Method of using expandable cannula

• US 6,338,730 B1
• Filed: 06/06/1995
• Issued: 01/15/2002
• Est. Priority Date: 02/04/1993
• Status: Expired due to Term

• Current Assignee: Bonutti Skeletal Innovations LLC (Acacia Research Corporation)
• Original Assignee: Peter M. Bonutti
• Inventors: Bonutti, Peter M., Hawkins, James S.
• Primary Examiner(s): Thaler, Michael H.
• Application Number:
  US08/470,142
• Time in Patent Office: 2,415 Days
• Field of Search: 606/198, 606/194, 604/53, 604/52, 604/239, 604/272, 604/508, 604/509
• US Class Current: 604/509
• CPC Class Codes: A61B 17/3417 Details of tips or shafts, e.g. grooves, expandable, bendable; Multiple coaxial sliding cannulas, e.g. for dilating syringe needles A61M5/32; dilators A61M29/00
• CPC Class Codes: A61B 17/3439 with means for changing the inner diameter of the cannula, e.g. expandable A61B17/3423, A61B17/3431 take precedence; catheters A61M25/0662
• CPC Class Codes: A61B 2017/0409 Instruments for applying suture anchors for applying suture clamps, clips or locks A61B2017/0488
• CPC Class Codes: A61B 2017/0414 having a suture-receiving opening, e.g. lateral opening lateral eyelet for attaching suture to needle A61B2017/06019
• CPC Class Codes: A61B 2017/0417 T-fasteners
• CPC Class Codes: A61B 2017/06052 Needle-suture combinations in which a suture is extending inside a hollow tubular needle, e.g. over the entire length of the needle hollow suture needles A61B2017/061
• CPC Class Codes: A61B 2017/3486 Balloon
• CPC Class Codes: A61M 2025/0024 Expandable catheters or sheaths
• CPC Class Codes: A61M 2025/0089 Single injection needle protruding axially, i.e. along the longitudinal axis of the catheter, from the distal tip
• CPC Class Codes: A61M 2025/0095 being one or more needles protruding from the distal tip and which are not used for injection nor for electro-stimulation, e.g. for fixation purposes
• CPC Class Codes: A61M 25/0084 being one or more injection needles
• CPC Class Codes: A61M 25/04 in the body, e.g. expansible A61M25/10, A61M16/0488 take precedence
• CPC Class Codes: A61M 25/06 Body-piercing guide needles or the like
• CPC Class Codes: A61M 25/0662 Guide tubes

Abstract

Cannulas for surgical and medical use expand along their entire lengths. The cannulas are inserted through tissue when in an unexpanded condition and with a small diameter. The cannulas are then expanded radially outwardly to give a full-size instrument passage. Expansion of the cannulas occurs against the viscoelastic resistance of the surrounding tissue. The expandable cannulas do not require a full depth incision, or at most require only a needle-size entrance opening. In one embodiment of the invention, the cannula has a pointed end portion. In this embodiment of the invention, the cannula includes wires having cores which are enclosed by jackets. The jackets are integrally formed as one piece with a sheath of the cannula. The cannula may be expanded by inserting members or by fluid pressure. The cannula is advantageously utilized to expand a vessel, such as a blood vessel. An expandable chamber may be provided at the distal end of the cannula.

Claims

1. A method of establishing communication with the interior of a vessel in a human body, said method comprising the steps of providing a cannula having a sheath which at least partially encloses a plurality of wires having leading end portions at a leading end portion of the sheath, engaging a surface area on a side wall of the vessel with at least a portion of the leading end portion of at least one of the wires and at least a portion of the leading end portion of the sheath, initiating formation of an opening in the surface area on the side wall of the vessel by pressing the leading end portion of at least the one wire and the leading end portion of the sheath against the surface area on the side wall of the vessel, and, thereafter, moving the leading end portions of the plurality of wires and the leading end portion of the sheath through the opening in the surface area on the side wall of the vessel.

2. A method as set forth in claim 1 wherein said step of moving the leading end portions of the plurality of wires and the leading end portion of the sheath through the opening in the surface area on the side wall of the vessel includes moving the leading end portion of a second wire of the plurality of wires through the opening in the surface area on the side wall of the vessel after moving the leading end portion of the one wire of the plurality of wires through the opening in the surface area on the side wall of the vessel.

3. A method as set forth in claim 2 wherein said step of moving the leading end portions of the plurality of wires and the leading end portion of the sheath through the opening in the surface area on the side wall of the vessel includes moving a portion of the leading end portion of the sheath through the opening in the surface area on the side wall of the vessel prior to movement of the leading end portion of the second wire through the opening in the surface area on the side wall of the vessel.

4. A method as set forth in claim 1 wherein said step of initiating formation of an opening in the surface area on the side wall of the vessel includes penetrating the surface area on the side wall of the vessel with the leading end portion of the one wire, and, thereafter, penetrating the surface area on the side wall of the vessel with a portion of the leading end portion of the sheath, said step of penetrating the surface area on the side wall of the vessel with a portion of the leading end portion of the sheath being performed with a leading end portion of at least a second wire in the plurality of wires spaced from the side wall of the vessel.

5. A method as set forth in claim 1 further including the step of expanding the leading end portion of the sheath while the leading end portions of the plurality of wires and the leading end portion of the sheath are disposed in the vessel, said step of expanding the leading end portion of the sheath includes moving portions of the wires of the plurality of wires equal distances apart throughout the length of portions of the wires disposed in the vessel.

6. A method as set forth in claim 1 further including the step of expanding the leading end portion of the sheath while the leading end portions of the plurality of wires and the leading end portion of the sheath are disposed in the vessel, said step of expanding the leading end portion of the sheath includes applying fluid pressure against an inner side surface of the sheath at locations between wires of the plurality of wires.

7. A method as set forth in claim 6 wherein said step of expanding the leading end portion of the sheath includes applying fluid pressure against outer side surfaces on the wires.

8. A method as set forth in claim 1 further including the step of expanding the leading end portion of the sheath while the leading end portions of the wires and the leading end portion of the sheath are disposed in the vessel, said step of expanding the leading end portion of the sheath includes inserting a tubular member into the leading end portion of the sheath.

9. A method as set forth in claim 8 wherein said step of inserting a tubular member into the leading end portion of the sheath includes sliding the tubular member along outer side surfaces on the wires while maintaining the tubular member spaced apart from inner side surface areas on the sheath.

10. A method as set forth in claim 1 wherein said step of moving the leading end portions of the plurality of wires and the leading end portion of the sheath through the opening in the surface area on the side wall of the vessel includes simultaneously moving a portion of the leading end portion of the sheath and a leading end portion of the one wire of the plurality of wires into and through an opening formed in a side wall of a blood vessel.

11. A method as set forth in claim 1 wherein the vessel is a blood vessel, said method further including moving the leading end portion of the sheath and leading end portions of the wires of the plurality of wires along a longitudinal axis of the blood vessel.

12. A method as set forth in claim 11 further including the step of expanding the leading end portion of the sheath while the leading end portion of the sheath is disposed in the blood vessel, said step of expanding the leading end portion of the sheath includes moving a tubular member into the leading end portion of the sheath and pressing an outer side surface of the sheath against the inner side surface of the blood vessel.

13. A method as set forth in claim 1 wherein the vessel is a blood vessel having a longitudinal central axis and the sheath has an oval cross sectional configuration, said step of initiating formation of an opening in the surface area on the side wall of the vessel is performed with a major axis of the oval cross section of the sheath aligned with the longitudinal central axis of the blood vessel.

14. A method of establishing communication with the interior of a longitudinally extending blood vessel in a human body, said method comprising the steps of providing a cannula having a sheath which at least partially encloses a plurality of wires, piercing a side wall of the blood vessel with a leading end portion of the cannula, moving the sheath and the plurality wires of the cannula through an opening, formed in the side wall of the blood vessel during performance of said step of piercing a side wall of the blood vessel with the leading end portion of the cannula, thereafter, moving the sheath and the wires along an inner side surface of the blood vessel with at least a portion of the sheath and at least portions of the wires enclosed by the blood vessel.

15. A method as set forth in claim 14 further including the step of expanding at least a portion of the cannula disposed in the blood vessel, said step expanding at least a portion of the cannula disposed in the blood vessel includes pressing an outer side surface area on the sheath which is free of discontinuities against an inner side surface area on the blood vessel.

16. A method as set forth in claim 15 wherein said step of expanding at least a portion of the cannula disposed in the blood vessel includes moving a member into the portion of the cannula disposed in the blood vessel, applying force against surface areas on the plurality of wires with the member, and transmitting force from the plurality of wires to the sheath to expand at least a portion of the sheath.

17. A method as set forth in claim 14 further including the step of expanding at least a portion of the cannula disposed in the blood vessel, said step of expanding at least a portion of the cannula disposed in the blood vessel includes conducting fluid pressure into the portion of the cannula disposed in the blood vessel and pressing a portion of the cannula against an inner side surface area on the blood vessel under the influence of fluid pressure.

18. A method as set forth in claim 17 wherein said step of conducting fluid pressure into the portion of the cannula disposed in the blood vessel includes conducting fluid pressure through at least a portion of the cannula into the blood vessel.

19. A method as set forth in claim 17 wherein said step of pressing a portion of the cannula against an inner side surface area on the blood vessel under the influence of fluid pressure includes applying fluid pressure against an inner surface area on the sheath.

20. A method as set forth in claim 14 further including the step of expanding at least a portion of the cannula disposed in the blood vessel, said step of expanding at least a portion of the cannula disposed in the blood vessel includes expanding a portion of the sheath which extends through the opening in the side wall of the blood vessel and increasing the size of the opening formed in the side wall of the blood vessel under the influence of force transmitted through the sheath to the blood vessel.

21. A method as set forth in claim 14 further including the step of expanding at least a portion of the cannula disposed in the blood vessel, said step of expanding at least a portion of the cannula disposed in the blood vessel includes sliding a tubular member along side surfaces on at least portions of the wires enclosed by the blood vessel and transmitting force from the wires to the sheath to press an outer side surface area on the portion of the sheath enclosed by the blood vessel against an inner side surface of the blood vessel.

22. A method as set forth in claim 21 wherein said step of expanding at least a portion of the cannula disposed in the blood vessel includes expanding a portion of the sheath which extends through the opening formed in the side wall of the blood vessel to increase the size of the opening formed in the side wall of the blood vessel.

23. A method as set forth in claim 21 wherein at least portions of the wires extend through the portion of the sheath which extends through the opening in the side wall of the blood vessel, said step of expanding the portion of the sheath which extends through the opening formed in the side wall of the blood vessel includes sliding a tubular member along side surfaces on the portions of wires which extend through the opening in the side wall of the blood vessel.

24. A method as set forth in claim 14 wherein said step of piercing a side wall of the blood vessel with a leading end of the cannula includes initiating formation of an opening in the side wall of the blood vessel by pressing a leading end portion of at least one wire and at least a portion of a leading end portion of the sheath against a surface area on the side wall of the blood vessel.

25. A method of establishing a flow of fluid between a longitudinally extending blood vessel in a human body and a location outside of the human body, said method comprising the steps of inserting a tubular sheath having a leading end portion with a continuous outer side surface which extends around the leading end portion of the sheath into the blood vessel while the continuous outer side surface on the leading end portion of the sheath has a first cross sectional size as viewed in a plane extending perpendicular to a longitudinal central axis of the sheath, thereafter, increasing the cross sectional size of the continuous outer side surface on the leading end portion of the sheath from the first cross sectional size to a second cross sectional size which is greater than the first cross sectional size, said step of increasing the cross sectional size of the continuous outer side surface on the leading end portion of the sheath includes resiliently stretching elastic material of the sheath by inserting a tubular member into the leading end portion of the sheath while the leading end portion of the sheath is in the blood vessel, increasing the cross sectional size of the blood vessel as viewed in a plane extending perpendicular to a longitudinal central axis of the blood vessel, said step of increasing the cross sectional size of the blood vessel includes pressing the continuous outer side surface on the leading end portion of the sheath against an inner side surface of the blood vessel as the cross sectional size of the continuous outer side surface on the leading end portion of the sheath increases from the first cross sectional size to the second cross sectional size, and thereafter, conducting a flow of fluid between the blood vessel and the location outside of the human body through the tubular member and the sheath while the continuous outer side surface on the leading end portion of the sheath has a cross sectional size which is greater than the first cross sectional size and while the continuous outer side surface on the leading end portion of the sheath is pressing against the inner side surface of the blood vessel.

26. A method as set forth in claim 25 wherein said step of inserting the sheath into the blood vessel while the continuous outer side surface on the leading end portion of the sheath has the first cross sectional size includes piercing an imperforate outer side surface area on the blood vessel with the leading end portion of the sheath.

27. A method as set forth in claim 25 further including the steps of reducing the cross sectional size of the leading end portion of the sheath after performing said step of conducting a flow of fluid through the tubular member and the sheath and while the leading end portion of the sheath is disposed in the blood vessel, said step of reducing the cross sectional size of the leading end portion of the sheath includes withdrawing the tubular member from the leading end portion of the sheath, and, thereafter, removing the leading end portion of the sheath from the blood vessel.

28. A method as set forth in claim 25 wherein said step of increasing the cross sectional size of the continuous outer side surface on the leading end portion of the sheath from the first cross sectional size to the second cross sectional size is performed with the sheath extending through an opening in a side wall of the blood vessel and includes increasing the size of the opening in the side wall of the blood vessel.

29. A method as set forth in claim 25 wherein said step of increasing the cross sectional size of the continuous outer side surface on the leading end portion of the sheath from the first cross sectional size to a second cross sectional size includes sliding the tubular member along side surfaces of a plurality of wires in the leading end portion of the sheath.

30. A method of establishing a flow of fluid between a longitudinally extending blood vessel in a human body and a location outside of the human body, said method comprising the steps of inserting a tubular sheath having a leading end portion with a continuous outer side surface which extends around the leading end portion of the sheath into the blood vessel while the continuous outer side surface on the leading end portion of the sheath has a first cross sectional size as viewed in a plane extending perpendicular to a longitudinal central axis of the sheath, thereafter, increasing the cross sectional size of the continuous outer side surface on the leading end portion of the sheath from the first cross sectional size to a second cross sectional size which is greater than the first cross sectional size, said step increasing the cross sectional size of the continuous outer side surface on the leading end portion of the sheath includes resiliently stretching elastic material of the sheath by applying fluid pressure against an inner side surface of the sheath while the leading end portion of the sheath is in the blood vessel, increasing the cross sectional size of the blood vessel as viewed in a plane extending perpendicular to a longitudinal central axis of the blood vessel, said step of increasing the cross sectional size of the blood vessel includes pressing the continuous outer side surface on the leading end portion of the sheath against an inner side surface of the blood vessel as the cross sectional size of the continuous outer side surface on the leading end portion of the sheath increases from the first cross sectional size to the second cross sectional size, and thereafter, conducting a flow of fluid between the blood vessel and the location outside of the human body through the sheath while the leading end portion of the sheath has a cross sectional size which is greater than the first cross sectional size, said step of conducting a flow of fluid through the sheath includes conducting the flow of fluid along the inner side surface of the sheath, said step of applying fluid pressure against an inner side surface of the sheath includes exposing the inner side surface of the sheath to fluid pressure in the flow of fluid through the sheath.

31. A method as set forth in claim 30 wherein said step of inserting the sheath into the blood vessel while the continuous outer side surface on the leading end portion of the sheath has the first cross sectional size includes piercing an imperforate outer side surface area on the blood vessel with the leading end portion of the sheath.

32. A method as set forth in claim 30 wherein said step of increasing the cross sectional size of the continuous outer side surface on the leading end portion of the sheath from the first cross sectional size to the second cross sectional size is performed with the sheath extending through an opening in a side wall of the blood vessel and includes increasing the size of the opening in the side wall of the blood vessel.

33. A method comprising the steps of providing a cannula having a tubular sheath which at least partially encloses a plurality of wires, pressing leading end surfaces on first and second wires of the plurality of wires and a leading end surface area disposed on the sheath between the first and second wires against a surface area on the patient'"'"'s body tissue, and moving the leading end surfaces on the first and second wires and the leading end surface area disposed on the sheath between the first and second wires into the patient'"'"'s body tissue, said step of moving the leading end surfaces on the first and second wires and the leading end surface area disposed on the sheath between the first and second wires into the patient'"'"'s body tissue includes cutting the patient'"'"'s body tissue with the leading end surface area disposed on the sheath between the first and second wires.

34. A method as set forth in claim 33 wherein said step of moving the leading end surfaces on the first and second wires and the leading end surface area disposed on the sheath between the first and second wires into the patient'"'"'s body tissue includes penetrating the patient'"'"'s body tissue with the leading end surface on at least one wire prior to cutting the patient'"'"'s body tissue with the leading end surface disposed on the sheath.

35. A method as set forth in claim 33 further including the step of moving a leading end surface on a third wire of the plurality of wires into the patient'"'"'s body tissue after performing the step of cutting the patient'"'"'s body tissue with the leading end surface area disposed on the sheath between the first and second wires.

36. A method as set forth in claim 33 wherein the patient'"'"'s body tissue has a longitudinal axis and the sheath has an oval configuration, said step of pressing leading end surfaces on first and second wires and the leading end surface area disposed on the sheath between the first and second wires against a surface area on the patient'"'"'s body tissue is performed with a major axis of the oval cross section of the sheath aligned with the longitudinal axis of the body tissue.

37. A method as set forth in claim 33 further including the step of expanding at least a portion of the sheath, said step of expanding at least a portion of the sheath includes stretching material of the sheath disposed between the first and second wires of the plurality of wires and increasing the extent of the leading end surface area disposed on the sheath between the first and second wires.

38. A method as set forth in claim 33 further including the steps of moving a longitudinally extending portion of the sheath having a continuous outer side surface area which extends around a leading end portion of the sheath into the patient'"'"'s body tissue, and conducting a flow of fluid through the sheath while the longitudinally extending portion of the sheath is disposed in the patient'"'"'s body tissue.

39. A method as set forth in claim 33 further including the steps of conducting fluid pressure through the sheath and expanding the sheath under the influence of fluid pressure conducted through the sheath.

40. A method as set forth in claim 33 further including the steps of moving a longitudinally extending portion of the sheath into the patient'"'"'s body tissue, and expanding the longitudinally extending portion of the sheath while the longitudinally extending portion of the sheath is in the patient'"'"'s body tissue, said step of expanding the longitudinally extending portion of the sheath includes moving portions of the wires of the plurality of wires disposed in the longitudinally extending portion of the sheath equal distances apart throughout the length of the portions of the wires disposed in the longitudinally extending portion of the sheath.

41. A method as set forth in claim 33 further including the steps of moving a longitudinally extending portion of the sheath into the patient'"'"'s body tissue, and expanding the longitudinally extending portion of the sheath while the longitudinally extending portion of the sheath is disposed in the patient'"'"'s body tissue, said step of expanding the longitudinally extending portion of the sheath includes applying fluid pressure against an inner side surface of the sheath at locations between wires of the plurality of wires.

42. A method as set forth in claim 41 wherein said step of expanding the longitudinally extending portion of the sheath includes applying fluid pressure against outer side surfaces of the wires.

43. A method as set forth in claim 33 further including the steps of moving a longitudinally extending portion of the sheath into the patient'"'"'s body tissue, and expanding the longitudinally extending portion of the sheath while the longitudinally extending portion of the sheath is disposed in the patient'"'"'s body tissue, said step of expanding the longitudinally extending portion of the sheath includes inserting a member into the longitudinally extending portion of the sheath disposed in the patient'"'"'s body tissue.

44. A method as set forth in claim 43 wherein said step of inserting a member into the longitudinally extending portion of the sheath disposed in the patient'"'"'s body tissue includes sliding a tubular member along outer side surfaces on the wires while maintaining the tubular member spaced apart from an inner side surface areas on the sheath.

45. A method of establishing communication with the interior of a vessel in a human body, said method comprising the steps of providing a cannula having a tubular sheath enclosing a plurality of wires, piercing a side wall of the vessel in the human body with leading end portions of the sheath and the wires, thereafter, moving the sheath and the wires into the vessel through an opening formed during performance of said step of piercing the side wall of the vessel with the leading end portions of the sheath and wires, and, thereafter, expanding the portion of the sheath disposed in the vessel.

46. A method as set forth in claim 45 further including the step of expanding the vessel during performance of said step of expanding the portion of the sheath disposed in the vessel, said step of expanding the vessel includes pressing a continuous outer side surface area which is disposed on and extends around the sheath against an inner side surface of the vessel.

47. A method as set forth in claim 45 wherein said step of expanding the portion of the sheath disposed in the vessel includes inserting a tubular member into the sheath and sliding the tubular member along outer side surface areas on the wires.

48. A method as set forth in claim 45 wherein said step of expanding the portion of the sheath disposed in the vessel includes conducting fluid pressure into the sheath and applying fluid pressure against an inner side surface of the sheath and against outer side surfaces of the wires.

49. A method as set forth in claim 45 wherein said step of expanding the portion of the sheath disposed in the vessel is performed with the sheath and the wires extending through the opening formed in the vessel during performance of said step of piercing the side wall of the vessel, said step of expanding the portion of the sheath disposed in the vessel includes increasing the size of the opening in the side wall of the vessel.

50. A method as set forth in claim 45 further including the step of conducting fluid through the sheath into the vessel after performing said step of expanding the portion of the sheath disposed in the vessel.

51. A method as set forth in claim 45 further including the step of piercing body tissue adjacent the side wall of vessel with the leading end portions of the sheath and the wires prior to performance of said step of piercing the side wall of the vessel with the leading end portions of the sheath and wires.

52. A method as set forth in claim 45 further including the step of piercing skin of the human body containing the vessel with the leading end portions of the sheath and wires prior to performance of said step of piercing the side wall of the vessel with the leading end portions of the sheath and wires.

53. A method as set forth in claim 45 wherein said step of moving the sheath and wires into the vessel includes moving the sheath and wires axially along a blood vessel with a continuous outer side surface area which is disposed on and extends around the sheath exposed to an inner side surface of the blood vessel and with the wires shielded from the inner side surface of the blood vessel by the sheath.

54. A method as set forth in claim 45 wherein the sheath is formed of an elastic material which is resiliently deflectable and the plurality of wires are connected with and extend along an inner side of the sheath, said step of piercing the side wall of the vessel includes transmitting an axial force through the wires and the sheath to the side wall of the vessel.

55. A method as set forth in claim 54 wherein said step of expanding the portion of the sheath disposed in the vessel includes resiliently stretching the material of the sheath and increasing spacing between longitudinally extending side surface areas on the wires as the material of the sheath is stretched.

56. A method as set forth in claim 45 wherein the vessel has a tubular configuration, said step of expanding the portion of the sheath disposed in the vessel includes pressing an outer side surface of the sheath against an inner side surface of the tubular vessel, increasing the size of the outer side surface of the sheath, and increasing the size of the inner side surface of the tubular vessel under the influence of pressure applied against the inner side surface of the vessel by the outer side surface of the sheath.

57. A method as set forth in claim 45 wherein said step of expanding the leading end portion of the sheath disposed in the vessel includes inserting a first longitudinally extending member into the portion of the sheath disposed in the vessel, and, thereafter, inserting a second longitudinally extending member having a cross sectional area which is greater than a cross sectional area of the first member into the portion of the sheath disposed in the vessel.

58. A method as set forth in claim 57 wherein the second member is tubular, said method further including conducting fluid into the vessel through the second member.

59. A method as set forth in claim 57 wherein said step of inserting a first member into the portion of the sheath disposed in the vessel includes sliding the first member along longitudinally extending outer side surface areas on the wires, said step of inserting the second member into the portion of the sheath disposed in the vessel includes sliding the second member along the outer side surface areas on the wires and moving the wires out of engagement with the first member.

60. A method as set forth in claim 59 wherein said step of moving the wires out of engagement with the first member is performed during performance of said step of sliding the second member along outer side surface areas on the wires.

61. A method as set forth in claim 45 wherein the vessel is a tubular vessel having a longitudinal central axis and a leading end portion of the sheath has an oval cross sectional configuration as viewed in a plane extending perpendicular to a longitudinal central axis of the sheath, said step of piercing a side wall of the vessel being performed with a major axis of the oval cross section of the sheath extending along the longitudinal axis of the tubular vessel and a minor axis of the oval cross section of the sheath extending transverse to the longitudinal axis of the tubular vessel.

62. A method of establishing communication with the interior of a longitudinally extending blood vessel in a human body with a cannula having an oval cross sectional configuration in a plane extending perpendicular to a longitudinal axis of the cannula, said method comprising the steps of aligning the cannula with the blood vessel with a major axis of the oval cross section of the cannula extending along a longitudinal axis of the blood vessel, piercing a side wall of the blood vessel with a leading end of the cannula while the major axis of the oval cross section of the cannula is aligned with the longitudinal axis of the blood vessel, said step of piercing a side wall of the blood vessel includes forming an elongated opening in the side wall of the blood vessel, and moving a longitudinally extending portion of the cannula through the elongated opening in the side wall of the blood vessel with the major axis of the oval cross section of the cannula aligned with a longitudinal axis of the opening in the side wall of the blood vessel.

63. A method as set forth in claim 62 wherein the cannula includes a sheath having a pointed end portion and a central passage with an oval cross section in a plane perpendicular to a longitudinal axis of said central passage, said step of piercing a side wall of the blood vessel includes cutting the side wall of the blood vessel with the pointed end portion of the sheath while a major axis of the oval cross section of the sheath extends along the longitudinal axis of the blood vessel.

64. A method as set forth in claim 62 further including the step of expanding the longitudinally extending portion of the cannula while the longitudinally extending portion of the cannula is disposed in the blood vessel, said step of expanding the longitudinally extending portion of the cannula includes pressing an outer side surface which is disposed on the longitudinally extending portion of the cannula and which is free of discontinuities against an inner side surface of the blood vessel while the longitudinally extending portion of the cannula extends through the elongated opening in the side wall of the blood vessel with the major axis of the oval cross section of the cannula aligned with the longitudinal axis of the opening in the side wall of the blood vessel.

65. A method comprising the steps of providing a cannula having a tubular sheath which at least partially encloses a plurality of wires, initiating formation of an opening in a surface area on a patient'"'"'s body tissue by pressing a leading end surface on at least one of the wires and at least a portion of a leading end surface on the sheath adjacent to the one wire against the surface area on the patient'"'"'s body tissue, thereafter, moving the leading end surface on the one wire and at least the portion of the leading end surface on the sheath adjacent to the one wire through the opening formed in the surface area on the patient'"'"'s body tissue, and moving a leading end surface on a second wire of the plurality of wires through the opening after having performed said step of moving the leading end surface on the one wire and at least the portion of the leading end surface on the sheath adjacent to the one wire through the opening.

66. A method comprising the steps of providing a cannula having a tubular sheath which at least partially encloses a plurality of wires, initiating formation of an opening in a surface area on a patient'"'"'s body tissue by pressing a leading end surface on at least one of the wires and at least a portion of a leading end surface on the sheath adjacent to the one wire against the surface area on the patient'"'"'s body tissue, thereafter, moving the leading end surface on the one wire and at least the portion of the leading end surface on the sheath adjacent to the one wire through the opening formed in the surface area on the patient'"'"'s body tissue, moving a longitudinal extending portion of the sheath through the opening into the body tissue, and pressing a continuous outer side surface area on the longitudinally extending portion of the sheath against the body tissue by expanding the longitudinally extending portion of the sheath while the longitudinally extending portion of the sheath is in the body tissue, said step of expanding the longitudinally extending portion of the sheath while the longitudinally extending portion of the sheath is in the body tissue includes moving a member into the longitudinally extending portion of the sheath and utilizing the wires to hold the member in a spaced apart relationship with inner side surface areas of the sheath as the member is moved into the longitudinally extending portion of the sheath.

67. A method comprising the steps of providing a cannula having a tubular sheath which at least partially encloses a plurality of wires, initiating formation of an opening in a surface area on a patient'"'"'s body tissue by pressing a leading end surface on at least one of the wires and at least a portion of a leading end surface on the sheath adjacent to the one wire against the surface area on the patient'"'"'s body tissue, thereafter, moving the leading end surface on the one wire and at least the portion of the leading end surface on the sheath adjacent to the one wire through the opening formed in the surface area on the patient'"'"'s body tissue, moving a longitudinal extending portion of the sheath through the opening into the body tissue, pressing a continuous outer side surface area on the longitudinally extending portion of the sheath against the body tissue by expanding the longitudinally extending portion of the sheath while the longitudinally extending portion of the sheath is in the body tissue, and conducting a flow of fluid through opposite ends of the tubular sheath after moving the longitudinally extending portion of the sheath into the body tissue, said step of expanding the longitudinally extending portion of the sheath while the longitudinally extending portion of the sheath is in the body tissue includes moving a tubular member into the longitudinally extending portion of the sheath by sliding the tubular member along the wires, said step of conducting a flow of fluid through opposite ends of the sheath includes conducting the fluid flow through the tubular member.

68. A method comprising the steps of providing a cannula having a tubular sheath which at least partially encloses a plurality of wires, initiating formation of an opening in a surface area on a patient'"'"'s body tissue by pressing a leading end surface on at least one of the wires and at least a portion of a leading end surface on the sheath adjacent to the one wire against the surface area on the patient'"'"'s body tissue, and, thereafter, moving the leading end surface on the one wire and at least the portion of the leading end surface on the sheath adjacent to the one wire through the opening formed in the surface area on the patient'"'"'s body tissue, the body tissue has a longitudinal axis and the sheath has an oval cross sectional configuration, said step of initiating formation of an opening in the surface area on the patient'"'"'s body tissue is performed with a major axis of the oval cross section of the sheath aligned with the longitudinal axis of the body tissue.

69. A method of establishing a flow of liquid between an interior of a vessel in a human body and a location outside of the human body, said method comprising the steps of providing a cannula having a tubular sheath, piercing a side wall of the vessel in the human body with a leading end portion of the cannula, moving the sheath into the vessel through an opening formed during performance of said step of piercing the side wall of the vessel with the leading end portion of the cannula, thereafter, expanding a portion of the sheath disposed in the vessel and having a continuous outer side surface area which extends around the sheath, said step of expanding the portion of the sheath disposed in the vessel includes pressing the continuous outer side surface area which extends around the sheath against a vessel inner surface area which extends around the sheath, and establishing a flow of liquid between the interior of the vessel at a location spaced from the cannula and the location outside of the human body, said step of establishing a flow of liquid includes conducting the flow of liquid through the sheath while pressing the continuous outer side surface area disposed on the sheath against the vessel inner side surface area which extends around the sheath, said step of expanding the portion of the sheath disposed in the vessel includes exposing an inner side surface area on the sheath to fluid pressure in the flow of liquid conducted through the sheath and stretching the portion of the sheath disposed in the vessel under the influence of fluid pressure applied against the inner side surface of the sheath by the flow of liquid conducted through the sheath.

70. A method of establishing a flow of liquid between an interior of a vessel in a human body and a location outside of the human body, said method comprising the steps of providing a cannula having a tubular sheath, piercing a side wall of the vessel in the human body with a leading end portion of the cannula, moving the sheath into the vessel through an opening formed during performance of said step of piercing the side wall of the vessel with the leading end portion of the cannula, thereafter, expanding a portion of the sheath disposed in the vessel and having a continuous outer side surface area which extends around the sheath, said step of expanding the portion of the sheath disposed in the vessel includes pressing the continuous outer side surface area which extends around the sheath against a vessel inner surface area which extends around the sheath, and establishing a flow of liquid between the interior of the vessel at a location spaced from the cannula and the location outside of the human body, said step of establishing a flow of liquid includes conducting the flow of liquid through the sheath while pressing the continuous outer side surface area disposed on the sheath against the vessel inner side surface area which extends around the sheath, said step of expanding the portion of the sheath disposed in the vessel being performed under the influence of fluid pressure in the flow of liquid through the sheath.

71. A method of establishing a flow of liquid between an interior of a vessel in a human body and a location outside of the human body, said method comprising the steps of providing a cannula having a tubular sheath, piercing a side wall of the vessel in the human body with a leading end portion of the cannula, moving the sheath into the vessel through an opening formed during performance of said step of piercing the side wall of the vessel with the leading end portion of the cannula, thereafter, expanding a portion of the sheath disposed in the vessel and having a continuous outer side surface area which extends around the sheath, said step of expanding the portion of the sheath disposed in the vessel includes pressing the continuous outer side surface area which extends around the sheath against a vessel inner surface area which extends around the sheath, and establishing a flow of liquid between the interior of the vessel at a location spaced from the cannula and the location outside of the human body, said step of establishing a flow of liquid includes conducting the flow of liquid through the sheath while pressing the continuous outer side surface area disposed on the sheath against the vessel inner side surface area which extends around the sheath, the sheath is formed of an elastic material which is resiliently deflectable, said step of expanding the portion of the sheath disposed in the vessel includes resiliently stretching the elastic material of the sheath to increase the extent of the continuous outer side surface area disposed on the sheath, said step of stretching the elastic material of the sheath is performed under the influence of fluid pressure in the flow of liquid through the sheath.

72. A method of establishing a flow of liquid between an interior of a vessel in a human body and a location outside of the human body, said method comprising the steps of providing a cannula having a tubular sheath, piercing a side wall of the vessel in the human body with a leading end portion of the cannula, moving the sheath into the vessel through an opening formed during performance of said step of piercing the side wall of the vessel with the leading end portion of the cannula, thereafter, expanding a portion of the sheath disposed in the vessel and having a continuous outer side surface area which extends around the sheath, said step of expanding the portion of the sheath disposed in the vessel includes pressing the continuous outer side surface area which extends around the sheath against a vessel inner surface area which extends around the sheath, and establishing a flow of liquid between the interior of the vessel at a location spaced from the cannula and the location outside of the human body, said step of establishing a flow of liquid includes conducting the flow of liquid through the sheath while pressing the continuous outer side surface area disposed on the sheath against the vessel inner side surface area which extends around the sheath, the vessel is a tubular vessel having a longitudinal central axis and a leading end portion of the sheath has an oval cross sectional configuration as viewed in a plane extending perpendicular to a longitudinal central axis of the sheath, said step of piercing a side wall of the vessel being performed with a major axis of the oval cross section of the sheath extending along the longitudinal axis of the tubular vessel and a minor axis of the oval cross section of the sheath extending transverse to the longitudinal axis of the tubular vessel.