Patent Publication Number: US-2019174998-A1

Title: Endoscope with secondary working channel

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation-in-part of PCT Patent Application No. PCT/US2017/046665, filed on Aug. 12, 2017, which claims priority to U.S. Provisional Patent Application Ser. No. 62/374,015, filed on Aug. 12, 2016, the disclosures of which are incorporated herein in their entireties by reference. 
    
    
     BACKGROUND 
     Field of the Invention 
     This disclosure relates to an endoscope with a secondary channel allowing for the continuous instillation of water or an aqueous cleaning solution. 
     Description of the Related Art 
     An endoscope is a widely used minimally invasive medical device that permits a user to investigate symptoms, confirm a diagnosis, or provide treatment to a patient. The user is typically a physician or other qualified health care provider. Endoscopes are used in a wide variety of examination and treatment procedures, including examination or treatment of the gastrointestinal tract using a device such as an esophagogastroduodenoscope, enteroscope, or colonoscope; examination or treatment of the respiratory tract using a device such as a rhinoscope, bronchoscope, or otoscope; examination or treatment of the urinary tract using a cystoscope; examination or treatment of the female reproductive system using a device such as a colposcope, hysteroscope, or falloposcope; and examination or treatment of normally closed body cavities using a device such as a laparoscope, arthroscope, thoracoscope, or mediastinoscope. Each type of endoscope is designed and manufactured to accommodate the specific needs and limitations of the particular area of the body in which it will be used. 
     An endoscope typically includes a rigid or flexible tube; a light delivery system for illumination of the organ, tissue, or other object to be examined or treated, wherein the light source may be outside the body and wherein the light may be delivered to the examination field by an optical fiber system; a camera system or other lens system that transmits an image of the examination field to the user or other viewer; and a working channel for delivery of medical instruments. 
     Certain procedures using an endoscope will require excision of a small tissue sample for biopsy. A common problem encountered in such procedures is obscuring of the examination field. This is typically caused by bleeding or release of other fluids from the excision site, wherein the blood or other fluid released prevents the user from clearly observing the examination field, and thus preventing additional biopsies if necessary. This problem may be alleviated by the delivery of water or an aqueous cleaning solution to the examination field, clearing debris and improving clarity of the examination field. However, the water or an aqueous cleaning solution must actually wash away the blood or other fluid obscuring the examination field without further obscuring the examination field, and must also not damage the tissue being examined. 
     U.S. Patent Application Publication No. 2007/0260113 discloses an endoscope comprising a secondary channel for introducing air, water, or a cleaning liquid to the examination field. U.S. Pat. No. 8,333,690 discloses a fluid feed system for an endoscope comprising a component for injection of a fluid to clean the examination field. These and other disclosed endoscopic examination field cleaning systems employ a single tube with a circular opening for delivery of a fluid. U.S. Pat. No. 8,888,683 discloses an endoscope with multiple secondary channels with approximately circular or semicircular openings that are situated on the exterior of the primary working channel and that may be used for delivery of a cleaning fluid. These cleaning systems all suffer from the limitation that at low fluid flow rates the surface tension of the fluid causes the fluid to exit the secondary channel as droplets rather than as a spray, thus often leading to further obscuring of the examination field rather than the desired cleaning effect. If the fluid flow rate is increased to exceed the threshold at which droplets will form, the impact pressure of fluid on the tissue being examined may damage the tissue. 
     Thus there remains a need for an endoscope with an examination field cleaning system that allows for introduction of a cleaning fluid in a way that does not cause further obscuring of the examination field or damage to the tissue being examined. 
     SUMMARY 
     An endoscope comprising an examination field cleaning system is disclosed herein. The endoscope comprises an inner channel comprising a primary working channel, lens system, and light delivery system and an outer secondary working channel comprising an examination field cleaning system. The inner channel has an approximately cylindrical shape and is encompassed by a rigid or flexible tube. The outer secondary working channel is configured to be encompassed by an outer cylinder that is approximately concentric with and fully encompasses the inner channel and tube, wherein the examination field cleaning system may comprise one or more fluid delivery channels. The endoscope may further comprise an anchoring bridge, wherein the anchoring bridge secures the outer cylinder to the inner channel and wherein the anchoring bridge may extend the length of the endoscope or may comprise a multi-part system comprising a primary anchoring bridge segment extending most of the length of the endoscope except near the distal end and a secondary anchoring bridge segment at the distal end of the endoscope. 
     A method of using the disclosed endoscope to clean an examination field in an internal body cavity is also described herein. A cleaning fluid may be introduced, via one or more fluid delivery channels that are configured to form an annular secondary channel, into the examination field to wash away blood or other fluids that are obscuring the examination field. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows the distal view of an embodiment of the endoscope. 
         FIG. 2  shows a comparison of distal views of an embodiment of the disclosed endoscope and a prior art endoscope. 
         FIG. 3  shows the distal view of an embodiment of the endoscope with an anchoring bridge. 
         FIG. 4  shows an embodiment of the endoscope wherein the anchoring bridge extends the length of the endoscope. 
         FIG. 5  shows an embodiment of the endoscope wherein the anchoring bridge comprises a primary anchoring bridge segment and a secondary anchoring bridge segment. 
         FIG. 6  shows an embodiment of the endoscope with an anchoring bridge that extends the entire length of the main body segment. 
         FIG. 7  shows an embodiment of the endoscope with a primary anchoring bridge segment that extends the length of the main body segment, a secondary anchoring bridge segment that extends the length of the distal end segment, and a position adjustment segment separating the primary and secondary anchoring bridge segments. 
     
    
    
     DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS 
     An endoscope comprising an examination field cleaning system is disclosed herein. The endoscope comprises an inner channel comprising a primary working channel, lens system, and light delivery system and an outer secondary channel comprising an examination field cleaning system. The inner channel has an approximately cylindrical shape and is encompassed by a rigid or flexible tube. The outer secondary channel is configured to be encompassed by an outer cylinder that is approximately concentric with and fully encompasses the inner channel and tube, wherein the examination field cleaning system may comprise one or more fluid delivery channels. 
       FIG. 1  shows a distal view of an embodiment  100  of the disclosed endoscope, wherein  101  is the primary working channel,  102  is a light source,  103  is a lens system, and  104  is the outer secondary channel, wherein outer secondary channel  104  consists of a single annular fluid delivery channel. Water or another cleaning fluid such as an aqueous saline solution is instilled via outer secondary channel  104 . The flow pattern allows the user to introduce the cleaning fluid at a desired flow rate while significantly reducing the likelihood that the cleaning fluid will form droplets that will further obscure the examination field rather than cleaning it as desired. The outer secondary channel  104  may be attached to a cleaning fluid storage vessel, wherein a valve controls the rate at which cleaning fluid enters the outer secondary channel from the cleaning fluid storage vessel. The flow rate of the cleaning fluid may optionally be controlled by a foot pedal, wherein the foot pedal is attached to the cleaning fluid storage vessel and wherein activation of the foot pedal actuates the valve. 
     In some embodiments, the endoscope is a bronchoscope, rhinoscope, enteroscope, esophagogastroduodenoscope, or a cystoscope. In applications where the overall diameter of the endoscope is limited by its use, such as for a bronchoscope, cystoscope, or other endoscope used in a narrow passage, the outer secondary channel eliminates the need for an additional tube within the inner channel that will not only significantly increase the overall diameter of the inner channel and thereby significantly increase the overall diameter of the endoscope but also compromise the diameter of the primary working channel. By distributing the flow of cleaning fluid substantially uniformly around the inner channel, the disclosed endoscope has a decreased overall diameter as compared to previously disclosed endoscopes comprising an examination field cleaning system. 
       FIG. 2  shows a comparison between an embodiment  200  of an endoscope with an annular secondary channel for instillation of cleaning fluid as disclosed herein and an embodiment  210  of a circular secondary channel for instillation of cleaning fluid as described in the prior art. As shown in  FIG. 2 a   , endoscope  200  comprises primary working channel  201 , one or more light sources  202 , a lens system  203 , and an annular secondary channel  204  consisting of a single annular fluid delivery channel for instillation of the cleaning fluid. As shown in  FIG. 2 b   , prior art endoscope  250  comprises primary working channel  251 , one or more light sources  252 , a lens system  253 , and a circular secondary channel  254  for instillation of the cleaning fluid. As discussed above, where secondary channel  204  and secondary channel  254  have the same overall cross-sectional area, the outer diameter of endoscope  200  will be less than the outer diameter of endoscope  250 . Since the maximum outer diameter of the endoscope will be constrained by its specific use, the annular design of the secondary channel allows endoscope  200  to comprise a wider primary working channel  201  as compared to the primary working channel  251  of endoscope  250 . 
     Moreover, the maximum flow rate of the cleaning solution will be limited by the need to avoid tissue damage caused by the instillation of cleaning solution. If the flow rate of cleaning solution is too high, the pressure created by instillation of cleaning solution will damage the tissue being examined during endoscopy. Thus, the flow rate must be sufficient to wash away contaminants such as blood from the examination field as described above, and also must be below the level that would cause damage to the tissue being examined. 
     Endoscopes with examination field cleaning systems described in the prior art typically suffer from the limitation that at low fluid flow rates the surface tension of the fluid causes the fluid to exit the endoscope as droplets rather than as a spray, thus often leading to further obscuring of the examination field rather than the desired cleaning effect. To avoid droplet formation, the flow rate at which cleaning solution is instilled must exceed a threshold flow rate (Q t ). The threshold flow rate will vary depending on the diameter of the secondary channel through which cleaning solution is instilled and also upon the design of the secondary channel. The secondary channel may be configured as an annular secondary channel  204  or as a circular secondary channel  254 , as shown in  FIG. 2 . The annular secondary channel may comprise one or more fluid delivery channels, wherein the one or more fluid delivery channels are arranged along the circumferential edge of the endoscope to collectively form a substantially annular configuration. 
     The results shown in Tables 1-4 below assume that the cleaning solution is water. A saline solution or other cleaning solution will likely have highly similar properties to water for the purpose of flow rate and impact pressure calculations. Any differences between actual cleaning solutions and water with respect to the results shown in Tables 1-4 are negligible. 
     Table 1 shows the threshold flow rate for a circular secondary channel of specified diameter (d) and the threshold flow rate for an annular secondary channel with a single fluid delivery channel with the same cross-sectional area as the specified circular secondary channel, where four possible values for the inner diameter (d i ) of the annular secondary channel are specified. The outer diameter (d o ) of the annular secondary channel that has the same cross-sectional area as the specified circular channel will vary with the diameter of the circular secondary channel, and thus the width of the annular secondary channel will vary accordingly. 
                                     TABLE 1                      Annular   Annular   Annular   Annular       Circular   (d i  = 3 mm)   (d i  = 4 mm)   (d i  = 5 mm)   (d i  = 6 mm)                                                     d (mm)   Q t  (mL/min)   d o  (mm)   Q t  (mL/min)   d o  (mm)   Q t  (mL/min)   d o  (mm)   Q t  (mL/min)   d o  (mm)   Q t  (mL/min)                                                             0.5   9   3.04   31   4.03   36   5.02   40   6.02   44       0.7   15   3.08   44   4.06   51   5.05   57   6.04   62       0.9   22   3.13   57   4.10   65   5.08   73   6.07   80       1.1   29   3.20   70   4.15   80   5.12   89   6.10   97       1.3   38   3.27   83   4.21   95   5.17   106   6.14   115       1.5   47   3.35   96   4.27   110   5.22   122   6.18   133       1.7   56   3.45   110   4.35   125   5.28   139   6.24   152       1.9   67   3.55   124   4.43   141   5.35   156   6.29   170       2.1   78   3.66   138   4.52   156   5.42   173   6.36   188       2.3   89   3.78   153   4.61   172   5.50   190   6.43   207       2.5   101   3.91   167   4.72   188   5.59   207   6.50   225       2.7   113   4.04   182   4.83   204   5.68   225   6.58   244       2.9   126   4.17   198   4.94   221   5.78   243   6.66   263       3.1   139   4.31   214   5.06   238   5.88   261   6.75   282                    
If the flow rate of the cleaning solution is below the threshold flow rate, the cleaning solution will bead up and exit the end of the secondary channel in droplets. If the flow rate of the cleaning solution is above the threshold flow rate, the cleaning solution will exit the end of the secondary channel as a spray.
 
     As shown in Table 1, the threshold flow rate to avoid droplet formation increases with the diameter of the secondary channel. In addition, the threshold flow rate for an annular secondary channel of equivalent cross-sectional area as a circular secondary channel is always significantly higher. This indicates that preventing droplet formation will require a higher flow rate of cleaning solution when employing an annular secondary channel with a single fluid delivery channel as compared to a circular secondary channel of equal cross-sectional area. 
     However, as shown in Tables 2-4, the impact pressure (P) of the cleaning solution on the tissue in the examination field is significantly lower when the cleaning solution is delivered by an annular secondary channel with a single fluid delivery channel as compared to a circular secondary channel. Table 2 shows the impact pressure caused by cleaning solution delivered at a flow rate of 230 mL/min via a circular secondary channel of a specified diameter (d). 
                                 TABLE 2                       d (mm)   P (Pa)                                                    0.6   91813           0.8   29050           1.0   11899           1.2   5738           1.4   3097           1.6   1816           1.8   1133           2.0   744           2.2   508           2.4   359           2.6   260           2.8   194           3.0   147           3.2   113                        
Table 3 shows the flow rate (Q) for fluid instilled via an annular secondary channel with a single fluid delivery channel with a specified inner diameter (d i ) and outer diameter (d o ) that is required to generate the same impact pressure as a circular secondary channel of diameter 1.0 mm instilling fluid at a flow rate of 230 mL/min, namely 11899 Pa as shown in Table 2.
 
                                         TABLE 3                                  Annular               Circular       (d i  = 3.0 mm)                                     d (mm)   Q (mL/min)   d o  (mm)   Q (mL/min)                                                 1.0   230   3.0   0                   3.1   140                   3.2   285                   3.3   435                   3.4   589                   3.5   748                   3.6   911                   3.7   1079                   3.8   1251                   3.9   1428                        
Table 4 shows the required flow rate (Q) for fluid instilled via an annular secondary channel with a single fluid delivery channel with a specified inner diameter (d i ) and outer diameter (d o ) to generate the same impact pressure as a circular secondary channel of diameter 2.0 mm instilling fluid at a flow rate of 230 mL/min, which is 744 Pa as shown in Table 2.
 
                             TABLE 4                      Annular   Annular       Circular   (d i  = 3.0 mm)   (d i  = 4.0 mm)                                     d (mm)   Q (mL/min)   d o  (mm)   Q (mL/min)   d o  (mm)   Q (mL/min)                                             2.0   230   3.0   0   4.0   0               3.1   35   4.1   47               3.2   71   4.2   94               3.3   109   4.3   143               3.4   147   4.4   193               3.5   187   4.5   244               3.6   228   4.6   297               3.7   270   4.7   350               3.8   313   4.8   405               3.9   357   4.9   461               4.0   403   5.0   517               4.1   449   5.1   576               4.2   497   5.2   635                    
As shown in Tables 3-4, for a given d i  and d o  of an annular secondary channel, generating a higher impact pressure will require a higher flow rate. The relationship is nonlinear.
 
     As shown in Tables 3-4, the inner and outer diameter of the annular secondary channel may be adjusted to generate the same impact pressure as a circular secondary channel at a correspondingly higher flow rate. A properly designed annular secondary channel thereby allows instillation of cleaning solution at a higher rate than a circular secondary channel that would generate the same impact pressure. For any given impact pressure the annular design of the secondary channel allows a higher flow rate of cleaning solution, and thus more solution is available to clear the examination field of impurities. A high impact pressure will damage tissue in the examination field. Thus the critical threshold for instillation of cleaning solution will be not to exceed a designated critical impact pressure. By allowing more solution to enter the examination field at or below the critical impact pressure, the annular secondary channel promotes better cleaning of the examination field by instillation of cleaning solution. 
     In some preferred embodiments, the endoscope may further comprise an anchoring bridge, wherein the anchoring bridge secures the outer cylinder that encompasses the outer secondary channel to the tube encompassing the inner channel.  FIG. 3  shows an embodiment  300  of the disclosed endoscope with an anchoring bridge, wherein  301  is the primary working channel,  302  is a light source,  303  is a lens system,  304  is the outer secondary channel, and  305  are anchoring segments which collectively comprise an anchoring bridge. The anchoring bridge may comprise three or more anchoring segments, and may preferably comprise four anchoring segments. The anchoring bridge may separate the outer secondary channel  304  into multiple fluid delivery channels. Water or another cleaning fluid such as an aqueous saline solution is instilled via outer secondary channel  304 . The outer secondary channel  304  may be attached to a cleaning fluid storage vessel, wherein a valve controls the rate at which cleaning fluid enters the outer secondary channel from the cleaning fluid storage vessel. The flow rate of the cleaning fluid may optionally be controlled by a foot pedal, wherein the foot pedal is attached to the cleaning fluid storage vessel and wherein activation of the foot pedal actuates the valve. 
     In some preferred embodiments, the endoscope may include a main body segment and a distal end segment that may be adjusted to assume an orientation relative to the main body segment, where both the inner channel and the outer secondary channel extend the entire length of the distal end segment and where the inner channel extends the entire length of the main body segment and the outer secondary channel extends at least a substantial portion of the length of the main body segment.  FIG. 4  shows an embodiment  400  of the disclosed endoscope with main body segment  411  and distal end segment  412 . The distal end segment may preferably extend from the distal end of the endoscope to a position about 2-3 centimeters from the distal end of the endoscope. The endoscope may further comprise a position adjuster  413 , wherein the position adjuster is located at the junction between the distal end segment and the main body segment, as shown in  FIG. 4 . The position adjuster may allow the user to adjust the direction of the distal end segment of the endoscope, as shown in  FIG. 5 . The direction of the distal end segment may be aligned with the radial axis of the endoscope or may be oriented to form an angle θ between the main body segment  511  and the distal end segment  512 . The angle θ may be varied using the position adjuster. By varying the angle θ, the user may insert the distal end segment into a section of the examined area that is oriented in various directions with respect to the main passage or organ through which the endoscope is inserted. 
     In some embodiments, the anchoring bridge may extend the entire length of the main body segment and the distal end segment.  FIG. 6  shows an embodiment  600  of the disclosed endoscope with an anchoring bridge that extends the entire length of the main body segment, wherein  601  is the primary working channel,  602  is a light source,  603  is a lens system,  604  is the outer secondary channel, and  605  are anchoring segments which collectively comprise an anchoring bridge. 
     In other embodiments, the anchoring bridge may comprise a primary anchoring bridge segment that extends the length of the main body segment and a secondary anchoring bridge segment that extends the length of the distal end segment or that extends through some part of the distal end segment from the distal end of the endoscope.  FIG. 7  shows an embodiment  700  of the disclosed endoscope comprising main body segment  711 , distal end segment  712 , and position adjustment segment  713  where primary anchoring segments  705  extend the length of the main body segment to form a primary anchoring bridge segment that extends the length of the main body segment, secondary anchoring segments  715  extend the length of the distal end segment to form a secondary anchoring bridge segment that extends the length of the distal end segment, and the position adjustment segment separates the main body segment from the distal end segment. The secondary anchoring segments may alternatively extend from the distal end of the endoscope through some part of the distal end segment but not its entire length. The distal end segment may preferably extend from the distal end of the endoscope to a position about 2-3 centimeters from the distal end of the endoscope, and the secondary anchoring segments may preferably extend between about 1 millimeter and 2-3 centimeters from the distal end of the endoscope through the distal end segment. The embodiment illustrated in  FIG. 7  may allow greater flexibility and ease of adjustment of the orientation of the distal end segment with respect to the main body segment. 
     As shown in  FIG. 3 , the anchoring bridge may comprise anchor segments that are sufficiently narrow so as not to appreciably alter the flow characteristics of the cleaning solution through the outer secondary channel as compared to embodiments of the disclosed endoscope that do not have an anchoring bridge, such as the embodiment shown in  FIG. 1 . Thus the results shown in Tables 1-4 are also relevant to embodiments of the endoscope comprising an anchoring bridge. 
     Alternatively, the anchoring bridge may comprise anchor segments which modify the flow characteristics of the cleaning solution through the outer secondary channel in a way that reduces the threshold flow rate (Q t ) or that reduces the impact pressure (P) generated by a given flow rate (Q) of cleaning solution. The secondary working channel may preferably be flushed with cleaning solution before use to remove any air bubbles that would alter the flow characteristics of the cleaning solution when the endoscope is in use. This flush procedure will effectively remove any air bubbles from the secondary working channel, regardless of whether the endoscope has an anchoring bridge and regardless of whether the anchoring bridge is continuous through the length of the endoscope or whether the anchoring bridge comprises a primary anchoring bridge segment and a secondary anchoring bridge segment as described above. 
     Although the flow rate required to instill cleaning solution as a spray rather than as droplets when employing an annular secondary channel is higher than the corresponding flow rate for a circular channel, the width of the annular secondary channel may be adjusted to exceed the threshold flow rate without exceeding the critical impact pressure. Since the critical impact pressure may differ for different types of endoscopes, the inner diameter and width of the annular secondary channel may be tuned via routine experimentation to identify the optimal inner diameter and width of the annular secondary channel for the desired type of endoscopy. Moreover, in an endoscope comprising an anchoring bridge, the size and configuration of the anchoring bridge may be adjusted by modifying the size and configuration of the anchor segments, thereby modifying the flow characteristics of the cleaning solution through the outer secondary channel in a way that reduces the threshold flow rate (Q t ) or that reduces the impact pressure (P) generated by a given flow rate (Q) of cleaning solution. Thus configuration of the annular secondary channel may be further adjusted to generate the desired flow properties of cleaning solution instilled. 
     Thus an annular secondary channel properly tuned to the desired type of endoscopy may obviate the limitation of droplet formation when using a circular secondary channel to instill cleaning solution. 
     A method of cleaning an examination field in an internal body cavity is also described herein. The internal body cavity may preferably be a human body cavity. The method may comprise an endoscope comprising an inner channel comprising a primary working channel, lens system, and light delivery system and an outer secondary channel comprising an examination field cleaning system, wherein the inner channel has an approximately cylindrical shape and is encompassed by a rigid or flexible tube and the outer secondary channel is configured to be encompassed by an outer cylinder that is approximately concentric with and fully encompasses the inner channel and tube to form an annular secondary channel and wherein the examination field cleaning system may comprise one or more fluid delivery channels. The method may be employed during an endoscopy procedure to clean the examination field while it is being observed by a user using the lens system of the endoscope. A cleaning fluid may be introduced via the one or more fluid delivery channels into the examination field to wash away blood or other fluids that are obscuring the examination field. The flow rate of the cleaning fluid may optionally be controlled by a foot pedal, wherein the foot pedal is attached to a cleaning fluid storage vessel attached to the outer secondary channel and wherein a valve controls the rate at which cleaning fluid enters the outer secondary channel from the cleaning fluid storage vessel and wherein activation of the foot pedal actuates the valve. 
     The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the invention disclosed herein. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the disclosure. Thus, the present disclosure is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein. All references cited herein are expressly incorporated by reference.