Abstract:
The present invention provides a catheter for use in delivering and/or recovering materials to and/or from a tissue site in the body, the catheter comprising one or more macroporous regions adapted to selectively deliver molecules and/or recover cells from the tissue site, based on one or more physical-chemical-biological characteristics. The macroporous region can be provided in the form of a helical hollow wires, and can be adapted to both recover cells from the tissue site (e.g., bacterial or other cells present in interstitial fluid) and optionally to permit the infusion of medicament to the site, under corresponding conditions.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to catheters adapted to be positioned in tissue sites within the body, including those used for delivering and/or withdrawing materials such as fluids, molecules, particles, and cells to and from the body. 
       BACKGROUND OF THE INVENTION 
       [0002]    Various sites within the body are difficult to access by minimally invasive means, e.g., in order to take biopsy or other samples, or for delivering materials to the site locally. Tissue sites that include infections of the skin and soft tissue, such as cellulitis, typically cannot be cultured, although tissue biopsy, fine needle aspiration, and blood cultures have been attempted. It is occasionally possible to recover bacteria from such sites by means of fine needle aspiration, with the best recovery in conditions of excess tissue fluid, such as congestive heart failure and kidney disease. When used to aspirate tissue or fluids, by the use of negative pressure, needles tend to entrap tissue, thereby preventing ingress of interstitial fluid. Without the ability to quickly access and sample such sites, however, the corresponding identification of the pathogen, and in turn treatment, are often delayed, or not possible at all. There exists a need for the recovery of samples in such circumstances, including the recovery of bacteria from sites in which no ulceration, abscess pocket, or other drainage site might exist. 
         [0003]    On another subject, a wide array of devices have been described for use in delivering fluids and compounds (e.g., molecules) to the body, e.g., by means that include anything from direct inoculation or injection to prolonged infusion. Relatively few of these devices are particularly well suited for the prolonged infusion of large molecules (e.g., macromolecules), particularly to regions of the body that are relatively less accessible to needles and the like. 
         [0004]    For instance, Tahlila et al. describe the manner in which arterial gene therapy requires efficient local gene delivery to the cells of the arterial wall (“The Dispatch™ catheter as a delivery tool for arterial gene transfer”, Cardiovascular Research, 33(1):181-187). Various vectors can be used, and can be delivered percutaneously using a host of delivery devices, such as double balloon catheters, hydrogel-coated balloon catheters, porous balloon catheters, and ‘channeled’ balloon catheters. 
         [0005]    On yet another subject, catheters have long existed for various applications within the body. Applicant has itself become a world leader in the field of catheters having microporous portions (e.g., in the form of “hollow fibers”), for use in various embodiments. See, for instance, U.S. Pat. Nos. 6,030,358; 6,537,241; 6,942,633; 6,942,634; 7,717,871; and 7,935,092; and U.S. Publication Nos. US-2005-0165342-A1; US-2007-0060834-A1; US-2010-0100061-A1; US-2010-0106140-A1; and US-2010-0286586-A1; the disclosures of each of which are incorporated herein by reference. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention provides a catheter that comprises one or more macroporous regions suitable for insertion in a body tissue site in order to deliver and/or recover materials (e.g., fluid, molecules, particles, and/or cells) to and/or from the tissue, and which is then subsequently suitable for safe removal from the tissue site. 
         [0007]    In a preferred embodiment, the invention provides a catheter for use in delivering and/or recovering materials to and/or from a tissue site in the body, the catheter comprising one or more macroporous regions adapted to selectively deliver and/or recover materials such as molecules and cells to and from the tissue site, based on one or more physical-chemical-biological characteristics. The catheter can include one or more macroporous regions selected from the group consisting of inorganic (e.g., metallic) and/or polymeric structures, such as helical hollow wires, that can be adapted to both recover bacterial cells from the tissue site and permit the infusion of therapeutic fluids (e.g., containing medicament) to the site, under corresponding conditions (e.g., the application of positive or negative pressure). 
         [0008]    The invention further provides a corresponding method of preparing and using a catheter as described herein, including for the sampling and/or identification of bacterial infection within an otherwise inaccessible tissue site, and in turn, optionally for the treatment of such infection by the delivery of medicament through the same catheter, preferably while in position within the tissue site. 
         [0009]    In a preferred embodiment, the catheter comprises a combination of a catheter body and one or more macroporous regions, preferably hollow macroporous regions, which can be provided in any suitable combination and arrangement, to provide a catheter having sufficient structural integrity for the macroporous region(s) to be positioned within a tissue site, optionally without the need for ancillary devices such as introducers or protective sheaths, and to there be used for the purpose of delivering and/or recovering materials to and/or from the surrounding tissue, with the catheter itself thereafter being capable of removal from the tissue site. 
         [0010]    In one such embodiment, the catheter body will include a substantially solid body portion that is coupled with and extends proximally from a generally hollow macroporous region(s). The catheter will have sufficient properties (e.g., strength, flexibility and patency) to permit the hollow macroporous region(s) to be placed, to remain in place, and to be used for their intended purpose. In a particularly preferred embodiment, the macroporous region is itself non-inflatable, as compared for instance to an inflatable balloon that might provide the desired porosity once positioned and inflated within the body. Optionally, however, the macroporous region is sufficiently (and ideally reversibly) expandable or flexible, e.g., to permit its porosity to be altered, for instance, in order to dislodge clogged pores while positioned within the tissue site. In one preferred embodiment, the catheter can be used, for instance, to remove bacteria from infected tissue in a minimally invasive manner, thereby allowing for fast and accurate diagnosis and proper treatment of skin and soft tissue infections. In an alternative preferred embodiment, the catheter can be used, for instance, for the delivery (e.g., by infusion) of medicaments that are themselves not amenable to either direct delivery (as by syringe) or prolonged delivery (as by infusion). 
         [0011]    In one preferred embodiment, the catheter can comprise a removable rigid stylet, for instance, to reinforce the catheter for insertion into tissue, e.g., by positioning the stylet within the catheter. It is generally desirable to remove the rigid stylet after positioning the catheter in the targeted tissue, so as to minimize tissue trauma from inadvertent movement of the catheter with a rigid stylet. In this manner, the catheter, including the macroporous region(s), can be retained in position after positioning of the catheter into body tissue using the rigid stylet, and prior to treatment (e.g., delivery and/or removal of fluid, fluid components, and cells). 
         [0012]    The macroporous region(s), in turn, will be of sufficient type, size, dimensions, configuration and porosity to permit them to be positioned, and to remain positioned, within a body tissue, including in the course of stylet removal, and there used to deliver or recover materials (e.g., fluid, molecules, and/or cells). The hollow macroporous region(s) can in the form of a microtube, that can be coupled to one or more positioning and/or reinforcing component(s) and/or to the catheter body at or near its proximal end, and extend distally therefrom. 
         [0013]    Similarly, a catheter of the present invention is, or can be adapted to be sufficiently steerable to permit the user to direct the distal end in vivo. Various approaches for imparting directional control to the distal tip (macroporous regions(s)) will become apparent to those skilled in the art, given the present description, and are incorporated herein by reference. 
         [0014]    In a particularly preferred embodiment, the invention provides a catheter comprising one or more macroporous regions, preferably in the form of a contiguous hollow region, such as a stranded wire. The word “macroporous” as used herein, will refer generally to a surface having sufficient porosity to permit desired fluid, fluid components, molecules (e.g., medicaments), and/or cells, to be delivered and/or recovered through the portion and in fluid contact with the lumen of the catheter. Such porosity can be based upon any principle, including size exclusion, and/or based upon other physical, chemical, or biological characteristics (e.g., by the use of binding agents, lubricious, or other coatings). 
         [0015]    In a particularly preferred embodiment, the proposed catheter comprises a macroporous portion having pores that are large enough to recover bacteria, which can then be quickly analyzed via molecular and/or other mechanisms to determine the species, strain, drug resistance, and virulence. Once identified, the proper medicament (e.g., antibiotic) can be identified and delivered directly to the body, either by conventional means (e.g., systemically), or optionally and preferably, directly to the same tissue site by means of the still positioned catheter of this invention. Direct tissue infusion of antibiotic can significantly increase local tissue concentration and reduce systemic complications. 
         [0016]    Suitable materials for use in providing the macroporous region of a catheter of this invention can be provided in any suitable form. Commercially available materials include those identified as helical hollow strands, and are available, for instance, from Fort Wayne Metals. Such materials are provided in the form of stranded wire having an open center working channel, and can be constructed from various material types (e.g., having desired properties, such as modulus). Suitable material types for use in preparing a macroporous catheter region include, for instance, nitinol, platinum, titanium, and are available commercially (e.g., as style nos. 302, 304V and 316L, as shown on www.fwmetals.com. 
         [0017]    In turn, those skilled in the art, given the present description, will appreciate the manner in which a macroporous region of this invention can be designed to any desired specifications, e.g., in terms of dimensions, tension, compression, torque, and pitch strength. So too can single, dual and triple layer tubes can be prepared as well, having desired flexibility and control, and providing suitable inner diameter, outer diameter, wire size, and filar diameter, filar number. For instance, a hollow helical strand can be provided with an inner diameter between about 0.02 mm to about 3.5 mm, an outer diameter between about 0.06 mm to about 5 mm, about 6 to about 18 filars, and a pitch selected from left, right, unidirectional, and reverse pitch. These and other characteristics, in turn, can be used to provide one or more macroporous regions having desired properties, particularly including size characteristics, porosity, and compatibility with the body. 
         [0018]    A catheter, including macroporous region, of this invention can be modified, e.g., coated, in order to provided desired properties, such as lubricity, hydrophobicity or hydrophilicity, and hemocompatability. 
         [0019]    A macroporous region is preferably tubular, and can be used to controllably permit the recovery and/or delivery of any desired materials through the tubular walls, including for instance, materials selected from the group consisting of fluid (including relatively small solutes with or without encapsulates), macromolecules (e.g., proteins and nucleic acids with or without encapsulates), viruses, and cells, including sub-cellular components, cell particulate, whole cells (e.g., bacterial cells, blood cells) and combinations of cells (e.g., agglomerated cells). Given the present description, those skilled in the art will understand the manner in which the selection and use of a macroporous region can depend on various factors, including for instance, the molecular weight, configuration, and physical-chemical characteristics of the macromolecules to be recovered or delivered, as well as on the various dimensions and properties of cells and corresponding subparts and combinations thereof. 
         [0020]    By contrast, the use of “microporous” hollow fiber (tubular) membranes can, of the type described in the Background section above, can at times be constrained by various factors, including by the lack of available fibers with various (and particularly large) porosities, as well as by the structural integrity of the fibers themselves, which tend to have very small diameters. The use of such fibers for in vivo applications can in turn be limited, under certain conditions, e.g., by the tendency of both the walls and lumen of such fibers to themselves become occluded or fouled, particularly under conditions of high concentrations of large molecules (e.g., albumin) and/or large volume infusions or aspirations. For these and other reasons, the use of conventional microporous hollow fiber members is typically limited to those having an effective upper most porosity of between 0.45 to 0.5 microns. This corresponds well with conventional ‘microfiltration’, as by the use of conventional (and generally non-tubular) membranes, for instance, having standard pore sizes that typically include 0.1, 0.2, 0.45 microns, though which can also include those having pore sizes of 0.65, 1 and 5 microns, depending on a wide array of factors (including the application for which they are used). See, for instance, “Ultrafiltration—Application and Product Guide”, Millipore. 
         [0021]    By contrast, a macroporous region of the present invention can provide effective porosity of 0.5 microns and greater, as by the use of helical hollow strands that can be constructed in order to provide an average porosity of about 0.5 microns, about 5 microns, about 10 microns, about 20 microns, about 30 microns, about 40 microns, about 50 microns, about 60 microns, about 70 microns, about 80 microns, about 90 microns, or about 100 microns. Given its preferred tubular structure, and the optional ability to limit or address fouling as described herein, the macroporous region of this invention can be used for applications that conventional hollow fibers are not generally suitable, such as for sampling interstitial fluid for the presence of bacteria or viruses. 
         [0022]    The “pore size” as used to describe a macroporous region of the present catheter will typically be provided in functional terms, as the porosity required to effectively permit the recovery and/or delivery of desired materials under the conditions of use. In turn, pore size can be provided as a micron value, indicating that particles larger than the rating will be precluded from passing into or through the region wall. The porosity can be rated as well in terms of the nominal molecular weight limit (NMWL), also sometimes referred to as the molecular weight cut-off. The NMWL indicates that most dissolved macromolecules with molecular weights higher than the NMWL will not be able to pass through the wall of the region. Those skilled in the art will appreciate the manner in which the selected porosity cut off will typically be well below the molecule weight of the solute(s) to be excluded. The ability of a desired material to be precluded by or delivered through the region wall will be a function of a variety of factors, including the molecular shape and size of the material (e.g., molecule, particle or cell), electrical characteristics, fluid or tissue concentration and composition, operating conditions, and device or system configuration. So too will performance be affected by parameters such as pressure, concentration, temperature, pH, and potential fouling. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  illustrates a catheter in accordance with an embodiment of the invention; 
           [0024]      FIG. 2  is a longitudinal cross-sectional view of a distal region of the catheter of  FIG. 1 ; 
           [0025]      FIG. 3  is a transverse cross-sectional view along section A-A in the distal region shown in  FIG. 2 ; 
           [0026]      FIG. 4  illustrates a catheter in accordance with an alternate embodiment of the invention; 
           [0027]      FIG. 5  is a longitudinal cross-sectional view of a distal region of the catheter of  FIG. 4 ; 
           [0028]      FIG. 6  illustrates a catheter in accordance with another embodiment of the invention; 
           [0029]      FIG. 7  is a longitudinal cross-sectional view of a distal region of the catheter of  FIG. 6 ; 
           [0030]      FIG. 8  shows exemplary flow paths in a section of the macroporous section of the distal region shown in  FIG. 7 ; 
           [0031]      FIG. 9  is a transverse cross-sectional view along section B-B in the distal region shown in  FIG. 7 ; and 
           [0032]      FIG. 10  is a longitudinal cross-sectional view of a distal region of an embodiment of a self-introducing catheter. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    While multiple embodiments of the invention are disclosed herein, still others may become apparent to those skilled in the art. In the following, certain illustrative and non-limiting embodiments are described in detail with reference to the accompanying drawings wherein like elements are designated by like numerals. It should be clearly understood that there is no intent, implied or otherwise, to limit the invention in any form or manner to that described herein. As such, all alternative embodiments are considered as falling within the spirit, scope and intent of the disclosure. The metes and bounds of the invention is defined by the appended claims and any and all equivalents thereof. 
       SELECTED NOMENCLATURE 
       [0000]    
       
           100  catheter 
           102  catheter body 
           104  macroporous section 
           106  lumen within catheter  100   
           108  proximal end of catheter  100  (catheter body  102 ) 
           110  distal end of catheter  100  (macroporous section  104 ; macroporous coil  122 ; internal support tube  124 ) 
           112  distal end of catheter body  102   
           114  proximal end of macroporous section  104   
           116  seal between catheter body  102  and macroporous section  104  (macroporous coil  122 ) 
           118  end piece 
           120  connector at proximal end of catheter  100  (catheter body  102 ) 
           122  macroporous coil 
           124  internal support tube 
           126  proximal end of macroporous coil  122   
           128  proximal region of macroporous coil  122   
           130  effective or exposed length of macroporous coil  122   
           132  proximal end of internal support tube  124   
           134  proximal region of internal support tube  124   
           136  distal region of catheter body  102   
           138  openings such as slots or perforations in internal support tube  124   
           140  wall of internal support tube  124   
           142  core wire 
           200  catheter (alternate embodiment) 
           204  macroporous section 
           300  catheter (alternate embodiment) 
           344  tube within lumen  206  of catheter  300   
           346  openings such as slots or perforations through wall  348  in distal region  350  of tube  344   
           348  wall of tube  344   
           350  distal region of tube  344   
           352  lumen within tube  344   
           354  infusion flow paths 
           356  aspiration flow paths 
           400  self-introducing catheter 
           402  catheter body 
           404  macroporous section of catheter  400   
           406  longitudinally extending lumen within catheter  400   
           408  distal region of catheter  400   
           410  distal end of catheter  400   
           414  proximal end of macroporous section  404   
           416  medical grade adhesive, weld, braze, solder joint 
           418  end piece of catheter  400   
           430  effective length of macroporous section  404   
           442  stylet within catheter  400   
           446  openings such as slots or perforations in distal region  450  of catheter body  402   
           448  wall of distal region  450  of catheter body  402   
           450  distal region of catheter body  402   
       
     
         [0080]      FIG. 1  illustrates an embodiment of elongate catheter  100  configured for delivering or recovering fluid and/or material, including medicament, to or from a tissue site in a body.  FIG. 2  is a longitudinal cross-sectional view of a distal region of catheter  100 ; and  FIG. 3  is a transverse cross-sectional view along section A-A in the distal region shown in  FIG. 2 . Catheter  100  is defined, at least in part, by interconnected catheter body  102  and macroporous section  104  having lumen  106  extending longitudinally there through between proximal and distal ends  108  and  110 . Proximal and distal ends  108  and  110 , respectively, further define a proximal end of catheter body  102  and a distal end of macroporous section  104 . Catheter body  102  extends longitudinally between proximal and distal ends  108  and  112 , and macroporous section  104  extends longitudinally between proximal and distal ends  114  and  110 . In general, catheter body  102  is made of any suitable flexible medical grade tubing material such as stainless steel or other metals, urethane, polymers, or fiber reinforced composites as will become apparent to those skilled in the art. While catheter  100  in general, and both catheter body  102  and macroporous section  104  in particular, are illustrated as having circular cross-sections, this does not always have to be the case. For instance, in some non-limiting exemplary embodiments, the one or more cross-sections are elliptical, triangular, square, rectangle, or any other geometrical shape. Also, catheter body  102  and macroporous section  104  can have the same or distinctly different cross-sections. 
         [0081]    As shown, catheter body  102  and macroporous section  104  are interconnected by securely attaching respective distal and proximal ends  112  and  114  to one another and forming seal  116  using a suitable medical grade adhesive as will become apparent to those skilled in the art, including an epoxy or urethane, or using a weld, braze or solder joint when metallic material are used. Catheter  100  includes end piece  118  such as a plug having a blunt or a sharp tip or a trocar or a stylet securely attached thereto for inhibiting the flow of any fluid and/or material into or out of lumen  106  across distal end  110 . Proximal end  108  includes connector  120  configured for removably attaching (or connecting) catheter  100  to a medical device (not shown) and providing fluid connectivity with lumen  106 . Accordingly, in some embodiments of catheter  100 , connector  120  is a leur connector or a leur lock fitting as will become apparent to those skilled in the art. 
         [0082]    In some embodiments of catheter  100 , macroporous section  104  is defined, at least in part, by macroporous coil  122  longitudinally circumscribing at least a portion of an outer surface of internal support tube  124 . As illustrated, distal end  110  of catheter  100  (and of macroporous section  104 ) further defines a distal end of both macroporous coil  122  and internal support tube  124 . Macroporous coil  122  extends longitudinally between proximal and distal ends  126  and  110  with at least a portion of proximal region  128  covered by seal  116  whereat catheter body  102  connects with (or attaches to) macroporous section  104 . As such, effective (or exposed) length  130  defines, at least in part, a longitudinal extent of macroporous coil  122  (or macroporous section  104 ) through which fluid and/or material can be delivered or recovered to or from a tissue site. 
         [0083]    In accordance with an embodiment of the invention, macroporous coil  122  is a tube having a porous wall made from filars, defining, at least in part, an open center working channel. As such, the porosity of macroporous coil  122 , or the ease with which, a fluid and/or material travels across the porous wall between an inner and an outer surface of macroporous coil  122  can be affected by, for example, one or more of the number of filars, a diameter of each one of the one or more filars, the distance (or spacing) between a surface of each one of the one or more filars, or any combination thereof. For instance, the porosity of macroporous coil  122  can be increased or decreased, respectively, by increasing or decreasing the distance between the surfaces of adjacent filars. Similarly, increasing or decreasing the diameter of the one or more filars can affect the porosity of macroporous coil  122 . One such device useable as macroporous coil  122  is sold under the trade name Helical Hollow Strand Tube (HHS® Tube) by Fort Wayne Metals; Fort Wayne, Indiana; USA (http://www.fwmetals.com/hhs-wire.php). 
         [0084]    In some embodiments of macroporous section  104 , lumen  106  is defined, at least in part, by internal support tube  124  positioned within the open center working channel of macroporous coil  122 . As shown, internal support tube  124  extends longitudinally between proximal and distal ends  132  and  110 , with proximal region  134  extending into at least a portion of lumen  106  extending through distal region  136  of catheter body  102 . In a non-limiting exemplary embodiment of catheter  100 , internal support tube  124  is a tube having one or more openings such as slots or perforations  138  through wall  140  thereof, with the outer surface of internal support tube  124  in contact with an inner surface of both macroporous coil  122  and distal region  136  of catheter body  102 . Accordingly, any fluid and/or material introduced under pressure into lumen  106  will flow distally through lumen  106 , through openings  138 , through the porous wall of macroporous coil  122 , and into the area (not shown) surrounding macroporous section  104 . And, fluid and/or material in the area surrounding macroporous section  104  can be extracted by applying a vacuum in lumen  106  causing the fluid and/or material to flow from the surrounding area, through the porous wall of macroporous coil  122 , through openings  138 , into lumen  106 , and out proximal end  108  (or connector  120 ) of catheter  100 . As such, openings  138  are configured and positioned (or distributed) along the longitudinal extent of macroporous section  104  in a manner conducive for enabling even (or equal) flow of fluid and/or material through the porous wall of macroporous coil  122 . 
         [0085]    Internal support tube  124  serves to protect or reinforce at least a distal region of catheter  100  defined, at least in part, by macroporous coil  122  and distal region  136  of catheter body  102  into which it extends. In some embodiments, internal support tube  124  is made of or fabricated from polymer or metal or metallic wire having sufficient strength and flexibility for maneuvering the distal region of catheter  100 . In a non-limiting exemplary embodiment, internal support tube  124  is rigid and, as such, is configured for providing rigidity and support for the distal region of catheter  100 . In other embodiments, internal support tube  124  is flexible and, as such, is configured for providing reinforcement and support for macroporous coil  122  and distal region  136  of catheter body  102  into which it extends. In some embodiments of internal support tube  124 , openings  138  are one or more of circles, ellipses, triangles, squares, rectangles, or any other geometrical shape as may be need to provide the necessary porosity, strength and flexibility. 
         [0086]    While the rigidity and support provided by macroporous coil  122  and/or internal support tube  124  may be sufficient for the introduction into or penetration of relatively soft tissues, a more stiffened distal region of catheter  100  may be desirable or necessary for other applications such as for the introduction into or penetration of relatively hard tissues. Accordingly, some embodiments of catheter  100  include elongate core wire  142  extending longitudinally within lumen  106  between proximal and distal ends  108  and  110 . As such, core wire  142  is of sufficient rigidity to facilitate the introduction or penetration of catheter  100  into the tissue. In some embodiments, core wire  142  is a stylet configured for imparting rigidity to catheter  100 . In other embodiments, a distal end of core wire  142  is attached or secured to end piece  118  and, as such, facilitates both the insertion and removal of catheter  100 . In yet other embodiments, the distal end of core wire  142  is not secured or attached to end piece  118  and is therefore extractable or removable from catheter  100  after macroporous section  104  has been positioned at the target tissue as desired. In certain embodiments of the invention, core wire  142  is a hollow tube defining a lumen therewithin. 
         [0087]    While  FIGS. 1-3  illustrate an embodiment of catheter  100  wherein macroporous coil  122  longitudinally circumscribes at least a portion of the outer surface of internal support tube  124 , this does not always have to be the case. For instance, in some embodiments of the invention (not shown), macroporous coil  122  and internal support tube  124  are radially spaced apart along at least a portion of their respective longitudinal extent within macroporous section  104 . In other embodiments of the invention (also not shown), the distal end of internal support tube  124  does not extend to (or coincide with) distal end  110  of catheter  100 . In one such embodiment, the distal end of internal support tube  124  terminates proximally of distal end  110  of catheter  100 ; whereas in other such embodiments, an additional elongated member bridges a gap between the distal end of internal support tube  124  and distal end  110  of catheter  100 . In yet other embodiments of the invention (also not shown), the distal ends of both macroporous coil  122  and internal support tube  124  do not extend to (or coincide with) distal end  110  of catheter  100 , and an additional elongated member bridges a gap between the distal ends of both macroporous coil  122  and internal support tube  124  and distal end  110  of catheter  100 . In another embodiment of the invention (not shown), an external support structure such as a tube or another macroporous coil longitudinally circumscribes an external surface of macroporous coil  122 . Generally, the wall of the external support structure will be configured for facilitating the flow of fluids and/or materials thereacross and, as such, will include one or more of a porous structure or one or more openings. In one such embodiment, an internal surface of the external support structure and the external surface of macroporous coil  122  are not radially spaced apart; whereas in other such embodiments, the internal surface of the external support structure and the external surface of macroporous coil  122  are radially spaced apart. In yet another embodiment of the invention, either one or both of internal support tube  124  and the external support structure are either radially spaced apart or are not radially spaced apart from macroporous coil  122 . 
         [0088]    As can be seen, several alternative configurations are contemplated as being within the spirit, scope and intent of the disclosed invention. Furthermore, additional configurations may become apparent to those skilled in the art. Accordingly, all variations or additional configurations are considered as falling within the metes and bounds of the instant invention. 
         [0089]      FIG. 4  illustrates an alternate embodiment of elongate catheter  200  configured for delivering or recovering fluid and/or material to or from a tissue site in a body; and  FIG. 5  is a longitudinal cross-sectional view of a distal region of catheter  200 . Elements of catheter  200  that are identical to or substantially similar to those of previously described catheter  100  are illustrated with like numerals. Therefore, in the interest of brevity, only those elements of catheter  200  that are substantially different from those of catheter  100  are described in the following. 
         [0090]    As shown, catheter  200  is defined, at least in part, by interconnected catheter body  102  and macroporous section  204  having lumen  206  extending longitudinally therethrough between proximal and distal ends  108  and  110 . Macroporous section  204  is defined, at least in part, by macroporous coil  122  extending longitudinally between proximal and distal ends  126  and  110 . Catheter body  102  and macroporous section  204  are interconnected by inserting at least a portion of proximal region  128  of macroporous coil  122  into lumen  206  extending through distal region  136  of catheter body  102 . In some embodiments of the invention, such an insertion forms a snug fit or a reinforced support between macroporous coil  122  and catheter body  102 . Macroporous coil  122  and catheter body  102  are securely attached to one another by forming seal  116  using a suitable medical grade adhesive as will become apparent to those skilled in the art, including an epoxy or urethane, or using a weld, braze or solder joint when metallic material are used. 
         [0091]    Fluid and/or material introduced into lumen  206  under pressure will flow outwardly from lumen  206 , through the porous wall of macroporous coil  122 , and into the surrounding tissue. And, fluid and/or material in the surrounding tissue can be extracted by applying a vacuum in lumen  206  causing the fluid and/or material to flow from the tissue, through the porous wall of macroporous coil  122 , into lumen  206 , and out proximal end  108  (or connector  120 ) of catheter  200 . 
         [0092]    While  FIGS. 4 and 5  illustrate an embodiment of catheter  200  wherein macroporous section  204  includes only macroporous coil  122  and does not include any additional external or internal support structure or tube such as internal support tube  124  described in the foregoing non-limiting exemplary embodiment with reference to  FIGS. 1-3 , this does not always have to be the case. As such, alternate embodiments of the invention include catheter  200  wherein an internal support tube is longitudinally circumscribed by macroporous coil  122 , or an external support structure longitudinally circumscribes macroporous coil  122 , or any combination thereof. Further embodiments of the invention include catheter  200  wherein, either one or both internal and external support structures are either radially spaced apart or are not radially spaced apart from macroporous coil  122 . Of course, the walls of all such internal or external support structures are configured for facilitating the flow of fluids and/or materials thereacross and, as such, will include one or more of a porous structure or one or more openings. All alternative and/or additional configurations that may become apparent to those skilled in the art are considered as falling within the metes and bounds of the instant invention. 
         [0093]      FIG. 6  illustrates another embodiment of elongate catheter  300  configured for delivering or recovering fluid and/or material to or from a tissue site in a body.  FIG. 7  is a longitudinal cross-sectional view of a distal region of catheter  300 ;  FIG. 8  illustrates the flow paths of the fluids and/or material in the macroporous section of catheter  300 ; and  FIG. 9  is a transverse cross-sectional view along section B-B in the distal region shown in  FIG. 7 . Elements of catheter  300  that are identical to or substantially similar to those of previously described embodiments are illustrated with like numerals. Therefore, in the interest of brevity, only those elements of catheter  300  that are substantially different from those of other embodiments are described in the following. 
         [0094]    Catheter  300  is defined, at least in part, by interconnected catheter body  102  and macroporous section  304  having lumen  306  extending longitudinally therethrough between proximal and distal ends  108  and  110 . Catheter  300  further includes tube  344  extending longitudinally within lumen  306  between proximal and distal ends  108  and  110 . In the illustrated embodiment, tube  344  includes one or more openings such as slots or perforations  346  extending through wall  348  in at least distal region  350  thereof. Lumen  352 , extending longitudinally within tube  344  between proximal and distal ends  108  and  110 , is configured for fluid communication between openings  346  and connector  320  at proximal end  108  of catheter  300 . As shown, macroporous section  304  is defined, at least in part, by distal region  350  of tube  344  in combination with macroporous coil  122 . Accordingly, openings  346  in distal region  350  are configured and positioned (or distributed) along a longitudinal extent of tube  344  (and of macroporous section  304 ) in a manner conducive for even (or equal) flow or distribution of fluid and/or material through the porous wall of macroporous coil  122 . 
         [0095]    Generally, tube  344  is of sufficient rigidity to facilitate the introduction or penetration of catheter  300  into the tissue. In some embodiments of catheter  300 , a distal end of tube  344  is attached or secured to end piece  118  and, as such, facilitates both the insertion and removal of catheter  300 . In other embodiments, the distal end of tube  344  is not secured or attached to end piece  118  and is either fully or partially retractable or removable from catheter  300 . The terms retractable and removable, as used herein, indicate a movement of the distal end of tube  344  in a proximal direction. In some embodiments of catheter  300  wherein tube  344  is at least partially retractable or removable, the distal end of tube  344  (and of lumen  352  defined thereby) is closed or plugged for inhibiting the flow of fluids and/or materials into or out of lumen  352  through the distal end of tube  344 . In other embodiments of catheter  300  wherein tube  344  is at least partially retractable or removable, it may be advantageous or desirable to not close or plug the distal end of tube  344  and therefore permit the flow of fluid and/or material into or out of lumen  352  through the distal end of tube  344 . For instance, if or when one or more of openings  346  gets clogged or obstructed, tube  344  can be retracted such that fluid and/or material can continue flowing through its distal end for aspiration or infusion across or through macroporous coil  122 . Alternatively, even if or when openings  346  are not clogged or obstructed, it may be desirable or advantageous to increase or decrease the flow of fluid and/or material across or through macroporous coil  122  by at least partially retracting or advancing the distal end of tube  344  away from or towards end piece  118 . In certain embodiments of the invention, an increase in the flow of fluids and/or material through lumen  352  of tube  344  may be desirable or advantageous for unclogging macroporous coil  122 . In alternate embodiments of the invention, it may be desirable or advantageous to induce clogging or obstruction of openings  346  and/or of macroporous coil  122 . 
         [0096]    In some embodiments of the invention, catheter  300  includes core wire  142  as described in the foregoing non-limiting exemplary embodiments with reference to  FIGS. 1-3 . In one such embodiment, the core wire extends longitudinally within lumen  352  of tube  344 ; whereas in another such embodiment, the core wire extends longitudinally within lumen  306  of catheter  300 . As previously described, core wire  142  is a stylet configured for imparting at some level of stiffness and rigidity in some embodiments of catheter  300 . In alternate embodiments of catheter  300 , core wire  142  is a hollow tube defining a longitudinally extending lumen therewithin, wherein a distal region of core wire  142  may or may not include openings such as openings  346  through a wall of the tube. 
         [0097]    In accordance with an embodiment of the invention, catheter  300  is configured for facilitating both aspiration and infusion of fluid and/or material from or to the tissue site whereat macroporous section  304  is positioned. Infusion generally includes the delivery of medicament or flushing with a saline solution; and aspiration generally includes the extraction of fluids and/or material from the surrounding tissue or a diseased site and from within the catheter or the lumen therein. Accordingly, connector  320  is a luer connector or a connector having two separate fittings, wherein one fitting is in fluid communication with lumen  306  of catheter  300  and the other fitting is in fluid communication with lumen  352  of tube  344  within catheter  300 . As such, the connector with two separate fittings can be a Y-connector. In some embodiments of catheter  300 , lumen  306  is used for aspiration by applying a vacuum at the corresponding fitting in connector  320 , and lumen  352  is used for infusion by injecting a fluid and/or material under pressure at the corresponding fitting in connector  320 . In other embodiments of catheter  300 , the functionalities of lumens  306  and  352  are reversed in that lumen  306  is used for infusion by injecting a fluid and/or material under pressure at the corresponding fitting in connector  320 , and lumen  352  is used for aspiration by applying a vacuum at the corresponding fitting in connector  320 . In some embodiments of the invention, when one of lumen  306  or  352  is used for aspiration, the other lumen not being used for aspiration is closed off in order to inhibit any “short circuiting” between the lumens. Similarly, when one of lumen  306  or  352  is used for infusion, the other lumen not being used for infusion is closed off in order to inhibit any “short circuiting” between the lumens. However, under certain operating conditions or operating modes, “short circuiting” between the lumens is desired or can be advantageous. Accordingly, in some embodiments of catheter  300 , the applied pressure and suction are adjusted for priming or removing the contents of lumens  306  and  352  or for filling lumens  306  and  352  with fluids and/or material prior to use at the tissue site. In such embodiments, one of lumens  306  and  352  is pressurized and/or suction is applied in the other lumen, and the applied pressure and/or suction are adjusted so as to induce “short circuiting” between the lumens and to inhibit the flow of fluid and/or material through macroporous coil  122 . 
         [0098]      FIG. 8  illustrates exemplary flow paths of fluids and/or materials across macroporous coil  122  and within lumens  306  and  352  in a portion of macroporous section  304  in accordance with a non-limiting exemplary embodiment of catheter  300  wherein lumen  306  is used for aspiration and lumen  352  is used for infusion. It will be apparent to those skilled in the art that the exemplary flow patterns illustrated in  FIG. 8  are representative of the flow pattern along the entire effective length  130  of macroporous section  304 . Of course, the flow patterns will be affected to a certain extent by any clogging or obstruction at any one or more points or locations anywhere along effective length  130  of macroporous section  304 . As shown, during the infusion mode of operation, fluid and/or material introduced under pressure into lumen  352  through the corresponding fitting in connector  320  flows along flow paths  354  to distal region  350  of tube  344 , through openings  346 , through the porous wall of macroporous coil  122 , and into the area (not shown) surrounding macroporous section  304  of catheter  300 . And, during the aspiration mode of operation, fluid and/or material in the area (not shown) surrounding macroporous section  304  of catheter  300  flows along flow paths  346 , through the porous wall of macroporous coil  122 , into lumen  306 , and out through the corresponding fitting in connector  320 . Although not shown, and as previously stated, the functionalities of lumens  306  and  352  are reversible in some non-limiting exemplary embodiments of catheter  300 . 
         [0099]    While  FIGS. 6-9  illustrate an embodiment of catheter  300  wherein macroporous section  304  does include an internal or external support structure or tube such as that described in the foregoing with reference to the non-limiting exemplary embodiments of catheters  100  and  200 , this does not always have to be the case. As such, alternate embodiments of the invention include catheter  300  wherein an internal support tube is longitudinally circumscribed by macroporous coil  122 , or an external support structure longitudinally circumscribes macroporous coil  122 , or any combination thereof. Further embodiments of the invention include catheter  300  wherein, either one or both internal and external support structures are either radially spaced apart or are not radially spaced apart from macroporous coil  122 . Of course, the walls of all such internal or external support structures are configured for facilitating the flow of fluids and/or materials thereacross and, as such, will include one or more of a porous structure or one or more openings. All alternative and/or additional configurations that may become apparent to those skilled in the art are considered as falling within the metes and bounds of the instant invention. 
         [0100]      FIG. 10  is a longitudinal cross-sectional view of a distal region of an embodiment of self-introducing catheter  400 . As will be apparent to one skilled in the art, a self-introducing catheter such as catheter  400  can provide one or more of several benefits including, and not limited to, faster delivery of macroporous section  404  to the tissue site of interest because it does not necessitate the use of an introducer, a relatively smaller profile or “footprint” in contrast to catheters that require an introducer, and in turn, is relatively less invasive than other types of catheters, and a tighter tissue fit with macroporous section  404  without use of an introducer for improved fluid flow between the tissue and the catheter. 
         [0101]    Self-introducing catheter  400  is defined, at least in part, by catheter body  402 , macroporous coil  122 , longitudinally extending lumen  406 , and end piece  418  at distal end  410  of catheter  400 . As illustrated, distal region  408  of catheter  400  includes macroporous section  404  having an effective length  430  along which fluid and/or material is aspired or infused at a tissue site. Macroporous section  404  is defined, at least in part, by distal region  450  of catheter body  402  longitudinally circumscribed by macroporous coil  122 . Distal region  450  of catheter body  402  includes a plurality of openings  446  such as slots or perforations through wall  448  of catheter body  402 . As such, during the infusion mode of operation, fluid and/or material introduced under pressure into lumen  406  at a proximal end of catheter  400  will flow to distal region  450  of catheter body  402 , through openings  446 , through the porous wall of macroporous coil  122 , and into the area (not shown) surrounding macroporous section  404  of catheter  400 . And, during the aspiration mode of operation, fluid and/or material in the area (not shown) surrounding macroporous section  404  of catheter  400  flows through the porous wall of macroporous coil  122 , through openings  446  into lumen  406 , and suctioned out through the proximal end of catheter  400 . 
         [0102]    End piece  418 , in an embodiment of self-introducing catheter  400  is a sharp needle tip for ease of penetrating the tissue. As shown, end piece  418  is securely attached to the distal ends of catheter body  402  and macroporous coil  122  using a suitable medical grade adhesive as will become apparent to those skilled in the art, including an epoxy or urethane, or using a weld, braze or solder joint when metallic material are used. 
         [0103]    Catheter  400  includes stylet  442  extending longitudinally within lumen  406 . In general, stylet  442  is configured for imparting rigidity for easing the introduction of end piece  418  through or into the tissue. In some embodiments, stylet  442  is used for introducing catheter  400  and then removed after macroporous section  404  is positioned at the tissue site. In other embodiments, stylet  442  is not removed or only partially extracted after macroporous section  404  is positioned at the tissue site. In yet other embodiments, stylet  442  is the same as or substantially the same as the various embodiments of core wire  142  as previously described. Accordingly, stylet  442 , in some embodiments, is a hollow tube defining a lumen therewithin. 
         [0104]    While  FIG. 10  illustrates a distal end of stylet  442  terminating proximally of proximal end  414  of macroporous section  404 , this does not always have to be the case. In some embodiments of the invention, the distal end of stylet  442  extends longitudinally to proximate end piece  418  at distal end  410  of catheter  400 . Regardless of its longitudinal extent, stylet  442 , as with core wire  142 , is of sufficient rigidity to facilitate the introduction or penetration of catheter  400 , aided by end piece  418 , into the tissue. In some embodiments, the distal end of stylet  442  is attached or secured to end piece  418  and, as such, facilitates both the insertion and removal of catheter  400 . In other embodiments, the distal end of stylet  442  is not secured or attached to end piece  418  and is therefore extractable or removable from catheter  400  after macroporous section  404  has been positioned at the target tissue as desired. In certain embodiments of the invention, stylet  442  is a hollow tube defining a lumen extending longitudinally therewithin, wherein a distal region of stylet  442  may or may not include openings such as openings  346 ,  446  through a wall of the tube. 
         [0105]    In view of the foregoing, it can be seen that several alternative configurations are contemplated as being within the spirit, scope and intent of the disclosed invention. Furthermore, additional configurations may become apparent to those skilled in the art. Accordingly, all variations and/or additional configurations are considered as falling within the metes and bounds of the instant invention.