CATHETER

Abstract: Catheter tubes of elastomeric material having novel lumen shapes which prevent occlusion and accommodate continued liquid flow even when kinked. Also, catheter tube slit valves are disclosed, the walls of which are not chemically weakened. Symmetrical and asymmetrical versions of said slit valves are disclosed. Combinations of highly reliable slit valves and catheter tubes are disclosed. Independently operable multi-lumen catheter assemblies of synthetic material, such as silicone rubber are disclosed, wherein the distal end of each lumen is normally clsoed by a three-position slit valve formed in a catheter tube covering. Multi-lumen catheters, and related methods, are also disclosed wherein the lumens are internal at the proximal and distal ends of the catheter tube but comprise separate tubes in between whereby, following placement of the distal end of the catheter tube in the body cavity of a patient, the unified proximal end of the tube is manipulated, sometimes subcutaneously, with the ultimately exposed tubes being thereafter severed and each equipped with a hub at a convenient exposed body site for selective independent passage of influent and effluent liquid along each lumen.

Description: THIS INVENTION relates to an indwelling catheter. Prior to U.S. Patent 4,327,722 those who proposed placement of a slit valve in the wall of a catheter did so on the basis of the valve being continuously open or the operation thereof being dependent upon unacceptably large pressure variations to open the valve. Chemically weakened slit valves provide high reliability. It has become state of the art to extrude catheter tubing in cylindrical form where the catheter tubing has one or more lumens which are circular in transverse cross section. When this tubing is kinked, inadvertently or otherwise, the lumen or lumens are fully occluded and flow of liquid therethrough is prevented. U.S. Patent 4,327,722, entitled "Method for Intravenous Therapy and Hyperalimentation", and like prior art discloses a single lumen flexible silicone rubber catheter which has one slit valve adjacent its closed distal end. However, heretofore the use of distal end valves to normally close each lumen of a multi-lumen catheter has been rejected, especially for silicone rubber multi-lumen catheters. See Reissue Patent 31,873 (U.S. Patent 4,072,146). Reissue 31,873 shows the mentioned state of the multi-lumen catheter art, i.e. use of an external sheath in which a random array of independent lumen-defining tubes are placed wherein the distal tip of each lumen-defining tube comprises an open port in an external sheath. Until the present invention, the superimposing of a valve at the interfacing site between each lumen-defining tube of amulti-lumen catheter and an external sheath thereof was thought impossible. Alternatively, a single lumen has been used at the distal end of a catheter, with the single lumen being joined to multi-lumens disposed away from the distal end of the catheter. This approach, however, undesirably co-mingles liquids within the single distal end lumen, and does not allow independent use, perhaps sumultaneous independent use, of each of several lumens. US Patent 4,549,879 (equivalent to EP-A-0125844), entitled "Valved Two-way Catheter", relates to a catheter tube made of soft, flexible material and formed with a closed end. A slit is formed through the tubing wall and is of such a length that it provides a valve which opens on application of a predetermined pressure differential. The term "distal end", as used herein, refers to the forward end of the catheter which is inserted into the patient's body. The term "proximal end", as used herein, refers to the rearward end thereof which remains outside the patient's body. The present invention comprises catheter tube slit valves, the walls of which are mechanically or chemically weakened and which provide greater reliability, while avoiding the need for large pressure variations during use. Symmetrical and asymmetrical versions of said slit valve are provided. The invention also provides novel combinations of highly reliable slit valves and catheter tubes. Other important objects of the present invention are: the provision of novel highly reliable catheter tube slit valves, which hingedly open and close with or without the need for chemically weakening of the material at the slit valve; the provision of extraordinarily reliable slit valves in catheter tubes which avoid any need for large pressure variations during use; the provision of novel highly reliable mechanically hinged catheter tube slit valves; the provision of novel highly reliable symmetrical and asymmetrical slit valves; and the provision of novel catheter tubes and slit valve combinations. According to the present invention and starting from EP-A-0 125 844 there is provided an indwelling catheter comprising a flexible tube made of biocompatible material and having longitudinally formed therewithin at least one fluid flow lumen which extends substantially the length of the tube from a proximal end configured for disposition outside the body of a patient to a terminus at a closed distal end configured for disposition inside the body of the patient, whereby the tube comprises at least one slit valve in the outer radial wall of the distal end of the or each lumen to provide for selective communication between the exterior of the tube and the respective lumen, each slit valve being biased into a closed position precluding the communication and being selectively operable therefrom into either an inwardly or an outwardly open position, wherein each slit valve comprises: a slit extending from the radial exterior of the distal end into the respective lumen the opposite first and second sides of the slit being sealingly engaged with each other in the closed position of the slit valve; a first slit valve wall comprising a portion of the outer radial wall of the tube adjacent the first side of the slit, the first slit valve wall being flexible either inwardly into the respective lumen in the inwardly open position of the slit valve, or outwardly to the exterior of the tube in the outwardly open position of the slit valve; and characterised by a first hinge means which comprises a region having enhanced flexibility relative to the portion of the slit valve wall between the said region and the slit. In one preferred embodiment a catheter according to the invention further comprises a plurality of independently usable fluid flow lumens each extending substantially the length of the tube, characterized in that at least one of the said lumens comprises a slit valve as defined above. A second of the said independently usable lumens may be independently capable of communication at its distal end with the exterior of the tube through an associated slit valve according to the invention. A catheter according to the invention, i.e. including at least one slit valve, may further comprise: (a) a second slit valve wall comprising a portion of the outer wall of the tube adjacent the second side of the slit, the second slit valve wall being flexible selectively inwardly into the respective lumen in the inwardly open position of the slit valve, or outwardly to the exterior of the tube in the outwardly open position of the slit valve; and (b) a second hinge means for concentrating flexing of the outer wall of the tube into either the inwardly or the outwardly open positions of the slit valve, said second hinge means being located at a side of the respective second slit valve wall remote from the slit. The or each slit may be located symmetrically or asymmetrically between its respective first and the second hinge means and is preferably disposed generally parallel to the longitudinal axis of the tube. The or each hinge means is preferably parallel to its associated slit. The slit valve wall at the or each slit is desirably at least as thick as at the hinge means corresponding thereto. The enhanced flexibility of the hinge means may be provided by chemical softening or by making the enhanced flexibility region of the hinge means thinner than the portion of the slit valve wall between the said region and the slit. A catheter according to the invention may comprise at least one lumen having a non-circular (e.g D-shaped) cross section and at least one corner. The corner may be located closer to the outer surface of the distal end of the tube than any other portion of the periphery proximate to the corner or may coincide with the hinge means. Catheters according to the invention are usable in the cardiovascular system of a patient. In order that the present invention may be readily understood, embodiments thereof will now be described, by way of example, with reference to the accompanying drawings, In which: Figures 1-8 are transverse cross-sectional views of catheter tubes suitable for use in the present invention. Figure 9 is an enlarged transverse cross-section of the distal end of another two-lumen catheter embodying the principles of the present invention; Figure 10 is a perspective representation of a three-lumen catheter fabricated in accordance with the principles of the present invention. Figure 11 is an enlarged transverse sectional view taken along the lines 11-11 of Figure 10, showing a larger primary and two smaller secondary lumens; Figure 12 is a cross-sectional view of a similar catheter showing one larger primary lumen and one smaller secondary lumen only; Figure 13 is an inverted enlarged longitudinal fragmentary sectional view taken along the lines 13-13 of Figure 11, showing the distal end portion of the catheter including two three-position slit valves, and also showing a removable insertion stylet abutting the closed distal tip of the catheter; Figure 14 is an enlarged fragmentary exploded elevation of the proximal end of one lumen-defining tube of the catheter of Figure 1 with the stylet partially removed; and Figure 15 is an enlarged longitudinally-directed fragmentary cross-section of the distal end portion of another multi-lumen catheter embodying the principles of the present invention. Reference is now made to the drawings, which illustrate several preferred embodiments of the present invention. Like numerals are used throughout the drawings to refer to like parts. Figures 1-8 illustrate in transverse cross-section several catheter tubes, each having one or more novel lumen shapes which prevent occlusion and accommodate continued liquid flow, even when inadvertently kinked, bent, twisted or collapsed. Figure 1 comprises a generally cylindrical catheter tube 30, formed of a body of elastomeric material 32 defining an outside smooth cylindrical surface 34 and a single D-shaped axial lumen 36. The lumen 36 comprises linear wall surfaces 38, 40 and 42. Linear wall surfaces 38 and 40 are joined tangentially by a small diameter fillet corner 44 and surfaces 38 and 42 tangentially by a small diameter fillet corner 46. Linear wall surfaces 40 and 42 are joined tangentially by an arcuate wall surface 48. The location and shape of the corners 44 and 46 define a relatively thin dimension 50 through the body 32, which makes the D-shaped lumen 36 amenable to utilisation of certain slit valves fashioned in accordance with the principles of the present invention, as hereinafter more fully described. Furthermore, the nature and shape of the lumen 36 has shown through experimentation to prevent occlusion of the lumen 36 of the catheter tube 30 when the same is kinked, bent, twisted or collapsed. To the contrary, catheter tubing according to the prior art, which utilises the cylindrical exterior surface and one or more cylindrical internal hollow lumens will result in total occlusion of the lumen or lumens when such prior art catheter tubing is, for example, kinked upon itself through essentially 180 degrees. The embodiment of Figure 2, generally designated 30′, is substantially identical in all respects to the catheter tubing 30 of Figure 1, except that the surfaces 40′ and 42′ are somewhat shorter in their transverse dimension than previously described wall surfaces 40 and 42. The non-occluding characteristic of catheter tubing 30 also exists when catheter tubing 30′ is used. Likewise, catheter tubing 30″ (Figure 1) is substantially similar to previously described catheter tubing 30 and 30′, identical numerals being used to identify substantially identical parts. Catheter tubing 30″ differs from catheter tubing 30 in that the flat wall surfaces 40″ and 42″ are of a substantially smaller width than wall surfaces 40 and 42. Furthermore, the fillet corners 44′ and 46′ are substantially larger in radius and arc distance than corners 44 and 46 and do not respectively join the adjacent wall surface tangentially. Accordingly, lumen 36″ is somewhat smaller than lumen 36 with modified corner structure at each end of the reduce size flat wall surface 38′. Reference is now made to Figures 4-6, which illustrate, respectively, double-lumen catheter tubes 52, 54 and 56. To the extent that catheter tubes 52, 54 and/or 56 have physical parts corresponding to heretofore described catheter tubes 30, 30′ or 30″, identical numerals are used on Figures 4-6. Catheter tube 52 comprises primary lumen 60 and secondary lumen 62, each of which define a relatively short distance 50 between an angular lumen corner and the external surface 34 of the catheter tube. The catheter tube 52 comprises an internal body of material 64 which defines and separates the two lumens 60 and 62. Lumen 60 comprises a centrally disposed flat wall surface 66 interposed between two other flat wall surfaces 68 and 70. Wall surface 66 joins wall surface 68 tangentially via corner 72 and wall surface 70 via corner 74. Wall surface 68 and 70 and non-tangentially joined directly one to another by an arcuate wall surface 76, which merges tangentially with the wall surfaces 68 and 70 at fillet corners 78 and 80 respectively. Catheter tube 52 further comprises a secondary lumen 62, as mentioned above, lumen 62 comprising heretofore described wall surface 30 and fillet corners 44 and 46 tangentially joining relatively small flat wall surfaces 40″ and 42″ to surface 38. Wall surface 40″ is joined angularly or non-tangentially at site 82 to a linear wall surface 84, which tangentially merges with an arcuate wall surface 86. Wall surface 42″ likewise joins a flat upwardly angularly directed wall portion 88 at fillet corner 90. Wall portion 88 merges tangentially with arcuate wall portion 86. Thus, catheter tube 52 provides two aligned lumens which provide the relatively short corner spaces 50 to accommodate utilisation of highly reliable slit valves as hereinafter more fully explained and which, when the catheter tube 52 is kinked upon itself, will still accommodate liquid flow, as mentioned above. Double lumen catheter tube 54 is illustrated in Figure 5. Tube 54 provides internal body and wall structure 64 which provides for separate definition of the two spaced lumens 36′. These lumens, while being somewhat different in size, are substantially identically shaped and each corresponds substantially to the lumen 36′ of Figure 2 already described. Catheter tube 56 (Figure 6) comprises a primary D-shaped lumen 92 and a secondary D-shaped lumen 62. Lumen 92 is substantially identical to previously described lumen 36″, except that rounded corners 44′ and 46′ are replaced by diagonally disposed non-tangential wall surfaces 94 and 96, respectively. Diagonal wall surface 94 joins wall surface 40″ at angular corner 98 and surface 38′ at angular corner 100. Likewise, diagonal wall surface 96 joins wall surface 42″ at angular corner 102 and wall surface 38′ at angular corner 104. Lumen 62 was heretofore described in connection with catheter tube 52. See Figure 4. The non-occluding catheter tubes may comprise more than two lumens defined within the catheter. For example, Figures 7 and 8, to which reference is now made, illustrate catheter tubes which comprise three lumens, respectively. The catheter tube of Figure 7 is generally designated 106 and the tri-lumen catheter of Figure 8 is designated generally as 108. Catheter tube 106 comprises one primary and two secondary lumens 36″. Catheter tube 38′ was described earlier in conjunction with in Figure 2. Accordingly, no further description is deemed necessary in respect to the lumen of catheter tube 106, except to say that the lumens are illustrated as being disposed, respectively, along predetermined radial lines, consistent with the requirements of structural integrity needed for indwelling catheters and so as to provide corner sites 50. Likewise catheter tube 108 comprises one primary and two secondary lumens 62, previously described in conjunction with catheter 56, shown in Figure 6. No further description is, therefore, deemed necessary, it being understood that the lumens 62 of catheter tube 108 are illustrated as being arranged along predetermined radial lines so that the corners 44 and 46 thereof create corner sites at locations 50. It is presently believed that the relatively thin regions 50 coupled with the adjacent lumen corner structure accounts for the aforementioned non-occluding feature of catheter tubes. Not only do the novel lumen shapes of catheter tubes prevent occlusion of the lumens where the catheter tube is kinked, flattened, or the like, the novel lumens have been found to aid materially in the provision of novel slit valves according to the invention. Two such hinge action slit valves 35 and 35′ are illustrated in Figure 9. Figure 9 shows the distal end portion of two-lumen catheter 54, described earlier in conjunction with Figure 5 and having D-shaped primary and secondary lumens 36′. The distal end portion of the tube 54 comprises exterior covering 32 and internal wall structure 64, which defines the lumens 36. Corners 44 and 46 of the lumens 36′ are located closer to the exterior covering surface 34 than any other part of the lumens 36′. Thus, corners 44 and 46, in each case define two hinge or fold lines or regions 50 where the catheter wall is thinnest. Relatively thicker areas 136 are disposed between hinge sites 50. The slit 138 of slit valve 35 is symmetrically disposed along a radial line equidistant between the hinge sites 50 of the primary lumen 36′. The D-shaped lumens 36′ are structurally stronger than conventional round catheter tube lumens. Therefore, lumens according to the present invention are more resistant to collapse under high negative pressures. The D-shaped lumens also offer two pincipal advantages in the operation of the valve 35. First, the thicker walls adjacent the self sealing slit 138 create a larger sealing surface area for the valve lips 136, and, therefore, create a more positive seal when the distal end portion of tube 54 is indwelling and under normal physiological pressures. Second, the flex of the valve 35 is concentrated at the hinge sites 50, which sites are located some distance from the slit 138. This concentration of the flex in a relatively small hinge site provides for more consistent operation, more reliable response to predetermined pressure differentials designed to open and close the valve, a wider valve opening, and a longer life of the valve 35. The use of thickened valve lips 136 also serves to raise the withdrawal threshold, providing for a more positive, highly reliable valve action. Figure 9 also diagrammatically illustrates an eccentric slit valve 35′ comprising a single slit 141 disposed in one corner 46 of the secondary lumen 36′. In this configuration, the hinge action is concentrated at the single hinge site 141, illustrated at intersecting the other lumen corner 44. Thus, the entire asymmetrical valve lip 142 is hingedly displaced, inwardly or outwardly, to create the valve orifice. This eccentric configuration accommodates, with high reliability, use of the slit valve 141 in catheters having lumen sized too small to provide consistent operation of a symmetrical slit valve. The two slit valves illustrated in Figure 9 are shown, for ease of illustration, as being in the same transverse plane. However, in actual fabrication the slit valves are preferably longitudinally and radially offset each from the others. In limited testing to date, the eccentric valve 35′ has proved better in use than concentric valve 35, where the catheter lumen size was relatively small. It is to be understood that the present invention embraces the aforedescribed slit valves comprising one or more mechanically weakened hinge regions independent of whether the wall regions of the slit valves are or are not chemically treated. Specific reference is made at this time to Figures 10 to 14 which illustrate a further presently preferred catheter, generally designated 230, fabricated according to the principles of the present invention. Figure 10 shows the catheter 230 to comprise several major parts: i.e. 1) a distal end portion 232, adapted for insertion into a vein or other body cavity of a medical patient and comprising an exposed external sheath or covering 233 and internal wall structure 255, which defines a plurality of independent and separately operable circular lumens for carrying liquids to or from a desired body cavity; 2) a three-position pressure activated slit valve 234 forming a normally closed lateral gate or port shown as being disposed at the distal end of each catheter lumen, each slit valve 234 being controlled by the application of positive or negative pressures to the associated lumen of the catheter 230; 3) a coupling or transitional member 236 connecting the distal end portion 232 to a proximal end portion 237 which comprises a number of lumen-defining tubes 238; 4) the proximal end portion 237 of the catheter 230 comprising tubes 238 which respectively extend the lumens of the catheter to exposed hubs 240, of a conventional type, which accommodate connection to various fluid infusion and withdrawal and like devices; and 5) terminal hubs 240, each shown as being closed by a conventional plug 241. Each three-way valve 234 normally prevents flow but provides for selective positive control of the liquid flow only through the associated lumen. By applying a predetermined positive pressure to the lumen terminal hub 240, with the stopper 241 removed, a desired liquid is infused into the vein of a patient by forcing the associated valve 234 to hingedly open. By applying a negative pressure, liquid within a body cavity is withdrawn. Under normal physiological pressures, the valve 234 will remain closed and sealed. The distal end portion 232 is typically cylindrical in shape, as shown in Figure 11. However, the exterior surface may take other forms. The distal end portion 232 is preferably slender in diameter, allowing the closed distal tip 242 to be facilely introduced into a vein or other cavity and advanced to a desired treatment location, while the proximal end 237 remains outside the body. The length of the distal end portion 232 will, therefore, vary with its intended application. The distal end portion 232 is illustrated as having a uniform through relatively small exterior diameter so that it can be readily inserted into a vessel, such as the subclavian vein, without causing undue trauma to the patient. Typically, this requires that the distal end portion 232 have an outside diameter not exceeding about 0,318 cm (0.125 inches). The distal tip 242 of the distal end portion 32 is preferably dome-shaped and smoothed to further minimize trauma. As shown in Figure 13 (in inverted and angular sectional view with respect to Figure 11), the array of all valves 234 is formed in the sheath 233 and exposed at the exterior cylindrical surface 248 thereof, at site 243. Each valve 234 is also exposed laterally to one of the lumens, at sites 245. The valve sites are radially distributed in offset relation around the distal end portion 232 near the tip 242 so that no two valves 234 lie in any one radial plane. The valves 234 are also longitudinally separated or offset in their placement at relatively short but different distances from the distal tip 242 so that no two valves 234 lie in any one axial plane. The radial and longitudinal separation of the valves 234 helps avoid structural weakness and helps prevent possible contamination of an influent sample withdrawn from one valve 234 by an infusion stream of effluent liquid from another valve 234 passing into the vein of a patient, which might adversely affect test results or result in premature mixing of incompatible therapeutic liquids. It should be noted that longitudinal separation should not be used where the effect would be to position any valve 234 out of the desired treatment or exposure area. The distal end portion 232 is made of a durable and pliable yet shape-retaining biocompatible synthetic elastomeric material. It is presently preferred that the material comprise an ultra soft synthetic material. Typically, such material should have a hardness of less than 100 durometer and an elongation percentage of up to 700. A preferred material is a silicone rubber tubing having a hardness of about 59 durometer sold under the trade name SILASTIC by Dow Corning Co., Midland, Michigan. The distal end portion 232 is preferably at least partially radiopaque so that its precise position in the body may be radiogically verified. Tubes 237 are preferably transparent so that the physician can visually determine the presence of air bubbles, blook, or other liquids in each of the lumens during and after insertion. As illustrated in Figure 11, three independent lumens 252, 253 and 254 are longitudinally disposed inside the distal end external covering 233, the lumens typically being radially distributed at predetermined angles beneath the exterior cylindrical surface 248 of the distal end portion 232 in such a way that an interior lumen wall surface passes within a relatively short distance of the exterior surface 248 of the exterior covering 233, as measured along a radial line passing through the centre of each lumen 252, 253 and 254. It is apparent from the radial disposition of the lumens in close proximity to the exterior surface 248 that valve 234 installed along a radial line in the fashion just described or installed in any consistent position relative to the lumens 252, 253 and 254 will necessarily be radially separated from each other as previously discussed. Interior walls 255 (Figure 11) respectively form and define the size and shape of the lumens 252, 253 and 254 at the distal end portion 232. Tubular, hollow walls 257 respectively form and define the size and shape of lumens 252, 253 and 254 at the proximal end portion 237. Note from Figure 12 that a double lumen catheter having a proximal end portion 232′ is also within the scope of the present invention. Proximal end portion 232′ comprises primary lumen 252 and secondary lumen 253′. Each lumen 252, 253 and 254 extends from the associated hub 240 at the proximal end portion 237 to a point near the distal tip 242. See Figure 10. The larger or primary lumen 252 extends substantially the entire length of the catheter 230, terminating in a closed tip wall portion 262 adjacent the distal tip 242 of the distal end portion 232. See Figure 13. Secondary lumen 253 and 254 terminate in a similar closed end wall portions 263, only one of which is illustrated in Figure 13. The lumens terminate at relatively short but different distances from the distal tip 242, for the purpose of providing longitudinal separation of the valves 234, as previously described. In the embodiments of Figures 10, 11 and 13, the proximal end portion 232 is preferably formed by extrusion, for reasons of simplicity and ease of construction, but other methods may be used. When extruded, the lumens 252, 253 and 254 and the interior walls 255 forming the lumens 252, 253 and 254 are continuously formed during extrusion; thus, each lumen is of a uniform cross-sectional shape, being cylindrical or circular in the embodiment of Figures 10, 11 and 13. In the extruded embodiment of Figures 10, 11 and 13, the closed end wall portions or plugs 262 and 263 are formed by injecting a suitable silicone rubber adhesive or the like into the leading ends of lumens 252, 253 or 254 for the distance from the distal tip 242. The adhesive then hardens to form the closed end wall portions or plugs 262 and 263, each up to the leading edge of the associated valve 234. If a radiopaque distal tip 242 is desired, this may be accomplished by mixing a radiopaque material with the adhesive prior to injection to form plugs 262 and 263. One three-position valve 234 is placed in the covering adjacent to and laterally interfacing with each lumen 252, 253 and 254 adjacent the plug 262 or 263. Each valve 234 is formed by a single relatively short slit 266 in the covering 233. Each slit extends longitudinally along the exterior of covering 233 parallel to but offset from the axis of the distal end portion 232. The thickness of each slit valve 234 is equal to the thickness of covering 233, so as to provide for selective liquid communication between the interior of the lumen 252, 253 and 254 with the exterior of the distal end portion 232. Each slit valve 234 is illustrated as being radially directed and symmetrically disposed in its corresponding lumen 252, 253 and 254 at the thinnest point in the covering 233. Thus, each slit valve 234 comprises two valve lips or walls 270 which comprise blunt edges. These edges contiguously mate and seal along the slit 266 under normal indwelling pressure conditions. Figure 11 shows the operation of each three-position slit valve 234. Upon application of a predetermined pressure differential between the interior and exterior of the distal end portion 232, the valve wall will hingedly deflect or flex causing the valve lips 270 to separate at slit 266, creating a flow path-defining orifice through which liquid may pass in or out of the selected catheter lumen 252, 253, 254, when the distal end portion 232 is indwelling. When the indwelling pressure inside the selected catheter lumen 252, 253, 254 extends the indwelling pressure outside the distal end of the catheter by a predetermined amount (the "infusion threshold"), the valve immediately surrounding the slit 266 deforms, and the lips 270 of the valve 234 are caused to separate hingedly in an outward direction thereby creating an orifice through which liquid is infused into the bloodstream, as shown in Figure 11. Likewise, the application of a sufficient degree of negative pressure (the "withdrawal threshold") to the selected catheter lumen 252, 253, 254 will cause the valve lips 270 to flex hingedly inwardly, also as shown in Figure 11, allowing withdrawal of blood or other fluids from the bloodstream or other body cavities. Under normal physiologic conditions, as stated above, each slit valve 234 remains closed and sealed, as shown in solid lines in Figure 11. This requires that the catheter tube have sufficient memory to return to the closed sealed edge-to-edge position when liquid flow conditions terminate. When used in the cardiovascular system, the withdrawal threshold must also be high enough to prevent back bleeding under normal systolic pressures in the circulatory system of a patient. The infusion threshold must likewise be high enough to overcome the nromal venturi effect of blood flowing past the indwelling valve 234. The infusion and withdrawal threshold should not be so high as to make infusion or withdrawal difficult. Both the infusion and the withdrawal thresholds can be adjusted either by controlling the thickness and configuration of the valve walls or lips 270 or by selectively treating the valve walls with a biocompatible softening agent such as dimethylsiloxane, as is more completely disclosed in U.S. Patent Application Serial No. 491,258, filed May 3, 1983. It should also be noted that the valve 234 may, if desired, be treated with an anticoagulant, such as Heparin. However, the design of the catheter 230 disclosed herein does not require such treatment. The liquid flow capacity of the lumens may vary with the intended application of the catheter 230. The lumens must, of course, be large enough to accommodate the desired fluid flow, while the thickness of the walls forming the lumens must be adequate to prevent rupture or inadvertent puncture and consequent leakage either between lumens or to or from the exterior. The slit valve 234 must be the weakest point in each lumen 252, 253 and 254. Each part of each catheter lumen must be stronger and more rigid than the valve lips 270, since collapse or rupture of any other part of the catheter would defeat the purpose of the catheter 230. It is, therefore, important that the lumen walls be strong enough to stand the full range of lumen pressure without rupture, inward collapse or other failure, which would impair proper operation of the slit valves 234. While from a practical point of view, the utilisation of a single extruded tube comprising multiple lumens for the distal end portion 232 is effective and low-cost, it is to be appreciated that the distal end portion 232 can be otherwise fabricated. For example, with reference to Figure 15, the distal end 232″ may comprise separate spaced lumen-defining tubes 274, 276 disposed within a hollow cavity 278 of an external thin walled cylindrical sheath or covering 233′, which has a smooth cylindrical exterior surface 248′. The proximal edges of the tubes 274, 276 are secured by satisfactory adhesive to the interior of the sheath 233′ at sites 280. The resulting lumens 252′ and 253″ respectively transversely interface with a slit valve 234 disposed in the wall of the sheath 233′. No further discussion of the slit valve 234 is deemed to be necessary in light of the prior description thereof. The distal tip 242′ of the distal end portion 232″ is configured so as to be shaped substantially the same as the heretofore described distal tip 242. The tip 242′ does provide an internal circular transverse flat wall 283 against which an insertion stylet or insertion stiffener abuts when placed within the primary lumen 252′, in a manner and for purposes hereinafter more fully described. Returning now to the embodiment of Figures 10, 11 and 13 the proximal end portion 237 of the catheter 230 is joined via connector 236 to a plurality of separate lumen-defining tubes 238. Tubes 238 may be made of an ultra-soft synthetic material or other elastomer, similar to the material of the distal end portion 232, previously described. However, the tubes 238 must be strong enough to resist collapse or rupture and the additional environmental hazrds of an exposed tube. Each tube 238 may, therefore, be strengthened by using a tubing with thicker walls and/or a higher durometer. Tubes 238 are preferably at least partially transparent or translucent to accommodate visual monitoring of the contents therein. Unlike distal end portion 232, however, the proximal tubes 238 have no need for radiopacity, because they are not intended to be indwelling. Tubes 238 are most economically constructed of a tubing with concentric inner and outer cylindrical wall surfaces, thereby forming walls of uniform thickness providing a predetermined inside diameter equal to that of lumens, 252, 253 and 254 of distal end portion 232. The outside diameter of connector tubes 238 should be large enough provide a wall thickness at 257 adequate to resist abrasion and puncture. The trailing edge of each tube 238 is preferably perpendicular to the axis thereof. This accommodates connection of hub 240 at short hollow shaft 282 thereof, using a sleeve coupling 284. See Figures 11 and 14. Each sleeve coupling may be secured in the stated and illustrated position using conventional material-shrinkage techniques. The connector 236 is constructed by permanently connecting each lumen 252, 253 and 254 to one of the tubes 238 by use of a hollow coupling tube 285. See Figure 20. Each coupling tube 285 may be made of surgical steel, although other materials can be used. Preferably each coupling tube 285 has an inside diameter substantially the same as the inside diameter of the catheter lumen 252, 253, 254, to which it is attached so as to minimize if not prevent any flow restriction at the connector 236. The outside diameter of each coupling tube 285 should, therefore, be slightly larger than the inside diameters of lumens 252, 253, 254 and tubes 238. Thus, each tube 285 is force fit into lumens 252, 253, 254 at the body of connector 236, expanding each at the insertion sites. The leading end 297 of each tube 238 is force fit over the trailing end of the associated connector tube 285. See Figure 21. The entire joint or connector 236 is preferably secured with silicone rubber adhesive 264 or other appropriate sealant, and finally shrink-wrapped by soaking a tubular silicone rubber sleeve 296 in Freon or other solvent material causing it to temporarily expand, and slipping the sheath 296 over the connector 236. As the solvent evaporates the sheath 296 permanently contracts firmly around the remainder of the connector 236, adhering to the adhesive 264 and forming a secure and protected joint. Suture wing 298 is illustrated as being attached to the connector 236 so that the catheter 230 at connector 236 may be sutured in placed after the distal end thereof is indwelling. The suture wing 298, shown in Figures 10, 20 and 21 is fashioned from a small piece of silicone rubber sheet cut in the illustrated elongated shape and having circular holes 300 disposed in the ends thereof to receive sutures. Suture wing 298 may also help to prevent the catheter 230 from rolling or shifting when taped in place on a patient as opposed to suturing in place. The suture wing 298 is preferably attached to the connector 236 using silicone rubber adhesive or another suitable method. When the catheter tube 232 is formed of soft, pliable material, a stylist or inserter 306 is preferably used to rigidify the distal end portion 232 during insertion. In the illustrated embodiment, stylet 306 is illustrated as being formed of twisted surgical grade wire. The stylet 306 is illustrated as being equipped with an integral proximal hub 307, by which the stylet is manipulated. See especially Figures 13 and 14. It could also be formed of any yieldable and shape retaining biologically inert material such as polypropylene. Stylet 306 is preferably inserted into the primary lumen 252, until its distal tip 308 abuts the closed wall 262. During insertion, a force manually applied to the stylet 306 causes the distal end thereof 308 to push against closed end 262 of the primary lumen 252. This places the covering 233 under tension, causing the distal end portion 232 to be pulled forward into the vein of the patient, for example. Primary lumen 252 must naturally be dimensioned large enough to accommodate the stylet 306. The walls 255 defining the primary lumen 252 and the covering 233 should also be thick enough to prevent accidental penetration by the stylet 306, which could result in undesired communication between lumens or trauma to the patient. The stylet tip 308 should also be constructed to prevent penetrating the primary lumen 252 through the slit valve 234 or through the tip or head 242. In this regard, the abutment 262 of primary lumen 252 may be formed a sufficient distance from the slit valve 234 to allow an adequate safety margin against stylet damage at the valve site 234. The distal tip 308 of stylet is kept in constant pressure contact with the abutment 262 of primary lumen 252, during storage and insertion, as shown in Figure 13. The stylet 306 is slightly longer overall length than the primary lumen 252, so that the distal tip 308 of stylet 306 not only abuts the distal closed end 262 of the primary lumen 252, but the stylet hub 307 is exposed beyond the terminal hub 240 in the fully assembled condition. When the stylet hub 307 is seated as a closure in the terminal hub 240, a tension is created in the distal end portion 232 and the remainder of the catheter 230 by the forced engagement of the distal tip 308 of the stylet 306 against the distal closed end 262 of the primary lumen 252. It will be recognized that a central feature of the invention is that the infusion and withdrawal thresholds of each three-position valve 234 may be selected to meet the needs of any particular application. In respect to the embodiment of Figures 10-15, this may be done chemically, as previously described. In the case of the embodiment of Figures 1-9, it is accomplished mechanically by providing a weakened hinge or fold line in the covering of the catheter tube. It is also to be noted that while the mechanically hinged valve is of particular importance in multi-lumen catheters, the principles thereof, comprising part of the present invention, also apply to single-lumen catheters. In Figure 11, for example, the lumens 252, 253, 254 have a circular cross-section. Because of the convex curve of the valve wall 268, the valve lips 270 flex somewhat more easily outwardly than inwardly. As a result, the withdrawal threshold is typically somewhat higher than the infusion threshold. Because the exterior surface 248 of the covering 233 is not concentric with respect to the curvature of the lumens 252, 253, 354, the valve wall lips 270 increase in thickness with distance from either side of the slit 266. As a result, the valve 234 requires higher pressure differentials to open fully than it does to merely break the seal at the slit. By modifying the dimensional relationship between the inside walls 255 defining the interior lumens 252, 253, 254 and the outside sheath surface 248 different valve threshold pressures and operating charcteristics may be obtained.

Claims: An indwelling catheter comprising a flexible tube (54) made of biocompatible material and having longitudinally formed therewithin at least one fluid flow lumen (36') which extends substantially the length of the tube (54) from a proximal end (237) configured for disposition outside the body of a patient to a terminus at a closed distal end (232) configured for disposition inside the body of the patient, whereby the tube (54) comprises at least one slit valve (35, 234) in the outer radial wall (32) of the distal end (232) of the or each lumen (36') to provide for selective communication between the exterior of the tube (54) and the respective lumen (36'), each slit valve (35, 234) being biased into a closed position precluding the communication and being selectively operable therefrom into either an inwardly or an outwardly open position, wherein each slit valve (35, 234) comprises: a slit (138) extending from the radial exterior of the distal end (232) into the respective lumen (36'), the opposite first and second sides of the slit (138) being sealingly engaged with each other in the closed position of the slit valve (35, 234); a first slit valve wall (136, 142) comprising a portion of the outer radial wall (32) of the tube (54) adjacent the first side of the slit, the first slit valve wall (136, 142) being flexible either inwardly into the respective lumen (36') in the inwardly open position of the slit valve, or outwardly to the exterior of the tube (54) in the outwardly open position of the slit valve (35, 234); and characterised by a first hinge means (50) which comprises a region having enhanced flexibility relative to the portion of the slit valve wall (136) between the said region and the slit (138). A catheter as claimed in claim 1, which comprises a plurality of independently usable fluid flow lumens (36') each extending substantially the length of the tube (54), characterized in that at least one of the said lumens (36') comprises a slit valve (35, 234) as defined in claim 1. A catheter as claimed in claim 2, characterized in that a second of the lumens (36') is independently capable of communication at its distal end (232) with the exterior of the tube (54) through an associated slit valve (35, 234) as defined in claim 1. A catheter as claimed in any preceding claim, including at least one slit valve (35, 234) which further comprises: (a) a second slit valve wall (136) comprising a portion of the outer wall of the tube (54) adjacent the second side of the slit, the second slit valve wall (136) being flexible selectively inwardly into the respective lumen (36') in the inwardly open position of the slit valve (35, 234), or outwardly to the exterior of the tube (54) in the outwardly open position of the slit valve (35, 234); and (b) a second hinge means (50) for concentrating flexing of the outer wall (32) of the tube (54) into either the inwardly or the outwardly open positions of the slit valve (35, 234), said second hinge means (50) being located at a side of the respective second slit valve wall (136, 142) remote from the slit (138). A catheter as claimed in claim 4, wherein the or each slit (138) is symmetrically located between its respective first and the second hinge means (50). A catheter as claimed in claim 4, wherein the or each slit (138) is asymmetrically located between its respective first and the second hinge means (50). A catheter as claimed in any preceding claim, wherein the or each slit (138) is disposed generally parallel to the longitudinal axis of the tube (54). A catheter as claimed in any preceding claim, wherein the or each hinge means (50) is parallel to its associated slit (138). A catheter as claimed in any preceding claim, wherein the slit valve wall (136) at the or each slit (138) is at least as thick as at the hinge means (50) corresponding thereto. A catheter as claimed in any one of claims 1 to 8, wherein the slit valve wall (136) at the or each slit (138) is thicker than at the hinge means (50) corresponding thereto. A catheter as claimed in any preceding claim, wherein the enhanced flexibility of the hinge means (50) is provided by chemical softening. A catheter as claimed in any one of claims 1 to 10, wherein the enhanced flexibility region of the hinge means (50) is thinner than the portion of the slit valve wall (136) between the said region and the slit (138). A catheter as claimed in any preceding claim, which comprises at least one lumen (36') having a non-circular cross section and at least one corner (44). A catheter as claimed in claim 13, in which the lumen (36') has a D-shaped cross section. A catheter as claimed in claim 13 or claim 14, in which the corner (44) is located closer to the outer surface of the distal end (232) of the tube (54) than any other portion of the periphery proximate to the corner (44). A catheter as claimed in any one of claims 13 to 15, wherein a corner (44) coincides with the hinge means (50). A catheter as claimed in any preceding claim, wherein each slit valve wall flexes into the inwardly open position of the slit valve (35, 234) when the pressure outside the distal end (232) of the tube (54) exceeds the pressure inside the respective lumen (36') by a predetermined withdrawal threshold. A catheter as claimed in claim 17, wherein the catheter is usable in the cardiovascular system of a patient, and wherein the withdrawal threshold exceeds the systolic pressure in the circulatory system of the patient outside the distal end of the tube (54). A catheter as claimed in any preceding claim, wherein each slit valve wall flexes into the outwardly open position of the slit valve (35, 234) when the pressure inside the respective lumen (36') exceeds the pressure outside the distal end (232) of the tube (54) by a predetermined infusion threshold. A catheter as claimed in claim 19, wherein the catheter is usable in the cardiovascular system of a patient, and wherein the infusion threshold exceeds the pressure arising from the venturi effect of blood flowing in the circulatory system of the patient outside the distal end (232) of the tube (54). A catheter as claimed in any preceding claim, further comprising a removable wire-like catheter push member (306) positionable within at least one of the lumens (36') from the proximal end of the tube (54), the push member (306) having sufficient stiffness whereby applying a longitudinally directed force to the proximal end of the push member (306) and to the tube (54) will advance the tube (54) along a preselected body cavity into which the tube (54) is to be inserted, and the push member (306) having sufficient flexibility to enable the push member (306) to follow the contours of the preselected body cavity when the tube (54) is advanced thereinto.

Inventors: MOOREHEAD, HARVEY ROBERT, NICHOLS, COLINS J., NORDGREN, GREGORY N.
Applicants: CATHETER TECHNOLOGY CORPORATION
Application year: 1987
Main classification: A61M25
IPC codes: A61M39, A61M25