Device and method for vascular access

Abstract

vascular access systems for performing hemodialysis are disclosed. The vascular access system contemplates a catheter section adapted for insertion into a vein and a graft section adapted for attachment to an artery. The catheter section may have metal or polymer wall reinforcements that allow the use of thin-walled, small outer diameter conduits for the vascular access system. One or more of the adhered, embedded or bonded conduit reinforcement structures may be removable without significant damage to the conduit sections to facilitate attachment of the sections, or to a connector between the sections. Various self-sealing materials are provided for use in the vascular access system, as well as temporary access sites and flow control/sensor systems.

Description

5
Where Q is flow rate, ΔP is the pressure differential, r is the radius of the catheter lumen, η is the viscosity, and 1 is the distance between the pressure measurement points. The equation shows that the flow rate is very sensitive to the radius of the catheter. However, the catheter is relatively non-thrombogenic compared to the graft and therefore one may approximate the flow rate by assuming that the catheter remains at a constant radius. In the preferred embodiment, the flow monitoring components of the VAS comprise an external component and an internal component.

In one embodiment, the external component comprises a power supply, a transmitter, a receiver, a signal processor and a flow readout. The VAS flow monitor may be powered by standard wall outlet electricity or by battery. If standard wall outlet power is used, the power supply regulates the voltage to match the requirements of the other components. The power supply may be used to power both the external device and the internal device. The transmitter comprises an antenna and a tuned circuit that transmits a radio frequency (RF) signal. The RF signal is tuned for optimal coupling to the implanted device in order to transfer power to the implanted device. A receiver is also contained in the external component. The receiver receives the flow signals from the implanted portion of the flow monitor. This antenna is tuned for optimal reception with the output signal of the implanted device. Preferably, the transmitter and receiver would use the same antenna. The signal processor takes the signal from the receiver, analyzes the signals to determine the flow rate, and converts the flow rate into an electronic format so the flow can be displayed by the flow readout. Electronic circuits are well known for converting electronic signals to a format that can be readily displayed. More details of the signal analysis are given below. In other embodiments of the invention, the flow rate information is not converted to an electronic format and instead is displayed on a calibrated analog display. Thus, the flow readout may comprise a standard digital or analog readout that provides a display of the flow value.

The internal or implanted component of the flow monitor comprises a receiver, a flow sensing unit, a signal processor and a transmitter. The receiver receives the RF signal from the external device and uses it to provide power to operate the other components in the implanted device. The preferred shape of the antenna is a coil embedded into the catheter wall. The preferred embodiment of the flow sensing unit comprises a series of individual pressure transducers embedded into the wall of the catheter. In some embodiments, the transducers are embedded into the catheter rather than the graft (ePTFE) because the catheter typically is made of a material (e.g. silicone) that is considerable less thrombogenic than the graft, thus allowing one to assume that the catheter diameter remains constant. One group of pressure transducers are separated by a known distance from another group of transducers by a known distance in order to measure the pressure drop from one portion of the catheter to another portion of the catheter. In one embodiment, each group of pressure transducers comprises one transducer, but in other embodiments, one or more group comprise at least two transducer each, spaced along the circumference, in order to allow averaging for more accurate measurements. Pressure transducer groups with multiple transducers about a circumference may compensate for possible localized pressure variations due to bends in the catheter and other local bias factors.

Although various types of pressure transducers are contemplated for the invention, one of the most common is the strain-gauge transducer. The conversion of pressure into an electrical signal is achieved by the physical deformation of strain gauges which are bonded into the diaphragm of the pressure transducer and wired into a Wheatstone bridge configuration. Pressure applied to the pressure transducer produces a deflection of the diaphragm which introduces strain to the gauges. The strain will produce an electrical resistance change proportional to the pressure. The strain gauges may be covered with a thin, flexible biocompatible material such as silicone or urethane and be positioned on the inside surface of the catheter for maximum sensitivity.

The signal processor for the implantable component takes the signals from each one of the transducers and, in the preferred embodiment, it amplifies, encodes, and multiplexes each signal for transmission by the transmitter so the external component can decode and identify the readings from each of the individual transducers. The electronics may be preferably designed to keep all of the time-dependent information (the pulse waveform) of the signals for analysis by the external system.

In another embodiment, the pressure monitoring system may be used to assess for possible clot formation in the catheter using the temporal information of the pulse waveform to help determine flow rate. For example, if the graft section begins to clot while the catheter remains patent, the absolute pressure in the catheter will drop, the pressure differential between the transducers will also drop, and the waveform shape will change to a less resistive shape (pressure waveform looks more like waveform of the central venous system). The external component of the flow monitoring system will analyze this information and determine the flow rate. On the other hand, if the catheter begins to form clot and the flow slows, the waveform shape will continuously become more resistive with decreased flow. In addition, the pressure differential will increase and the absolute pressure will decrease as the flow decreases. This will occur until the pressure differential reaches a threshold, at this point both pressures will drop with decreased flow. The transmitter is driven by the electronics and preferable uses the receiver antenna to transmit the RF signals to the external device.

While this invention has been particularly shown and described with references to embodiments thereof, it will be understood by those skilled in the art that the various changes in form and details may be made therein without departing from the scope of the invention. For all of the embodiments described above, the steps of the methods need not be performed sequentially. Furthermore, any references above to either orientation or direction are intended only for the convenience of description and are not intended to limit the scope of the invention to any particular orientation or direction.

Claims

1. An apparatus for providing needle access to a blood pathway comprising:

a first fluid conduit comprising a graft conduit configured for attachment to an artery at a proximal end of the first fluid conduit;

a second fluid conduit separate from the first fluid conduit comprising a catheter conduit configured for insertion in a vein at a distal end of the second fluid conduit, the distal end of the second fluid conduit being sized to permit collateral flow of blood around the second fluid conduit and through the vein in which the second fluid conduit is inserted;

a connector element having an internal passageway in fluid communication with the first and second fluid conduits to form a blood pathway, the a first end of the connector element being connected to a distal end of the first fluid conduit and a second end being connected to a proximal end of the second fluid conduit; and

a self-sealing element comprising a wall structure forming, at least in part, a portion of a wall of the second fluid conduit or the connector element, the wall structure being formed of a tubular material that can be punctured by a needle to permit needle access to the blood pathway and that re-seals upon withdrawal of the needle,

wherein the connector element has a transition zone occupying at least a portion of the internal passageway therein, the transition zone being configured to reduce turbulent or non-laminar flow in the blood pathway between the first and second fluid conduits.

2. The apparatus for providing needle access to a blood pathway as in claim 1, wherein the tubular material is selected from the group consisting of: material subject to compressive stress; material having a porous structure enhancing microthrombosis; low durometer materials, thixotropic materials; gelatinous materials; and combinations thereof.

3. The apparatus for providing needle access to a blood pathway as in claim 1, wherein the tubular material comprises material subject to compressive stress.

4. The apparatus for providing needle access to a blood pathway as in claim 1, wherein the tubular material comprises at least two layers subject to compressive stress of different orientations.

5. The apparatus for providing needle access to a blood pathway as in claim 1, wherein the tubular material comprises material having a porous structure.

6. The apparatus for providing needle access to a blood pathway as in claim 1, wherein the tubular material comprises gelatinous material.

7. The apparatus for providing needle access to a blood pathway as in claim 1, wherein the connector element is integrally formed with the second fluid conduit.

8. The apparatus for providing needle access to a blood pathway as in claim 1, wherein the connector element is integrally formed with the first fluid conduit.

9. The apparatus for providing needle access to a blood pathway as in claim 1, further comprising a strain relief tube about the second fluid conduit, the strain relief tube having a first end and a second end, the second end comprising two or more flexural sections and two or more separations between the flexural sections.

10. The apparatus for providing needle access to a blood pathway as in claim 1, further comprising a means for controlling blood flow rate through the blood pathway.

11. The apparatus for providing needle access to a blood pathway as in claim 1, further comprising a means for monitoring blood flow rate through the blood pathway.

12. The apparatus for providing needle access to a blood pathway as in claim 1, wherein the connector element further comprises one or more securing structures for securing the connector element to the first and second fluid conduits.

13. The apparatus for providing needle access to a blood pathway as in claim 12, wherein the securing structure is selected from the group consisting of a clamshell assembly, a tension clips, a collet securing device, a compression ring/collar, one or more barb-like protrusions, and combinations thereof.

14. A vascular access system for hemodialysis comprising:

a catheter conduit having a proximal end and a distal end with a lumen therethrough, wherein the distal end is configured for insertion in a vein and sized to permit collateral flow of blood around a distal end of the catheter conduit and through the vein in which the catheter conduit is inserted;

a connector element having a fluid passageway therethrough, wherein the connector element comprises a first end configured for connection to a distal end of a graft conduit that is separate from the catheter conduit and a second end connected to the proximal end of the catheter conduit; and

a self-sealing element integrally formed with the catheter conduit or connector element, the self-sealing element comprising a wall structure formed of a self-sealing material suitable for puncture by a needle to permit needle access to the fluid passageway and configured to re-seal upon withdrawal of said needle,

wherein the connector element has a different internal diameter at its first and second ends and is configured to provide a smooth transition in the fluid passageway between the proximal end of the catheter conduit and the distal end of the graft conduit.

15. The vascular access system as in claim 14, further comprising a graft conduit connected to the first end of the connector element.

16. The vascular access system as in claim 14, wherein the connector element is integrally formed with the catheter conduit.

17. The vascular access system as in claim 14, wherein the connector element further comprises one or more securing structures for securing the catheter conduit and graft conduit to the connector element.

18. The vascular access system as in claim 17, wherein the securing structure is selected from the group consisting of a clamshell assembly, a tension clips, a collet securing device, a compression ring/collar, one or more barb-like protrusions, and combinations thereof.

19. The vascular access system as in claim 17, wherein the securing structure comprises a clamshell assembly having a pair of complementary connecting structures configured to secure the conduit to the connector element.

20. A vascular access system for hemodialysis comprising:

a graft conduit having a proximal end and a distal end, wherein the proximal end is configured for anastomosis to an artery;

a connector element having a fluid passageway therethrough, wherein the connector element comprises a first end connected to the distal end of the graft conduit and a second end configured for connection to a proximal end of a catheter conduit that is separate from the graft conduit; and

a self-sealing element integrally formed with the graft conduit or connector element, the self-sealing element comprising a wall structure formed of a self-sealing material suitable for puncture by a needle to permit needle access to the fluid passageway and configured to re-seal upon withdrawal of said needle,

wherein the connector element has a different internal diameter at its first and second ends and is configured to provide a smooth transition in the fluid passageway between the distal end of the graft conduit and the proximal end of the catheter conduit.

21. An apparatus for providing needle access to a blood pathway comprising:

a first fluid conduit comprising a graft conduit configured for attachment to an artery at a proximal end of the first fluid conduit;

a second fluid conduit separate from the first fluid conduit comprising a catheter conduit configured for insertion in a vein at a distal end of the second fluid conduit, the distal end of the second fluid conduit being sized to permit collateral flow of blood around the second fluid conduit and through the vein in which the second fluid conduit is inserted;

a connector element having an internal passageway in fluid communication with the first and second fluid conduits to form a blood pathway, the first end of the connector element being connected to a distal end of the first fluid conduit and a second end being connected to a proximal end of the second fluid conduit; and

a self-sealing element comprising a wall structure forming, at least in part, a portion of a wall of the first fluid conduit, the wall structure being formed of a material that can be punctured by a needle to permit needle access to the blood pathway and that re-seals upon withdrawal of the needle,

wherein the connector element has a transition zone occupying at least a portion of the internal passageway therein, the transition zone being configured to reduce turbulent or non-laminar flow in the blood pathway between the first and second fluid conduits.

22. The apparatus for providing needle access to a blood pathway as in claim 21, wherein the material of which the wall structure is formed is tubular.

23. An apparatus for providing needle access to a blood pathway comprising:

a first fluid conduit comprising a graft conduit configured for attachment to an artery at a proximal end of the first fluid conduit;

a second fluid conduit separate from the first fluid conduit comprising a catheter conduit configured for insertion in a vein at a distal end of the second fluid conduit, the distal end of the second fluid conduit being sized to permit collateral flow of blood around the second fluid conduit and through the vein in which the second fluid conduit is inserted; and

a connector element having an internal passageway in fluid communication with the first and second fluid conduits to form a blood pathway, a first end of the connector element being connected to a distal end of the first fluid conduit and a second end being connected to a proximal end of the second fluid conduit,

wherein the connector element has a transition zone occupying at least a portion of the internal passageway therein, the transition zone being configured to reduce turbulent or non-laminar flow in the blood pathway between the first and second fluid conduits.

24. The apparatus for providing needle access to a blood pathway as in claim 23, wherein the connector element comprises one or more securing structures for securing the first fluid conduit and the second fluid conduit to the connector element.

25. The apparatus for providing needle access to a blood pathway as in claim 24, wherein the one or more securing structures comprises a clamshell assembly.

26. The apparatus for providing needle access to a blood pathway as in claim 25, wherein the connector element further comprises a connector having a first end connected to the first fluid conduit and a second end connected to the second fluid conduit, and wherein the clamshell assembly is configured to clamp around a portion of the connector.

27. The apparatus for providing needle access to a blood pathway as in claim 26, wherein the first end of the connector is positioned at an interior of the first fluid conduit, the second end of the connector is positioned at an interior of the second fluid conduit, and the clamshell assembly is positioned at an exterior of one or more of the first fluid conduit and the second fluid conduit when the clamshell assembly is clamped around the portion of the connector.

28. The apparatus for providing needle access to a blood pathway as in claim 25, wherein the connector element further comprises a connector coupled with each of the first fluid conduit and the second fluid conduit, the connector defining one or more reduced diameter portions, and wherein the clamshell assembly comprises one or more radially inwardly extending protrusions that interface with the one or more reduced diameter portions of the connector to secure the first and second fluid conduits onto the connector.

29. The apparatus for providing needle access to a blood pathway as in claim 25, wherein the clamshell assembly is generally C-shaped and comprises a pair of complementary connecting structures that can be joined to close the C-shape and form a tubular structure.

30. The apparatus for providing needle access to a blood pathway as in claim 25, wherein the connector element comprises a connector that defines the internal passageway, and wherein the clamshell assembly comprises a pair of complementary connecting structures that can be joined to secure the first and second fluid conduits to the connector.

31. The apparatus for providing needle access to a blood pathway as in claim 24, wherein the one or more securing structures comprises a tension clip.

32. The apparatus for providing needle access to a blood pathway as in claim 23, wherein the connector element has a different internal diameter at its first and second ends and is configured to provide a smooth transition in the fluid passageway between the distal end of the graft conduit and the proximal end of the catheter conduit.

33. The apparatus for providing needle access to a blood pathway as in claim 32, wherein an internal diameter of the first fluid conduit is larger than an internal diameter of the second fluid conduit.

34. The apparatus for providing needle access to a blood pathway as in claim 23, wherein an internal diameter of the first fluid conduit is larger than an internal diameter of the second fluid conduit.

35. An apparatus for providing needle access to a blood pathway comprising:

a first fluid conduit comprising a graft conduit configured for attachment to an artery at a proximal end of the first fluid conduit;

a second fluid conduit separate from the first fluid conduit comprising a catheter conduit configured for insertion in a vein at a distal end of the second fluid conduit, the distal end of the second fluid conduit being sized to permit collateral flow of blood around the second fluid conduit and through the vein in which the second fluid conduit is inserted;

a strain relief structure configured to resist kinking of the first fluid conduit; and

a connector element having an internal passageway in fluid communication with the first and second fluid conduits to form a blood pathway, a first end of the connector element being connected to a distal end of the first fluid conduit and a second end being connected to a proximal end of the second fluid conduit,

wherein the connector element has a transition zone occupying at least a portion of the internal passageway therein, the transition zone being configured to reduce turbulent or non-laminar flow in the blood pathway between the first and second fluid conduits.

36. The apparatus for providing needle access to a blood pathway as in claim 35, wherein the strain relief structure comprises a flexible coil.

37. The apparatus for providing needle access to a blood pathway as in claim 36, wherein the flexible coil is positioned around an outer surface of the first fluid conduit.

38. The apparatus for providing needle access to a blood pathway as in claim 36, wherein the connector element comprises a connector and a securing structure for securing the first fluid conduit to the connector, wherein the flexible coil is attached to a tubular structure, wherein the tubular structure is positioned around an outer surface of the first fluid conduit, and wherein the securing structure is positioned around an outer surface of the tubular structure and secures the tubular structure and the first fluid conduit onto the connector.

39. The apparatus for providing needle access to a blood pathway as in claim 38, wherein the tubular structure comprises a polymer.

40. The apparatus for providing needle access to a blood pathway as in claim 39, wherein the tubular structure comprises silicone.

41. The apparatus for providing needle access to a blood pathway as in claim 38, wherein the flexible coil is positioned entirely outside of the securing structure when the securing structure secures the tubular structure and the first fluid conduit onto the connector.

42. The apparatus for providing needle access to a blood pathway as in claim 38, wherein the securing structure comprises a clamshell assembly.

43. The apparatus for providing needle access to a blood pathway as in claim 42, wherein the clamshell assembly is generally C-shaped and comprises a pair of complementary connecting structures that can be joined to close the C-shape to form a tube around the tubular structure.

44. The apparatus for providing needle access to a blood pathway as in claim 36, wherein the connector element comprises a connector and a clamshell assembly for securing the first fluid conduit to the connector, wherein the flexible coil is attached to a sleeve that comprises a polymer, wherein the sleeve is positioned around an outer surface of the first fluid conduit, and wherein the clamshell assembly is positioned around an outer surface of the sleeve and secures the sleeve and the first fluid conduit onto the connector.

45. The apparatus for providing needle access to a blood pathway as in claim 35, wherein the strain relief structure is a structure that is separate from the connector element.

46. The apparatus for providing needle access to a blood pathway as in claim 35, wherein the connector element comprises a connector that defines the internal passageway, wherein the first fluid conduit is inserted into the strain relief structure and is positioned over a first end of the connector.

47. The apparatus for providing needle access to a blood pathway as in claim 35, wherein the connector element comprises a securing structure for securing the catheter conduit and the graft conduit to the connector element, and wherein a portion of the strain relief structure is layered between the securing structure and the first conduit and is maintained in position by radial compression from the securing structure.

48. The apparatus for providing needle access to a blood pathway as in claim 47, wherein the securing structure comprises a tubular structure.

49. The apparatus for providing needle access to a blood pathway as in claim 48, wherein the securing structure comprises a connector sleeve.

50. The apparatus for providing needle access to a blood pathway as in claim 48, wherein the strain relief structure comprises a flexible coil.