Patent Publication Number: US-2013237755-A1

Title: Flexible visually directed medical intubation instrument and method

Description:
FIELD OF THE INVENTION 
     This invention relates to medical instrumentation and more particularly to a method and apparatus for facilitating intubation of an animal or human patient. 
     BACKGROUND OF THE INVENTION 
     In many medical procedures it is often necessary to place an instrument into the body of the patient for drainage, for viewing a part of the body, or for performing a surgical operation such as the endoscopic removal of a tumor, to take a biopsy, or for feeding the patient. The invention has general application in medicine including the field of urology as well as in the field of gastroenterology and in other medical and surgical specialties. The placement of a catheter in the urethra for the purpose of draining urine or for diagnostic purposes, for example, is one of the most common urological procedures for draining urine or fluid to determine the amount of urine present, to diagnose problems, or to maintain anatomic continuity. This procedure is commonly performed by inserting the catheter manually while noting any resistance to forward movement as shown by a failure of the catheter to slide smoothly into the urethra. While most placements proceed without problems, typically more than forty percent of male urinary catheter placements are difficult because of the problematic normal anatomy of the male lower urinary tract such as the external sphincter, the S-curve of the bulbuous urethra and angulated prostatic urethra and/or pathologic conditions, such as urethral stricture disease, stones, trauma, tumors, enlarged prostate, iatrogenic false passages, and/or congenital disorders causing a substantial burden on the delivery of effective care through the healthcare system. The most common problem is tetany, a spasm of the external urinary sphincter or stricture of the urethra. Stones, and even clots descending from the bladder, also constitute urethral obstructions. In addition, urethral lumen calibers vary considerably, and particularly with urethritis, BPH, urethritis stricture disease and prostate disorders in males. These costs to the healthcare system, hospitals, clinics and doctors&#39; offices are substantial. In addition, the delay in servicing urological catheter patients in a timely manner constitutes poor medical efficiency, delivery, and control. When difficulty is encountered, the resulting frustration among healthcare professionals, especially nurses, physician extenders and physician assistants, creates a very real feeling of ineffectiveness on the part of these healthcare workers, to say nothing of the dissatisfaction on the part of the patients caused by the delay and added discomfort. Difficult catheterizations can also be a source of urinary tract infection. While the dollar cost to the healthcare system is not the only concern, such elements as added labor and material costs, time delays for patient rectification, excess space and equipment required, catheter kit value, nurse technician and physician costs constitute an expense to the healthcare system of surprising proportions. The best available current data indicates about 55,000 urinary catheter placements are made in the United States per day. Of these, conservatively about 40% are difficult which means that they require multiple advances and pull-backs of the urinary catheter to negotiate the urethra, multiple catheters on the same patient, several staff workers attending to the same patient, or special instrumentation such as filoforms/followers, cystoscope or radiologic services. 
     Two prior U.S. patents by the present inventor; U.S. Pat. Nos. 6,599,237 and 6,994,667 are directed to some of these problems and, while they provide excellent results, they are not ideal in all applications, have some limitations in specific areas of use, and cannot therefore be considered completely versatile with respect to their application in certain surgical specialties. Another important consideration is the high cost of surgical instruments, which may be from several hundred to several thousand dollars. Some endoscopes for example may cost more than $10,000.00. Other instruments may be suited for urological use but not be suited for use in gastroenterology. Certain intubation devices such as the Councill catheter are only capable of a blind insertion and must rely on a guide wire to navigate to the bladder. Consequently, if the Councill catheter encounters resistance during insertion, there is no way to know its cause. By contrast, one aspect of the present invention is the provision of a visually directed instrument to permit continuous observation of the field just ahead of the tip of the instrument during insertion so that abnormal conditions such as obstructions or other anomalies can be continuously observed and dealt with by the physician as the instrument is being inserted. Currently, in the field of gastroenterology, intubation by means of a nasogastric tube is commonly carried out blindly or by means of a wire guide for placement into the stomach. Any obstructions, anomalous conditions, or anatomical idiosyncrasies can interfere with successful insertion of the tube. Heretofore irrigation has required an endoscope with a passage for irrigation. Moreover, no provision is made for sensing conditions at or near the distal tip of the intubation instrument with traditional analog sensors and/or actuators or smart digital sensors or actuators. 
     It is therefore one object of the present invention to provide surgical instrumentation for intubation that provides a sensor or multiple sensors including chemical, ultrasound, pressure, temperature sensors, or a visual sensor such as a highly versatile visually directing sensor to facilitate insertion of a catheter or other tube into the body of an animal or human patient. 
     Another object of the invention is the provision of a surgical instrument for visually directed intubation that is suited for use in the field of urology as well as in gastroenterology and other surgical specialties. 
     Yet another object is to provide a surgical intubation instrument for providing visually directed placement into the body of the patient that makes possible a dramatic reduction in the cost of the instrument. 
     Another object is to provide a way of permitting a medical procedure to be conducted through a catheter to protect the patient from injuries while observing a selected part of the body of the patient. 
     A more specific object of the invention is the provision of an improved surgical intubation instrument that allows a catheter to be routinely passed even in a difficult situation, includes a provision for enabling the patient to tolerate the catheter more readily by reducing pain and the risk of injury or infection, the elimination of many steps and procedures currently used to pass a common Foley style catheter, as well as the need for a guide wire or a filoform/follower procedure or the need for cystoscopy to pass a guide wire that is thereafter used for directing the movement of a catheter so as to reduce the frequency of complications during the insertion of a catheter. 
     A further object is to provide the forgoing characteristics and advantages while permitting the insertion of surgical instruments into the body without the need to remove a previously inserted catheter as well as to permit the passage of relatively large surgical instruments that cannot be inserted through an ordinary catheter. 
     These and other more detailed and specific objects of the invention will be better understood by reference to the following Figures and detailed description which illustrate by way of example of but a few of the various forms of the invention within the scope of the appended claims. All references listed herein are incorporated by reference to the same degree as if reproduced in their entirety herein. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and apparatus for facilitating medical intubation procedures. In accordance with one aspect of the invention, there is provided a flexible direct vision viewing instrument or viewer that includes a catheter or sheath formed from a highly flexible biocompatible polymer such as natural or synthetic rubber or plastic having a longitudinal working channel extending the length of the catheter with an outlet port that is positioned in alignment with the channel at the distal end of the catheter. The catheter has a second longitudinal channel or lumen that contains a flexible sensor cable such as viewing cable for optical sensing. In place of or in conjunction with an optical sensor, there can be provided any of various kinds of sensors such as a chemical sensor, a pH sensor, a temperature sensor, in vivo infection, or the like. In the case of a visual sensor, one of the channels contains an optical cable providing illumination in the proximity of the distal end of the catheter for enabling the body of the patient to be viewed during placement of the instrument through a body opening or percutaneously through a surgical opening. An objective optical sensor or other sensor at the distal end of the cable provides information, e.g. continuous viewing the body of the patient just ahead of the tip of the instrument during insertion of the instrument as well as after placement of the instrument within the body. The invention is adapted to be produced in either a disposable version or a reusable version that can be sterilized after use. 
     The invention also provides a catheter that is able to serve as a working sheath which can be thought of as a temporary and removable artificial tract or liner that is placed through an opening in the body of the patient at the beginning of a surgical procedure to facilitate endoscopic evaluation and treatment of the digestive tract, urinary tract, or other body cavity while minimizing trauma and patient pain. During use, it allows multiple insertions and removals, i.e., the interchange of endoscopic instruments, catheters, sensors, drains, etc. The viewing cable can act as a stiffener during insertion into the patient to provide a greater degree of firmness, especially when the sheath or catheter is relatively thin or tends to fold back upon itself during insertion. Once in place, the viewing cable can be removed and replaced by other sensors such as a temperature sensor, a pH sensor, or an infection sensor, or by other medical devices. At its proximal, i.e. exterior end, the lumen of the sheath has an entry port for instruments with a removable cap that provides a nipple seal to preclude backflow of fluid from the body after the visual element or other sensor has been removed. The instrument can be placed into the stomach or other part of the digestive tract or the urethra under direct vision, i.e., with a flexible condition sensor extending through the sheath to act as a temperature, pH, or visual sensor. The sensor can include a sensor/actuator cable that provides an interoperable medium for transmitting optical or electrical signals, e.g. a fiber-optic bundle for illuminating and viewing a body cavity through the sheath, both during the insertion of the sheath and thereafter. 
    
    
     
       THE FIGURES 
         FIG. 1  is a side elevational view of one form of the invention showing a viewing device at its proximal end; 
         FIG. 2  is a longitudinal vertical sectional view of the instrument of  FIG. 1  on a larger scale; 
         FIG. 3  is a vertical transverse sectional view taken on line  3 - 3  of  FIG. 2 ; 
         FIG. 4  is a vertical transverse sectional view taken on line  4 - 4  of  FIG. 2 ; 
         FIG. 5  is an end view of the distal end of the instrument taken on line  5 - 5  of  FIG. 2 ; 
         FIG. 5A  is a partial enlarged vertical sectional view of the distal end of the instrument shown in  FIG. 2  on a larger scale; 
         FIG. 5B  is a partial enlarged vertical sectional view of the distal end of the instrument showing an objective lens built into the end of the catheter; 
         FIG. 6  is a side elevational view partly in vertical section showing the instrument of the invention in place within the male urethra; 
         FIG. 7  is a partial front elevational view of a patient showing a medical intubation appliance of the present invention connected to the patient for gastric feeding; 
         FIG. 8  is a side elevational view partly in vertical section to show the invention in use as a nasogastric tube; 
         FIG. 9  is a vertical longitudinal sectional view of the tube of  FIG. 8  on a larger scale; 
         FIG. 10  is a transverse vertical sectional view taken on line  10 - 10  of  FIG. 9 ; 
         FIG. 11  is an end elevational view taken on line  11 - 11  of  FIG. 9 ; 
         FIG. 12  is a transverse sectional view showing an optional expansion feature in accordance with the invention as it appears prior to use; 
         FIG. 13  is a transverse vertical sectional view of  FIG. 12  as it appears after being dilated by the insertion of an oversized surgical device through its central lumen; and 
         FIG. 14  is a schematic diagram of the viewing instrument and camera assembly. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Refer now to the Figures wherein the same numerals refer to corresponding parts in the several views. The invention will be described by way of example with reference to  FIGS. 1-7  and  14  which illustrate a visually directed intubation instrument in accordance with the invention that can be placed into the body of the patient under direct and continuous visual control in any of a variety of different surgical specialties. The invention is especially versatile and can be dimensioned and configured for use in urology, in gastroenterology, and in other surgical fields. The embodiment of  FIGS. 1-7  and  14 , illustrate the versatility of the invention since it can be employed as a drain or for exploratory purposes as well as a working channel to be used during a surgical operation or even in the field of gastroenterology as a feeding tube. 
     The instrument  10  comprises a flexible catheter  12  formed from natural or synthetic rubber or from a flexible biocompatible polymer of any suitable known composition such as synthetic rubber, latex rubber, polytetraflouroethylene (PTFE), polyethylene (PE), perfluoroalkoxy (PFA), polyurethane (PU), perfloromethylvinylether (MFA), perfluoropropylvinylether (PPVE) or other polymeric materials which would be apparent to those skilled in the art. The flexibility of the catheter  12  is apparent in  FIG. 1 . The catheter can also be thought of as a sheath since it is able to function in some instances as a protective sleeve for accommodating other surgical instruments that are passed through it as will be described more fully below. The catheter  12  has a proximal end  16  and a distal end  14  terminating at a tip  15 . Inside the catheter  12  is a lumen that serves as working channel  18  which extends the entire length of the catheter  12  and is provided with a distal opening  18   a  at one end and a proximal opening  22  at the opposite end. It will be noted that the distal end  14  portion of the catheter  12  adjacent the opening  18   a  is tapered so that its outer diameter is progressively reduced proceeding toward the opening  18   a  at its tip  15 . The catheter  12  can vary in length to suit the application to which it is applied, but is typically from about 30 cm to 50 cm in length and is preferably about 40 cm in length when it is to be used in gynecological procedures. It can be longer, say, 50 cm in length, when used in the male, for example, in a transurethral resection of a bladder tumor. For transurethral use, the outside diameter is typically about 9 mm (27 French) and the inside diameter about 5 mm (15 French). It should be understood that the dimensions presented herein are merely typical and can be varied to suit the circumstances in which the instrument is used. When used as a nasogastric or jejunostomy tube it can be at least 100 cm or more in length. 
     At the distal end  14  of the catheter  12  is provided an inflatable circumferentially extending annular balloon  24  formed from a ring of resilient elastomeric biocompatible material that extends around the catheter  12  adjacent the distal opening  18   a.  Inflation air or liquid is supplied to the balloon  24  when required through a tubular extension  32  at the proximal end  16  of the catheter  12  which communicates through inflation duct  33  through channel  28  with the balloon  24 . If the catheter  12  is formed from an elastomer such as rubber, the balloon  24  can be integral with the sheath. However, if the catheter  12  is formed from a firm plastic material such as polypropylene, the balloon  24  is formed from rubber that is bonded to the outside surface of the catheter  12  by means of a suitable adhesive. The free end of the tubular extension  32  is provided with an inflation port through which inflation fluid (gas or liquid) can be introduced and retained until a valve, e.g. Luer lock  31  is opened. 
     It will be noted that the catheter  12  is provided with three channels or lumens including a lateral channel  34  that serves to accommodate the visual element, in this case a flexible fiber-optic bundle  35  for illumination and viewing, a channel  18  that can be used for drainage or as a working channel to accommodate rigid or flexible instruments that are passed through it in succession during a surgical operation, and the inflation channel  28  already described for inflating the balloon  24 . It will be noted that the proximal end of the working channel  18  has an enlarged partially tapered entry port  19  with an enlarged circular open mouth  21  to give the distal end of the working channel  18  a funnel-like entry passage to accommodate the insertion of instruments during the course of a surgical operation. If desired, as shown in  FIG. 3 , the catheter  12  can be provided with an additional optional longitudinally extending duct  25  having an inlet port at the proximal end of the catheter and an outlet port  27  positioned at the proximal end of the balloon  24  as described in my prior patents U.S. Pat. Nos. 6,599,237 and 6,994,667 for the purpose of introducing topical anesthetics and other medicament into the passage through which the catheter has been inserted where it will be trapped between the catheter and the surrounding body tissue. 
     For most purposes, the fiber-optic bundle  35  is embedded within the lumen  34  of the catheter  12  so as to be fixed in place and thus not removable during the course of its useful life. However, the fiber-optic bundle can, if desired, be made removable in certain applications, for example, when the lumen  34  is used for a lavage and the central lumen  18  used for drainage. An embedded optic bundle provides a very effective yet inexpensive flexible visual catheter that can be sterilized and used repeatedly or can even be produced in a disposable form because of its low cost. This is an important feature since sterilization is expensive and sometimes may not be completely effective. 
     As best seen in  FIG. 5A , the fiber-optic bundle  35  is provided with a viewer comprising an objective viewing element, e.g. a lens  37  that is adjacent to the opening  18   a  of the working channel  18 . It will thus be seen that the both the objective viewing element  37  of the fiber-optic bundle  35  and the outlet port  18   a  of the working channel  18  face forwardly along laterally spaced apart parallel axes  39  and  41  ( FIG. 5A ) of which axis  39  is the optic axis of lens  37 . The objective viewing element comprising the lens  37  in the embodiment illustrated projects in this case slightly beyond the free end or tip  15  of the catheter which makes wide angle viewing possible. However, if desired, for certain applications, the lens  37  can be recessed slightly within the lumen  34  so that it does not extend beyond the tip  15  of the catheter  12 , but in that event wide angle viewing will be severely limited or impossible. The location of the port  18   a  on the end of the catheter rather than on its side allows channel  18  to be used for irrigation and other applications without the need of an endoscope for that purpose. Thus, the invention enables expensive endoscopes to be dispensed within many instances. 
     Refer now to  FIG. 5B  which shows a modified form of catheter  12  in which the lumen  34  at the tip  15  of the catheter  12  is provided with a built in, i.e. permanently attached, objective lens  38 . In the example illustrated, lens  38  has a convex outer surface  38   a  to assure smooth passage through the urethra or other body opening and a planar inner surface  38   b.  The lens surfaces can, however, have any desired configuration to provide the desired optical qualities as will be apparent to those skilled in the art. To provide a secure connection, the lens  38  can be provided with an externally ribbed tubular bonding sleeve  38   a  adhered to the inner wall of the lumen  34  to act as a non-removable connection. One or more lenses  37  at the distal end of the optic cable  35  is selected to complement lens  38  so as to reduce or eliminate chromatic, spherical, or fisheye aberration or other possible aberration to thereby provide an integrated lens combination when the cable  35  is inserted to bring the lens  37  at its end into contact with the surface  38   b  of lens  38 . However, if lens  38  alone provides a good image, the lenses  37  can be eliminated and the ends of the optic fibers themselves brought into contact with the lens  38  when the optic cable  35  is inserted. The lens  38  can thus provide a smoothly contoured external surface outside of and ahead of the tip  15  for achieving excellent wide angle viewing while at the same time being shaped to assure easy movement through restrictions or around obstructions. In addition, lens  38  is permanently positioned in the optimum location at the end of the tip  15  while sealing the lumen  34  to prevent the entry of fluid or other foreign material. 
     Upon encountering an obstruction during insertion, the curve shown in the tip  14  can be redirected by the operator for steering the catheter to facilitate insertion, i.e. by passive steering. The flexibility of the entire catheter including the distal end  14  is shown in  FIG. 1  as well as at  14   a  in  FIG. 2  which illustrates how the curved tip  14  can be deflected in any direction. Thus,  14   a  represents an alternate position of the tip as it appears when deflected upwardly or in any other direction, a feature made possible owing to the flexibility of the composite structure composed of the catheter  12  itself and the flexible visual element or cable  35 . 
     The flexible fiber-optic cable  35  which has been shown diagrammatically, can consist of crystal or glass and/or polymeric optical fibers of any suitable commercially available construction for illumination and viewing. In one preferred form, the fiber-optic bundle  35  has a fiber bundle terminating at  37   a  ( FIG. 5A ) for providing illumination from a light source  84  ( FIG. 14 ) and a second set of fibers coupled to the lens  37  for carrying an image to a viewer or other output device  80  ( FIG. 1 ). When cable  35  is removable, it will be seen that both the illumination fibers and imaging fibers are contained together in one removable bundle. In an alternative form, the optical fibers can be replaced by electrical conductors connected to another type of sensor such as an electronic microcamera  43  ( FIG. 5A ). While the medium for transmitting the optical representation of the object viewed at the tip of the catheter can be a flexible fiber optic cable made of glass or a polymeric material, when microcamera  43  is used, the medium is a flexible conductive wire consisting of copper or a pure element such as gold or silver or an alloy formulated to meet resistivity requirements, or a conductive or non-conductive liquid. For wireless transmission of video signals by radio frequency signal transmition from microcamera  43  the medium can be a pure gas or mixture of gasses or vacuum. The instrument  10  is thus provided with a sensor such as the objective viewing lens  37  focusing an image onto the microcamera  43 , for example, a suitable commercially available integrated circuit having light sensitive material onto which an image is focused such as a model FSC2 camera by Schoelly GmbH of Denzlinger, Germany. 
     Any of several types of activators or sensors can be used for determining the state of one or more characteristics or conditions in the region ahead of or surrounding the sensor. The term “sensor” or “condition sensor” herein includes any of the following: a visual sensor, i.e. an optical viewer for producing an image, a chemical sensor including O 2 , CO 2 , and pH sensors, infection sensor, a pressure sensor, an audio or sonic sensor, or a temperature sensor among others. Moreover, the sensor can be a multi-sensor device which measures multiple phenomena simultaneously in real-time thus avoiding the removal of one sensor and the insertion of another sensor. Each sensor is connected to an appropriate output device  80  ( FIG. 1 ). The output device can be a meter or oscilloscope, video display unit, or other suitable output device well known to those skilled in the art. The removal of one sensor such as an optical sensor cable following insertion, allows replacement with a different kind of sensor such as a chemical sensor or temperature sensor which is then inserted into the catheter through lumen  34  while the catheter  12  remains in place as a protective sheath within the body of the patient while sensing one or a series of different conditions or characteristics in the region ahead of or surrounding the sensor. The sensor cable can also transmit actuator signals to a proximal output instrument  83  ( FIGS. 1 and 14 ), e.g. actuator signals for performing a predetermined function such as actuating a signal light or audible alarm (not shown) when the temperature or pH exceeds a critical level or to turn on a visual display screen, etc. The actuator can also be a valve for metering medication or anesthetic to the body tissue. 
     In the embodiment shown in  FIGS. 1 and 14  by way of example, the fiber-optics  35  comprising glass or polymeric fibers exit the catheter at  30  to an output device  80  such as a viewing instrument which in this case is a light source and camera assembly  82  provided to receive an image from the objective lens  37  and a portable display monitor  83 . The camera assembly  82  includes a miniature electronic integrated circuit camera  81  as well as a light source, e.g. the LED  84  for illuminating the area ahead of the lens  37  via fiber bundle  37   a.  The camera  81  is connected by electrical bus  85  to the display monitor  83  which includes a video display screen  87  for displaying the image received from the objective viewing lens  37 . During operation, the image from optic cable  35  is focused by lens  86  onto electronic camera  81 . While various known data display processor circuits can be employed, the display monitor  83  in this embodiment includes camera and light interface  83   a  feeding data to a system control  83   b  via bus  83   c  which is coupled to data storage unit  83   d  and to a data acquisition and processing center  83   e.  The system control  83   b  feeds data to LCD color monitor  87  via bus system  83   f  in video format for displaying an image of the patient&#39;s body. One suitable electronic camera and light source assembly  82  is FSC2 (FlexiScope 2). The signal from bus  85  can also be routed to digital output ports (not shown) to display the image on a local color monitor or for streaming the video over the Internet. If the signal is to be stored for future use, the video signal is processed through a computer hard drive for storage. The invention makes possible the continuous display of the image of the body passage obtained from lens  37  in real time as the catheter  12  is being inserted so that any discontinuities or obstructions can be observed and circumvented during the insertion procedure. Following insertion, an image of the urinary tract, gastrointestinal tract, or other body cavity that has been entered can be observed. If a sensor other than an optical sensor is used, the condition being sensed, e.g. the temperature, chemical composition, pH, etc. at the distal tip  15  of the instrument can be monitored on a suitable output device, e.g. meter or oscilloscope, etc. that is used in place of the display monitor  83 . If desired, the microcamera  43  ( FIG. 5A ) can also include a radio signal transmitter for transmitting a signal depicting or representing a condition or a visual image, in which case the radio transmission sent to the output device replaces the electrical bus  85  and fiber-optics  35  which are then eliminated. The cable  35  is “resposable” after use, i.e. it can be pulled out of the catheter  12 , cleaned and resterilized, inspected for functionality, then inserted into a new and sterile catheter. It is then inspected to determine that it is functioning properly and is ready for its next use. The catheter  12  is intended to be disposed of after each use. After a specified number of uses, the cable  35  is also disposed of. The cable  35  is preferably compatible with standard sterilization techniques such as EtO (ethylene oxide), glutaraldehyde, Steris, Sterrad sterilization or other industry standard sterilization techniques. 
     The transmission cable  35  as already mentioned can also be embedded in the catheter  12 . The term “embedded” or “non-removable” herein is intended to mean that the cable  35  whether it be fiber-optics or an electrical cable is mounted securely enough so that it is not meant to be removed or easily removed in a simple manner by the user, although it is apparent, however, that it might be possible for a person to remove even an embedded cable with sufficient time and effort. The embedded cable can be held in place either mechanically. for example by means of surface irregularities which are gripped by the surrounding rubber of the catheter  12 , or by being bonded in place within the passage  34 , i.e. held in place by adhesion as the rubber or other flexible polymer forming the catheter  12  is cured. During manufacture, a cable  35  can be inserted into the passage  34  after the catheter has been completely formed then bonded in place or, if desired, it can be molded in situ as the catheter is being molded and before the polymer is cured or otherwise fixed within the catheter in any other manner known to those skilled in the art. 
     It is important to note that both the cable  35  and the catheter  12  are highly flexible so that together they form a composite structure which can flex in any direction as it is being inserted. This is especially advantageous during a difficult passage or through a curved duct such as the male urethra or when an obstruction is encountered. Flexing of the entire catheter is illustrated in  FIG. 1 . Flexing of the distal tip  14 , e.g. to alternate position  14   a  is shown in  FIG. 2  so as to enable the instrument to bend around corners or dodge obstructions. The cable  35  can also add a degree of stiffness to the instrument  10  so that sufficient stiffness is provided to ensure that the entire instrument consisting of the catheter  12  and cable  35  can be easily inserted even through a tight passage, e.g. through the urethra without buckling, a problem sometimes referred to as a “wet noodle” effect wherein the entire instrument buckles as an axial force is applied to the proximal end by the operator in an attempt to push the distal end around a curve, past an obstruction or under other circumstances where resistance is encountered. If desired, to provide additional stiffness, the cable  35  can be enclosed in a tubular casing  33  ( FIG. 3 ) enabling it to serve as an obturator having a predetermined stiffness which makes the instrument  10  less subject to the possibility of buckling when axial pressure is applied. 
     Refer now to  FIG. 6  which illustrates how the catheter  12  is inserted into the male urinary tract to allow examination of the urethra and the bladder. It will be noted that the catheter  12  is able to easily flex so as to negotiate curves in the urethra without difficulty and as the instrument is being inserted, the image just ahead of the distal end of the instrument can be continuously observed while noting pathological conditions or abnormalities in case the insertion becomes difficult or an obstruction is encountered. If the optical cable  35  is embedded, i.e. fixed in the catheter  12 , it remains in place following insertion thereby making continuous observation possible. The working channel  18  which can be temporarily plugged by means of a cap or other seal (not shown) is then opened at its proximal end to allow one or several successive instruments to be introduced through the open mouth  21  as required during a surgical operation by passing them through the channel  18  into the bladder or other organ while the catheter  12  remains in place, thereby serving as a protective sheath in the manner described in my prior patents U.S. Pat. Nos. 6,599,237 and 6,994,667 to prevent injury to the patient. The present invention however, has the added benefit of permitting visual observations to be made continuously via the optic cable  35  while the working channel  18  ( FIG. 2 ) is used contemporaneously for drainage, for the passage of instruments used in surgery, or for any other purpose. 
     An important feature of the invention is ability of any channel (channel  18  or  34 ) to be used for irrigation of the bladder or other organ, whereas heretofore an endoscope was required for this purpose. The invention, besides providing visualization, thus allows irrigation to be performed without the need for an expensive endoscope. Once the instrument  10  has been completely inserted, the balloon  24  is inflated by introducing a fluid or gas through the passage  28  to hold the catheter  12  in place. 
     Refer now to  FIG. 7  which illustrates how the invention can be used in gastroenterology, in this case as a gastronomy/gastrostomy tube that serves as a gastric feeding tube. When used as a gastric feeding tube, the instrument  10  is preferably provided with an abdominal mounting disc  11  which is bonded conventionally to the outside wall of the abdomen to hold the instrument which is inserted percutaneously in place where it enters the abdomen through the skin. The tube  10 , which can be referred to as a percutaneous endoscopic gastrostomy tube, provides a convenient visually directed access route for the delivery of long-term enteral nutrition through the stomach. It is surgically placed in the abdominal wall as shown in  FIG. 7  below the rib cage and slightly to the left in this case for feeding an infant. The optic cable  35  or other condition sensor permits continuous visual or non-visual monitoring both during insertion and following insertion. When used as a feeding tube as shown in  FIG. 7 , the catheter  12  is held in place by means of the inflated balloon  24  as well as sutures, if desired. 
     Refer now to  FIGS. 8-11 , which illustrate a visually directed nasogastric tube in accordance with the invention wherein the same numerals refer to corresponding parts already described. In this embodiment, the flexible optical cable  35  is connected at  100  to a viewing instrument  83 . In this embodiment, the cable  35  includes a tapered barrel  101  that fits into a tapered socket  19  within the catheter  12 . As described earlier, a light source is provided to which the optic cable  35  is connected. In  FIG. 8 , a light source and camera assembly (not shown) similar to  82  of  FIGS. 1 and 14  is provided within monitor  83  for directing light into the fiber-optic bundle  35  and out through the lens  37  to illuminate the field just ahead of the tip  15  of the instrument  10 . The image proximate the lens  37  is then carried back through the fiber-optic bundle  35  to the monitor  83  and viewing screen  84 . Cable  35  extends from port  21  at the proximal end of the channel  18  to the distal end  14  and as shown in  FIG. 9  for most purposes projects slightly beyond the tip  15  of the catheter  12 . With the objective viewing lens  37  located just beyond the tip  15  of the catheter, enhanced viewing ahead and also to the side is made possible by the wide angle of view that is permitted both while the catheter  12  is being inserted as well as after it is in place within the body of the patient. In the nasogastric tube of  FIGS. 8-11 , the fiber-optic bundle  35  is preferably removable. 
     As shown in  FIG. 9 , the cable  35  has a distal segment of reduced diameter which can be any length, e.g. 2-3 inches long to define a shoulder  35   a  in the cable so as to provide a proximal portion having a relatively large diameter and a distal segment of a reduced diameter with a shoulder between them which acts as a retainer. The channel  18  in the catheter is shaped like the cable  35 . Thus, when the cable is fully inserted, the shoulder  35   a  rests against a similarly shaped restriction in the channel  18  which serves as a retainer or stop to check the distal movement of the cable. In a preferred form, a circular washer  35   b  of a selected thickness and having an outside diameter the same as the larger diameter of the cable  35  is mounted on the cable at the shoulder  35   a  to act as a retainer for determining the position of lens  37  relative to the tip  15  of the catheter  12  during use to thereby control the extension, if any, of lens  37  beyond the tip  15 . 
       FIG. 9  thus shows a removable transmission cable  35  slideably mounted within a channel  18  as well as a working channel  119  positioned laterally of the channel  18 . Channel  119  has an outlet port  119   a  at the distal tip of the instrument just below the outlet port through which the cable  35  extends. The proximal end of the working channel  119  extends at  119   b  through a proximal extension  119   c  terminating at an opening  119   d  through which fluid can be drained from the body or surgical instruments can be passed when required through the catheter  12  into the patient. The fibers within the cable  35  can be enclosed within a tubular casing  33  ( FIG. 10 ) to hold the fibers together. During use, as shown in  FIG. 8 , the visually directed instrument  10  comprising a nasogastric tube can be held in place conventionally where it enters the nose with adhesive tape (not shown) and accordingly no balloon is required for holding the tube in place or within the body. The viewing instrument  100  as shown in  FIG. 8  is connected by means of a cable  35  to the visual display  83  which includes the video display screen  87  for continuously displaying in real time an image of the area just ahead of the distal tip  15  of the instrument. 
     Instrument  10  comprising the visually directed nasogastric tube is used for patients who are unable to ingest nutrients by mouth and is inserted through either nostril and passed down through the pharynx and esophagus into the stomach, typically for short-term feeding. Placement must be checked before each feeding. This can be done by viewing the area just ahead of the tip  15  by displaying it on the viewing screen  87 . Another use for the nasogastric tube is to drain accumulated fluids from the stomach and small intestine due to a blockage of the bowel from an obstruction or bowel inactivity. The present invention is particularly advantageous in overcoming the problems that resulted previously from the conventional feeding tube curling up in the esophagus, becoming diverted into the trachea, or coming to rest in a less than optimal location in the stomach. When these problems arose prior to the present invention, the solution was to take a static x-ray (using abdominal film) or measure the presence of CO 2  to rule out placement of the tube in the trachea. These procedures were complicated and took time since it was necessary to move the patient to the radiology department or transport x-ray equipment to the patient&#39;s room for the x-rays, adjust the tube, then take additional x-rays to verify the actual location of the tube and, of course, a radiologist is required to read the x-rays. 
     The visually directed nasogastric tube in accordance with the invention thus has two lumens; channel  18  in which the visual element or cable  35  is preferably removably mounted and the working channel  119 , which serves as the primary working channel for drainage and/or feeding. However, if the visual element  35  is removed, channel  18  can also be used as a working channel, for example, to pass an instrument or succession of instruments through the catheter  12  into the body of the patient. Consequently, the invention provides continuous visually directed insertion of the catheter while also providing, if desired, a pair of parallel laterally spaced apart working channels that can each be used as a working channel for different purposes during surgery or convalescence. For example, channel  18  can be used for drainage while at the same time the channel  119  is used for inserting and removing a variety of surgical instruments or guide wires through the catheter which then acts as a protective sheath that reduces discomfort, eliminates pain that would otherwise be experienced, and the tissue trauma that would occur if the instruments were passed directly through a body opening without the catheter  12  in place. Channel  18  which is preferably the largest in diameter is well suited for drainage and/or feeding the patient. When the visual element  35  is removable, it is preferably enclosed within the flexible protective plastic casing  33  and coated on the outside with a suitable surgical lubricant so that it can be removed when desired from the instrument  10 . The visual element  35  and casing  33  also provides a degree of stiffness for the catheter  12  so that it can be reliably pushed through a tight passage and yet is able to flex freely around and through curved body openings and easily pass obstructions. In such a case, the visual element acts to assist in insertion and thus serves as an obturator for adding a degree of stiffness to the catheter. 
     It will be thus understood that the invention provides continuous visually directed placement as well as allowing the position of the distal end of the instrument to be confirmed by the operator at the time of placement. Consequently, it eliminates the need for x-rays and the services of a radiologist to read them as well as the need for a CO 2  determination procedure. As already described in connection with  FIGS. 1-7 , in place of a visual sensor, the invention can employ any other known form of sensor for evaluating one or more conditions along the length of the cable  35  or in the region just ahead of the tip  15  of the instrument, e.g. a chemical sensor, a temperature sensor, a pressure sensor, etc. 
     To more fully explain the invention and the results that can be achieved, an additional example will be presented to illustrate its capabilities. Once the instrument  10  comprising the nasogastric tube ( FIGS. 8-11 ) is in place within the stomach, the visual element  35  and the light beam on axis  39  provided by the light source  84  permits the doctor to identify the exact location for retrograde placement of a percutaneous guide wire, that is to say, where a hole is to be punched with the guide wire from the outside of the patient through the skin of the abdomen into the stomach while being guided by the light within the stomach that is directed as a beam through the lens  37 . The light transmitted along the optic axis  39  ( FIG. 8 ) at the tip  15  of the instrument  10  comprising the nasogastric tube is bright enough for the doctors to see it by transillumination through the skin when observing the patient from the exterior. The beam can be positioned conventionally by guide wires (not shown) in the catheter  12  as described in patent U.S. Pat. No. 6,994,667. The doctor can then choose to insert the guide wire from the inside out (antegrade) through the lateral working channel  119  while the light is on, or from the outside in retrograde, whichever is preferred. If the retrograde procedure is used, the guide wire is inserted from the exterior of the body through the skin into the stomach at the exact location of the light transmitted from the tip  15  of the instrument along the axis  39  ( FIG. 8 ). Thus, the visual element of  35  of the instrument  10  comprising the nasogastric tube allows the doctor to place the guide wire precisely. The instrument  10  comprising the nasogastric tube is then used as a working channel device to pull the guide wire and/or feeding tube of  FIG. 7  into the stomach via the working channel  119 . On the other hand, in the antegrade procedure, the doctor is assisted by the light from the visual element to correctly pass the guide wire from the stomach out through the skin of the abdomen. 
     Refer now to  FIGS. 12 and 13  which illustrate a modified form of the invention in which the catheter  12  is provided with a longitudinally extending area designated  120  running throughout the length of the catheter that has a reduced wall thickness which is bridged across by a stretchy elastic sheet or band  122 . The reduced wall thickness can be seen in  FIG. 12  as a gap  123  adjacent band  122 . During use, when the catheter  12  is in a relaxed resting state as shown in  FIG. 12 , the lumen  18  has a predetermined diameter A capable of accommodating surgical instruments of a certain size that are to be passed through it. However, as shown in  FIG. 13 , when a surgical instrument  124  of a much larger size is passed through the lumen  18 , the elastic band  122  that covers the area of reduced wall thickness, the band  122  becomes stretched as the wall of the catheter  12  is extended by the instrument  124 , thus allowing surgical instruments  124  of a much larger size than the initial diameter of lumen  18  to be passed through the catheter  12  and into the body of the patient for carrying out various surgical procedures, e.g. cauterization, tumor removal, or for other purposes. The invention thus provides an expansion zone  120  extending the length of the catheter  12  that is bridged by the relatively thin elastic expansion band  122  so as to allow enlargement of the lumen  18  along the entire length of the catheter  12  for introducing or removing instruments  124  that are larger than the lumen  18 . 
     The band  122  over the thin wall area at  120  thus provides a catheter having a greatly expandable lumen  18  yet which maintains its integrity, i.e. lumen  18  does not open out into the body passage or communicate with any other part of the body except through the opening at the distal tip  15 . The catheter is therefore able to expand substantially to enable oversize instruments such as that shown at  124  to be passed into the body, yet the wall of the body opening is protected at all times by the catheter and the elastic band  122  so as to avoid injury that might otherwise be induced by the instrument  124  as it is being inserted or retracted. 
     Many variations of the present invention within the scope of the appended claims will be apparent to those skilled in the art once the principles described herein are understood.