Vascular access port with elongated septum

• US 6,213,973 B1
• Filed: 01/12/1998
• Issued: 04/10/2001
• Est. Priority Date: 01/12/1998
• Status: Expired due to Term

• Current Assignee: C.R. Bard, Inc. (Becton, Dickinson & Co)
• Original Assignee: C.R. Bard, Inc. (Becton, Dickinson & Co)
• Inventors: Powers, Kelly B., Christian, Kelly J., Eliasen, Kenneth A.
• Primary Examiner(s): Weiss, John G.
• Assistant Examiner(s): Thanh, LoAn H.
• Application Number:
  US09/005,608
• Time in Patent Office: 1,184 Days
• Field of Search: 604/93, 604/890.1, 604/891.1, 604/175, 604/93.01, 604/174, 604/905, 604/183, 604/244, 604/523, 178/DIG.12
• US Class Current: 604/93.01
• CPC Class Codes: A61M 2039/0072 Means for increasing tightness of the septum, e.g. compression rings, special materials, special constructions
• CPC Class Codes: A61M 2039/0226 having means for protecting the interior of the access site from damage due to the insertion of a needle
• CPC Class Codes: A61M 39/0208 Subcutaneous access sites for injecting or removing fluids transcutaneous access sites A61M39/0247; implantable infusion devices A61M5/14276
• CPC Class Codes: Y10S 604/905 Aseptic connectors or couplings, e.g. frangible, piercable

Abstract

An elongated access port has a needle-impenetrable housing enclosing a fluid reservoir. The housing includes a base having a floor with an upstanding encircling sidewall and a cap having a top wall with a depending encircling skirt. The skirt of the cap receives the sidewall of the base. An access aperture extends through the top wall of the cap to communicate with the fluid reservoir. The access aperture is encircled by a continuous rim having an elongated shape in the plane of the access aperture. The rim of the access aperture may be elliptical, oval, polygonal, or parabolic-ended. An elastomeric, needle-penetrable, generally planar septum is disposed in the access aperture with the periphery of the septum in sealing engagement with the rim of the access aperture. Prior to installation, the septum has a periphery with a cross section in the plane of the septum that is geometrically proportional to and larger than the shape of the access aperture. Installation causes the periphery of the septum to be displaced inwardly by the rim of the access aperture in a direction parallel to the plane of the septum. In view of the relative shapes of the rim of the access aperture and the periphery of the septum, this produces substantially uniform hydrostatic pressure in regions of the installed septum that are subjected in use of the access port to needle penetrations. Opposite faces of the periphery of the septum are urged toward each other between the cap of the housing and the top of the sidewall of the base of the housing.

Claims

1. An implantable vascular access port comprising:

(a) a needle-impenetrable housing enclosing a fluid reservoir, said housing having formed therethrough an access aperture communicating between said fluid reservoir and the exterior of said housing, said access aperture having a generally elongated rim and extreme ends defining therebetween the maximum extent of said access aperture;

(b) an outlet stem projecting from said housing at a location adjacent one of said extreme ends of said access aperture. said outlet stem enclosing a longitudinal fluid passageway extending from the end of said outlet stem remote from said housing through said housing to said fluid reservoir; and

(c) an elastomeric, needle-penetrable, generally planar septum, said septum having a periphery in a cross section of said septum taken in the plane thereof that is geometrically proportional to and larger than said rim of said access aperture, said septum being disposed in said access aperture with said periphery of said septum in sealing engagement with said rim of said access aperture, whereby in disposing said septum in said access aperture said periphery of said septum is displaced inwardly in a direction parallel to said plane of said septum by said rim of said access aperture.

2. An access port as recited in claim 1, wherein said housing comprises:

(a) a base comprising a floor and a continuous encircling sidewall upstanding therefrom, the interior of said base corresponding to said fluid reservoir of said housing; and

(b) a cap comprising a top wall and a skirt depending therefrom, said cap being configured to receive in said skirt thereof the end of said sidewall of said base remote from said floor thereof, and said access aperture being formed through said top wall of said cap at a location that communicates with said fluid reservoir of said housing when said sidewall of said base is received in said skirt of said cap.

3. An access port as recited in claim 2, wherein:

(a) said sidewall of said base terminates remote from said floor of said base in a continuous septum support shoulder disposed in a plane parallel to said floor of said base; and

(b) said cap comprises a septum retention lip projecting radially inwardly into said access aperture from the side of said rim thereof adjacent the exterior of said top wall of said cap, said septum retention lip having a generally planar bearing surface on the side of said septum retention lip opposite from the exterior of said top wall of said cap, said bearing surface of said septum retention lip being in parallel spaced-apart relationship to said septum support shoulder, when said sidewall of said base is received in said skirt of said cap.

4. An access port as recited in claim 3, wherein the edge of said septum retention lip remote from said rim of said access aperture is geometrically proportional to and smaller than said shape of said rim of said access aperture.

5. An access port as recited in claim 4, wherein said edge of said septum retention lip is congruent with the cross section of said fluid reservoir taken in a plane parallel to said floor of said base of said housing.

6. An access aperture as recited in claim 3, further comprising:

(a) a first septum gripping ridge projecting from and normal to said bearing surface of said septum retention lip; and

(b) a second septum gripping ridge projecting from and normal to said septum support shoulder.

7. An access port as recited in claim 6, wherein:

(a) said first septum gripping ridge is disposed along the edge of said bearing surface of said septum retention lip adjacent said fluid reservoir; and

(b) said second septum gripping ridge is disposed along the edge of said septum support shoulder remote from said rim of said access aperture.

8. An access port as recited in claim 3, wherein said periphery of said septum is thicker than the distance between said septum support shoulder and said bearing surface of said septum retention lip, when said sidewall of said base is received in said skirt of said cap, whereby said periphery of said septum is axially compressed between said septum support shoulder and said bearing surface of said septum retention lip when said sidewall of said base is received in said skirt of said cap with said septum disposed in said access aperture.

9. An access port as recited in claim 2, wherein said access aperture has a longitudinal axis coincident with the maximum extent of said access aperture, and said longitudinal axis of said access aperture intersects said rim thereof at respective extreme ends of said access aperture, and said outlet stem projects from said housing at a location adjacent one of said extreme ends of said access aperture.

10. An access port as recited in claim 9, wherein said outlet stem is carried by said base of said housing and projects through said skirt of said cap of said housing when said sidewall of said base is received in said skirt of said cap.

11. An access port as recited in claim 2, wherein said skirt of said cap is a single continuous structure encircling said sidewall of said base when said sidewall of said base is received in said skirt of said cap.

12. An access port as recited in claim 1, wherein said access aperture has a longitudinal axis coincident with the maximum extent of said access aperture, and said longitudinal axis of said access aperture intersects said rim thereof at respective extreme ends of said access aperture, and said outlet stem projects from said housing at a location adjacent one of said extreme ends of said access aperture.

13. An implantable vascular access port comprising:

(a) a needle-impenetrable housing enclosing a fluid reservoir, said housing having formed therethrough an access aperture communicating between said fluid reservoir and the exterior of said housing, said access aperture being defined by a continuous elongated encircling rim, and said housing further including a septum support shoulder projecting radially inwardly into said access aperture at the side of said rim of said access aperture opposite from said exterior of said housing, the edge of said septum support shoulder remote from said rim of said access aperture defining said fluid reservoir, whereby said fluid reservoir at said septum support shoulder is smaller than said access aperture at said support shoulder; and

(b) an elastomeric, needle-penetrable, generally planar septum, said septum being disposed in and sealing said access aperture in an installed configuration of said septum with the periphery of said septum in continuous engagement with said rim of said access aperture, said septum in said installed configuration thereof being precluded from entering said fluid reservoir bv said septum support shoulder said septum when free of externally imposed forces being capable of assuming a natural configuration wherein the periphery of the cross section of said septum taken in the plane thereof is geometrically proportional to and larger than said rim of the access aperture, whereby in assuming said installed configuration said periphery of said septum is displaced inwardly in said plane of said septum relative to said natural configuration thereof by forces imposed on said periphery of said septum by said rim of said access aperture.

14. An access port as recited in claim 13, wherein said septum comprises:

(a) an outer face on the side of said septum oriented to the exterior of said housing in said installed configuration of said septum;

(b) an inner face on the side of said septum opposite from said outer face; and

(c) support means integrally formed with said septum for preventing buckling of said septum in said installed configuration thereof.

15. An access port as recited in claim 14, wherein said support means comprises a needle target dome on said outer face of said septum.

16. An access port as recited in claim 15, wherein said needle target dome is smaller in extent than said outer face of said septum.

17. An access port as recited in claim 15, wherein in said installed configuration of said septum said needle target dome is displaced toward the exterior of said housing by said forces imposed on said periphery of said septum by said rim of said access aperture.

18. An access port as recited in claim 14, wherein said support means comprises a reinforcing plug on said inner face of said septum.

19. An access port as recited in claim 18, wherein said reinforcing plug is smaller in extent than said inner face of said septum.

20. An access port as recited in claim 18, wherein in said installed configuration of said septum said reinforcing plug is displaced toward the interior of said housing by said forces imposed on said periphery of said septum by said rim of said access aperture.

21. An access port as recited in claim 13, wherein said forces imposed on said periphery of said septum by said rim of said access aperture in said installed configuration of said septum produce substantially uniform hydrostatic pressure in the portion of said septum accessible for needle penetration in said installed configuration of said septum.

22. An access port as recited in claim 21, wherein said substantially uniform hydrostatic pressure in said portion of said septum is in a range from about 5 pounds per square inch to about 56 pounds per square inch.

23. An access port as recited in claim 21, wherein said substantially uniform hydrostatic pressure in said portion of said septum is in a range from about 10 pounds per square inch to about 46 pounds per square inch.

24. An access port as recited in claim 21, wherein said substantially uniform hydrostatic pressure in said portion of said septum is in a range from about 18 pounds per square inch to about 30 pounds per square inch.

25. An access port as recited in claim 13, wherein said periphery of said septum in said cross section thereof is substantially elliptical.

26. An access port as recited in claim 13, wherein:

(a) said septum has a longitudinal axis coincident with the maximum extent of said septum in said plane thereof, said longitudinal axis of said septum intersecting said periphery of said septum at respective longitudinal extremes of said septum, said longitudinal extremes of said septum being inwardly displaced from said natural configuration thereof into said installed configuration thereof by substantially equal nonzero first displacements directed parallel to said longitudinal axis of said septum;

(b) said septum has a lateral axis coincident with the maximum extent of said septum in said plane thereof measured perpendicular to said longitudinal axis of said septum, said lateral axis of said septum intersecting said periphery of said septum at respective medial extremes of said septum, said medial extremes of said septum being inwardly displaced from said natural configuration thereof into said installed configuration thereof by substantially equal nonzero second displacements directed parallel to said lateral axis of said septum; and

(c) the ratio of the combination of said first displacements to said distance between said longitudinal extremes of said septum in said natural configuration thereof is equal to the ratio of the combination of said second displacements to said distance between said medial extremes of said septum in said natural configuration thereof.

27. An access port as recited in claim 13, wherein:

(a) said septum has a longitudinal axis coincident with the maximum extent of said septum and a lateral axis coincident with the minimum extent of said septum measured perpendicular to said longitudinal axis of said septum, said longitudinal axis of said septum and said lateral axis of said septum defining a plane of said septum;

(b) the distance between a first pair of points on said periphery of said septum disposed on said longitudinal axis thereof is reduced in said installed configuration relative to said natural configuration by a first compression distance;

(c) the distance between a second pair of points on said periphery of said septum disposed on said lateral axis is reduced in said installed configuration relative to said natural configuration by a second compression distance; and

(d) the ratio of said first compression distance to said distance between said first pair of points in said natural configuration of said septum is equal to the ratio of said second compression distance to said distance between said second pair of points in said natural configuration of said septum.

28. An implantable vascular access port comprising:

(a) an elastomeric, needle-penetrable, generally planar septum having an elongated periphery in a cross section of said septum taken in the plane thereof; and

(b) a needle-impenetrable housing defining;

(i) a fluid reservoir enclosed within said housing;

(ii) a target aperture formed in the exterior of said housing;

(iii) a septum receiving aperture communicating between said target aperture and said fluid reservoir, said septum receiving aperture having a generally elongated rim and extreme ends defining therebetween the maximum extent of said septum receiving aperture, said rim of said septum receiving aperture being geometrically proportional to and smaller than said periphery of said septum, said septum being disposed in said septum receiving aperture with said rim of said septum receiving aperture inwardly displacing said periphery of said septum; and

(iv) a longitudinal fluid passageway communicating between said fluid reservoir and said exterior of said housing through an outlet stem projecting from said housing at a location adjacent one of said extreme ends of said septum receiving aperture.

29. An access port as recited in claim 28, wherein said housing comprises a septum retention lip projecting radially inwardly into said septum receiving aperture from said rim of said septum receiving aperture at the side thereof adjacent said exterior surface of said housing, the edge of said septum retention lip remote from said rim of said septum receiving aperture defining the periphery of said target aperture.

30. An access port as recited in claim 29, wherein said housing comprises a septum support shoulder projecting radially inwardly from said rim of said septum receiving aperture at the side thereof opposite said septum retention lip, the edge of said septum support shoulder remote from said rim of said septum receiving aperture being coincident with the periphery of said fluid reservoir.

31. An access port as recited in claim 30, wherein said edge of said septum support shoulder remote from said rim of said septum receiving aperture is substantially elliptical.

32. An access port as recited in claim 30, wherein said periphery of said septum is compressed between said septum retention lip and said septum support shoulder when said septum is disposed in said septum receiving aperture.

33. An access port as recited in claim 29, wherein said edge of said septum retention lip remote from said rim of said septum receiving aperture is substantially elliptical.

34. An access port as recited in claim 28, wherein the cross section of said septum taken in said plane thereof is substantially elliptical.

35. An access port as recited in claim 28, wherein said target aperture is substantially elliptical in the plane thereof.

36. An access port as recited in claim 28, wherein said septum is comprised of a material having a Shore “

A”

durometer in a range from about 25 to about 85.

37. An access port as recited in claim 28, wherein said septum is comprised of a material having a Shore “

A”

durometer in a range from about 35 to about 75.

38. An access port as recited in claim 28, wherein said septum is comprised of a material having a Shore “

A”

durometer in a range from about 45 to about 65.

39. An access port as recited in claim 28, wherein said septum comprises.

(a) an outer face on the side of said septum oriented to said exterior surface of said housing in an installed configuration of said septum;

(b) an inner face on the side of said septum opposite from said outer face; and

(c) support means integrally formed with said septum for preventing buckling of said septum in said installed configuration thereof.

40. An implantable vascular access port comprising:

(a) a needle-impenetrable housing enclosing a fluid reservoir, said housing comprising;

(i) a base comprising a floor and a continuous encircling sidewall upstanding therefrom, said sidewall terminating in a continuous septum support shoulder remote from said floor, the space interior of said sidewall of said base corresponding to said fluid reservoir of said housing; and

(ii) a cap configured to receive said septum support shoulder and said sidewall of said base, said cap having formed therethrough an access aperture that communicates with said fluid reservoir of said housing when said septum support shoulder and said sidewall of said base are received in said cap, said access aperture having an elongated rim comprising a continuous encircling surface oriented perpendicular to the plane of said access aperture;

(b) an elastomeric, needle-penetrable, generally planar septum, said septum being disposed in and sealing said access aperture in an installed configuration of said septum with the periphery of said septum in continuous engagement with said rim of said access aperture and with the periphery of said septum secured against said septum support shoulder of said sidewall of said base by said cap, said septum when free of externally imposed forces being capable ofassuming a natural configuration wherein said periphery of said septum in a cross section taken in the plane thereof is geometrically proportional to and larger than the rim of said access aperture, whereby in assuming said installed configuration said periphery of said septum is displaced inwardly in said plane of said septum relative to said natural configuration thereof by forces imposed on said periphery of said septum by said rim of said access aperture; and

(c) an outlet stem projecting from said housing and enclosing a longitudinal fluid passageway communicating between the end of said outlet stem remote from said housing through said housing to said fluid reservoir.

41. An access port as recited in claim 40, wherein:

(a) said septum has a longitudinal axis coincident with the maximum extent of said septum in said plane thereof, said longitudinal axis of said septum intersecting said periphery of said septum at respective longitudinal extremes of said septum, said longitudinal extremes of said septum being inwardly displaced from said natural configuration thereof into said installed configuration thereof by substantially equal nonzero first displacements directed parallel to said longitudinal axis of said septum;

(b) said septum has a lateral axis coincident with the maximum extent of said septum in said plane thereof measured perpendicular to said longitudinal axis of said septum, said lateral axis of said septum intersecting said periphery of said septum at respective medial extremes of said septum, said medial extremes of said septum being inwardly displaced from said natural configuration thereof into said installed configuration thereof by substantially equal nonzero second displacements directed parallel to said lateral axis of said septum; and

(c) the ratio of the combination of said first displacements to the distance between said longitudinal extremes of said septum in said natural configuration thereof is equal to the ratio of the combination of said second displacements to the distance between said medial extremes of said septum in said natural configuration thereof.

42. An access port as recited in claim 40, wherein the cross section of said septum taken in said plane thereof is substantially elliptical.

43. An access port as recited in claim 40, wherein said septum comprises:

(a) a substantially planar septum body having an outer face on a side of said septum oriented to the exterior of said housing in said installed configuration of said septum and an inner face on the side of said septum opposite from said outer face;

(b) a needle target dome on said outer face of said septum body; and

(c) a reinforcing dome on said inner face of said septum body.

44. An access port as recited in claim 40, wherein said base and said cap are comprised of plastic.

45. An access port as recited in claim 40, wherein said base and said cap are comprised of metal.

46. An access port as recited in claim 40, wherein said septum is comprised of silicone.

47. An implantable vascular access port comprising:

(a) a needle-impenetrable housing enclosing a fluid reservoir, said housing comprising;

(i) a top wall having formed therethrough an elongated access aperture communicating between said fluid reservoir and the exterior of said housing; and

(ii) a septum support shoulder projecting radially inwardly into said access aperture at the side thereof opposite from said exterior of said housing, the edge of said septum support shoulder remote form said access aperture defining said fluid reservoir whereby said fluid reservoir at said septum support shoulder is smaller than said access aperture at said support shoulder; and

(b) an elastomeric, needle-penetrable, generally planar, elongated septum having a periphery in a cross section of said septum taken in the plan thereof that encloses an area larger than the cross-sectional area of said access aperture, said septum being disposed in said access aperture in an installed configuration thereof wherein forces exerted on said septum by said access aperture inwardly displace said periphery of said septum and produce substantially uniform hydrostatic pressure in the portion of said septum accessible for needle penetration in said installed configuration of said septum, said septum in said installed configuration being precluded from entering said fluid reservoir by said septum support shoulder.

48. An access port as recited in claim 47, wherein said septum comprises:

(a) an outer face on the side of said septum oriented to the exterior of said housing when said septum is disposed in said access aperture;

(b) an inner face on the side of said septum opposite from said outer face; and

(c) a needle target dome on said outer face of said septum.

49. An access port as recited in claim 48, wherein said needle target dome has an eccentricity in a range greater than 0.72.

50. An access port as recited in claim 48, wherein said needle target dome has an eccentricity in a range greater than 0.81.

51. An access port as recited in claim 48, wherein said needle target dome has an eccentricity in a range greater than 0.90.

52. An access port as recited in claim 48, wherein said needle target dome is smaller in extent than said outer face of said septum.

53. An access port as recited in claim 47, wherein said housing comprises:

(a) a base comprising a floor and a continuous encircling sidewall upstanding therefrom, the space interior of said sidewall of said base corresponding to said fluid reservoir of said housing; and

(b) a cap comprising a top wall and a skirt depending therefrom, said cap being configured to receive in said skirt thereof the end of said sidewall of said base remote from said floor thereof, and said access aperture being formed through said top wall of said cap at a location that communicates with said fluid reservoir of said housing when said sidewall of said base is received in said skirt of said cap.

54. An access port as recited in claim 47, wherein said cross section of said septum taken in said plane thereof has an eccentricity in a range greater than about 0.72.

55. An access port as recited in claim 47, wherein said cross section of said septum taken in said plane thereof has an eccentricity in a range greater than about 0.81.

56. An access port as recited in claim 47, wherein said cross section of said septum taken in said plane thereof has an eccentricity in a range greater than about 0.90.

57. An access port as recited in claim 47, wherein said access aperture has an eccentricity in a range greater than about 0.72.

58. An access port as recited in claim 47, wherein said access aperture has an eccentricity in a range greater than about 0.81.

59. An access port as recited in claim 47, wherein said access aperture has an eccentricity in a range greater than about 0.90.

60. An access port as recited in claim 47, wherein:

(a) said septum has a longitudinal axis coincident with the maximum extent of said septum in said plane thereof, and a lateral axis coincident with the maximum extent of said septum in said plane thereof measured perpendicular to said longitudinal axis of said septum;

(b) the distance between a first pair of points on said periphery of said septum disposed on said longitudinal axis thereof is reduced in said installed configuration thereof relative to a natural configuration by a first compression distance;

(c) the distance between a second pair of points on said periphery of said septum disposed on said lateral axis is reduced in said installed configuration relative to said natural configuration by a second compression distance; and

(d) the ratio of said first compression distance to the distance between said first pair of points in said natural configuration of said septum is equal to the ratio of said second compression distance to the distance between said second pair of points in said natural configuration of said septum.

61. An access port as recited in claim 47, wherein said cross section of said septum taken in said plane thereof is substantially elliptical.

62. An access port as recited in claim 47, wherein said cross section of said septum taken in said plane thereof is substantially oval.

63. An access port as recited in claim 47, wherein said septum has a longitudinal axis coincident with the maximum extent of said periphery of said septum in said cross section thereof taken in the plane thereof, said longitudinal axis of said septum intersects said periphery thereof at respective extreme end portions of said septum, and the periphery of each of said extreme end portions of said septum is substantially parabolic.

64. An implantable vascular access port comprising:

(a) a needle-impenetrable housing enclosing a fluid reservoir;

(b) an elastomeric, needle-penetrable, generally planar septum having an elongated periphery in a cross section of said septum taken in the plan thereof;

(c) access means formed in said housing between said fluid reservoir and the exterior of said housing for receiving said septum and for producing substantially uniform hydrostatic pressure in the portion of said septum accessible for needle penetration when said septum is received in said access means; and

(d) an outlet stem projecting from said housing and enclosing a longitudinal fluid passageway extending from the end of said outlet stem remote from said housing through said housing to said fluid reservoir, said outlet stem having a longitudinal axis disposed parallel to said plane of said septum when said septum is received in said access means.

65. An access port as recited in claim 64, wherein said access means comprises:

(a) constriction means for displacing said periphery of said septum radially inwardly in said plane of said septum; and

(b) clamp means for urging toward each other the opposite faces of said septum at said periphery thereof.

66. An access port as recited in claim 65, wherein said constriction means comprises an access aperture communicating between said fluid reservoir and the exterior of said housing, the rim of said access aperture being substantially geometrically proportional to and smaller than said periphery of said septum.

67. An access port as recited in claim 66, wherein said clamp means comprises:

(a) a septum retention lip projecting radially inwardly into said access aperture from the side of said rim thereof adjacent the exterior of said housing; and

(b) a septum support shoulder projecting radially inwardly into said access aperture from the side of said rim opposite said septum retention lip, the distance between said septum retention lip and said septum support shoulder being less than the thickness of said septum between said opposite faces thereof at said periphery thereof.

68. An access port as recited in claim 67, further comprising a first septum gripping ridge projecting from and normal to said bearing surface of said septum retention lip.

69. An access port as recited in claim 68, further comprising a second septum gripping ridge projecting from said septum support shoulder opposite said septum support shoulder.

70. An access port as recited in claim 67, wherein said septum support shoulder comprises a continuous, encircling planar surface.

71. An access port as recited in claim 67, wherein the side of said septum retention lip opposite said septum support shoulder comprises a continuous, encircling planar surface.

72. An access port as recited in claim 64, wherein said access means comprises an access aperture communicating between said fluid reservoir and the exterior of said housing, the rim of said access aperture being substantially geometrically proportional to and smaller than said periphery of said septum, whereby said rim of said access aperture radially inwardly displaces said periphery of said septum when said septum is received in said access aperture.

73. An access port as recited in claim 64, wherein said access means comprises:

(a) an access aperture communicating between said fluid reservoir and the exterior of said housing and having an encircling continuous elongated rim;

(b) a septum retention lip projecting radially inwardly into said access aperture from the side of said rim thereof adjacent said exterior of said housing; and

(c) a septum support shoulder projecting radially inwardly from said rim of said access aperture at the side thereof opposite said septum retention lip, said periphery of said septum being compressed between said septum retention lip and said septum support shoulder, when said septum is received in said access aperture.

74. An access port as recited in claim 64, wherein said periphery of said septum is substantially elliptical.

75. An implantable vascular access port comprising:

(a) a needle-impenetrable housing enclosing a fluid reservoir communicating with the exterior of said housing through an access aperture having a substantially elliptical rim and extreme ends defining therebetween the maximum extent of said access aperture;

(b) an outlet stem projecting from said housing at a location adjacent one of said extreme ends of said access aperture, said outlet stem enclosing a longitudinal fluid passageway extending from the end of said outlet stem remote from said housing through said housing to said fluid reservoir; and

(c) an elastomeric, needle-penetrable, generally planar septum having a periphery in a cross section of said septum taken in the plane thereof that is substantially elliptical and that is larger than said rim of said access aperture, said septum being disposed in said access aperture with said periphery of said septum in sealing engagement with said rim of said access aperture, whereby in disposing said septum in said access aperture, said periphery of said septum is displaced radially inwardly by said rim of said access aperture in a direction parallel to said plane of said septum.

76. An access port as recited in claim 75, wherein said septum exhibits substantially uniform hydrostatic pressure in the portion of said septum accessible for needle penetration, when said septum is disposed in said access aperture.

77. An access port as recited in claim 76, wherein said substantially uniform hydrostatic pressure in the portion of said septum accessible for needle penetration is in a range from about 10 pounds per square inch to about 26 pounds per square inch.

78. An access port as recited in claim 75, wherein said periphery of said septum comprises an elongated polygon.

79. An access port as recited in claim 78, wherein said polygon has at least eight sides.

80. An access port as recited in claim 78, wherein said polygon has at most eight sides.

81. An access port as recited in claim 75, wherein said periphery of said septum is oval in shape.

82. An access port as recited in claim 75, wherein said septum has a longitudinal axis coincident with the maximum extent of said periphery of said septum in said cross section thereof taken in the plane thereof, said longitudinal axis of said septum intersects said periphery thereof at respective extreme end portions of said septum, and the periphery of each of said extreme end portions of said septum is substantially parabolic.

83. An access port as recited in claim 75, wherein said periphery of said septum is a true ellipse.

84. An access port as recited in claim 75, wherein said periphery of said septum is a continuous curve definable by a single mathematical equation.

85. An access port as recited in claim 75, wherein said septum is comprised of a material having a Shore “

A”

durometer in a range from about 45 to about 65.

86. An access port as recited in claim 75, wherein when said septum is disposed in said access aperture, said septum exhibits a substantially uniform needle retention force in a range from about 0.2 pounds to about 3.5 pounds.

87. An access port as recited in claim 75, wherein when said septum is disposed in said access aperture, said septum exhibits a substantially uniform needle retention force in a range from about 0.35 pounds to about 2.5 pounds.

88. An access port as recited in claim 75, wherein when said septum is disposed in said access aperture, said septum exhibits a substantially uniform needle retention force in a range from about 0.5 pounds to about 1.5 pounds.