tip tip shaft shaft Mean 11.178 10.750 6.782 17.604 13.089 26.895 Std dev. 1.4880 0.7486 1.1711 1.4037 0.7734 0.8703 Max 13.360 12.062 8.670 19.713 14.021 28.099 Min 9.395 10.207 5.581 15.932 12.339 26.025

[0104] The results of the micro Shore A measurements are presented in the following table 2:

TABLE-US-00002 TABLE 2 Hardness [μShA] for different materials, and for tip and shaft Mat. B Mat. C Mat. D IQ-Cath Mat. A IQ-Cath tip tip tip tip shaft shaft Mean 40.23 40.23 13.58 52.63 81.65 91.79 Std dev. 0.818 0.612 0.121 2.547 0.858 1.832 Max 41.10 41.00 13.67 55.13 82.77 93.57 Min 39.27 39.47 13.43 49.60 80.43 89.17

[0105] In the insertion test in the artificial urethra, it was found that the IQ-cath could not be introduced through the narrow opening simulating the sphincter, and failed in all the tests. However, the catheters made in accordance with the invention could find their way into this narrow passage. From this is was generally concluded that the usability and maneuver properties of the new catheters are very good. More specifically, the catheters having tips of material B and C could pass the defined obstacle at all tested occasions. The catheters having the very soft tip of material D passed the narrow passage at many occasions, but sometimes had a tendency of bending at the top, thereby stopping the insertion. This catheter with the tip of material D passed the test at about 40% of the tests.

[0106] Based on the above discussed experimental results, the following conclusions can be drawn: [0107] The catheter tips of materials B-D all have a micro Shore A hardness much lower than that of the shaft. [0108] The shafts made of material A and PVC (IQ-Cath) had a micro Shore A hardness exceeding 80. [0109] The catheter tips made of materials B-D had a micro Shore A hardness in the range 13.58-40.23. [0110] Based on this, the conclusion is reached that tips made of materials having a micro Shore A hardness equal to or below 60, and preferably equal to or lower than 50, and more preferably equal to or lower than 45 are very useful and show advantageous properties. [0111] Since the very soft tip made of material D had problems of passing the very difficult obstacle in the artificial urethra test, is also assumed that the tip material should preferably have a micro Shore A hardness exceeding 20. [0112] The E-modulus of the tips made of materials B-D are in the range 6.8-11.2 MPa. [0113] The E-modulus of the tip in the IQ-cath (17.6 MPa), and in the shafts made of material A (13.1 MPa) and PVC in the IQ-Cath (26.9 MPa) are all much higher than in the tips made of materials B-D. [0114] Based on this, the conclusion is reached that tips made of materials having an E-modulus equal to or lower than 16 MPa, and preferably equal to or lower than 13 MPa are very useful and show advantageous properties. [0115] Since the very soft tip made of material D had problems of passing the very difficult obstacle in the artificial urethra test, is also assumed that the tip material should preferably have an E-modulus equal to or higher than 9 MPa. [0116] Based on this, the conclusion is reached that tips made of materials having an E-modulus in the range 6-16 MPa, and preferably in the range 9-13 MPa are very useful and show advantageous properties.

[0117] The person skilled in the art realizes that the present invention by no means is limited to the preferred embodiments described above. On the contrary, many modifications and variations are possible within the scope of the appended claims. For instance, the tip need not be continuously tapering, but have other geometrical shapes. Further, the tip may be either straight, pointing directly in the longitudinal direction of the catheter, or be slightly curved, so that the end of the tip points in a direction which is non-parallel to the longitudinal direction of the catheter. Further, many different materials and material combinations may be used to produce the tubular shaft and the tip, and still obtain the desired material properties. Still further, the access openings/drainage eyes may be provided in either the tip or in the forward end of the tubular shaft, or even in both. Such and other modifications should be construed to fall within the scope of the appended claims.