`Gabriel
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,173,199 B1
`Jan. 9, 2001
`
`US006173199B1
`
`5,271,400
`5,273,025
`5,316,024
`
`,
`
`,
`
`12/ 993 Dumoulin ct al.
`12/ 993 Sakiyama et al.
`5/ 994 Hiisclii et al.
`..
`
`.
`
`. 128/653.2
`128/6
`128/899
`
`I
`
`,
`
`-~
`
`/
`
`5386328
`5,419,325
`5,425,367
`5,431,640
`5,445,150
`594929538
`5,507,731
`5,542,938
`5,596,991
`5,681,260
`5,758,667 '
`5,902,238
`5,906,579
`
`128/653.1
`- 604/.264
`604/264
`604/280
`128/662.06
`600/114
`. 128/899
`600/424
`600/424
`
`gevggrd et 31'
`e
`arco
`2" 995 Owens et el-
`- 128/6534
`5/ 995 Dumoulin et al.
`128/653.2
`6/ 995 Shapiro et al.
`................. .. 128/653.1
`7/ 995 Gabriel.
`8/995 Dumoulin et al.
`2/ 996 John“, J“
`4/ 996 Hernandez ct a.
`.
`8/ 996 Avellanet etal.
`1/ 997 Taiiaka ................ ..
`10/ 997 Ueda etal.
`6/ 998 Slettenmark
`5/ 999 Golden et al.
`..
`5/ 999 Vander Salm et al.
`(List continued on next page.)
`
`METHOD AND APPARATUS FOR
`INTUBATION OF A PATIENT
`
`Inventor: Sabry Gabriel, Macon, GA (US)
`Assignee: Syncro Medical Innovations, Inc.,
`Macon’ GA (US)
`
`.
`.
`Noticc.
`
`.
`.
`_
`Under 35 U.S.C. 134(b), the term of this
`Patent She“ be emended fer 0 d“Y5~
`
`May 5a 1993
`
`Appl. No.: 09/073,226
`,
`Flledi
`............... N A613 5 05
`I t_ CL7
`600/424; 128599
`fills. Cl.
`Field of Search ................................... .. 600/424, 373;
`128/899; 604/264, 270, 280; 324/260, 207.11,
`207.13
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`3,043,309
`33674914
`4,004,298
`4,024,855
`4,063,561
`4,077,412
`4;“4fi01
`
`7/1962 McCarthy
`7/1972 Tfllandeli
`1/1977 Freed
`5/1977 Bucalo ..
`12/1977 McKei1i1a.
`3/1978 Moossun
`9/1973 A5613
`
`.... .. 128/347
`---- -- 128/1 R
`12513/23;)§4IE{;
`~~ 128/[283
`7/1982 Iergaiea T~
`9338337
`’,
`’
`‘
`‘
`” ’
`’
`’
`128/737
`11/1983 Bresler ..
`,416,289
`128/656
`2/1984 Mccormic
`74317005
`. 128/200.26
`6/1986 Gray et al.
`5937687
`1/1988 Tnoue et 31, ..................... U 604/264
`9717337
`12/1988 Kuntz . . .. .. . .. . . . . . .
`. . .. . .. 604/8
`,790,809
`7/1989 Sparks et al
`. 600/29
`,850,963
`9/1989 Hedbefg
`604/93
`;865;530
`4/1990 Renew --
`128/200-ll
`2913339
`7/1990 A5hl°y'R°Hman ct a1‘
`' 324’207'17
`3943770
`4/1991 Cartmell ......... ..
`128/899
`5,005,592
`8/1991 Pfefler et al.
`....U 128/653
`5,042;486 *
`5,253,647 * 10/1993 Takahashi etal.
`.............. .. 128/653.1
`5,257,636
`11/1993 White .
`
`FOREIGN PATENT DOCUMENTS
`W0 96/05768
`2/1996 (W0) .
`W0 96/32060
`10/1996 (W0) .
`
`........ .. 128/348
`' 128/2'05 R
`......... .. 3/1
`.... .. 128/1 R
`
`Primary FxamL'rter—Marvin M. Lateef
`Assistant Exammer_ShaWna J Shaw
`(74) Attorney Agent or Firm—Arnall Golden & Gregory
`LU,
`’
`’
`’
`
`(57)
`
`ABSTRACT
`
`A catheter having a distal end portion including a sensor
`responsive to the presence of a magnetic field or flux of a
`predetermined stretlgth is Provided. Also Provided is a
`catheter system which further includes an external magnet.
`Th
`_
`p
`.
`lh
`1.‘ _1
`1
`1.
`.‘
`p
`1 1 it
`V
`1
`e sensor .111
`e Lista em por ion is se cc ec
`o responc
`when the distal end portion of the catheter is exposed to 21
`magnetic field, such as provided by the external magnet,
`suflicient to capture and maneuver the distal end of the
`cathctcr. Acathctcr having a distal end portion that includes
`a steering portion for mancuvcring the distal cnd of the
`catheter during intubation of a patient is also provided. A
`method for intubating a patient using the catheter systems
`-
`-
`-
`-
`-
`provided, including an external magnet, is also disclosed.
`
`32 Claims, 7 Drawing Sheets
`
`CORPAK Ex 1008, Page 1
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`
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`US 6,173,199 B1
`Page 2
`
`US. PATENT DOCUMENTS
`
`8/1999 Ponzi
`5,938,603 *
`5,997,473 * 12/1999 Taniguchietal.
`
`600/424
`.............. .. 600/117
`
`6,007,478 * 12/1999 Siess et al.
`6,015,414 *
`1/2000 Wcrp ct al.
`
`.... .. 600/16
`606/108
`
`* cited by examiner
`
`CORPAK Ex 1008, Page 2
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`
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`U.S. Patent
`
`Jan. 9, 2001
`
`Sheet 1 of 7
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`US 6,173,199 B1
`
`ESOPHAGUS
`
`LESSER
`
`CURVATURE
`
`ANGULAR
`
`DUODENUM
`
`CORPAK Ex 1008, Page 3
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`
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`U.S. Patent
`
`Jan. 9, 2001
`
`Sheet 2 of 7
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`US 6,173,199 B1
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`CORPAK Ex 1008, Page 4
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`U.S. Patent
`
`Jan. 9, 2001
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`Sheet 3 of 7
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`US 6,173,199 B1
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`CORPAK Ex 1008, Page 5
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`
`
`U.S. Patent
`
`Jan. 9, 2001
`
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`U.S. Patent
`
`Jan.9,2001
`
`7f05t66hS
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`US 6,173,199 B1
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`Jan. 9, 2001
`
`Sheet 6 of 7
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`US 6,173,199 B1
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`CORPAK Ex 1008, Page 8
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`U.S. Patent
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`Jan. 9, 2001
`
`Sheet 7 of 7
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`US 6,173,199 B1
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`CORPAK Ex 1008, Page 9
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`
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`US 6,173,199 B1
`
`1
`METHOD AND APPARATUS FOR
`INTUBATION OF A PATIENT
`BACKGROUND OF THE INVENTION
`
`The present invention is generally in the area of medical
`catheters, and specifically to catheters constructed to facili-
`tate guidance and placement of a distal end portion thereof
`at a predetermined site within the body of a patient.
`Avariety of methods for placing catheters and tubes in a
`patient’s body are known. For example, enteral nutritional
`products can be delivered to a patient’s gastrointestinal tract
`via a tube which is introduced through the naris of the
`patient’s nose. The tube is advanced through the patient’s
`esophagus and into the patient’s stomach. In the event that
`it
`is preferable to deliver the enteral nutritional product
`directly to the patient’s small bowel,
`the tube is further
`advanced beyond the pylorus into the patient’s duodenum or
`small bowel. However, advancement of the tube into the
`patient’s duodenum can be diflicult in many patients. One
`method for advancing a tube through the stomach and into
`the duodenum entails the use of the natural peristaltic
`movement of the gastrointestinal tract. Such advancement
`may require as long as three to five days in some patients.
`Pharmaceutical products can be used in order to enhance the
`peristaltic action within the gastrointestinal tract and thereby
`decrease the time required to advance the feeding tube into
`the small bowel.
`
`Serial X-rays typically are used to determine the location
`of the distal end of the tube as it advances by peristaltic
`action through the pylorus to the duodenum, thereby expos-
`ing the patient repeatedly to radiation and increasing the
`costs associated with placement of the tube. For these
`reasons, the use of naturally occurring or pharmaceutically
`enhanced peristalsis provides a sub-optimal method for
`placing a tube in a patient’s small bowel.
`It is known in the art to use magnetic flux or a magnetic
`field in the placement of catheters in the gastrointestinal
`tract. For example, U.S. Pat. No. 3,043,309 to McCarty
`describes the use of a localized magnetic field generated by
`an electrical magnet to manipulate a suction tube having a
`magnetic member at
`its distal end. The suction tube is
`constructed to be manipulated through an intestinal obstruc-
`tion. The electrical magnet enables a medical professional to
`turn ofl the magnet when using fluoroscopy radiation to
`determine the precise location of the distal end of the tube.
`Without the ability to deactivate the magnetic field in this
`manner, the field would distort the image on the fluoroscopy
`screen, thereby preventing a precise determination of the
`location of the distal end of the tube.
`U.S. Pat. No. 3,794,041 to Frei, et al. discloses beads of
`a ferromagnetic material constructed to be inserted in a body
`part with a catheter for moving the body part using an
`external magnet. U.S. Pat. No. 3,847,157 to Caillouette, et
`al. discloses the use of a magnetic indicator in a medico-
`surgical tube to identify the location of a tube containing a
`ferromagnetic material. U.S. Pat. No. 3,674,014 to Tillander
`discloses a distal end portion of a catheter having a plurality
`of magnetic t11b1Ilar elements with ball-shaped ends to allow
`deflection of the sections with respect to each other for
`guidance of the catheter distal end. U.S. Pat. Nos. 3,961,632
`and 4,077,412 to Moossun disclose a trans-abdominal stom-
`ach catheters of the Foley type used to direct the placement
`of the catheter by way of an external puncture from outside
`the abdomen through the stomach wall. U.S. Pat. No.
`3,358,676 to Frei, et al. shows the use of magnets for
`remotely controlling propulsion of a magnet-containing
`beads through a duct of a human.
`
`2
`U.S. Pat. No. 5,431,640 to Gabriel discloses the use an
`external magnet to establish a magnetic field for permeating
`body tissue and enveloping the lesser curvature of the
`stomach for magnetic direction of a distal end of a catheter
`feeding tube having a permanent magnet associated there-
`with. The presence of the permanent magnet on the distal
`end portion of the catheter tube presents the advantage of
`steering the catheter magnet by the external magnet.
`Maneuvering a catheter to the distal duodenum of a
`patient using the magnetic field produced by an external
`magnet requires precise knowledge of the anatomy of the
`stomach and duodenum in relation to the abdominal surface
`of a patient. This knowledge is necessary so that the operator
`can maneuver the external magnet over the abdomen of the
`patient in a precise path resulting in advancement of the
`catheter through the stomach and into the duodenum of the
`patient. An operator maneuvering an external magnet cannot
`see through the abdominal wall to decide whether the distal
`end portion of the catheter is continuously captured by the
`magnetic field of the external magnet during the advance-
`ment of the catheter. Thus, an additional procedure is
`required to determine whether the distal end of the catheter
`is properly advancing into the patient’s duodenum. One
`method discussed previously and having apparent shortcom-
`ings involves the use of X-ray monitoring to confirm the
`position of the distal end of the catheter. An alternative
`method, described in U.S. Pat. No. 5,431,640, entails the
`aspiration of fluid from the distal end of the catheter and the
`measurement of the pH of the aspirated fluid. However, pH
`values for a particular individual may vary from expected
`values, as occasionally occurs in response to medications,
`thereby resulting in false position information. What
`is
`needed is an apparatus and method for advancing the distal
`end portion of a catheter using the field of an external
`magnet which provides an indication whether the catheter
`distal end is captured by the external magnet,
`thereby
`indicating whether the distal end of the catheter is being
`properly advanced into the patient’s duodenum.
`It is an object of the present invention to provide catheters
`which are more easily and accurately positioned than the
`catheters currently available.
`
`SUMMARY OF THE INVENTION
`
`Acatheter having a distal end portion preferably including
`a sensor responsive to the presence of a magnetic field or
`flux of a predetermined strength is provided. Also provided
`is a catheter system which further includes an external
`magnet. The sensor in the distal end portion is selected to
`respond when the distal end portion of the catheter is
`exposed to a magnetic field, such as provided by the external
`magnet, sufficient to capture and maneuver the distal end of
`the catheter.
`
`The catheter system further includes a catheter having a
`distal end portion that includes a steering portion for maneu-
`vering the distal end of the catheter during intubation of a
`patient. In one embodiment, the steering portion takes the
`form of a portion provided with increased flexibility as
`compared with the flexibility of an adjacent portion of the
`distal end portion of the catheter. In another embodiment,
`the catheter system further includes a catheter having a distal
`end portion that
`includes a steering portion having an
`asymmetrical projection which facilitates advancement of
`the catheter as it encounters surfaces that are substantially
`perpendicular to its direction of advancement.
`Also provided is a method for intubating a patient includ-
`ing the use of a catheter system as disclosed herein with an
`
`CORPAK Ex 1008, Page 10
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`US 6,173,199 B1
`
`3
`external magnet. The catheter is placed in a portion of a
`patient’s body, and the external magnet
`is brought
`into
`proximity of the distal end portion of the catheter such that
`the sensor indicates that the distal end portion of the tube has
`been captured by the external magnet. The external magnet
`is then used to position the distal end portion of the catheter
`in a selected position within the patient’s body. The method
`may also be used with the catheter having a distal end
`portion that includes a steering portion and using the steer-
`ing portion to maneuver the distal end portion of the catheter
`during intubation of the patient. The catheter may also be
`adapted for insertion within the Vasculature of a patient, with
`or without the use of the sensor.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a schematic illustration of the anatomical
`configuration of the stomach and duodenum through which
`the catheter of the present invention is navigated.
`FIG. 2 is a schematic illustration of a patient showing a
`catheter feeding tube in place through the naris of the nose
`to deliver nutrition or medication directly into the small
`intestine.
`
`FIG. 3 is a schematic illustration of a patient showing a
`catheter feeding tube in place through the abdominal wall to
`deliver nutrition or medication directly into the small intes-
`tine.
`
`FIG. 4 is an enlarged plan view, partly in section, of a
`catheter according to the present invention in which the
`distal end portion includes a permanent magnet arranged
`such that lines of flux will travel from a first side of the
`catheter to an opposite side.
`FIG. 5 is an enlarged plan view, partly in section, showing
`the distal end of the catheter of FIG. 4 in the proximity of
`an external magnet.
`FIG. 6 is an enlarged sectional view of the distal end
`portion of a catheter according the present invention having
`a permanent magnet in the distal end portion, which is
`differently arranged than the magnet in the catheter tip of
`FIG. 4 such that the lines of flux travel from a generally
`planar face of the magnet adjacent the terminal end of the
`catheter to an opposite generally planar face of the magnet.
`FIG. 7 is an enlarged sectional view of the distal end
`portion of a catheter according to the present
`invention
`having a ferromagnetic tubular member in the distal end
`portion.
`FIG. 8 is an enlarged sectional view of the distal end
`portion of a catheter according to the present invention
`having bits of ferromagnetic material embedded in the distal
`end portion to magnetically respond to a magnetic field of an
`external magnet.
`FIG. 9 is an enlarged sectional view of the distal end
`portion of a catheter according to the present invention
`which includes a waisted portion having a reduced cross-
`section for increased flexibility of a terminal end of the distal
`end portion and an asymmetrical projection for increased
`maneuverability of the terminal end.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`Catheters
`In a preferred embodiment of the catheter disclosed
`herein, the distal portion of the catheter must be navigated
`through the stomach and placed in the duodenum so that
`nutrition or medication can be delivered directly into the
`small intestine. The anatomical configuration of the stomach
`
`4
`is illustrated in FIG. 1, with salient features of the stomach
`and associated esophagus and duodenum labeled.
`One embodiment of the catheter system is illustrated in
`FIG. 2, wherein catheter 10 has a catheter body portion 12
`wl1icl1 is elongated and extends to a distal end portion 14 for
`delivery of nutrition or medication. It will be appreciated
`that catheter 10 can be used to deliver various fluids to a
`variety of locations within a patient’s body. For the purposes
`of this disclosure, reference will be made to use of catheter
`10 to deliver an enteral nutritional product to a patient’s
`duodenum. However, it will be appreciated that the present
`invention is not limited to this application; other embodi-
`ments are described below.
`The distal end portion 14 of the catheter 10 is introduced
`through the naris 16 of the nose and advanced by the
`application of a longitudinally compressive force to the
`catheter 10, thus urging distal end portion 14 in the direction
`of the backward portion of the patient’s head and thence to
`the esophagus 18. Preferably, the distal end portion 14 of the
`catheter 10 is coated with a lubricant while a numbing agent
`is applied to the nasal mucosa. The passageway of the
`esophagus affords ample guidance to the distal end portion
`14 of the catheter 10 when it enters the stomach body portion
`20 of the stomach 22 at the lower portion of the fundus 24.
`The movement of the distal end portion 14 along the
`esophagus and into the body of the stomach occurs within
`the left upper quadrant (“LUQ”).
`The stomach 22 has a generally J-shaped configuration.
`The largest transverse anatomical size of stomach 22 is
`located at
`the cardiac orifice,
`i.e.,
`the site at which the
`esophagus enters the stomach. The transverse dimension of
`the stomach narrows moving away from the cardiac orifice
`in the direction of the normal passage of food through the
`gastrointestinal tract. An angular notch 26 is present at the
`border between the left upper quadrant (“LUQ”) and the
`right upper quadrant (“RUQ”). From the angular notch,
`there commences a smaller transverse dimension at
`the
`pyloric part 28 typically residing in the right upper quadrant
`(“RUQ”) with pyloric sphincter 30. The pyloric sphincter 30
`is a muscular closure which dilates to permit the passage of
`food from the stomach 22 into the small bowel 32. The small
`bowel 32 includes a duodenum 34 and the distal duodenum
`36. Food passes through the pyloric sphincter 30 into the
`duodenum 34, the duodenum 34 extending to the right lower
`quadrant (“RI.Q”) and then in a general horizontal direction
`into the left
`lower quadrant
`(“LLQ”) where the distal
`duodenum 36 of the small intestine is situated.
`The generally J-shaped configuration of the stomach 22 is
`arranged with the longer limb of the “J” lying to the left of
`the median plane and the major part
`in the left upper
`quadrant (“LUQ”). The long axis of the stomach passes
`downwardly, forwardly, and then to the right and finally
`backwardly and slightly upwardly. The size and shape of the
`stomach 22 vary greatly from patient to patient, for example,
`in short, obese persons the stomach is high and transverse
`whereas in tall persons the stomach is elongated. It is known
`that in a given patient the shape of the stomach depends on
`wl1etl1er the stomach is empty or full, the position of the
`patient, and the phase of respiration. At the cardiac orifice,
`an acute angle is formed which tends to misdirect the distal
`end of the catheter toward the fundus 24 rather than toward
`the pyloric part 28 as the catheter is urged through the
`stomach.
`An alternative entry site to the stomach 22 for the catheter
`10 is illustrated in FIG. 3. The distal end of the catheter
`enters through a stoma tract in the patient’s abdominal wall
`38 to the stomach body portion 20 of the stomach 22 rather
`
`CORPAK Ex 1008, Page 11
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`US 6,173,199 B1
`
`5
`than through the naris of the nose. This stomach formation
`technique is well known in the art and is referred to as
`percutaneous endoscopic gastrostomy (“PEG").
`Alternatively, the catheter 10 can be placed through a stoma
`tract in the patient’s abdominal wall 38 directly into the
`patient’s duodenum or jejunum. The apparatus and method
`of placement of the present invention are particularly suited
`for use in placing a feeding tube through a stoma tract
`formed through the patient’s abdominal wall by a PEG
`procedure and in placing a feeding tube through the patient’s
`nose.
`One embodiment of the catheter disclosed herein is shown
`in FIG. 4, enlarged to illustrate catheter 10 in greater detail.
`When the catheter 10 is configured as a feeding tube, the
`catheter 10 is about 50 inches long. Catheter body portion 12
`typically has a diameter of about 3 mm and can be con-
`structed in whole or in part of a radiopaque material in order
`to facilitate identification thereof using known X-ray tech-
`niques. The distal end portion 14 of the catheter 10 typically
`has an outside diameter of about 5 mm. The distal end
`portion 14 can be integrally form ed with the remainder of
`catheter body portion 12. Alternatively, distal end portion 14
`can be mounted mechanically on, or chemically bonded to,
`the remainder of catheter body portion 12. Alumen 40 in the
`catheter body portion 12 is in fluid communication with an
`external environment of distal end portion 14 through one or
`more apertures. The aperture can be defined as an axial
`orifice 42A at the terminal end of distal end portion 14. The
`apertures also can be defined through the walls of distal end
`portion 14 as eyelets 42B. The apertures allow a fluid to be
`directed through l11n1en 40 and into the site in which the
`distal end portion 14 of catheter 10 is positioned.
`Magnetically Responsive Elements
`The catheter is provided with a magnetically responsive
`member at distal end portion 14. In a first embodiment of the
`present
`invention,
`the magnetically responsive member
`includes a cylindrically shaped permanent magnet 44 posi-
`tioned in distal end portion 14 of catheter 10. The magneti-
`cally responsive member can alternatively be constructed of
`a ferromagnetic material, i.e., a material in which a magnetic
`state can be induced. Permanent magnet 44 in the embodi-
`ment of FIG. 4 has a diameter of about 5 mm and a length
`of about 6 mm. A slight bulge 46 in the lumen 40 occurs
`when the permanent magnet 44 is inserted through axial
`orifice 42A. In an alternative configuration, permanent mag-
`11et 44 is placed on an exterior wall of distal end portion 14.
`The permanent magnet 44 can include opposite, hemi-
`cylindrical pole faces 44A and 44B which exhibit polariza-
`tion across a diameter 44C such that lines of magnetic flux
`travel from hemi—cylindrical pole 44A to hemi—cylindrical
`pole 44B.
`An external magnet 48 is illustrated in FIG. 5 in a
`proximal relation with the distal end portion 14 of the
`catheter which encounters the magnetic field of the external
`magnet. The wall of the stomach 22 and the abdominal wall
`38 are between the distal end portion 14 of the catheter 10
`and the external magnet 48. The inclusion of the permanent
`magnet 44 polarized along the diameter, as illustrated,
`results in the orientation of the distal end portion 14 trans-
`versely with respect to the external magnet 48 when the field
`of the external magnet has captured the permanent magnet
`44 in the distal end portion 14. This is favorable for guiding
`the catheter through the curves of the gastrointestinal tract.
`In an alternative embodiment, the magnetically respon-
`sive member is a permanent magnet 50 arranged in the distal
`end portion 14 of the catheter 10 as illustrated in FIG. 6.
`Permanent magnet 50 is constructed with a cylindrical
`
`6
`surface between opposing planar pole faces. The permanent
`magnet 50 is supported in the lumen 40 with the cylindrical
`surface producing a slight bulge identified by reference
`numeral 52. The permanent magnet 50 inserted through
`axial orifice 42A is distinctly polarized when compared with
`the permanent magnet 44 illustrated in FIGS. 4 and 5. The
`lines of flux of permanent magnet 50 in FIG. 6 extend from
`a first generally planar pole face 50A adjacent a terminal end
`of the catheter to an opposite second generally planar pole
`face 50B. As described hereinbefore,
`the magnetically
`responsive member can take the form of a ferromagnetic
`insert 54 in the distal end portion 14 of the catheter as
`illustrated in FIG. 7. According to this embodiment of the
`catheter system disclosed herein, the ferromagnetic insert 54
`is tubular in cross-section. The insert can be encapsulated
`within the catheter wall at the distal end portion 14 or can be
`provided on an interior surface of lumen 40 or an external
`surface of distal end portion 14. It has been found that the
`selection of an external magnet can be made so as to provide
`a magnetic field strength suflicient to induce magnetization
`in the ferromagnetic insert 54. The induced magnetization
`provides a magnetic coupling between the external magnet
`and the ferromagnetic insert 54, thus allowing the distal end
`portion 14 to be manipulated by movement of the external
`magnet.
`The material comprising ferromagnetic insert 54 can be
`an alloy which is defined as a ferromagnetic alloy that
`becomes magnetized readily upon application of a field and
`that resumes practically a nonmagnetic condition when a
`field is removed. Suitable ferromagnetic materials include,
`but are not necessarily limited to, permandure, iron, iron
`silicone steel, iron cobalt alloys, and iron nickel alloys. The
`magnetization of ferromagnetic insert 54 which occurs in the
`presence of the applied field by the external magnet
`is
`defined as the induced magnetization and is distinguished
`from permanent magnetization which is present without an
`applied field. Sensors
`Sensor 56 is positioned at distal end portion 14 of the
`catheter 10. Sensor 56 can be integral with or attached to
`catheter 10, or can be positioned on a stylet 68 inserted into
`catheter 10. The sensor 56 is preferably constructed to detect
`the presence of a magnetic field of a predetermined magni-
`tude. The magnetic field can be either the result of the
`magnetic llux of the external magnet 48 or the induced
`magnetism of ferromagnetic insert 54, or a combination
`thereof. The predetermined magnitude of the magnetic field
`is selected to be sufficient to ensure that permanent magnet
`44, 50 or ferromagnetic insert 54 is magnetically coupled to
`the external magnet. Sensor 56 preferably is constructed to
`provide an audio, visual, or tactile indication through indi-
`cator 58 when the threshold magnetic field is present at distal
`end portion 14. In the embodiments in which permanent
`magnets 44 and 50 are provided on distal end portion 14 of
`the catheter 10, sensor 56 is constructed such that it does not
`respond to the magnetic field or magnetic flux density of
`permanent magnets 44 and 50. In FIGS. 5 and 6, sensor 56
`is spaced from the permanent magnet 44 and 50 in the distal
`end portion 14 of the catheter in order to avoid false
`triggering of sensor 56. Sensor 56 can have any of a variety
`of forms utilizing principles of operation well known in the
`art
`to respond to the presence of a magnetic field or a
`magnetic flux of a predetermined magnitude.
`As described above, sensor 56 preferably is constructed to
`provide an indication of the presence of a threshold mag-
`netic flux or field at distal end portion 14. In the embodiment
`of the catheter system depicted in FIG. 4, sensor 56 is
`connected to an audio or visual signal generator 58 and a
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`power supply 60. In this embodiment, sensor 56 includes an
`envelope 62 forming a protective housing containing elec-
`trically conductive limbs consisting of leaf-like reeds 64
`having a predetermined elasticity such that the electrical
`state of the sensor 56 changes in response to the presence of
`the magnetic field or flux at the predetermined threshold
`level. The electrically conductive leaf-like reeds 64 extend
`from opposite ends of the envelope 62 in a spaced apart and
`overlying relation. In the embodiment of FIG. 4, the leaf—like
`reeds are constructed such that they are out of electrical
`contact with one another in the absence of a magnetic field
`or magnetic flux of a predetermined magnitude. However,
`the leaf-like reeds are elastically forced into electrical con-
`tact with one another in the presence of a magnetic field or
`magnetic flux of suflicient strength to provide a magnetic
`coupling between the external magnet and the distal end
`portion 14, thereby allowing electricity to flow through the
`sensor 56 and actuate a signal generator 58. Movement of
`the leaf-like reeds 64 between their electrical contact and
`separated positions is responsive to the presence or absence
`of a magnetic field or magnetic flux.
`Signal Generators
`Signal generator 58 preferably is positioned external to
`the patient during placement of catheter 10. The requisite
`electrical connection between sensor 56 and signal generator
`58 can be achieved using a variety of known technologies.
`For example, electrically insulated wire 66 can be wrapped
`around stylet 68, with wire 66 providing an electrical
`coupling between sensor 56 and signal generator 58. In an
`alternative embodiment, stylet 68 can be formed of an
`electrically conductive material which provides the requisite
`electrical coupling between sensor 56 and signal generator
`58. Electrical
`insulators preferably are provided around
`stylet 68 in order to prevent the inadvertent delivery of an
`electrical shock to the patient.
`The signal generator 58 is preferably a light bulb or other
`visual signal which provides a detectable signal indicating
`that sensor 56 is detecting a threshold level of a magnetic
`field or magnetic flux. A physician is thereby informed that
`distal end portion 14 of catheter 10 has been captured by
`external magnet 48 and that the external magnet 48 can be
`used for manipulating the distal end portion 14 of the
`catheter 10.An audible signal emitted by a buzzer or bell, for
`example, may be used instead of a light bulb without
`departing from the present invention. A vibrating element
`could also be provided in order to provide a tactile signal
`indicating that the requisite magnetic coupling is present.
`A further embodiment of a ferromagnetic insert in the
`distal end portion 14 of a catheter is illustrated in FIG. 8 The
`distal end portion of the catheter includes a plurality of bits
`70 consisting of a ferromagnetic material. The bits 70 are
`embedded in the wall of the distal end portion 14 of the
`catheter wall material as a matrix. Magnetic flux from the
`external magnet 48 will be drawn to the bits 70 embedded
`in the catheter,
`thereby increasing the flux density and
`inducing magnetization within bits 70. The induced magne-
`tization functions as described in regard to the ferromagnetic
`insert 54 in FIG. 7.
`An alternative form of a sensor 56 is illustrated in FIG. 8
`and comprises a length of wire wrapped in a cylindrical form
`to provide a coil 80. The coil is electrically connected to the
`stylet in the same manner illustrated and described in regard
`to sensor 56 for delivering an electrical current to a signal
`generator. Preferably the length of wire is wrapped about an
`iron core thereby to increase the induced current in a manner
`well known in the art.
`A cap 72 receives the proximal end of the stylet 68 as
`illustrated in FIG. 4. The stylet 68 extends along substan-
`
`8
`tially the entire length of the lumen 40. The stylet 68 adds
`a desired degree of stiffness and rigidity to the catheter to
`facilitate the placement procedure. After placement of the
`catheter is completed, the cap is used for extracting the stylet
`68 from the catheter body portion 12. The lumen 40 can then
`be used for the supply of nutrients or medication for the
`patient. The cap 72 is fitted to a cavity formed in a fixture 74
`which is joined to the proximal end of the catheter which is
`opposite the distal end portion 14. The fixture 74 is provided
`with an additional duct section 76 having a removable
`closure cap 78 for access to the lumen when it is desired t
`o introduce fluids into the lumen of the catheter. It is also
`possible for a syringe to be connectable to the duct section
`76 in a fluid tight manner, as is well known in the art, should
`it be desired to withdraw fluid from the lumen.
`An alternative embodiment of the catheter disclosed
`herein is illustrated in FIG. 9, showing distal end portion 82.
`The construction of the distal end portion 82 provides
`increased flexibility of one portion of the catheter as com-
`pared with the flexibility of an adjacent distal end portion of
`the catheter. In the depicted embodiment, the first portion of
`the distal end portion 14 of catheter 10 has a different
`diameter resulting in greater elasticity and thereby increased
`flexibility when compared to the adjacent distal end portion
`of catheter 10. Preferably the increased flexibility at the
`distal end of the catheter is provided by a waisted portion 84
`extending along the distal end portion from a first location
`86 to a second location 88. The waisted portion 84 has a
`reduced cross-sectional dimension at an intermediate loca-
`tion 90 with respect to the dimensions at the first and second
`locations 86 and 88. This results in increased flexibility of a
`terminal end por