Vascular access device with arteriovenous fistula support

Abstract

A vascular access device with arteriovenous fistula support includes an upper portion and a lower portion. The upper portion has a partial arterial passage, a partial vascular passage, and a partial arteriovenous junction between the partial arterial passage and the partial vascular passage, wherein the partial vascular passage has a vascular access hole for exposing a blood vessel. The lower portion has a corresponding partial arterial passage, a partial vascular passage, and a partial arteriovenous junction between the partial arterial passage and the partial vascular passage. When the upper portion is coupled to the lower portion, the two partial arterial passages are coupled together to form an arterial passage, the two partial vascular passages are coupled together to form a vascular passage, and the two partial arteriovenous junctions are coupled together to form an arteriovenous junction for an arteriovenous fistula.

Description

Background Art

[0001] Typically, when a person loses most of their kidney function, dialysis is needed to perform some of the kidney's functions. That is, dialysis removes waste products, salts, and excess water from the blood to prevent toxic buildup in the body. Dialysis also helps maintain safe levels of chemicals in the blood (such as potassium, sodium, and biocarbonates), as well as helping to control a person's blood pressure. About 500,000 Americans receive dialysis treatment alone.

[0002] The most common dialysis method is hemodialysis. In hemodialysis, blood is removed from the patient's blood vessels, flows through a dialysis machine that acts as an artificial kidney, and then returns to the patient's blood vessels. Typically, in hemodialysis, an arteriovenous (AV) fistula is established to provide appropriate blood pressure and blood flow within the patient's blood vessels. An AV fistula is a connection between an artery and a blood vessel, usually established in the arm through surgery. Surgical establishment of an AV fistula is the preferred mode of vascular access for long-term vascular dialysis treatment and is more favored by Medicare than other options. An AV fistula causes an increase in flow and pressure within a blood vessel, which becomes an access point for the dialysis needle. In fact, the closer the access point in the blood vessel is to the AV fistula itself, the better the blood flow. After surgery, an average waiting period of 60 days is required for the fistula to mature before use.

[0003] In approximately 40% of cases, the AV fistula is unusable and requires subsequent surgery. Approximately 33% of cases require a transposition surgery, which is required when the vessel is too deep in the arm to access. After a usable AV fistula is established, patients and caregivers are still challenged with "good access" every time there is a dialysis treatment, which is performed at least 3 times a week. The access vessel must be accurately aimed, sometimes requiring the use of two 15-gauge needles for access. Poor puncture is common and, in the most severe cases, can result in massive blood loss and fistula collapse (approximately 5.2% of patients have massive infiltration, which is a result of poor puncture and often leads to the disappearance of the AV fistula). In addition, most AV fistulas only last about three years, mainly due to failure due to excessive and poor punctures. Failed AV fistula sites require additional surgical or radiological interventions to recover. If recovery is unsuccessful, a new AV fistula needs to be established at a different location.

[0004] In some cases, the increased blood flow through the blood vessels due to the AV fistula can cause the blood vessels to enlarge over time, which further increases the blood flow through the blood vessels. Too much blood flowing through the AV fistula and into the blood vessels can deprive the outer limbs, which are supplied by arteries, of adequate blood, causing pain and discomfort to the patient. Too much blood flowing through the AV fistula and into the blood vessels can also send too much blood directly to the heart, causing heart problems, including heart failure. Summary of the invention

[0005] A vascular access device with arteriovenous fistula support is provided. An arteriovenous fistula is typically required to supply sufficient blood flow and blood pressure to support hemodialysis of a patient's blood. The vascular access device provides a location for withdrawing blood from a blood vessel near the artery (and thus has sufficient blood flow and blood pressure to support hemodialysis of the patient's blood), and provides structural support for the blood vessel, artery, and arteriovenous fistula to prevent damage. Advantageously, the described vascular access device can protect the AV fistula, and thus prevent invasive surgery and unnecessary surgery, or at least minimize the likelihood of invasive surgery and unnecessary surgery, and prevent too much blood from flowing through the AV fistula, which can cause heart problems and / or insufficient blood reaching the patient's outer extremities.

[0006] The vascular access device with arteriovenous fistula support may include an upper portion and a lower portion coupled together. The upper portion has a partial arterial channel for receiving the upper half of the artery, a partial vascular channel for receiving the upper half of the blood vessel, and a partial arteriovenous joint for receiving the upper half of the arteriovenous fistula between the partial arterial channel and the partial vascular channel. The partial vascular channel of the upper portion includes a vascular access hole for exposing the blood vessel so that blood can be withdrawn from the blood vessel. The lower portion has a partial arterial channel for receiving the lower half of the artery, a partial vascular channel for receiving the lower half of the blood vessel, and a partial arteriovenous joint for receiving the lower half of the arteriovenous fistula between the partial arterial channel and the partial vascular channel. When the upper portion is coupled to the lower portion, the partial arterial channel of the upper portion and the partial arterial channel of the lower portion are coupled to each other to form an arterial channel, the partial vascular channel of the upper portion and the partial vascular channel of the lower portion are coupled to each other to form a vascular channel, and the partial arteriovenous joint of the upper portion and the partial arteriovenous joint of the lower portion are coupled to form an arteriovenous joint for the arteriovenous fistula.

[0007] In some instances, the partial arterial channel of the upper portion and the partial arterial channel of the lower portion are semi-cylindrical, and when the upper portion is coupled to the lower portion, the semi-cylindrical arterial channel of the upper portion and the semi-cylindrical arterial channel of the lower portion are coupled to each other to form a cylindrical arterial channel. In some instances, the partial vascular channel of the upper portion and the partial vascular channel of the lower portion are semi-cylindrical, and when the upper portion is coupled to the lower portion, the semi-cylindrical vascular channel of the upper portion and the semi-cylindrical vascular channel of the lower portion are coupled to each other to form a cylindrical vascular channel. In some instances, the partial arterial channel and the partial vascular channel are all semi-cylindrical such that the arterial channel and the vascular channel are both cylindrical.

[0008] In some instances, a partial blood vessel passage of a lower portion is elongated relative to a partial blood vessel passage of an upper portion such that when a dialysis needle is inserted into a blood vessel at an angle relative to the surface of a patient's skin, the needle does not rupture or damage the posterior wall of the blood vessel (i.e., does not completely pass through the blood vessel and exit from the other side). In some instances, a blood vessel access hole is elongated parallel to a patient's blood vessel such that when a dialysis needle is inserted into the blood vessel at an angle relative to the surface of the patient's skin, the needle does not rupture or damage the posterior wall of the blood vessel (i.e., does not completely pass through the blood vessel and exit from the other side).

[0009] In some instances, surfaces of the upper portion and the lower portion are porous to allow collagen to form around the upper portion and the lower portion after implantation into a patient. In some instances, a guiding edge of a blood vessel access hole including a partial blood vessel passage of the upper portion is provided to assist in guiding a dialysis needle into a correct position required for dialysis treatment.

[0010] In some implementations, a blood vessel passage of a blood vessel access device is curved toward an arteriovenous junction, while an arterial passage of the blood vessel access device is straight. In some implementations, an arterial passage of the blood vessel access device is curved toward the arteriovenous junction, while a blood vessel passage of the blood vessel access device is straight. In some implementations, both the arterial passage and the blood vessel passage are curved toward the arteriovenous junction. In some implementations, both the arterial passage and the blood vessel passage are straight.

[0011] In some implementations, an angle between a vertical axis perpendicular to a blood vessel access hole of the device and an axis extending through a center point of the blood vessel passage and the arterial passage is greater than 45 degrees. In some implementations, an angle between a vertical axis perpendicular to a blood vessel access hole of the device and an axis extending through a center point of the blood vessel passage and the arterial passage is between 30 degrees and 45 degrees. In some implementations, an angle between a vertical axis perpendicular to a blood vessel access hole of the device and an axis extending through a center point of the blood vessel passage and the arterial passage is less than 30 degrees.

[0012] In some implementations of establishing an end-to-side AV fistula, a blood vessel passage is perpendicular to an arterial passage and an arteriovenous junction is disposed at a position where the arterial passage abuts the blood vessel passage.

[0013] A method of using a vascular access device may include: creating an incision to insert the vascular access device; positioning a portion of the arterial access of a lower portion of the vascular access device around a lower half of an artery and positioning a portion of the vascular access of the lower portion of the vascular access device around a lower half of a blood vessel; positioning a portion of the arterial access of an upper portion of the vascular access device around an upper half of an artery and positioning a portion of the vascular access of the upper portion of the vascular access device around an upper half of a blood vessel to couple the upper portion to the lower portion; closing the incision used to insert the vascular access device and allowing tissue surrounding the vascular access device to heal; and, after the incision has healed, establishing an AV fistula between the artery and the blood vessel without decoupling the upper portion of the vascular access device from the lower portion of the vascular access device.

[0014] This Summary is provided to introduce a selection of concepts in a simplified form that are further described below in the Detailed Description. This Summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1A Angled views of an example vascular access device with side-to-side arteriovenous fistula support are shown.

[0016] Figure 1B A cross-sectional view of a vascular access device housing a portion of a patient's artery, blood vessel, and AV fistula is shown.

[0017] Figures 2A - 2D Various embodiments of example vascular access devices with side-to-side arteriovenous fistula support are shown.

[0018] Figure 3A An exploded view of an example vascular access device with side-to-side arteriovenous fistula support is shown.

[0019] Figure 3B A cut-away front view of an example vascular access device with side-to-side arteriovenous fistula support is shown.

[0020] Figure 3C A side view of an upper portion of an example vascular access device with side-to-side arteriovenous fistula support is shown.

[0021] Figure 3D A top view of a lower portion of an example vascular access device with side-to-side arteriovenous fistula support is shown.

[0022] Figure 3E A side view of a lower portion of an example vascular access device with side-to-side arteriovenous fistula support is shown.

[0023] Figure 4is based on Figures 3A - 3E an image of a vascular access device implanted in a goat.

[0024] Figure 5 is a view of a blood vessel and an artery after formation of a side-to-side arteriovenous fistula.

[0025] Figure 6A shows an angled view of a vascular access device with a side-to-side arteriovenous fistula support, where the blood vessel and the artery are not parallel to each other with respect to the surface of the patient's skin.

[0026] Figure 6B shows a side view of a vascular access device with a side-to-side arteriovenous fistula support, where the blood vessel and the artery are not parallel to each other with respect to the surface of the patient's skin.

[0027] Figure 6C and Figure 6D shows a cross-sectional view of a vascular access device with a side-to-side arteriovenous fistula support, where the blood vessel and the artery are not parallel to each other with respect to the surface of the patient's skin.

[0028] Figure 6E shows a poor puncture in a vascular access device with a side-to-side arteriovenous fistula support, where the blood vessel and the artery are not parallel to each other with respect to the surface of the patient's skin.

[0029] Figure 7 shows two needles in the blood vessel, one upstream and one downstream, as they are during dialysis.

[0030] Figure 8 shows an angled view of a vascular access device with two vascular access holes.

[0031] Figure 9A and Figure 9B shows an exemplary vascular access device with a vascular access hole offset from the AV fistula.

[0032] Figure 10A is a view of a blood vessel and an artery after formation of an end-to-side arteriovenous fistula.

[0033] Figure 10B shows a top view of a vascular access device with an end-to-side arteriovenous fistula support.

[0034] Figure 10C shows a bottom view of an upper portion of a vascular access device with an end-to-side arteriovenous fistula support.

[0035] Figure 11 shows a top view of a vascular access device with a side-to-side arteriovenous fistula support around an arterial graft and a blood vessel.

[0036] Figure 12 Disclosed is a method of implanting a vascular access device and subsequently creating an AV fistula. DETAILED DESCRIPTION

[0037] A vascular access device with arteriovenous fistula support is provided. An arteriovenous fistula is generally required to supply sufficient blood flow rate and blood pressure to support hemodialysis of a patient's blood. The vascular access device provides a location for withdrawing blood from a blood vessel near the artery (and thus has sufficient blood flow rate and blood pressure to support hemodialysis of the patient's blood), and provides structural support for the blood vessel, artery, and arteriovenous fistula to prevent damage. Advantageously, the described vascular access device can protect the AV fistula, and thus prevent invasive surgeries and redundant surgeries, or at least minimize the possibility of invasive surgeries and redundant surgeries, and prevent too much blood from flowing through the AV fistula, which can cause heart problems and / or insufficient blood reaching the outer limbs of the patient.

[0038] As used herein, "successful cannulation" or "good puncture" means when a needle / cannula is placed in a blood vessel to provide vascular access and the needle / cannula does not damage any tissue more than is necessary for it to be placed in the blood vessel.

[0039] As used herein, "unsuccessful cannulation" or "poor puncture" means when a needle / cannula damages more tissue than is necessary for it to be placed in the blood vessel, regardless of whether the needle / cannula is actually placed in the blood vessel and / or enters the AV fistula and / or artery. Examples of poor puncture include when the needle / cannula penetrates the blood vessel and exits through the posterior wall of the blood vessel, or when the blood vessel is completely missed, both of which can damage the blood vessel and / or the tissue surrounding the blood vessel, and cause collapse of the blood vessel and / or AV fistula, and cause blood loss into the surrounding tissue and formation of a hematoma. Another example of poor puncture includes when the needle / cannula enters an artery, which can be dangerous if any air (e.g., air bubbles) from the needle / cannula enters the artery, which can cause an air embolism.

[0040] As used herein, referring to a portion of a device as "curved" or having "curvature" means that a portion of the device has a deviation that is generally consistent with a straight line relative to a plane perpendicular to the lower surface of the device.

[0041] As used herein, "semicylindrical" refers to an object having a shape with a cylindrical cross-section (of a cylindrical surface), where the intersecting plane of the cylinder forms the overall shape of a horizontal cylindrical segment. However, the shape of a semicylindrical does not require the cylindrical cross-section of the cylindrical surface to be presented as formed by a single plane. For example, the cross-section perpendicular to the axis of a semicylindrical shape can be presented as a pie-shaped / sector-shaped.

[0042] As used herein, "junction" refers to the connection and / or material absence between a vascular channel and an arterial channel, which may or may not include the structure surrounding the connection and / or material absence.

[0043] As used herein, "side-by-side" means that the sides of a blood vessel and the side of an artery (or another blood vessel) are adjacent and / or close to each other. As used herein, "end-to-side" means that the end of a blood vessel is adjacent to the side of an artery (or another blood vessel).

[0044] As used herein, "artery" may refer to an actual artery or an arterial graft.

[0045] Figure 1A An angled view of an exemplary vascular access device having a side-by-side arteriovenous fistula support is shown; and Figure 1B A cross-sectional view of a vascular access device accommodating a portion of a patient's artery, blood vessel, and AV fistula is shown. Referring Figure 1A and Figure 1B , the vascular access device 100 includes an upper portion 102 and a lower portion 104 that are coupled together to form a vascular channel 110 and an arterial channel 120. The vascular channel 110 may surround a blood vessel 115, and the arterial channel 120 may surround an artery 125. Of course, two blood vessels instead of a blood vessel and an artery may be surrounded in the channels 110, 120 if the practitioner so chooses.

[0046] The vascular channel 110 provides structural support and external protection for the patient's blood vessel 115. By providing structural support and external protection for the patient's blood vessel 115, the vascular channel 110 prevents adverse punctures (e.g., through the posterior wall of the blood vessel 115), which also reduces the amount of trauma to the patient's blood vessel 115 and reduces subsequent scarring and stenosis of the blood vessel 115. The vascular channel 110 also includes a vascular access hole 112 that extends parallel to the patient's blood vessel. The vascular access hole 112 provides easy access for dialysis needles to achieve good puncture of the patient's blood vessel and limits the risk of infection by using the skin as a natural barrier against pathogens. In fact, the vascular access hole 112 provides a larger surface area for good puncture compared to other devices or no device at all. This allows for good puncture at different locations along the surface of the patient's skin, which helps prevent skin rupture and gives the patient's skin a chance to heal.

[0047] The arterial channel 120 provides structural support and external protection for the patient's artery 125. By providing structural support and external protection for the patient's artery 125, the arterial channel 120 prevents the artery from being punctured or damaged (e.g., by adverse puncture of the blood vessel).

[0048] An AV fistula 130 can be formed between the blood vessel 115 and the artery 125 and is enclosed in the AV junction 135. The blood vessel channel 110 and the artery channel 120 can be of any shape suitable for accommodating the blood vessel and the artery, and thus, although the channels 110, 120 are shown as cylindrical, the cross-section perpendicular to the axis of the cylinder does not need to be a perfect circle or ellipse. In fact, in other instances, the cross-sectional shape of the channels 110, 120 can be of any shape and / or size to completely enclose the portions of the blood vessel 115 and the artery 125 near the AV fistula 130.

[0049] In the illustrated example, the blood vessel channel 110 curves towards the artery channel 120. However, as Figures 2A - 2D shown, various configurations of straight and curved channels can be implemented.

[0050] In some instances, the surface of the device 100 is porous. After implanting the device 100 into a patient, the pores in the device 100 allow collagen (i.e., scar tissue) to form around the upper portion 102 and the lower portion. The porosity of the device 100 allows ingrowth of fibrovascular tissue that adheres to the device 100. The fibrovascular tissue allows the body to mount an immune response to any bacteria introduced during needle cannulation and prevents bacterial implantation on the surface of the device 100. The porosity of the channels 110, 120 allows collagen to integrate into the blood vessel wall and the artery wall, thereby biologically and mechanically supporting them. The collagen formed around the blood vessels and into the porous channels 110, 120 serves as a scaffold to help keep the blood vessels and arteries open. Collagen also helps prevent the blood vessels from collapsing due to repeated punctures and weakening of the blood vessel wall and establishes a biological seal across the blood vessel access hole 112. The porosity of the device 100 can include spaces / pores with sizes ranging from one nanometer up to almost 1 millimeter. In some implementations, the pores can have a size range or a specific size, with the range or specific size being 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, and / or 800 microns. The porosity of the surface of the device 100 provides radial support to the patient's blood vessels and helps keep them open during needle entry into the blood vessels. It should be noted that the pores are small enough to prevent the passage of the needle through the surface of the device 100. The surface of the device 100 (with pores) can be formed by sintering metal beads (such as titanium beads) or metal powder onto the surface, machining, sandblasting, laser etching, injection molding, and / or 3D printing. It should also be noted that in some instances, all surfaces of the device 100 that are exposed to human tissue are porous.

[0051] In some instances, some or all of the device 100 is made of biocompatible plastics, metals, or ceramics, such as titanium, polyetheretherketone (PEEK), alumina, stainless steel, polyvinyl chloride, etc. In some instances, some or all of the device 100 is made of radiopaque and / or radiolucent materials. This can assist the surgeon if any subsequent surgery is needed (e.g., creating an AV fistula after implanting the device 100). For example, radiopaque and / or radiolucent markers can be fixed to the device 100 such that the surgeon and / or interventionalist implanting / modifying / accessing the device 100 can see the device in various imaging modalities. Radiopaque and / or radiolucent markers can be used to identify suitable sites for fluid withdrawal and / or injection.

[0052] Figures 2A - 2D Illustrates various embodiments of an exemplary vascular access device having side-by-side arteriovenous fistula support. Figure 2A Illustrates a vascular access device 200, where the vascular channel 202 of the vascular access device 200 curves toward the arteriovenous junction 204, while the arterial channel 206 of the vascular access device 200 is straight. Figure 2B Illustrates a vascular access device 210, where both the vascular channel 212 and the arterial channel 216 curve toward the arteriovenous junction 214. Figure 2C Illustrates a vascular access device 220, where the arterial channel 226 of the vascular access device 220 curves toward the arteriovenous junction 224, while the vascular channel 222 of the vascular access device 220 is straight. Figure 2D Illustrates a vascular access device 230, where both the vascular channel 232 and the arterial channel 236 are straight, with the arteriovenous junction 234 supported therebetween. This embodiment may be advantageous in situations where the artery and vein are already close enough to each other to create an AV fistula without moving the vein or artery (e.g., 5 to 10 millimeters).

[0053] Figure 3A Illustrates an exploded view of an exemplary vascular access device having side-by-side arteriovenous fistula support; Figure 3B Illustrates a pre-sectioned front view of an exemplary vascular access device having side-by-side arteriovenous fistula support; Figure 3C Illustrates a side view of an upper portion of an exemplary vascular access device having side-by-side arteriovenous fistula support; Figure 3D Illustrates a top view of a lower portion of an exemplary vascular access device having side-by-side arteriovenous fistula support; Figure 3E Illustrates a side view of a lower portion of an exemplary vascular access device having side-by-side arteriovenous fistula support; and Figure 4 is according to Figures 3A - 3E an image of a vascular access device implanted in a goat. Refer to Figure 3A, the vascular access device 300 includes an upper portion 310 and a lower portion 320. As Figure 3A and Figure 3C can be seen, the upper portion 310 includes a partial vascular channel 312 for receiving the upper half of a blood vessel, a partial arterial channel 314 for receiving the upper half of an artery, a partial arteriovenous junction (not shown in the figure), and a vascular access hole 318. As Figure 3A , Figure 3D and Figure 3E can be seen, the lower portion 320 includes a partial vascular channel 322 for receiving the lower half of a blood vessel, a partial arterial channel 324 for receiving the lower half of an artery, and a partial arteriovenous junction 326. The partial vascular channel 312, partial arterial channel 314, and partial arteriovenous junction (not shown) of the upper portion 310 correspond to the partial vascular channel 322, partial arterial channel 324, and partial arteriovenous junction 326 of the lower portion 320. When the upper portion 310 is coupled to the lower portion 320, these partial channels form a vascular channel (e.g., Figure 4 's vascular channel 330) and an arterial channel (e.g., Figure 4 's arterial channel 340). In addition, when the upper portion 310 is coupled to the lower portion 320, the partial arteriovenous junction forms an arteriovenous junction (see Figure 3B 's arteriovenous junction 350).

[0054] In some instances, the partial vascular channel 312 of the upper portion 310 and the partial vascular channel 322 of the lower portion 320 are semi-cylindrical. Thus, when the upper portion 310 is coupled to the lower portion 320, the partial vascular channel 312 of the upper portion 310 and the partial vascular channel 322 of the lower portion 320 are coupled to each other to form a cylindrical vascular channel. In some instances, the partial arterial channel 314 of the upper portion 310 and the partial arterial channel 324 of the lower portion 320 are semi-cylindrical. Thus, when the upper portion 310 is coupled to the lower portion 320, the partial arterial channel 314 of the upper portion 310 and the partial arterial channel 324 of the lower portion 320 are coupled to each other to form a cylindrical arterial channel. In some instances, the partial vascular channels 312, 322 and the partial arterial channels 314, 324 are all semi-cylindrical, such that the arterial channel and the vascular channel are both cylindrical.

[0055] As Figure 3BAs shown, when the upper portion 310 and the lower portion 320 are coupled to each other, an arteriovenous junction 350 is formed. When implanted, the arteriovenous junction 350 provides structural support around the arteriovenous fistula. The arteriovenous junction 350 can protect the fistula from being punctured or otherwise damaged by the insertion of a needle. The arteriovenous junction 350 can be any suitable shape as long as the shape allows blood to travel from the artery to the blood vessel through the arteriovenous fistula.

[0056] In addition, because the puncture (through the vascular access hole) is very close to the AV fistula, a very high blood flow rate (e.g., about 400 ml / min) and blood pressure are provided (compared to standard hemodialysis performed through a blood vessel that is relatively far from the AV fistula). This allows the patient and / or technician performing hemodialysis to reduce the volume required by the pump or possibly eliminate the pump required for normal hemodialysis. This is because the blood, in the artery rather than in a blood vessel not connected to the artery via the AV fistula, is naturally pressurized and pumped by the patient's heart. In other words, compared to a blood vessel without an AV fistula or even a blood vessel with an AV fistula but not relatively close to the AV fistula, the blood flow rate and blood pressure in a blood vessel directly connected to the AV fistula and relatively close to the AV fistula will be greater.

[0057] Reference Figure 3A and Figure 4 When the vascular access device 300 is implanted, the lower portion 320 is positioned away from the surgeon implanting the device 300, where a portion of the vascular channel 322 of the lower portion 320 is placed around the lower portion of the patient's blood vessel 331, and a portion of the arterial channel 324 is placed around the lower portion of the patient's artery 341. The upper portion 310 is positioned close to the surgeon implanting the device 300 such that the vascular access hole 318 is arranged parallel to the surface of the patient's skin (and is accessible). Once implanted, the upper portion 310 can be coupled to the lower portion 320 by any available means and within the standards required by the surgeon.

[0058] Advantageously, when the upper portion 310 is coupled to the lower portion 320, the structure of the upper portion 310 and the lower portion 320 around the blood vessel prevents improper punctures or at least minimizes the chance of improper punctures by preventing the needle from entering areas of the patient that are not desired to be entered. In addition, the porous surface of the device 300 allows the device 300 to integrate into the surrounding tissue, which allows the body to mount an immune response to any bacteria introduced during needle cannulation. Integrating the device into the surrounding tissue removes the bare surface on which bacteria can grow and form a biofilm.

[0059] Figure 5View of the blood vessel and artery after formation of a side-to-side arteriovenous fistula. The device (not shown in this figure) surrounds the blood vessel 510 and the artery 520. During (or before or after) implantation of the device, an AV fistula 530 is established. In fact, the device can be implanted around an existing AV fistula (e.g., in order to "preserve" the existing AV fistula). In other instances, the device can also be implanted and an AV fistula established after implantation of the device (e.g., in order to allow the device time to adhere to the surrounding tissue; see the corresponding method regarding Figure 12 . In still other instances, the device can be implanted when the AV fistula is established (e.g., during the same surgical procedure). In any instance, an AV fistula 530 is established and can be completely surrounded by the device such that a dialysis needle (or any other type of needle) cannot penetrate the AV fistula 530. This allows for good access to the patient's blood vessel 510 (e.g., through the blood vessel access holes of the device) without fear of damaging the AV fistula 530. Additionally, as explained above and below, the device also completely surrounds the artery 520 and all parts of the blood vessel 510 except for the portion that is exposed through the blood vessel access holes of the device (which is the portion of the blood vessel 510 closest to the surface of the patient's skin).

[0060] In some patients, depending on the part of the body where the AV fistula 530 is established and the physiological condition of the individual patient, the blood vessel 510 may be close to the surface of the patient's skin while the artery 520 may be far from the surface of the patient's skin (i.e., relative to the surface of the patient's skin, the artery 520 is below the blood vessel 510). Thus, as explained below regarding Figures 6A - 6E , the position of the blood vessel access device can be arranged such that the upper part of the blood vessel access holes is in a position close to the surface of the patient's skin as allowed by the patient's physiological condition. In other words, the position of the blood vessel access holes of the blood vessel access device can be individualized for each patient such that the device can be positioned around the patient's blood vessel and artery using the least invasive method of implanting the device and / or the convenient position of the blood vessel and artery.

[0061] Figure 6A An angled view of a blood vessel access device with a side-to-side arteriovenous fistula support is shown, where the blood vessel and artery are not parallel to each other relative to the surface of the patient's skin; Figure 6B A side view of a blood vessel access device with a side-to-side arteriovenous fistula support is shown, where the blood vessel and artery are not parallel to each other relative to the surface of the patient's skin. As Figure 6A can be seen, the device 600 surrounds a portion of the blood vessel 602 and a portion of the artery 604 on both sides leading to the AV fistula. The artery 604 is close to the surface of the patient's skin (not shown in the figure), and the blood vessel 602 is far from the surface of the patient's skin. Thus, the device 600 provides an artery passage 606 positioned below and to the side of the blood vessel passage 608.

[0062] AsFigure 6B As can be seen, the blood vessel 602 is positioned relatively close to / near the surface of the patient's skin 610 (allowing for good puncture through the vascular access hole 612), while the artery 604 is positioned further below / further away from the surface of the patient's skin 610. In fact, in this example, the artery 604 is transposed (e.g., during implantation of the device 600) to be closer to the surface of the patient's skin 610, but is transposed along the shortest path because the artery passage 606 is below and / or offset from the vascular passage 608. In this way, the surgeon performing the transposition surgery on the artery 604 does not have to move the artery 604 as far as possible in the vertical direction relative to the surface of the patient's skin 610, as would be required for artery passages 606 and artery passage 608 that are parallel to each other relative to the surface of the patient's skin 610. This also provides another advantage for the patient because the surgeon performing the transposition surgery does not have to move the artery 604 as much as possible in the horizontal direction relative to the surface of the patient's skin 610 to prevent the artery 604 from kinking, as would be required for artery passages 606 and vascular passage 608 that are parallel to each other relative to the surface of the patient's skin 610. It should be understood that in some cases where the artery 604 is deeper below the patient's skin 610 than the blood vessel 602, due to the offset between the artery passage 606 and the vascular passage 608 in this embodiment, transposition surgery may not be required at all.

[0063] Figure 6C and 6D shows a cross-sectional view of a vascular access device with side-to-side arteriovenous fistula support, where the blood vessel and the artery are not parallel to each other relative to the surface of the patient's skin. In Figure 6C , the angle 620 between the vertical axis 622 perpendicular to the vascular access hole 624 of the device 626 and the axis 628 extending through the center point 630 of the vascular passage 634 and the center point 632 of the artery passage 636 is 45 degrees. It can be seen that the angle 620 is large enough to prevent poor puncture.

[0064] In Figure 6D , the angle 640 between the vertical axis 642 perpendicular to the vascular access hole 644 of the device 646 and the axis 648 extending through the center point 650 of the vascular passage 654 and the center point 652 of the artery passage 656 is 30 degrees. It can be seen that the angle 640 is not large enough to prevent poor puncture (e.g., as described below in Figure 6E654). Thus, a technician or patient using the device may use a needle that is not able to reach a depth sufficient to access the AV fistula 658 / arterial passage 656 (e.g., due to an external device or shortened needle length), or may have to be extra careful not to insert the needle to a depth sufficient to cause an undesirable puncture. In some instances, an external device (not shown) may be used to position the needle for insertion into the vascular passage 654 at an angle and / or length that does not result in an undesirable puncture.

[0065] It should be understood that Figure 6C and 6D The angles 620, 640 shown in the figures are merely examples relevant to the embodiments shown in these figures. Furthermore, the range of angles that are not sufficiently large to prevent an inappropriate puncture may vary between different vascular access devices, as a sufficient angle is also a function of the width of the vascular access hole. Thus, in other embodiments, Figure 6D The angle 640 may be large enough to prevent undesirable punctures.

[0066] Figure 6E A poor puncture in a vascular access device with a side-to-side arteriovenous fistula support is shown, where the blood vessel and artery are not parallel to each other relative to the surface of the patient's skin. Figure 6E As can be seen in the figure, an undesirable puncture is formed when needle 670 enters device 672 through vascular access hole 674, continues through vascular channel 676 and AV fistula 678, and enters arterial channel 680. This is an undesirable puncture because when needle 670 enters arterial channel 680, if any air (e.g., air bubbles) from needle 670 enters artery 682, an air embolism may form, which can block the flow of blood further downstream of AV fistula 678, resulting in poor circulation in the distal limb. It should also be understood that in all examples, the vascular access device prevents undesirable punctures where the needle passes out of the end of the vascular channel.

[0067] Figure 7 Two needles are shown in a blood vessel, one upstream and one downstream, as they would be during dialysis. It can be seen that the upstream needle 702 and the downstream needle 704 are inserted through the vascular access hole 706 of the device 700 and into the patient's blood vessel 708. The needles 702, 704 can be taped to the patient's skin after being inserted into the blood vessel 708, or can be left in place. Figure 7The positions shown in [Fig. 0] depend on the preferences of the patient undergoing dialysis treatment and / or the technician. Once inserted, the upstream needle 702 "withdraws" blood from a high-pressure position in the blood vessel 708 adjacent to the AV fistula. The downstream needle 704 is inserted into a position downstream of the upstream needle 702 in the blood vessel 708. Notably, the upstream needle 702 withdraws the patient's blood, which is cleaned in the dialysis machine, and the cleaned blood returns to the patient's blood vessel 708 via the downstream needle 704. The return of the cleaned blood downstream of the withdrawn (dirty) blood prevents the recirculation of the patient's blood. The efficiency of the recirculation of the patient's blood is very low and results in dialysis taking longer to complete because at least some of the already cleaned blood will be re-cleaned in the dialysis machine in a basically endless cycle. Therefore, the dialysis machine does not clean (dirty) blood as much as possible because the dialysis machine can only clean so much blood at a time.

[0068] In addition, because the needles 702, 704 draw blood (via the vascular access holes) so close to the AV fistula, a very high blood flow rate and blood pressure are provided (compared to standard hemodialysis performed through blood vessels relatively far from the AV fistula). This allows the patient undergoing dialysis treatment and / or the technician to reduce the capacity required by the pump or possibly eliminate the pump required for normal hemodialysis treatment. This is because the blood, in the artery 710, rather than in a normal blood vessel, is naturally pressurized and pumped by the patient's heart; the blood vessel 708 is directly connected to the artery 710 through the AV fistula, thereby generating a pressure and flow rate in the blood vessel 708 similar to those in the artery 710.

[0069] Figure 8 An angled view of a vascular access device having two vascular access holes is shown. It can be seen that the device 800 includes an upstream vascular access hole 802 and a downstream vascular access hole 804. This design may be particularly useful in instances where external devices and / or markings are used to identify each vascular access hole 802, 804 beneath the patient's skin. By having separate vascular access holes 802, 804 for the upstream and downstream needles (e.g., Figure 7 the needles 702 and 704), the patient undergoing dialysis treatment and / or the technician may be less likely to confuse the needles (and thus prevent recirculation). Another advantage of the two vascular access holes 802, 804 is that the patient can have more confidence in correctly performing the dialysis treatment, which is often an obstacle for patients performing home dialysis treatment themselves.

[0070] Figure 9A and Figure 9B shows a vascular access device having vascular access holes offset from the arteriovenous junction. Figure 9A Arc-shaped channel openings (910, 911) for each channel are shown; and Figure 9BAn alternative opening (912) configuration is shown. It can be seen that each of the devices 900A, 900B includes a vascular access hole 902 that is downstream and offset from the arteriovenous junction 904. The vascular access hole 902 and the AV junction 904 can be offset such that their cross-sections do not overlap.

[0071] In cases where the doctor and / or patient are very concerned about AV fistula damage, the offset design may be useful. In fact, because the vascular access hole 902 is offset from the AV fistula / arteriovenous junction 904, the possibility of AV fistula damage due to poor puncture is further reduced. In addition, due to the reduced possibility of AV fistula damage caused by poor puncture, the patient may be more confident in performing home dialysis treatment on their own. It should also be understood that, except for those that are inconsistent with the devices and techniques described with respect to Figure 9A and Figure 9B the same features described with respect to Figures 1A to 8 can be present in the devices 900A, 900B shown in Figure 9A and Figure 9B .

[0072] Figure 10A is a view of the blood vessel and artery after end-to-side arteriovenous fistula formation; Figure 10B shows a top view of a vascular access device with an end-to-side arteriovenous fistula support; Figure 10C shows a bottom view of the upper part of a vascular access device with an end-to-side arteriovenous fistula support. The vascular access device 1010 surrounds the blood vessel 1020 and the artery 1030. In this embodiment, during (or before or after) the implantation of the device 1010, an AV fistula 1040 is established by cutting the blood vessel 1020 and attaching it directly to the artery 1030. It can be seen that the blood vessel 1020 is attached to the artery 1030 in an approximately vertical manner, so the device 1010 is T-shaped (instead of the H-shaped, X-shaped, or K-shaped described in Figures 2A - 2D ). Here, the blood vessel channel is perpendicular to the artery channel, and the arteriovenous junction is arranged at the position where the artery channel and the blood vessel channel are adjacent.

[0073] In any instance, the AV fistula 1040 is established and can be completely surrounded by the device 1010, such that a dialysis needle (or any other type of needle) does not penetrate the AV fistula 1040. This allows the needle to provide a good puncture of the patient's blood vessel 1020 through the vascular access hole 1070 of the device 1010 without worrying about damaging the AV fistula 1040.

[0074] During implantation of the device 1010, the upper portion 1012 and the lower portion 1014 of the device 1010 are coupled together to form a vascular channel 1050 and an arterial channel 1060. The vascular channel 1050 can surround the blood vessel 1020, and the arterial channel 1060 can surround the artery 1030. The vascular channel 1050 provides structural support and external protection for the patient's blood vessel 1020. By providing structural support and external protection for the patient's blood vessel 1020, the vascular channel 1050 prevents adverse punctures, which also reduces the amount of trauma to the patient's blood vessel 1020 and reduces subsequent scar formation and stenosis of the blood vessel 1020. The vascular channel 1050 also includes a vascular access hole 1070 that extends parallel to the patient's blood vessel 1020. The vascular access hole 1070 provides easy access for a dialysis needle to achieve good puncture of the patient's blood vessel 1020 and limits the risk of infection by using the skin as a natural barrier against pathogens. In fact, the vascular access hole 1070 provides a larger surface area for good puncture compared to other devices or no device at all. This allows for good puncture at different positions along the surface of the patient's skin, which helps prevent skin rupture and gives the skin a chance to heal.

[0075] The arterial channel 1060 provides structural support and external protection for the patient's artery 1030. By providing structural support and external protection for the patient's artery 1030, the arterial channel 1060 prevents the artery 1030 from being punctured or damaged (e.g., by adverse puncture of the blood vessel 1020).

[0076] An AV fistula 1040 can be formed by connecting the end of the blood vessel 1020 and the side of the artery 1030. The AV fistula 1040 is completely surrounded by the device 1010. The vascular channel 1050 and the arterial channel 1060 can be any shape suitable for accommodating the blood vessel 1020 and the artery 1030. Thus, although the channels 1050, 1060 are shown as cylindrical, the cross-section perpendicular to the axis of the cylinder does not need to be a perfect circle or ellipse. In fact, in other instances, the cross-sectional shape of the channels 1050, 1060 can be any shape and / or size to completely surround the portions of the blood vessel 1020 and the artery 1030 near the AV fistula 1040.

[0077] In some instances, the surface of the device 1010 is porous. As explained above with respect to Figure 1A and Figure 1B after the device 1010 is implanted into the patient, the holes in the device 1010 allow collagen (i.e., scar tissue) to form around the upper portion 1012 and the lower portion 1014. In some instances, all surfaces of the device 1010 that are exposed to human tissue are porous.

[0078] It should be understood that in addition to those related toFigures 10A - 10C Except for those in which the described devices and techniques are inconsistent, with respect to Figures 1A to 9B the same features described may be present in Figure 10B and Figure 10C the devices shown in. It should also be noted that blood flow in artery 1030 enters blood vessel 1020, as Figure 10A and Figure 10C shown in.

[0079] Figure 11 A top view of a vascular access device having a side-to-side arteriovenous fistula support around an arterial graft and a blood vessel is shown. Similar to the vascular access device described above, the vascular access device 1100 includes an arterial channel 1102 and a blood vessel channel 1104 having a vascular access hole 1106. Specifically, the upper and lower portions of the vascular access device 1100 are coupled together to form the blood vessel channel 1104 that surrounds the blood vessel 1110 and the arterial channel 1102 that surrounds the arterial graft 1120. In this example, the arterial graft 1120 is attached to the artery 1122 at an upstream point and a downstream point such that some of the blood flow from the artery 1122 will flow into the arterial graft 1120 at the upstream point and return to the artery 1122 at the downstream point. Because the arterial graft 1120 does not have as much blood flow as the artery 1122 itself, the use of the arterial graft 1120 can further reduce the potential problems that lead to heart problems and / or insufficient blood reaching the outer limbs of the patient, while the vascular access device 1100 still provides structural support for the blood vessel, artery, and arteriovenous fistula to prevent damage. In some examples, the arterial graft 1120 is made of polytetrafluoroethylene (PFTE). In some examples, the arterial graft 1120 is made of a blood vessel surgically removed from another part of the body. It should be understood that the arterial graft 1120 can be made of any material that is safely used as an artificial blood vessel.

[0080] Figure 12 A method of implanting a vascular access device and subsequently establishing an AV fistula is shown. Referring to Figure 12, Method 1200 includes: creating an incision to insert the vascular access device 1202; positioning a partial arterial passage of the lower portion of the vascular access device around the lower half of the artery and positioning a partial vascular passage of the lower portion of the vascular access device around the lower half of the blood vessel 1204; positioning a partial arterial passage of the upper portion of the vascular access device around the upper half of the artery and positioning a partial vascular passage of the upper portion of the vascular access device around the upper half of the blood vessel to couple the upper portion to the lower portion 1206; closing the incision for inserting the vascular access device and allowing the tissue around the vascular access device to heal 1208; and after the incision has healed, establishing an AV fistula between the artery and the blood vessel without decoupling the upper portion of the vascular access device from the lower portion of the vascular access device 1210.

[0081] Certain aspects of the present invention provide the following non-limiting embodiments:

[0082] Example 1. A vascular access device, comprising: an upper portion having a partial arterial passage for receiving the upper half of an artery, a partial vascular passage for receiving the upper half of a blood vessel, and a partial arteriovenous junction between the partial arterial passage and the partial vascular passage, the partial vascular passage having a vascular access hole for exposing the blood vessel; and a lower portion having a partial arterial passage for receiving the lower half of the artery, a partial vascular passage for receiving the lower half of the blood vessel, and a partial arteriovenous junction between the partial arterial passage and the partial vascular passage; wherein, when the upper portion is coupled to the lower portion: the partial arterial passage of the upper portion and the partial arterial passage of the lower portion are coupled to each other to form an arterial passage; the partial vascular passage of the upper portion and the partial vascular passage of the lower portion are coupled to each other to form a vascular passage; and the partial arteriovenous junction of the upper portion and the partial arteriovenous junction of the lower portion are coupled to form an arteriovenous junction for an arteriovenous fistula.

[0083] Example 2. The vascular access device of Example 1, wherein the partial arterial passage of the upper portion and the partial arterial passage of the lower portion are semi-cylindrical; wherein when the upper portion is coupled to the lower portion, the semi-cylindrical arterial passage of the upper portion and the semi-cylindrical arterial passage of the lower portion are coupled to each other to form a cylindrical arterial passage.

[0084] Example 3. The vascular access device of Example 1 or 2, wherein the partial vascular passage of the upper portion and the partial vascular passage of the lower portion are semi-cylindrical; wherein when the upper portion is coupled to the lower portion, the semi-cylindrical vascular passage of the upper portion and the semi-cylindrical vascular passage of the lower portion are coupled to each other to form a cylindrical vascular passage.

[0085] Example 4. The vascular access device of any of the foregoing examples, wherein the partial vascular passage of the lower portion is elongated relative to the partial vascular passage of the upper portion.

[0086] Example 5. The vascular access device of any one of the preceding examples, wherein the vascular access holes extend parallel to the length of the patient's blood vessel.

[0087] Example 6. The vascular access device of any one of the preceding examples, wherein the surfaces of the upper portion and the lower portion are porous to allow collagen to form around the upper portion and the lower portion after implantation.

[0088] Example 7. The vascular access device of any one of the preceding examples, wherein the blood vessel channel curves towards the arteriovenous junction.

[0089] Example 8. The vascular access device of any one of the preceding examples, wherein the arterial channel curves towards the arteriovenous junction.

[0090] Example 9. The vascular access device of any one of Examples 1-6, wherein the blood vessel channel extends perpendicular to the arterial channel; and wherein the arteriovenous junction is arranged at the position where the arterial channel abuts the blood vessel channel.

[0091] Example 10. The vascular access device of any one of the preceding examples, wherein the angle between the vertical axis perpendicular to the vascular access holes and the axis extending through the center points of the blood vessel channel and the arterial channel is greater than 45 degrees.

[0092] Example 11. The vascular access device of any one of Examples 1-9, wherein the angle between the vertical axis perpendicular to the vascular access holes and the axis extending through the center points of the blood vessel channel and the arterial channel is between 30 degrees and 45 degrees.

[0093] Example 12. The vascular access device of any one of Examples 1-9, wherein the angle between the vertical axis perpendicular to the vascular access holes and the axis extending through the center points of the blood vessel channel and the arterial channel is less than 30 degrees.

[0094] Example 13. The vascular access device of any one of the preceding examples, wherein the arteriovenous junction is offset from the vascular access holes.

[0095] Example 14. A method of using a vascular access device of any of the foregoing examples, comprising: creating an incision to insert the vascular access device; positioning a partial arterial passage of a lower portion of the vascular access device around a lower half of an artery, and positioning a partial vascular passage of the lower portion of the vascular access device around a lower half of a blood vessel; positioning a partial arterial passage of an upper portion of the vascular access device around an upper half of the artery, and positioning a partial vascular passage of the upper portion of the vascular access device around an upper half of the blood vessel to couple the upper portion to the lower portion; closing the incision for inserting the vascular access device and allowing the tissue around the vascular access device to heal; and after the incision has healed, establishing an AV fistula between the artery and the blood vessel without decoupling the upper portion of the vascular access device from the lower portion of the vascular access device.

[0096] Although the subject matter has been described in language specific to structural features and / or acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the above specific features and acts are disclosed as examples for implementing the claims, and other equivalent features and acts are intended to be within the scope of the claims.

Claims

1. A vascular access device, comprising: an upper portion having a partial arterial passage for receiving an upper half of an artery, a partial vascular passage for receiving an upper half of a blood vessel, and a partial arteriovenous junction between the partial arterial passage and the partial vascular passage, the partial vascular passage having a vascular access hole for exposing the blood vessel; and a lower portion having a partial arterial passage for receiving a lower half of the artery, a partial vascular passage for receiving a lower half of the blood vessel, and a partial arteriovenous junction between the partial arterial passage and the partial vascular passage; wherein when the upper portion is coupled to the lower portion: the partial arterial passage of the upper portion and the partial arterial passage of the lower portion are coupled to each other to form an arterial passage; the partial vascular passage of the upper portion and the partial vascular passage of the lower portion are coupled to each other to form a vascular passage; and the partial arteriovenous junction of the upper portion and the partial arteriovenous junction of the lower portion are coupled to form an arteriovenous junction for an arteriovenous fistula, wherein the upper portion and the lower portion are separable from each other.

2. The vascular access device according to claim 1, wherein, the partial arterial passage of the upper portion and the partial arterial passage of the lower portion are each semi-cylindrical; and wherein when the upper portion is coupled to the lower portion, the semi-cylindrical partial arterial passage of the upper portion and the semi-cylindrical partial arterial passage of the lower portion are coupled to each other to form a cylindrical arterial passage.

3. The vascular access device according to claim 1, wherein, the partial vascular passage of the upper portion and the partial vascular passage of the lower portion are each semi-cylindrical; and wherein when the upper portion is coupled to the lower portion, the semi-cylindrical partial vascular passage of the upper portion and the semi-cylindrical partial vascular passage of the lower portion are coupled to each other to form a cylindrical vascular passage.

4. The vascular access device according to claim 1, wherein, the partial arterial passage of the upper portion, the partial arterial passage of the lower portion, the partial vascular passage of the upper portion, and the partial vascular passage of the lower portion are each semi-cylindrical; wherein when the upper portion is coupled to the lower portion, the semi-cylindrical partial arterial passage of the upper portion and the semi-cylindrical partial arterial passage of the lower portion are coupled to each other to form a cylindrical arterial passage, and the semi-cylindrical partial vascular passage of the upper portion and the semi-cylindrical partial vascular passage of the lower portion are coupled to each other to form a cylindrical vascular passage.

5. The vascular access device according to claim 1, wherein, the partial vascular passage of the lower portion is elongated relative to the partial vascular passage of the upper portion.

6. The vascular access device according to claim 1, wherein, the vascular access hole extends parallel to the length of the patient's blood vessel.

7. The vascular access device according to claim 1, wherein, the surfaces of the upper portion and the lower portion are porous to allow collagen to form around the upper portion and the lower portion after implantation.

8. The vascular access device according to claim 1, wherein, the vascular passage curves toward the arteriovenous junction.

9. The vascular access device according to claim 1, wherein, the arterial passage curves toward the arteriovenous junction.

10. The vascular access device according to claim 1, wherein, both the vascular passage and the arterial passage curve toward the arteriovenous junction.

11. The vascular access device according to claim 1, wherein, The blood vessel channel extends perpendicular to the artery channel; and wherein the arteriovenous junction is disposed at a position where the artery channel abuts the blood vessel channel.

12. The vascular access device according to claim 1, wherein, The angle between the vertical axis perpendicular to the blood vessel access hole and the axis extending through the center points of the blood vessel channel and the artery channel is greater than 45 degrees.

13. The vascular access device according to claim 1, wherein, The angle between the vertical axis perpendicular to the blood vessel access hole and the axis extending through the center points of the blood vessel channel and the artery channel is between 30 degrees and 45 degrees.

14. The vascular access device according to claim 1, wherein, The angle between the vertical axis perpendicular to the blood vessel access hole and the axis extending through the center points of the blood vessel channel and the artery channel is less than 30 degrees.

15. The vascular access device according to claim 1, wherein, The arteriovenous junction is offset from the blood vessel access hole.

16. The vascular access device according to claim 1, wherein, When the upper portion is coupled to the lower portion: The artery channel has two ends and an intermediate portion disposed between the two ends, and the artery channel is open outward at each end; The blood vessel channel has two ends and an intermediate portion disposed between the two ends, and the blood vessel channel is open outward at each end; The arteriovenous junction connects the intermediate portion of the artery channel and the intermediate portion of the blood vessel channel and communicates the artery channel with the blood vessel channel.

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