Abstract:
A bronchoscopic sheath adapted to be fit over the outside surface of the proximal portion of a bronchoscope to assist with measuring or spacing of treatment. The measurement or spacing sheath is preferably made of braided polymer filament and is configured to collapse under tension and open/expand when the ends of the sheath are pushed towards one-another. Markings are provided on the sheath at regular intervals to reflect distance. The markings may be woven into the braid, or printed on the exterior of the braid. The proximal end of the sheath may be flared and the distal end may be tapered. Each end may be provided with a cuff that may be part of the braid, or a separate elastomeric material, or a thermally sealed edge with atraumatic tip.

Description:
RELATED APPLICATIONS 
       [0001]    The present application claims priority to U.S. Patent Application Ser. No. 62/047,936, entitled “Bronchoscopic Sheath for Measuring or Spacing” and filed on Sep. 9, 2014. The contents of the aforementioned application are incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The invention relates generally to the field of diagnosing, staging and or treating pulmonary diseases utilizing bronchoscopy. 
       BACKGROUND OF THE INVENTION 
       [0003]    Examination and treatment of the airway in humans is generally carried out using a flexible fiber-optic video bronchoscope that is extended into a patient&#39;s airway (pharynx, larynx, trachea, bronchi, etc.) through the mouth or nares. Movement of the bronchoscope into and out of the patient&#39;s airway is visually monitored by observation of the bronchoscope as it is advanced or withdrawn into the patient and/or by video visualization of the interior of the airway using fiber optics located at the proximal tip of the bronchoscope. 
       SUMMARY OF THE INVENTION 
       [0004]    The present invention is a sheath or sleeve, designed to fit snugly over the outside surface of a bronchoscope during a bronchoscopic procedure. The exterior surface of the sleeve bears markings at pre-determined increments to reflect distance along the length of the sheath which are designed to be used by the practitioner to help gauge and measure movement of the bronchoscope into and out of the patient&#39;s airway. The reference markings then are used to reference or align to another object such as the endotracheal tube or rigid bronchoscope. 
         [0005]    According to one embodiment, the sheath is made of braided polymer thread/filament. The braid structure is analogous to a Chinese finger puzzle, increasing in diameter when compressed longitudinally, and collapsing/locking down when it is placed under tension. When the sheath is compressed longitudinally, the inner diameter of the sheath expands significantly more than its braided diameter, permitting it to slide over scopes or catheters of a broad range of diameters. When permitted to relax and recover to its original braided dimension, and particularly when it is placed under tension, it fits snugly on the surface of the scope. This allows the sheath to accommodate and provide insulation and reference markings for multiple scope diameters. The braided sleeve Inner Diameter (ID) is intentionally sized smaller than the Outer Diameter (OD) of the preferred bronchoscope such that it expands and fits snuggly to the scope upon insertion. Therefore, the sheath stays tightly fixed to the exterior surface of the flexible bronchoscope during use, but may be easily loaded and unloaded by pushing the ends of the sheath towards one-another, and “inch-worming” the sheath down the length of the bronchoscope shaft. 
         [0006]    The reference markings may be printed on the exterior surface of the sheath, e.g., using a pad printer or other method, or may be braided into the sheath, for example using a different colored filament. In either event, the markings are set at defined intervals, e.g., 0.5 cm, 1.0 cm, 1.5 cm, etc. According to an embodiment of the invention, the markings may be made in one color to indicate major lengths, e.g., every 10 cm, and the markings may be made in a different color to indicate minor lengths, e.g., every 1 cm. Whatever markings are used, they may be made according to any known method. 
         [0007]    According to an embodiment of the invention, the proximal end of the sheath may be cuffed and/or flared and/or bear a hub to facilitate loading and unloading of the sheath from a flexible bronchoscope. A hub may be a molded or machined plastic component that is joined to the braided sheath by bonding or insert molding. 
         [0008]    According to yet another embodiment, the distal end of the sheath may be tapered and or cuffed to facilitate insertion of the sheath-mounted bronchoscope into the sealing gasket of the endotracheal tube, to provide an atraumatic end so that the sheath does not scythe the tissue when moving proximal to distal, and/or to prevent fraying and/or unraveling of the braid. 
         [0009]    According to a cuffed embodiment, the cuffs at either end may be thermally formed from the braided material, or they may be formed from a different elastomeric or plastic material and fixed to the end of the braided material according to one of any number of known methods. According to an alternative embodiment, the distal end of the braided sleeve may be dipped in or otherwise coated with a flexible adhesive to create a distal tip that is stiffer to aid with insertion into an endotracheal tube gasket, but still flexible enough to assemble onto the bronchoscope. 
         [0010]    According to an embodiment of the invention, the bronchscopic measurement sheath is configured to extend over the flexible bronchoscope a sufficient length to cover the portion of the scope that is visible to the user/operator outside of the patient&#39;s body during use, including portions of the scope that are inside the patient&#39;s body during part of the treatment but that are withdrawn from the patient&#39;s body as progressive parts of the airway tissue are treated. A portion of the distal end of the scope may be left uncovered to avoid interruption of diagnostic and therapeutic devices or gases delivered via the bronchoscope e.g. LN2 cryospray delivery and LN2 gas egress 
         [0011]    According to an embodiment of the invention, the bronchoscopic measurement sheath provides thermal insulation of portions of the scope that are inside the patient&#39;s body during procedures such as radio frequency, laser, or cryotherapy to provide protection from thermal injury. The braided construction and mix of monofilament and multifilament fibers provide both thermal insulation and a physical barrier between the smooth surface of the bronchoscope and endothelium. As the braided construction can comprise of any combination of polymeric material, there will also be the insulating contribution provided by the polymer. According to other embodiments, the braid may be made from filaments of other compositions (e.g., polypropylene, nylon, polyester) or the braid may be made from a hybrid of filaments made from PET and other materials. 
     
    
     
       DESCRIPTION OF THE DRAWINGS 
         [0012]    The following figures accompany the Detailed Description of the Invention which describes the methods and results of specific examples of the practice and success of the invention. 
           [0013]      FIGS. 1A-1E  depict a bronchoscopic measurement sheath according to an embodiment of the invention, loaded onto the proximal end of a bronchoscope; 
           [0014]      FIG. 2  is a close-up view of a bronchoscopic measurement sheath according to an embodiment of the invention, specifically showing how the sheath expands when the ends are forced together; 
           [0015]      FIG. 3  is a close-up view of a bronchoscopic measurement sheath according to an embodiment of the invention, showing an optional flared proximal end and an optional tapered distal end, with an optional elastomeric cuff at both ends; 
           [0016]      FIG. 5  is a close-up of a bronchoscopic measurement sheath according to another embodiment of the invention, mounted on a flexible fiber-optic bronchoscope; 
           [0017]      FIG. 6  shows the proximal end of a bronchoscopic measurement sheath according to an embodiment of the invention, next to a flexible bronchoscope; 
           [0018]      FIG. 7  shows the proximal end of a bronchoscopic measurement sheath according to an embodiment of the invention mounted on the outside of a flexible bronchoscope. 
           [0019]      FIGS. 8A-8D  show an exemplary bronchoscopic measurement sheath having an introducer and bronchoscope locking mechanism, suitable for use with embodiments of the invention; 
           [0020]      FIGS. 9A-9C  show an exemplary sheath-side portion of the locking mechanism shown in  FIG. 8A . 
           [0021]      FIGS. 10A-10E  show an exemplary bronchoscope-side portion of the locking mechanism shown in  FIG. 8A . 
           [0022]      FIGS. 11A-11D  show the exemplary introducer of  FIG. 8A  in more detail. 
           [0023]      FIGS. 11E-11I  depict an alternative example of an introducer. 
           [0024]      FIG. 12  depicts an alternative embodiment in which the sheath is deployed over the bronchoscope using a retaining tube. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0025]    Referring to  FIG. 1A , a bronchoscopic measurement sheath is shown which is configured to be placed over the outer surface of a flexible fiber-optic bronchoscope along a portion of its length during a bronchoscopic procedure. Bronchoscopic measurement sheath  401  may be made of an elongated tube  403  having a lumen configured to receive a bronchoscope  40 , a securing device  405 , for example a Tuohy-Borst, at one end of said tube configured to secure a proximal end of said sheath to a proximal end of the bronchoscope. According to other embodiment, the securing device is a hub (see, e.g.,  FIG. 5 ) fixed to a proximal end of the sheath. 
         [0026]    A bronchoscopic measurement sheath may be placed on the outer surface of the flexible bronchoscope to provide reference markings to aid practitioner in measuring movement of the bronchoscope into and out of the patient&#39;s airway during diagnostic or therapeutic bronchoscopy 
         [0027]    A bronchoscopic measurement sheath may be placed on the outer surface of the flexible bronchoscope to aid in discreet placement of doses to prevent overlapping doses when multiple doses are delivered in an anatomical lumen of the same diameter. 
         [0028]      FIGS. 1B-1E  depict the sheath as it is manufactured, prior to being cut to an application-specific size. As shown in more detail in  FIGS. 1B, 1C, and 1E , the sheath preferably bears a plurality of markings  407  along a portion of the external surface of the tube configured to denote a distance that said scope is moved relative to a fixed position of a patient, a patient feature, or other fixed reference point.  FIG. 1B  shows the markings  407  from the front side of the sheath, while  FIG. 1C  shows the markings  407  from the rear side of the sheath. 
         [0029]    According to an exemplary embodiment, a distance  409  between the end of the first marking and the end of the final marking is preferably 30 cm (11.81 inches). A distance  411  between the start of the first marking and the end of the tube  403  is preferably 7.9 cm (3.11 inches). An overall length  413  of the tube  403  is preferably 48 cm (18.9 inches). These measurements are taken with respect to the tube  403  when the tube  403  is loaded on a 4.8 mm (+0.1 mm/−0.2 mm) mandrel and allowed to relax, as shown in  FIG. 1D . When in an expanded state, the wall thickness of the tube  403  may be about 0.76 mm (about 0.003 inches). 
         [0030]    It is noted that, although particular sizes and dimensions are described in connection with exemplary embodiments throughout the application, the present invention is not limited to the described sizes and dimensions. The sizes and dimensions may vary depending on the application. 
         [0031]    As shown in more detail in  FIG. 1E , the markings  407  may include wide markings spaced at a distance  415  of 1 cm apart from each other, and narrower markings spaced at a distance  417  of 0.5 cm from the 1 cm markings. The wide markings may wrap around the circumference of the tube  403  and may have a width  419  of, for example, about 1 mm (+/−0.51 mm). The narrow markings may be broken lines consisting of two bands that have a width  421  of about 0.5 mm and are about 4.3 mm long. 
         [0032]    The markings  407  may optionally be associated with printed numbers  423 . The numbers  423  may be, for example, about 2 mm tall and written in Arial font, spaced 0.38 mm below each wide 1 cm band. 
         [0033]    Accordingly, the markings  407  may be circumferential marker bands outside the working channel of the scope and may optionally be associated with printed numbers. When aligned with a venting tube (e.g. Rigid bronchoscope or endotracheal tube), the markings provide an extracorporeal proximal reference mark prior to dosing. In subsequent doses or treatments, the reference markers assist the physician when the scope is moved to new treatment locations. In the case of dose spacing, the reference markers assist the physician so as not to overlap doses. 
         [0034]      FIG. 2  shows how the braid of the sheath is configured to expand and open when the two ends of the sheath are forced together. In order to advance the sheath over the bronchoscope prior to a procedure, or to withdraw the sheath from the bronchoscope after a procedure, the user need only squeeze one end of the sheath tightly against the bronchoscope, and advance the other end toward the fixed end. When the pinched/fixed end is released, the sheath will relax in that direction. However, when one end of the sheath is pulled, the configuration of the braid causes the sheath to tighten tightly around the bronchoscope. Accordingly, the braid of the sheath causes the sheath to work like a Chinese finger puzzle. Accordingly, the sheath will not slide off the bronchoscope as it is being advanced into the endotracheal tube and down a patient&#39;s airway. According to a preferred embodiment, the sheath is packaged in a pre-loaded compressed state, so that when it is removed from the packaging for use it is already in the compressed, braid-expanded state which facilitates its application onto the outside surface of the scope. 
         [0035]      FIG. 3  shows a close up of an embodiment of a bronchoscopic measurement sheath according to an embodiment of the invention in which a proximal end of the sheath is cuffed or hubbed and a distal end of the sheath is cuffed and tapered. The optional hub at the proximal end is configured to aid with loading of the sheath onto a bronchoscope, and the optional taper at the distal end is configured to assist with introduction of a sheath-loaded bronchoscope into an endotracheal tube. 
         [0036]    According to various embodiments, the sheath may be made of a braided PET (polyethylene terephthalate) polymer monofilament, and the markings are printed on the exterior of the sheath. According to other embodiments, the braid may be made from filaments of other compositions (e.g., polypropylene, nylon, polyester) or the braid may be made from a hybrid of filaments made from PET and other materials. According to a preferred embodiment, the braid is a 72-carrier construction in a  1  over 2 under 2 pattern, the 72 elements comprising 24 elements of 0.0052″PET monofilament at each end, and 48 elements of 85/24 PET multifilament (85 denier/24 filaments). The material may be braided onto a 0.076″ acetal substrate core at 38 ppi (pics per inch). According to other embodiments, the braid may be comprised of up to 150 elements of different diameter filaments from 0.004″ to 0.01 and up to 50 ppi (pics per inch). 
         [0037]    As shown in  FIG. 3 , either or both ends of the sheath may be formed with a cuff or bonded to prevent or inhibit fraying and/or unraveling of the braid and assist in insertion and removal from the scope. 
         [0038]    The end cuffs may be a heat-fused end of the braid itself, or it may be a separate elastomeric (e.g., polyurethane, silicon, etc.) or rigid plastic hub fixed or bonded to the end of the braid. In the case a proximal hub is used, it is preferably shaped to fit the tapered portion of the bronchoscope that connects the working end to the hand piece. According to one embodiment, the hub may be a separate elastomeric element that sandwiches the end of the braid. The hub may be affixed to the braid according to any known methods, including heat bonding, joint bonding, ultra violet light cure, adhesive, or mechanical bonding, such as dipping. According to a preferred embodiment, the hub may be formed with an annular recess (see  FIG. 5 ) configured to receive the heat-sealed edge of the braid. Once the end of the braided tube has been inserted into the annular recess of the hub, adhesive may be dispensed to fill the annular space that receives the braid, bonding the braid into the annular recess. As shown in  FIG. 3 , the distal end may be tapered for atraumatic insertion in anatomy. According to another embodiment, the distal end may be made have greater stiffness than the remainder of the braid to assist with insertion of the bronchoscope and mounted measurement sheath into the sealing gasket of an endotracheal tube or other laryngeal mask airway, preventing the sheath from buckling and retracting on itself and the bronchoscope as it passes through the tight passage. 
         [0039]      FIG. 4  shows an embodiment of a bronchoscopic measurement sheath mounted on the proximal end of a bronchoscope. The proximal portion of the braided sheath may be a heat-fused end of the braid itself, or it may have a separate elastomeric (e.g., polyurethane, silicon, etc.) or rigid plastic element fixed to the end of the braid in order to slide the sheath onto the scope and fix it in place (see, e.g.,  FIGS. 6 and 7 ). According to a preferred embodiment, the proximal end has a thermoplastic molded component or “hub” (see, e.g.,  FIG. 5 ) molded onto the braid and having tapered interior profile to accommodate the tapered junction between the proximal end of the flexible fiber optic bronchoscope (the “working portion”) and the handpiece. 
         [0040]      FIG. 6  shows an embodiment of the braided sheath according to the invention, bearing a rigid plastic cuff at the proximal end, next to a flexible bronchoscope onto which it might be loaded.  FIG. 7  shows an embodiment of the braided flexible sheath according to the invention loaded onto the outside surface of a flexible bronchoscope, with the rigid plastic cuff at the proximal end of the sheath tightly fitted to the tapered portion of the bronchoscope that connects the working end of the bronchoscope to the handpiece of the bronchoscope. 
         [0041]      FIG. 8A  depicts an exemplary sheath having features for facilitating the insertion of the apparatus into a patient and for securing the apparatus to a bronchoscope. 
         [0042]    The sheath includes a distal tip extrusion  425 , which is shown in more detail in  FIGS. 8B  (side view) and  8 C (cross-section). The distal tip extrusion  425  shown in  FIGS. 8A-8C  is cuffed to facilitate insertion of the sheath-mounted bronchoscope into the sealing gasket of the endotracheal tube, to provide an atraumatic end so that the sheath does not scythe the tissue when moving proximal to distal, and/or to prevent fraying and/or unraveling of the braid. The outer diameter of the extrusion  425  may be larger than the inside diameter of the introducer  427 , which may help to keep the introducer captive on the assembly. Moreover, the short, stiff section created by the extrusion  425  provides a member for the introducer to push against with the introducer, facilitating insertion of the assembly into the endotracheal tube gasket. 
         [0043]    A distance  433  between the end of the distal tip extrusion  425  and the nearest end of the final one of the markings  407  may be about 55 mm (2.17 inches). The outer diameter of the distal tip extrusion  425  may be about 0.240 inches. 
         [0044]    The sheath can be locked to a bronchoscope through a proximal hub  429  disposed at the proximal end of the sheath. The proximal hub  429  is shown in more detail in  FIGS. 9A-9C . A distance  435  between the nearest end of the first marking  407  may be between about 14 mm (0.5 inches) and about 24 mm (0.9 inches), and preferably is about 19 mm (0.7 inches). 
         [0045]    According to some embodiments, one or both of the introducer  427  and the proximal hub  429  may have features or be otherwise configured so that the introducer  427  and the proximal hub  429  can lock together, as described in more detail below in connection with  FIGS. 11E-11H . 
         [0046]    A slide lock  431  connects to the proximal hub  429  to secure the sheath to a bronchoscope. As shown in the detail view of  FIG. 9C , the proximally-facing side of the slide lock  431  includes a feature  433  for which no corresponding feature is present on the distally-facing side of the slide lock  431 . Thus, the feature  433  provides an indication of which side of the slide lock  431  should face outward when the apparatus is assembled. A distance  437  between the end of the distal tip extrusion  425  and the end of the slide lock  431  may be between 389.3 mm (15.33 inches) and 427.4 mm (16.83 inches), and preferably is about 408.35 mm (16.08 inches). The slide lock  431  is shown in more detail in  FIGS. 10A-10B . 
         [0047]    An introducer  427  serves to prop open a gasket on an endotracheal tube to allow the sheath to be deployed in a patient. The introducer  427  is shown in more detail in  FIGS. 11A-11D . 
         [0048]    The detailed views of the introducer  427 , the proximal hub  429 , and the slide lock  431  are now described with reference to  FIGS. 9A-11D . 
         [0049]      FIG. 9A  is a perspective view of the proximal hub  429 , whereas  FIG. 9B  is an end-on view and  FIG. 9C  is a cross section of the proximal hub  429  taken along the line A-A in  FIG. 9B . As shown in  FIGS. 9A-9C , the proximal hub  429  includes a proximal end  435  (facing the bronchoscope) and a distal end  437  (which attaches to the sheath). The distal end includes one or more distal features  439  for securing the proximal hub  429  to the sheath. Optionally, the distal end also includes secondary features  440  that provide an indication of a location for securing the introducer  427  to the proximal hub  429 . When assembled, the sheath may be pulled up to the distal features  439  and may be bonded to the proximal hub  429  with a bonding agent, such as cyanoacrylate, at the distal outer diameter in the vicinity of the area labeled  443 . Alternatively or in addition, the sheath and proximal hub  429  may be insert molded. In one embodiment, the outer diameter at the radially outer end of the distal features  439  is about 0.33 inches, while the outer diameter at the radially outer end of the distal features  440  is about 0.4 inches. This may be compared to an initial radially outer diameter of the proximal hub  429  on the distal side of about 0.28 inches. 
         [0050]    The angle of the interior walls changes at a point represented by the broken line  441 . On the distal side of the line  441 , the walls  443  are angled at about one degree (1°) with respect to a line passing axially through the center of the tube  403  forming the sheath. On the proximal side of the line  441 , the walls  445  are angled at about 2.9° from the axial line. As a result, the interior diameter grows from the distal side to the proximal side. For example, in one embodiment, the interior diameter at the line  441  is about 0.230 inches, whereas the interior diameter at a more proximal point  445  is about 0.304 inches. This may be compared to an initial interior diameter on the distal side of 0.22 inches. 
         [0051]    Proximal to the point  445 , the proximal hub  429  flares outwards into two arms  447 . The arms extend a set interior distance  449  from the point  445  before terminating in flanges  451 ; according to one embodiment, the distance is about 0.310 inches. A distance  453  between the radially interior walls of the arms  447  may be, for example, 0.6 inches. In comparison, an outer radial diameter at the proximal end  435  of the proximal hub  429  may be about 0.72 inches, while a radially outer diameter of a circular support  455  for the arms  447  may be about 0.53 inches. 
         [0052]    The slide lock  431  is depicted in detail in  FIGS. 10A-10E .  FIG. 10A  is a perspective view of the slide lock  431 , while  FIG. 10B  is an end-on view.  FIG. 10C  is a cross-section taken at the line A-A in  FIG. 10B .  FIG. 10D  is a side view, and  FIG. 10E  is a cross-section taken at the line B-B in  FIG. 10D . 
         [0053]    The slide lock  431  is configured to slot inside of the arms  447  of the proximal hub  429 , as shown in  FIG. 8A , and to engage with the proximal hub  429  such that the slide lock  431  is secured between the distally-facing interior wall of the flanges  451  and the proximally-facing wall of the circular support  455  for the arms  447  at the point  445 . In one embodiment, the slide lock is about 0.30 inches in the width direction  457 , 0.8 inches in the height direction  459  as measured at the most radially-exterior points. 
         [0054]    The slide lock  431  includes a set of lips  461 , and the distance between the lips  461  may be established to facilitate securing the slide lock inside the arms  447  of the proximal hub  429 . For example, the distance  463  between the lips  461  may be about 0.550 inches. Excluding the lips  461 , the slide lock  431  may have a size of about 0.590 in the length direction  465 . 
         [0055]    The slide lock  431  includes a central key-shaped hole through which the bronchoscope may pass. The central hole has a central axis  465  extending in the radial direction, and the interior walls of the hole may be angled with respect to the radial direction. The more proximal walls  469  may be angled to a greater degree than the more distal walls  467 . For example, the proximal walls  469  may be angled at about 5° with respect to the central axis  465 , while the distal walls  467  may be angled at about 0.5° with respect to the central axis  465 . 
         [0056]    The introducer  427  is depicted in more detail in  FIGS. 11A-11D .  FIG. 11A  is a perspective view of the introducer  427 , while  FIG. 11B  is a side view.  FIG. 11C  is a cross-section taken at line A-A in  FIG. 11B , while  FIG. 11D  is an end-on view. 
         [0057]    The introducer  427  may have a size of about 0.75 inches in the length direction  474 . The introducer  427  flares out from a distal end  471  to a proximal end  473 . The introducer  427  includes a cylindrical section  475  and a conical section  477 . The cylindrical section  475  may be about 0.28 inches long. A radially interior wall  479  of the cylindrical section  475  may have an inner diameter of about 0.22 inches (5.70 mm). The radially interior wall  481  of the conical section  477  may extend at an angle from a central axis passing through the introducer  427  in the axial direction, for example at an angle of about 7°. As a result an inner diameter of the introducer  427  at the proximal end may be about 0.33 inches. At a point where the cylindrical section  475  meets the conical section, the outer diameter of the introducer  427  may grow, for example from 0.28 inches (7 mm) to about 0.37 inches. The outer diameter at the proximal end may be about 0.43 inches. 
         [0058]    An alternative introducer  427  is shown in  FIGS. 11E-11I . This introducer  427  is designed to lock onto the features  439  of the proximal hub  429  to secure the introducer  427  and proximal hub  429  together. When assembled, a set of wings  482  on the introducer  427  are retained between the secondary features  440  of the proximal hub  429  and the features  439  of the proximal hub  440 , as shown in  FIG. 11I .  FIG. 11E  is a perspective view of the alternative introducer  427 , while  FIG. 11G  is an end-on view.  FIG. 11G  is a cross-section taken at line A-A in  FIG. 11B , while  FIG. 11H  is a cross-section taken at line B-B in  FIG. 11F .  FIG. 11I  shows the introducer  427  locked to the proximal hub  429 . 
         [0059]    As noted above, the sheath  401  may be deployed by “inch-worming” the sheath down the length of the bronchoscope shaft. As an alternative deployment technique (depicted in  FIG. 12 ), a restraining tube  483  may be deployed in connection with the introducer  427 . The restraining tube  483  serves to hold the proximal end of the sheath  401  in its compressed (expanded ID) state. The proximal end of the sheath  401  may optionally include a proximal feature designed to be attached to the restraining tube  483  to hold the sheath  401  in place during insertion. The sheath  401  may then be slid onto the scope without the need to inch-worm the sheath  401  up the scope. Once the assembly is deployed on the scope, the restraining tube  483  is removed and the sheath  401  is allowed to extend to its full deployed length. 
         [0060]    According to an embodiment of the invention for dose spacing, the invention was initially designed for use in connection with cryospray treatment of a patient&#39;s airway using a bronchoscope to allow a user to carefully monitor how far the bronchoscope was being advanced into and/or withdrawn from a patient&#39;s airway to ensure that all desired portions of the airway received treatment, but no portion of the airway received more than a single treatment. A flexible bronchoscope is introduced through the nose or mouth as appropriate and the airway is inspected before starting the procedure. The user then navigates the bronchoscope to the targeted site and positions the bronchoscope so that the targeted treatment site is viewed. The dose spacing sheath provides dose spacing guidance when referenced against a fixed reference point such as an endotracheal tube, to allow the bronchoscopist not to dose the same anatomical location more than once. 
         [0061]    For example, using the dose spacing sheath to assist with cryospray treatment in Right Lobar Bronchi, the user would navigate sheath-mounted bronchoscope to most distal point of RLL (Right Lower Lobar), noting the marking on the dose spacing sheath relative to a fixed point, e.g. endotracheal tube. The user would then initiate a spray treatment, allow the area to thaw, then withdraw the bronchoscope a discrete distance using the markings on the dose spacing sheath, and then spray a second dose at a second non-overlapping location in the in RLL. The same procedure would be used at any location within the airway to make sure that multiple contiguous or nearly contiguous regions are treated without overlap. 
         [0062]    While use of the bronchoscopic measurement sheath and the concept of dose spacing is described herein in the context of cryospray therapy, it can be used for any type of airway treatment in which measure of distance is important. 
         [0063]    While use of the bronchoscopic measurement sheath is described herein in the context of airway reference measurement and treatment it can be used for any type of bronchoscopic or endoscopic treatment in which measure of distance is important. 
         [0064]    In addition to assisting with dosing, the dose spacing sheath of the invention may be used as a measuring device for any bronchoscopic procedure to document the location of lesions, strictures, treatment sites or length of airway segments.