Patent Publication Number: US-2010121279-A1

Title: Apparatus and Method for Establishing Access to the Body

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of provisional application Ser. No. 60/077,624 filed on Mar. 6, 1998 and of provisional application Ser. No. 60/081,399 filed on Apr. 10, 1998 in the United States Patent and Trademark Office. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to an apparatus and method for percutaneous access to the inside of the body. In particular, the invention relates to a transparent sheath with a radiopaque marking at the distal end and a fastener for securing a guidewire or catheter near the proximal end of the sheath. 
     BACKGROUND OF THE INVENTION 
     Medical procedures utilizing interventional instruments (e.g., endoscopes) inserted through the skin often require preservation of the access path after the instrument is withdrawn from the body. Typically, these procedures require insertion of a sheath into the body along a guidewire previously coupled to the interventional instrument. The sheath prevents the tract established by the interventional device from closing or collapsing. One example procedure involves insertion of a dilation catheter and a guidewire along the nephrostomy tract. Once properly positioned in the body, a balloon near the distal end of the catheter is inflated to dilate the tract. A sheath is then advanced through the nephrostomy tract before the tract substantially collapses. 
     This procedure has inherent problems. The sheath is typically radiopaque, thus the physician cannot observe objects within or obstructed by the sheath by standard fluoroscopic techniques. In addition, optical imaging devices inserted through the sheath are unable to look out radially, thus prohibiting accurate location of objects adjacent to the sheath. Moreover, the guidewire may migrate during the exchange of instruments through the sheath, thus inhibiting placement of additional instruments along the tract. 
     SUMMARY OF THE INVENTION 
     A transparent sheath for access to the inside of a human or animal body has been developed which is useful in a variety of medical applications including, but not limited to, the exchange of instruments, drainage of fluids and removal of objects (e.g., kidney stones). The sheath can be used to provide percutaneous access to the inside of the body or it can be used in natural body orifices. Applications include urological procedures, stent delivery and laparoscopic procedures. In one embodiment, the sheath includes an elongated hollow member with a radiopaque marking at the distal end. In another embodiment, the sheath includes an elongated hollow member with at least one radiopaque marking along the length of the sheath and one or more fasteners near the proximal end of the sheath for securing other medical devices thereon such as guidewires and catheters. The sheath can be optically or fluoroscopically transparent or transparent to ultrasound. Preferably, the sheath is transparent to all three visible light (including IR and UV lights), ultrasound, and x-rays. The radiopaque marking may be disposed on the outer or inner circumference of the sheath. The radiopaque marking may be disposed on an end face of the distal end or may occupy the whole length of the sheath such as a line or spiral. One or more additional radiopaque markings may be used for identification such as in a broken line, a series or rings, or alphanumerical characters disposed along the length of the sheath (e.g., product numbers and logos). An additional radiopaque line or spiral running the length of the sheath from the distal end to the proximal end may be used to enhance visibility during the procedure. 
     The distal end face may be approximately perpendicular to the longitudinal axis of the sheath. In an alternative embodiment, the distal end face and longitudinal axis may define an angle less than 90° to minimize trauma to the issue during insertion and facilitate placement of the sheath. 
     The transparent sheath may include one or more fasteners at its proximal end for securing other medical devices thereon such as a guidewire or catheter and maintaining the sheath at a desired position within the body. The fastener may be any device or adaptation at the proximal end of the sheath which prevents other medical devices from migrating during the procedure. Example fasteners include clips, slots, or straps such as Velcro™ straps or elastic bands or a combination thereof. In one embodiment, the fastener is a retaining slot which provides an interference fit to hold the other medical device. The retaining slot may also include an opening at the end of the slot which is opposite the proximal end face of the sheath wherein the opening accepts the other medical device and restricts its longitudinal movements back and forth or migration back out of the slot through an interference fit. In yet another embodiment, a magnet is disposed adjacent to the retaining slot to secure a ferromagnetic medical device such as a guidewire. 
     The invention also features a method for access to the inside of a body. The method includes the steps of inserting a first medical device through a body lumen, then inserting over the second medical device such as the transparent sheath of the invention. Once the sheath is disposed at a desired location in the body, the first medical device is secured to the second medical device in the fastener. In one embodiment, the first medical device is secured by an interference fit in an opening adjacent to an end of a slot disposed at the proximal end of the second medical device, the end of the slot being opposite the proximal end face. In another embodiment, the first medical device is secured within the slot by a magnet fixed adjacent to the slot. 
     The method may be used for naturally existing body lumens or body lumens created by the practitioner with the use of an interventional device such as a needle or a trochar. Thus, in one embodiment, the method of the invention permits access to the inside of a body percutaneously. The percutaneous method further includes the step of inserting an interventional device into the body. The interventional device may be coupled to a guidewire or catheter. Once, the lumen is created the interventional device is decoupled from the guidewire or catheter. A transparent sheath of the invention with a fastener near its proximal end and radiopaque markings along its length is inserted into the body over the guidewire or catheter. The interventional device is then removed from the body. In one embodiment, the sheath may be inserted into the body over the guidewire after removal of the interventional device. In another embodiment, the sheath may be inserted over the interventional device before its removal. 
     In yet another embodiment, the methods of the invention further include the step of viewing through the first medical device objects in the body relative to a radiopaque marking at the distal end. The invention also features a method of viewing objects within or near the first medical device in a body. Objects inside or near the first medical device are viewed relative to the radiopaque marking at the distal end with an imaging device or disposed along the length of the elongated hollow body. The imaging device may be located within the first medical device or be outside of the body. In one embodiment, the imaging device is a side-viewing endoscope placed within the first medical device. In another embodiment, the imaging device is a fluoroscopic imaging system viewing from outside the body. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, like reference characters generally refer to the same parts throughout the different views. Also, the drawings are not necessarily to scale, emphasis instead generally being placed upon illustrating the principles of the invention. 
         FIG. 1  is an illustration of an embodiment of a transparent sheath of the invention and guidewire inserted in a body. 
         FIGS. 2A through 2D  are sectional views of the proximal end of an embodiment of a transparent sheath of the invention illustrating the process of securing a guidewire to the sheath using a single retaining slot;  2 A is a cross-section along the line A-A of  FIG. 2B ;  2 B- 2 D are longitudinal sections. 
         FIGS. 3A through 3F  illustrate examples of fasteners at the proximal end of the transparent sheath of the invention used for securing a guidewire or catheter. 
         FIGS. 4A through 4D  are illustrations of the distal end of a transparent sheath having a radiopaque marking on the distal end face  4 A,  4 C, and  4 D are side views, and  4 B is a front view. 
         FIGS. 5A and 5B  are side and front views, respectively, of the distal end of an embodiment of a transparent sheath of the invention having a small radiopaque marking near the extreme distal end of a 45° distal end face. 
         FIGS. 6A and 6B  are side and front views, respectively, of an embodiment of a transparent sheath of the invention featuring a radiopaque marking that occupies the bottom half circumference of the sheath. 
         FIG. 6C  is a side view of an embodiment of a transparent sheath of the invention featuring a spiral radiopaque marking. 
         FIG. 6D  is a side view of an embodiment of a transparent sheath of the invention featuring a series of rings disposed along the length of the sheath from the distal end to the proximal end. 
         FIGS. 7A-7F  are plots of the transmittance of visible light ranging from 400 to 750 nm through pieces of transparent or translucent polymers: A, polyvinyl chloride (PVC)0.022 in thick; B, 0.017 PVC 0.017 in thick; C, Tecoflex™ 0.022 in thick; D: Teflon (TFE) 0.026 in thick; E, Nylon 0.030 in thick; F, Polyethylene (PE) 0.030 in thick. 
         FIG. 8  is a flowchart of a method of access to the inside of a body according to the invention. 
         FIG. 9  is a flowchart of a method of viewing objects within or adjacent to a sheath within a body according to the invention. 
     
    
    
     DETAILED DESCRIPTION 
     Referring to  FIG. 1 , a transparent sheath  10  providing percutaneous access to the body  22  is partially advanced through a body tract  27  established by an interventional instrument over a guidewire  20 . The sheath  10  can alternatively be used through natural body lumens for some procedures wherein percutaneous access is not required. The sheath  10  includes an elongated hollow member  12  and distal and proximal end faces  14  and  16 , respectively. Radiopaque markings  18  and  19  are disposed along the elongated member  12  at known locations along the length of the elongated hollow member  12  and at the distal and  14  respectively. These multiple markings may be used as scaling features and observed during fluoroscopic imaging. Radiopaque markings  18  can also take other configurations or conformations such as lines, spirals, circles, bars, rings or alphanumeric characters to improve the visibility of the sheath  10  or identify the sheath  10 . The markings may occupy the whole circumference of the sheath, such as for rings and spirals, or a portion only such as for lines, bars and other small size markings. A retaining slot  24  is adapted to receive the guidewire  20  which can be secured or locked in the opening  26  by an interference fit. The slot  24  must be narrow enough to preserve the structural rigidity of the proximal end of the sheath  10 , yet be sufficiently compliant to accommodate the passage of the guidewire  20  therethrough to the opening  26 . In addition, the slot  24  must be sufficiently narrow to prevent the guidewire  20  from retreating back spontaneously through the slot  24  after the guidewire  20  is position in the opening  26 , yet be sufficiently compliant to permit voluntary retrieval of the guidewire or catheter  20  and withdrawal of the sheath  10  from the body track  27  once the desired medical procedure is completed. 
     The elongated hollow member  12  can be made from any optically clear plastic. Urethane or rigid vinyl such as polyvinylchloride (PVC) are good sheath materials owing to their flexibility. Polycarbonate materials (e.g., Plexiglas) can also be used. At least a portion of the length of the elongated member  12  is optically and/or fluoroscopically transparent, semi-transparent, or translucent to permit visualization of objects within or near the elongated member  12 . Suitable material for use in the sheath of the present invention have a transmittance of at least 20% and above at a given wavelength. The transmittance (Tr) is a standardized measurement of the percentage of light intensity transmitted (Ir) through a length (m) of material normalized by the intensity of the incident light (Io): 
     
       
         
           
             Tr 
             = 
             
               100 
                
               
                   
               
                
               
                 Ir 
                 Io 
               
             
           
         
       
     
     The length of the path traveled by the light through the material affects the transmittance value: in the same material, the longer the path is, the lower the transmittance will be, and vice versa. Thus, high transmittance materials may be used to form sheath with thicker walls, and still provide suitable transparency for observation through the walls of the sheath. Low transmittance materials may also be used either with thinner wall, or in conjunction with higher intensity incident light or higher sensitivity light receptors. 
     As an illustration,  FIGS. 7A-7F  shows the transmittance of several transparent or semi-transparent materials suitable for use in the sheath of the present invention recorded in the visible range of 400-750 nm. To evaluate the suitability of the material for use in the sheath of the invention, transmittance may also be recorded in the wavelength of desired observation range including IR, UV or X-ray regions. As can be seen in  FIGS. 7A-7F , the transmittance varies from one material to another. Also, the transmittance varies with the wavelength. A material may have a poor transmittance (below 20%) in an area of the light spectrum and a good transmittance (above 50%) in another area of the light spectrum. Observation through the sheath will be possible so long as a wavelength may be selected at which the material constituting the sheath has a transmittance of at least 20% and above. As the transmittance of the material increases clearer images may be obtained. Preferably, the wavelength will be selected in the area of highest transmittance for the material such as 40% and above, and most preferably 70% and above. 
     Preferable materials also maintain sufficient rigidity at body temperature to maintain the body opening propped open. Suitable material will maintain a durometer of about 50-72 Shore D at body temperature. Softer materials may be used with reinforcing materials such as, rings, coils or braids to maintain the lumen open. 
     The radiopaque markings  18 , including a marking  19  on the distal end face  14  at the sheath  10 , permit visualization of the sheath  10  inside the track  27  with a fluoroscopic imaging system and facilitate accurate positioning of the sheath  10  within the body  22 . The markings  18  and  19  can be coatings made from paints, inks, or films which contain materials opaque to the imager adhered, sprayed, or painted on the sheath. For example, the radioopaque substance is preferably metal components such as metal salts, metal oxide or elemental metal or mixtures of metal components in the form of particles or powders dispersed in the coating (e.g., barium, strontium, tantalum, tungsten, gold, iridium, stainless steel and platinum). Alternatively, the particles or powders are dispersed into a portion of the elongated hollow member  12  directly at the desired location. The markings  18  and  19  may also be pieces of opaque materials such as pieces of metal or foils inserted into recesses carved into the elongated hollow member  12  or disposed on either the inner or outer surface  36  and  38 , respectively, of the elongated hollow member  12  and secured into place by glue, heat and/or a covering tape. 
       FIGS. 2A and 2B  are cross and longitudinal sectional views, respectively, of the proximal end of the sheath  10  over an unsecured guidewire  20 . A retaining slot  24  extends from the proximal end face  16  to a circular opening  26  in the elongated hollow member  12 . A physician can secure the guidewire  20  by directing the guidewire  20  through the slot  24  to the opening  26 . 
       FIG. 2C  illustrates a guidewire  20  partially advanced through slot  24 . The opening  26  is defined about an axis  28  which forms an angle θ  25  of approximately 45° with the local longitudinal axis  30  of the sheath  10 . Angle θ  25  can be any angle which prevents kinks or short radius bends in the guidewire  20 . Typically, angle θ is a function of the wall thickness of the elongated member  12 . The diameter of the opening  26  is selected to accommodate the diameter of the guidewire  20  and provide sufficient restraining force when the guidewire  20  is secured in the opening  26 .  FIG. 2D  illustrates a guidewire  20  secured to the sheath  10 . The guidewire  20  is held in place by compressive forces exerted by the wall  32  of the opening  26 . 
       FIGS. 3A through 3F  illustrate various fasteners that can be utilized to secure a guidewire  20  or catheter to a sheath.  FIG. 3A  shows a linear retaining slot  24  and circular opening  26  used in the embodiment illustrated in  FIG. 2 .  FIG. 3B  shows a retaining slot  24  having longitudinal and cross-sectional portions in an L-shape. The guidewire  20  is secured by first passing it through the longitudinal portion of the slot  24  having a width slightly greater than the diameter of the guidewire  20 . The guidewire  20  is then moved around the 90° bend and into the cross-sectional portion of the slot  24  having a width slightly narrower than the diameter of the guidewire  20 . A compressive force exerted by the wall  32  of the slot  24  holds the guidewire  20  in place. Alternatively, the bend between the longitudinal portion and the cross sectional portion may be of an angle less that 90°. In  FIGS. 3C and 3D , the slot  24  has an additional cross-sectional portions forming a T-shape with two openings  26  to permit two guidewires  20  to be secured therein. In  FIG. 3D , the tapered sections  21  of the slot  24  narrow to a width which is less than the diameter of the guidewire  20 , thus holding it in place by an interference fit. Alternatively, one or both of the cross-sectional portions may form an angle with the longitudinal portion less than 90°.  FIG. 3E  shows two separate slots  24  for holding two guidewires.  FIG. 3F  shows a slot  24  over which a strap of self-adhesive material  29  is circumferentially arranged. Alternatively, the strap  29  can be fabricated from an interlocking material such as Velcro™. In  FIG. 3G , a grommet  33  is shown in a position for securing the guidewire  20  at the end of the slot  24 . The guidewire  20  first is moved to the end of the slot  24 . Next, the grommet  33  is placed onto the elongated member  12  near the proximal end face  16  and slipped over an annular ridge  31 . In this position, compressive force exerted by the grommet  33  keeps the guidewire  20  clamped at the end of the slot  24 . 
     It should be understood in conjunction with the descriptions of fasteners for securing a guidewire described above that multiple retaining slots  24  can be used to secure multiple guidewires  20  to the sheath  10 . Furthermore, it should be understood that safety wires, catheters, and other medical instruments having geometries resembling guidewires can be similarly secured to the sheath  10 . In addition, clips, latches, magnets, small locking devices and other fasteners can be integrated or attached to the proximal end of the sheath  10  to secure guidewires, in place of, or in combination with, those described above. 
       FIGS. 4A and 4B  are lateral and front views of the distal end of the sheath  10 , respectively. The normal  34  to the end face  14  defines a tip angle φ  40  of approximately 45° to facilitate a traumatic advancement of the sheath  10  within the body  22 . Angle φ  40  can range anywhere between 0° and 90° and can be selected according to the specific procedure for which the sheath  10  will be employed. Alternatively, the sheath  10  can be tapered near the end face  14  to reduce trauma as shown in  FIGS. 4C and 4D . A radiopaque marking  19  covers the elliptically-shaped surface of the distal end face  14  thus providing accurate information on the position of the distal end of the sheath  10  within the body  22  when observed with a fluoroscopic imaging system. The marking  19  can extend around the edge of the distal end face  14  and onto the adjacent outer wall of the elongated member  12  so that the distal end of the sheath  10  can still be observed when the axis  30  of the elongated hollow member  12  is perpendicular to the viewing axis of the fluoroscopic imager. 
     Referring to  FIGS. 5A and 5B , accurate knowledge of the location of the extreme distal end  37  within the body  22  is necessary to avoid injury to internal organs. Thus, a small radiopaque marking  35  embedded in the elongated member  12  near the extreme distal end  37  can be more advantageous than larger marking configurations such as band or stripe. Encapsulation or thermal bonding techniques can be used to dispose the small radiopaque marking  35  in the elongated hollow member  12 . Alternatively, the marking  35  may be secured into a recess with glue or covering tape. 
       FIGS. 6A-6D  show alternative embodiments of the sheath having various configurations of radiopaque markings. In  FIGS. 6A and 6B  the radiopaque marking  18  is a line that extends from the distal end face  14  to the proximal end face  16  and occupy the bottom half circumference of the elongated hollow member  12 . In  FIG. 6C , the radiopaque marking  18  is a spiral line that extends form the distal end face  14  to the proximal end face  16 . In  FIG. 6D , the radiopaque markings  18  and  19  are a series of rings distributed along the length of the sheath at regular intervals. 
     Referring to the flowchart of  FIG. 8 , a method for access to the inside of a body is shown as a series of steps. In step  100 , an interventional device (e.g., a cannula and stylet) is inserted into a body to create an access tract. In step  110 , a guidewire or catheter is inserted through the interventional device. The interventional device is removed in step  120 , leaving the guidewire in place. Depending on the requirements of the procedure, step  120  can be performed before step  110  is performed. In some procedures, it is desirable to insert a second guidewire (e.g., safety wire) after removal of the interventional device. A dilation catheter (interventional device) coupled to the guidewire is then used to expand the tract to accommodate larger instrumentation, as indicated in step  130 . The guidewire is detached from the dilation catheter in step  140 . In step  150 , a transparent sheath having at least one fastener at its proximal end is inserted into the tract over the dilation catheter. The dilation catheter is withdrawn from the body in step  160 . Depending on the requirements of the procedure, step  160  can be performed before step  150  is performed. The guidewire is then secured to the sheath in step  170 . The sheath can include various types of fasteners, including retaining slots, clips, latches, magnets, small locking devices or other fasteners. The sheath can also include a radiopaque marking to aid in its positioning and for reference when viewing objects within the body. 
     Referring to the flowchart of  FIG. 9 , a method for viewing objects within or near a sheath within a body is shown as a series of steps. In step  200 , an interventional device (e.g., dilation catheter) is inserted into the body. In step  210 , a transparent sheath with a radiopaque marking is inserted into the body over the interventional device. The interventional device is removed from the body according to step  220 . In some procedures it is preferable to remove the interventional device before insertion of the transparent sheath. A guidewire can be inserted along the tract created by the interventional device and can be secured to the sheath by a fastener disposed near the proximal end of the sheath. In step  230 , objects located in or near the sheath are observed relative to the sheath using an imaging device. The imaging device can be a viewing catheter which can include miniature imaging optics and/or a solid state imager disposed at the distal end of the catheter. The imaging device can be located substantially within the sheath and used for forward-viewing or side-viewing (i.e., radial-viewing) through the wall of the sheath. In some instances, the sheath may act as a magnifier of nearby objects. The image information is transmitted via fiber optics or electrical conductor to processing and display optics near the proximal end of the catheter. A forward-viewing or side viewing endoscope can be also be used to view objects located within or near the sheath. Alternatively, a fluoroscopic imaging system external to the body can be used to view objects relative to the sheath. 
     EQUIVALENTS 
     While the invention has been particularly shown and described with reference to specific preferred embodiments, it should be understood by those skilled in the art that various changes in form and detail may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.