Abstract:
A catheter with an elongated catheter body which, with regard to a position of use, has a distal and a proximal end, wherein at the distal end, a sponge- or cushion-like elastic deformation body is arranged which has, in particular, electrically, mechanically or optically acting measuring means or a measuring connection for detecting a pressing force exerted on the deformation body.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This patent application claims the benefit of co-pending U.S. Provisional Patent Application No. 61/588,195, filed on Jan. 19, 2012, which is hereby incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates generally to a catheter with an elongated catheter body which, with regard to a position of use, has a distal and a proximal end. The present invention further relates to a catheter arrangement and a measuring device connected thereto. 
       BACKGROUND 
       [0003]    In medical practice, a variety of differently designed catheter and/or catheter-like devices (e.g., electrode lines) are known and in widespread use. In some cases, they are used by experienced specialists; however, in some cases, they are used by physicians and/or also medical personnel without special knowledge and experience. Nevertheless, harm and/or impairment in the patient have to be reliably excluded. 
         [0004]    When using known catheters having a plastic tip or a metal tip, there is a risk of perforation. In order to keep the surface pressure and, thus, the risk of perforation low, compromises in terms of stiffness of the catheter shaft and the catheter tip have to be accepted. These compromises limit, among other things, the maneuverability and the positional stability of the catheter. 
         [0005]    The present invention is directed toward overcoming one or more of the above-identified problems. 
       SUMMARY 
       [0006]    It is therefore an object of the present invention to provide an improved catheter which can also be used by less experienced persons, the construction of which nevertheless readily meets the requirements for clinical use, and the practical value of which is generally increased. 
         [0007]    An object of the present invention is achieved by a catheter with the features of claim  1 . The present invention further provides a catheter arrangement with the features of claim  16 . 
         [0008]    The present invention is based on the idea to modify known catheter structures by a special perforation protection element. The present invention further includes the idea to provide a deformation body at the distal end of the catheter. Finally, the present invention comprises the idea to obtain, via suitable measuring means, data from the deformation behavior of the deformation body which permit an improved evaluation of the specific situation of use. When the catheter is in use, the deformation body is subjected to a pressure change when pressed against the wall of a vessel or hollow organ, and the pressure change can be converted distally or proximally. The pressure change occurring when pressed against the tissue can result in a change of the electrical properties of the deformation body (e.g., resistance, capacitance, etc.), which can be measured and can be used for determining the pressure area and/or pressure force. A direct mechanical signal transmission is also possible. 
         [0009]    In suitable configurations of the present invention, it is provided that the deformation body contains a plastic foam or a fluid, in particular a liquid or a gel, or a filling of pourable particles. Since the deformation body has to react elastically, a filling level adapted to the surface and nature of the sheath layer is to be considered when filling in a fluid. 
         [0010]    In a metrological embodiment already generally mentioned above, measuring electrodes, each with one measuring voltage connection, are provided in shell sections of the deformation body which oppose each other. In one configuration, the deformation body comprises a foam from an electrically conductive polymer or with electrically conductive, finely distributed inclusions, or with conductive particles which are coated with a dielectric, or has particles from a ferroelectric film. 
         [0011]    In further configurations of the present invention it is provided that at the distal end, and rigidly connected thereto, a first measuring device element is provided, and a second measuring device element interacting with the first measuring device element is provided on the inner wall of a sheath of the deformation body. Due to its own elasticity, and/or its interaction with a filling, and/or its interaction with at least one spring element which supports the sheath with respect to the catheter body, the sheath of the deformation body is configured in a self-resetting manner. 
         [0012]    A particularly simple, purely mechanical embodiment of the provided measuring means can be configured such that at a distal end of the deformation body, a freely displaceable measuring wire is provided which extends up to the proximal end of the catheter and runs within the catheter body. The stiff measuring wire&#39;s displacement along the catheter body, caused by the compression of the deformation body, is visible and quantitatively detectable at the proximal end of the catheter body; however, a force measurement requires additional metrological provisions. In one modification, the function of the measuring wire can also be assumed up to a certain extent by the inner hose itself. 
         [0013]    In a further embodiment, the deformation body is a multi-piece design from a plurality of sub-bodies, wherein the sub-bodies have a different deformation behavior and/or separate measuring means or connections for detecting a pressing force specifically exerted on said sub-bodies. It is in particular provided in this embodiment that the sub-bodies comprise optically or electrically acting measuring means or connections. 
         [0014]    In a further embodiment, the inventive catheter is configured as an electrode line with at least one electrode arranged on the deformation body or at the distal end of the inner hose enclosed by the deformation body. Here, in particular, the, or at least one, electrode is elastically deformable and is in particular, for example, made from a conductive plastic. 
         [0015]    Further features, aspects, objects, advantages, and possible applications of the present invention will become apparent from a study of the exemplary embodiments and examples described below, in combination with the figures, and the appended claims 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0016]    Advantages and usefulness of the present invention arise also from the following schematic description of exemplary embodiments based on the figures. In the figures: 
           [0017]      FIGS. 1A-1E  show schematic illustrations (side views and cross-sectional illustrations) of an embodiment of the catheter according to the present invention in the initial state and in the deformed state of the catheter end; 
           [0018]      FIGS. 2A-2B  show schematic perspective illustrations of a further embodiment of the inventive catheter; 
           [0019]      FIGS. 3A-3C  show schematic perspective illustrations of a further embodiment of the inventive catheter; 
           [0020]      FIG. 4  shows a perspective illustration of a further embodiment of the catheter according to the present invention; 
           [0021]      FIG. 5  shows a schematic illustration of an embodiment of the proposed inventive catheter as a bipolar electrode line; 
           [0022]      FIG. 6  shows a schematic illustration of a further embodiment of the catheter according to the present invention; and 
           [0023]      FIGS. 7A-7B  show schematic diagrams of embodiments of the catheter arrangement according to the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0024]      FIGS. 1A-1E  show schematically a catheter  10  with a distal end  10   d  and a proximal end  10   p , wherein a deformation body  11  is attached at the distal end  10   d . The illustrated embodiment involves a foamed plastic body with a dimensionally elastic sheath  11   a  which, upon contact of the distal catheter end  10   d  with the wall, as shown in  FIG. 1C , deforms into a curved shape. 
         [0025]    A catheter body  13  of the catheter  10  comprises an inner hose  15  and an outer hose  17  which can be proximally displaced relative to the inner hose  15 . The deformation body  11  is secured at the distal end of the inner hose  15 , and the outer hose  17 , in an initial state of the catheter  10  (see  FIG. 1A ), fully covers the inner hose  15  as well as the deformation body  11 , which encloses the inner hose  14  in the distal region, and allows the deformation body  11  to unfold only after it is pulled back far enough. (See  FIG. 1B ). Due to the displaceability of the inner  15  and outer  17  hoses relative to one another, as shown in  FIG. 1C , the action of a pressure force “F” onto the distal end  10   d  of the catheter  10  results not only in a deformation of the balloon  11 , but also in a displacement of the inner hose  15  relative to the outer hose  17  in the proximal direction. This displacement can be detected and evaluated; with respect to the metrological use of the proposed catheter, see also the explanations below. 
         [0026]      FIGS. 2A-2B  show a further catheter according to the present invention, wherein the selected reference numbers are based on  FIGS. 1A-1E , and explanations given above with regard to the first embodiment are not repeated here. 
         [0027]      FIG. 2A  shows an initial state and  FIG. 2B  shows a state of use under the influence of a distally acting force “F”. The catheter  10 ′ differs from the one shown in the  FIGS. 1A-1E  and described above in that the deformation body  11 ′ protrudes beyond the distal end of the inner hose  15 ′. A wall contact with the wall of a vessel or hollow organ in the distal direction thus results first in a compression of the deformation body  11 ′, as shown in  FIG. 2B . Only a further forward displacement results finally (besides a further development of said compression or deformation) in a sufficiently high pressure on the distal end of the inner hose  15  so that the latter moves in the proximal direction. However, the catheter  10 ′ can also be structured such that—after releasing the deformation body  11 ′ by pulling back the outer hose  17 ′—the inner hose  15 ′ is locked with respect to the outer hose  17 ′ and cannot deflect in the proximal direction. 
         [0028]    As in the first-mentioned embodiment, due to the displacement in connection with the deformation of the deformation body  11 ′, the surface pressure at the distal catheter end and, thus, the risk of perforation, is reduced. Providing a deformation measuring wire  19 , which extends through the entire length of the inner hose  15 ′ of the catheter  10 ′ and which is fixed via a fixing pad  19   a  at the point located most distal on the deformation body  11 ′, allows, in addition, an approximate detection of the deformation of the deformation body  11 ′ taking place upon a wall contact. In particular, the deformation body  11 ′ is displaced to the extent of the occurring deformation in the proximal direction, as symbolically illustrated in  FIG. 2B  by the arrow at the proximal end. 
         [0029]      FIGS. 3A-3B  show schematically the functional principle of a further embodiment of the proposed catheter, namely, a catheter  30  with a deformation body  31  at the distal end of a catheter body  33  which (in the context of the function described below) is regarded as being rigid. In its center axis, the catheter  30  comprises a first pole  34  of an electrical (for example, inductive) measuring device, the second pole of which is formed by the (particularly conductive) sheath  31   a  of the deformation body  31 . Both measuring poles  34 ,  31   a  are, in each case, connected to a proximal measuring connection  36   a ,  36   b  of the catheter  30 . The (conductive) sheath or shell layer  31   a  is elastically braced in a self-centering manner with respect to the centrally fixed first measuring pole  34  by a plurality of spring elements  38 . For clarification of the functional principle, the spring elements  38  are drawn as springs; however, in practice, this can involve deformation elements with a different structure, wherein in the context of the above-mentioned inductive measurement, a function as inductivities can be useful, as will be appreciated by one of ordinary skill in the art. 
         [0030]    As shown in  FIG. 3B , the configuration of spring elements  38  and sheath  31   a  of the deformation body  31  is displaced under the influence of a force “F” which results in the generation of an electrical measuring signal at the connections  36   a ,  36   b . This signal correlates with the amount of displacement and/or deformation of the deformation body  31 , and is therefore useful as a measure for the force acting on the wall. The dependence of the measuring signal on the deformation is retrieved, e.g., from a predetermined look up table. Depending on the actual configuration, an arrangement of the type shown can function as an inductive or capacitive or even as an ohmic measuring sensor or, where applicable, can realize a combination of a plurality of measuring principles. 
         [0031]      FIG. 3C  shows a modified catheter  30 ′, the structure of which corresponds substantially to the one of the catheter  30  according to  FIGS. 3A-3B , wherein, however, the arrangement of a plurality of spring elements  38  (see  FIGS. 3A-3B ) is replaced by a single, special spirally shaped spring element  38 ′. With regard to the implementable measuring principles, the above statements apply principally also to this modification. 
         [0032]    As another embodiment of the present invention,  FIG. 4  schematically shows a three-section catheter  40 , wherein the catheter body  43  (including inner hose  45  and outer hose  47 ), as well as the deformation body  41 , is divided into three cylinder segments. If during use, the catheter  40  has wall contact near its distal end  40   d  with the wall of a vessel or hollow organ, this wall contact has a different effect on the individual sections of the deformation body  41  and, for example, through the detection of the electrical resistance of the individual parts, not only the total force but also the direction can be determined, and thus additional knowledge about the position of the catheter  40  can be obtained. 
         [0033]      FIG. 5  schematically shows the distal end of an electrode catheter  50  according to the present invention with a deformation body  51  and a catheter body  53  which comprises an inner hose  55  and an outer hose  57  and, in its distal region, carries two electrodes which can be used for tissue stimulation and/or for sensing tissue potentials. At the distal end  50   d  of the electrode catheter  50 , a tip electrode  56  is provided which can be generated, for example, through a metal coating of the distal end of the inner hose  55 . Also, provided on the circumference of the deformation body  51  is a ring electrode  52  which can be formed, for example, from an elastic conductive plastic. As an alternative, providing a meandering-shaped metal strip or the like is also possible. 
         [0034]      FIG. 6  schematically shows a further catheter, wherein the designation of the parts is based on the ones of the catheter  30  according to  FIGS. 3A-3B . The catheter is generally designated by the number  30 ″ and comprises a deformation body  31 ′ and a catheter body  33 ′ which is to be regarded as being rigid, wherein a first measuring device element  34 ′ is provided positioned on the axis of the catheter  30 ″ and is stationary with respect to the catheter body  33 ′, and a second measuring device element  31   b ′ is provided on the inner side of the sheath of the deformation body  31 ′. 
         [0035]    Deviating from the embodiment according to  FIGS. 3A-3B , the measuring device of  FIG. 6  involves an optical measuring device, and the first measuring device element  34 ′ is a light source uniformly emitting all around, and the second measuring device element  31   b ′ is a spherical array of solar cells. The deformation body  31 ′ is filled with a fluid having a light-damping effect such as, for example, a cloudy elastogel  31   c ′. The light source  34 ′ is connected through first proximal connections  36   a ′ to an external power supply (not illustrated), and the solar cell array  31   b ′ is connected via second proximal connections  36   b ′ to an external measuring and evaluating unit (not illustrated). 
         [0036]    The light source  34 ′ radiates through the light-damping medium  31   c ′ and the arriving radiation is continuously integrated by the spherical array of solar cells  31   b ′. The spherical array of solar cells  31   b ′ on the inner surface of the sheath  31 ′ can be generated, for example, by means of a printing method which has recently been considered for generating solar cells. The integral value changes when the light portions, due to their displacement out of the center of the deformation body  31 ′ (caused by forces acting on the deformation body  31 ′), have to cover longer distances through the light-damping medium  31   c ′ and, thus, are damped in a manner different from the undisturbed resting state of the deformation body  31 ′. 
         [0037]      FIG. 7A  shows a catheter arrangement with a catheter  60  which has a plastic foam body  61  made from a conductive foam and serving as a deformation body. 
         [0038]    Detecting the deformation of the deformation body  61 , which has a conductive foam which, based on direction-dependent changes in impedance, responds to deformation degree and direction, takes place via two measuring electrode surfaces  66   a ,  66   b  in the distal and proximal region, respectively, of the deformation body  61 . Said measuring electrode surfaces  66   a ,  66   b  are connected via measuring lines  68   a  and  68   b  to a measuring current supply  72  with an associated current sensor  74 . An evaluating unit  76  and finally a display unit  79  for providing wall contact information for the surgeon or other medical personnel are connected downstream of the current sensor  74 . A deformation of the deformation body  61  results in a decrease of the distance between the measuring electrodes  66   a ,  66   b  and, at the same time, results in a compression of the foam which is expressed in a change of the resistance in the current path between the measuring electrodes  66   a ,  66   b  and thus in a change of the amperage. The evaluation of the amperage provides the necessary information about the existence of a wall contact and its intensity. 
         [0039]    Similarly structured is the embodiment with a catheter  60 ′, schematically shown in  FIG. 7B , the deformation body  61 ′ of which has a plastic foam composition which is transparent to a certain degree. Said deformation body  61 ′ allows the detection of the weakening of the light passing in the longitudinal direction through the deformation body  61 ′ during a compression of the latter (e.g., as sketched in  FIG. 2B ). Accordingly, instead of measuring electrodes, an optical transmitter element (e.g., an LED)  66   a ′ and an optical receiver element (e.g., a photodiode)  66   b ′ are provided which are connected via electrical supply lines  66   a ′ and  66   b ′ to an adequately adapted measuring current supply  72 ′ and an evaluating unit  76 ′, respectively, which are controlled via an operating control unit  74 ′. The arrangement comprises again a display unit  79 ′ on which the measurement results are visualized for the surgeon or other medical personnel. 
         [0040]    The embodiments of the present invention are not limited to the above-described examples and emphasized aspects but, rather, are also possible in a multiplicity of modifications, all of which lie within the scope of persons skilled in the art. 
         [0041]    It will be apparent to those skilled in the art that numerous modifications and variations of the described examples and embodiments are possible in light of the above teachings of the disclosure. The disclosed examples and embodiments are presented for purposes of illustration only. Other alternate embodiments may include some or all of the features disclosed herein. Therefore, it is the intent to cover all such modifications and alternate embodiments as may come within the true scope of this invention, which is to be given the full breadth thereof. Additionally, the disclosure of a range of values is a disclosure of every numerical value within that range.