Vascular Access Tube

Abstract

A vascular access tube (2) for a fluid subject to a driving pressure comprises a wall (4) defining a main lumen. A portion of the wall comprises an access port (10) for an object (14) to be introduced through the wall. The access port comprises a biasing structure (12) which provides a self-closing behaviour that is sufficiently strong to remain fluid-tight when exposed to a driving pressure of up to 50 mmHg. The access port is therefore sufficiently fluid-tight to contain pressurised fluid flowing through the vascular access tube.

Claims

1. An arterial access graft for blood subject to a driving pressure, the arterial access graft being configured for surgical attachment to an axillary artery and for providing access to the axillary artery via an access port, the arterial access graft comprising a wall defining a main lumen, wherein a portion of the wall comprises the access port into the graft through the wall, wherein the access port comprises a biasing structure providing a self-closing behaviour sufficiently strong to remain fluid-tight when exposed to a driving pressure of up to 50 mmHg (0.0658 atm) or higher, whereby the access port is sufficiently fluid-tight to contain pressurised blood flowing through the arterial access graft.

2. The arterial access graft according to claim 1, wherein the biasing structure comprises a self-sealing membrane and/or a valve.

3. The arterial access graft according to claim 2, wherein the self-closing behaviour of the biasing structure is stronger than that of the wall.

4. The arterial access graft according to claim 1, wherein the access port comprises an access arm comprising an access lumen, the access arm extending from the wall.

5. The arterial access graft according to claim 4, wherein the access lumen has a smaller diameter than the main lumen.

6. The arterial access graft according to claim 4, wherein the biasing structure is positioned to seal an end of the access arm distal to the main lumen of the arterial access graft.

7. The arterial access graft according to claim 1, wherein the main lumen comprises a partition structure extending along at least a portion of the length of the graft to separate the main lumen into at least two passages, wherein, optionally, the cross-section of one of the passages is greater than another passage.

8. The arterial access graft according to claim 7, wherein the access port joins into one passage.

9. The arterial access graft according to claim 7, wherein the partition structure is collapsible and/or flexible.

10. The arterial access graft according to claim 4, wherein the access arm extends at an angle of at least 10°, 20°, 30°, or at least 45° from the wall of the arterial access graft.

11. A blood removal assembly suitable for removing blood from a left ventricular cavity, the assembly comprising an arterial access graft as defined in claim 1, and a catheter dimensioned to fit through the access port of the arterial access graft, the catheter being of sufficient length to extend from outside the access port beyond an end of the arterial access graft.

12. The blood removal assembly according to claim 11, wherein the catheter comprises a connector so as to be suitable for connection to a flow control device to be provided, wherein, optionally, the connector is a Luer connector.

13. (canceled)

14. The blood removal assembly according to claim 11, wherein the assembly further comprises a removable guide wire of sufficient length to extend through the arterial access graft, for guiding the catheter.

15. The blood removal assembly according to claim 11, wherein the assembly further comprises a flow sensor configured to measure a flow value representative of a flow rate of fluid flowing through the catheter.

16. (canceled)

17. The blood removal assembly according to claim 15, further comprising a controller configured to obtain the flow value and to modulate flow control parameters of a flow control device in response to the flow value.

18. (canceled)

19. A method of accessing the luminal side of an axillary artery through the wall of an arterial access graft comprising an access port in accordance with claim 1, the method comprising: attaching the arterial access graft to the axillary artery, traversing the access port with an object such as a catheter, and inserting the object through the access port beyond a distal end of the arterial access graft.

20. The method according to claim 19, comprising: using a guide wire to insert the object through the access port and beyond the distal end of the arterial access graft, and withdrawing the guide wire.

21. The method according to claim 19, wherein the object is a catheter, the method comprising using a flow control device to apply a driving pressure to the catheter to withdraw fluid via a distal end of the catheter.

22. The method according to claim 21, comprising: using a flow sensor to measure a flow value representative of the flow rate of fluid flowing through the catheter, and modulating flow control parameters of the flow control device in response to the flow value.

23. The method according to claim 19, comprising: removing the object from the vascular access tube, and manually shutting the access port.

24. (canceled)

25. (canceled)

Description

SUMMARY OF THE FIGURES

[0092] The present invention will now be described by way of example and with reference to the following figures:

[0093] FIG. 1A shows a schematic side view of a vascular access tube in accordance with an embodiment;

[0094] FIG. 1B shows the FIG. 1A embodiment in an assembly with an additional component;

[0095] FIG. 2 shows a cross-sectional view across the line X-X of the tube of FIG. 1B;

[0096] FIG. 3 shows a cross-sectional view of a vascular access tube in accordance with another embodiment;

[0097] FIG. 4 shows a schematic illustration of the FIG. 1B embodiment in a blood removal system; and

[0098] FIG. 5 shows steps of a method of using a vascular access tube in accordance with an embodiment.

DETAILED DESCRIPTION

[0099] FIG. 1A shows a side view of a vascular access tube 2. The vascular access tube comprises a wall 4 which has a generally tubular cross-section defining a main lumen. The tube 2 has a first end 6 and a second end 8. Extending from an outer side of the wall 4 of the tube 2 is an access arm 10 that is tubular and which provides the access port of the tube. The access arm 10 has a first end connected to the wall 4 of the vascular tube, such that the lumen of the access arm 10 is in fluid communication with the lumen of the vascular access tube 2. A second end of the access arm 10 is distal to the lumen of the vascular access tube and constitutes a free end. In the absence of any barriers, the free end of the access arm 10 provides a passage into the main lumen of the vascular access tube 2 through the wall 4, without requiring access from either the first end 6 or the second end 8. The fluid passage leads from the distal end through the access arm 10 and through the first end through an aperture in the wall 4 where the access arm joins the main lumen, and into the vascular access tube 2.

[0100] The access arm 10 extends at an angle alpha (α) from the wall 4. In the present embodiment angle α is approximately 45°, but other angles can be envisaged. The vascular access tube 2 and the access arm 10 may be flexible and so the angle α may vary in practice.

[0101] The access arm 10 extends from a portion of the wall 4 closer to the first end 6 than the second end 8, such that the access port, in this embodiment the access arm 10, is positioned off-centre.

[0102] Also shown in FIG. 1A is a collapsible wall 26 extending part-way along the main lumen and separating the main lumen into a first passage 22 and a second passage 24. The collapsible wall 26 is optional.

[0103] A self-sealing membrane 12 providing a biasing structure with self-closing behaviour is located at the free end of the access arm 10. It will be appreciated that in other embodiments, the self-sealing membrane 12 can be positioned to reversibly close the end of the access arm 10 proximal to the vascular access tube 2, i.e. at or near to the junction between the access arm 10 and the vascular access tube 2. Alternatively, the membrane 12 can be positioned at any site along the length of the access arm 10. In embodiments without access arm 10 the self-sealing membrane 12 may be directly on the wall 4.

[0104] Instead of a self-sealing membrane 12, other suitable structures may be provided, such as a valve, such as a haemostatic valve. The self-sealing property of the membrane 12 allows it to be punctured, for instance with a catheter to be provided, while remaining fluid-tight. This allows the main lumen to be accessed when fluid at driving pressures up to 50 mmHg or higher is flowing through the main lumen.

[0105] FIG. 1B schematically shows the vascular access tube 2 of FIG. 1A with a catheter 14 inserted through the membrane 12 with the help of a guide wire 16. It will be appreciated that an object other than the catheter 14 may be inserted into the lumen. With the catheter 14 (or other object) inserted, the self-sealing properties of the membrane 12 cause the membrane 12 to draw together around the catheter 14 and thereby provide a seal around the a catheter 14 that is sufficiently fluid-tight to reduce, and practically prevent, the risk of pressurised fluid spraying from the main lumen toward the outside. In practice, a small amount of leakage may be tolerable. The membrane 12 practically avoids any spraying of pressurised blood flowing through the tube 2 that would be observed when piercing the wall 4. Once the catheter 14 (or other object) is removed, the self-sealing membrane 12 closes to seal the aperture so that the membrane is sufficiently fluid-tight to maintain the sealed characteristic of the wall 4. Seals and valve structures (such as duck-bill valves) are known in the art that are sufficiently fluid-tight to prevent fluid loss particularly of blood flowing at pressures and at flow rates typically expected in a patient during surgery.

[0106] FIG. 1B shows the catheter 14 inserted into the self-sealing membrane 12, through the access arm 10, through the second passage 24 of the main lumen, and through and beyond the second end 8. In FIG. 1B, a distal end 15 of the catheter 14 protrudes outside the second end 8 to indicate that the distal end 15 protrudes beyond the end of the vascular access tube 2. It will be understood that a suitably long catheter may extend much further beyond the vascular access tube. As such, with a sufficiently long catheter 14, practically any point of the lumen of the vascular access tube 2, as well as a region beyond the vascular access tube 2 can be accessed by the catheter 14. This is achieved without requiring access through the first end 6 of the vascular access tube 2. It will be appreciated that the membrane 12 continues to maintain a fluid-tight seal as it gathers around the catheter 14, while a fluid passage into and out of the lumen from the access port is provided via the catheter 14.

[0107] In the present embodiment the access arm 10 is a separate component to the vascular access tube 2, the access arm 10 having being joined to the vascular access tube such that the lumen of the access arm 10 is in fluid communication with the lumen of the vascular access tube 2. However, it will be appreciated that the access arm 10 may be integral with the vascular access tube 2.

[0108] As shown in FIGS. 1A and 1B, the diameter of the access arm 10 is smaller than the diameter of the main passage of the vascular access tube. It will, however, be appreciated that other diameters and diameter differences can be envisaged. For instance, the access arm 10 may have the same diameter as the vascular access tube.

[0109] In the present embodiment, the access arm 10 and the vascular access tube are formed of the same flexible material. A suitable flexible material is dacron. In other embodiments, the access arm 10 and the vascular access tube may be formed of different flexible material, both being formed of the same material or different.

[0110] FIG. 2 shows a cross-sectional view across the line X-X of the tube of FIG. 1B, in a plane perpendicular to the axis of the main lumen, approximately at the joint of the access arm 10 with the vascular access tube 2. The same numerals are used in FIG. 2 as for corresponding elements in FIG. 1 and the description of corresponding parts is not necessarily repeated. FIG. 2 also shows, in section, the catheter 14 which extends (through the plane of the section of FIG. 2) along the access arm 10 and within the collapsible wall 26 of the vascular access tube 2.

[0111] FIG. 3 shows a cross-section across the line Y-Y of the tube of FIG. 1B. The same numerals are used in FIG. 3 for corresponding structures in the other Figures. The FIG. 3 cross section is taken further along of the main lumen of the vascular access tube 2 and does not show the access arm 10. FIG. 3 shows more clearly that the lumen 16 of the vascular access tube 20 is separated into a first passage 22 and a second passage 24 by an internal partition structure, in this embodiment a collapsible wall 26. The first passage 22 has a greater cross-section than the second passage 24, e.g. at a ratio 1:2 or 1:3. Other suitable ratios between the cross-sections may be used.

[0112] Only the second passage 24 is in fluid communication with the access arm 10 (not shown in FIG. 3). The first passage 22 is fluidly isolated from the access arm due to the internal partition structure. As such, the catheter 14 is not exposed to fluid flowing through the first passage 22. It will be understood that the first passage 22 may or may not be fluidly isolated depending on the wall structures defining the first and second passages 22, 24. In some embodiments, no internal partition structure is provided.

[0113] The smaller second passage 24 serves as a guide channel for the catheter 14. The second passage 24 may be sealed against the first end 6 such that no fluid from the first end 6 enters the second passage 24. Thereby, any object inserted into the second passage is not directly exposed to the fluid in the first passage 22.

[0114] If no object is inserted in to the second passage 24 then the collapsible wall 26 may collapse, due to the fluid pressure in the first passage 22, against the inner surface of the wall 4. In that case, the cross-section of the first passage 22 corresponds practically to the cross-section of the wall 4.

[0115] In use, the vascular access tube 2 is attached (anastomosed) with the second end 8 into or onto the vessel of a subject, such that the second end 8 is implanted into or onto the vessel of the subject. A portion of the access arm 10 may remain external to the subject.

[0116] In the absence of a catheter 14, the vascular access tube 2 provides a passage from the first end 6 to the second end 8 whose main lumen is practically fluid isolated from the outside. The access arm 10 is sealed by the seal 12 in a sufficiently fluid-tight manner to maintain the fluid isolation of the vascular access tube 2.

[0117] If, after implantation of the vascular access tube 2, it is necessary to have access to the patient's vessel, this can be achieved as follows. The first and second ends 6, 8 may no longer be accessible from the outside. Furthermore, it may not be practical to open the wall 4 of the vascular access tube 2, because it may be practically impossible to restore its fluid-tight property. This is the case particularly for arterial access grafts, as these have to withstand high driving pressure.

[0118] However, by way of the self-sealing membrane 12, a mechanism is provided to allow access into the main lumen of the vascular access tube and/or to organs beyond the second end 8. The self-sealing membrane 12 can be traversed by an object suitable for the procedure, for example, the catheter 14 as shown in FIG. 1B. The catheter 14 is inserted through the self-sealing membrane 12, into the access arm 10 and further pushed into the vascular access tube such that the catheter 14 extends beyond the second end 8 of the vascular access tube and into the vessel of the patient.

[0119] The self-sealing nature of the membrane ensures that the membrane maintains a fluid-tight seal with the catheter 14 such that fluid access to the lumen of the tube is possible via the catheter 14.

[0120] FIG. 4 shows the device of FIG. 1B as part of a blood removal system, with the catheter 14 introduced into the vascular access tube 2. The same numerals are used in FIG. 4 for corresponding elements in the preceding Figures. In FIG. 4, the guide wire (cf. FIG. 1B) has been removed.

[0121] At the outer (distal) end of the catheter 14, there is a connector 30 (illustrated schematically) for connection to a flow control device 32 (illustrated schematically). The catheter 14 may also comprise an integral flow sensor 36 (illustrated schematically) or a flow sensor that is operationally linked with the flow path through the catheter 14. Prior to or after insertion of the catheter 14, the connector 30 is inserted to or operationally linked to the flow control device 32, for example an arterial pump. The pump may be a roller pump or a centrifugal pump, to name two examples. The flow control device 32 may be a controller of a low-pressure or “vacuum”-induced flow mechanism.

[0122] Once the catheter is introduced into the vessel of the patient and the flow control device 32 is connected, the flow control device 32 applies a negative pressure to the catheter 14. This generates suction which serves to pull blood out of the vessel, or an area such as the left ventricle, of the patient into and through the catheter 14 so that the blood can be removed. This is especially beneficial in left ventricular assist procedures, where a build-up of stagnant or clotted blood in the left ventricle of the subject can, otherwise, risk complications, and which needs to be carried out while the heart continuously supplied by oxygenated blood at the necessary driving pressures.

[0123] As the blood flows through the catheter, the flow rate may be measured by the integral flow sensor 36. The flow rate may be provided to a controller 34 (illustrated schematically) as an input. This may be provided as part of a closed loop control. For instance, to maintain the blood flow at a pre-determined threshold, if the flow rate is below the pre-determined threshold the flow control device 32 may be controlled by the controller 34 to increase the negative pressure (such that a stronger suction is applied). If the flow rate is above the pre-determined threshold the flow control device 32 may be controlled by the controller 34 to decrease the negative pressure (such that a weaker suction is applied).

[0124] As such, the controller 34 may include a control loop allowing the flow rate through the access arm 10 to be modulated in response to temporary fluctuations. The control loop allows the flow through the catheter to be maintained at a pre-determined level.

[0125] This allows a closed-loop control to be provided of the amount of blood removed from the left ventricular cavity. For instance, in practice, a clinician may determine a suitable flow rate target level at which blood should be continuously removed from the left ventricular cavity. The flow rate target level may be low to reduce any stress on the patient by maintaining a steady removal of fluid.

[0126] A processor of the controller 34 may determine the volume of blood removed from the left ventricular cavity, either from deriving this from a flow sensor 36 or from a reservoir into which the blood is collected. The amount of blood in a reservoir may be determined by a level sensor. The volume of blood may be indicative of aortic valve condition. The processor may determine the total volume of blood removed during a procedure or the volume of blood removed per unit time.

[0127] FIG. 5 shows steps of a method 50 of using a vascular access tube. In step 52, an arterial access tube, such as vascular access tube 2, is provided. The vascular access tube comprises a self-sealing membrane 12 or a valve to provide an access port. In step 54, the arterial access tube is inserted into a blood vessel. This step may involve implanting on anastomosing the arterial access tube onto a blood vessel. In step 56, a catheter 14 is introduced via the access port into the arterial access tube. In step 58, an end of the catheter is introduced beyond an end of the arterial access tube. In step 60, a driving pressure is applied to the catheter. The driving pressure is sufficiently strong to suck fluid from the distal catheter tip to remove fluid. This procedure may be used to remove stagnant blood from the left ventricular cavity. In an optional step 62, the driving pressure is modulated, for instance in response to a flow sensor measurement, to ensure the flow rate through the catheter is close to or at a target flow value. In an optional step 64, the catheter is removed from the arterial access tube. This may be necessary due to an occlusion of the catheter. In optional step 66, a non-occluded catheter is provided. This may involve removing an occlusion from the catheter. This may involve providing a new catheter. The method may be continued at step 56 by inserting the non-occluded catheter via the access port into the arterial access tube.

[0128] The vascular access tube of the invention, once implanted or attached, provides repeated access via the walls of the vascular access tube without having to open up other portions of the body. For instance, even during routine blood-removal operation with a pigtail catheter, it is possible that the catheter tip is occluded by blood or blood clots. In that event, the present vascular access tube allows removal of the catheter, cleaning or replacing the catheter, and inserting a non-occluded catheter to continue with the blood removal procedure. This catheter replacement may be carried out while blood is flowing through the arterial access graft at the required driving pressure. As such, the access port of the invention may be used for other procedures.