Shunt with blood flow indicator

Abstract

To provide an apparatus for shunting blood.SOLUTION: An apparatus (20) for shunting blood (22) includes a flow-indication chamber (24) shaped to define an entry port (26) and an exit port (28), and one or more moveable objects (46) disposed within the flow-indication chamber (24) and configured to move in response to a flowing of the blood (22) from the entry port (26) to the exit port (28). At least a portion of a wall (52) of the flow-indication chamber (24) is transparent so as to expose the moveable objects (46) to sight. Other embodiments are also described.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to medical procedures such as shunting a subject's blood from one blood vessel to another. [Background technology]

[0002] In some procedures, blood is shunted from one blood vessel to another. Summary of the Invention [Means for solving the problem]

[0003] According to some embodiments of the present invention, there is provided a device for shunting blood. The device includes a flow rate indicating chamber shaped to define an inlet port and an outlet port, and one or more movable bodies disposed within the flow rate indicating chamber and configured to move in response to blood flow from the inlet port to the outlet port. At least a portion of the wall of the flow rate indicating chamber is transparent to allow visualization of the movable bodies.

[0004] In some embodiments, the movable body comprises a plurality of beads.

[0005] In some embodiments, at least one of the beads comprises multiple faces.

[0006] In some embodiments, each of the beads is coated with an anticoagulant.

[0007] In some embodiments, the movable body includes a rotating member configured to rotate in response to a force exerted by the blood.

[0008] In some embodiments, the rotating member comprises a wheel comprising a plurality of spokes.

[0009] In some embodiments, the wheel is positioned relative to the inlet and outlet ports such that each of the spokes intersects the unobstructed path of blood when perpendicular to the unobstructed path of blood from the inlet port to the outlet port.

[0010] In some embodiments, the most proximal point on each spoke that intersects the unobstructed path is located 50% to 80% of the length of the spoke from the proximal end of the spoke.

[0011] In some embodiments, the device further includes a filter chamber configured to couple to the flow-indicating chamber and to hold a blood filter therein.

[0012] In some embodiments, the device further comprises a threaded ring; the filter chamber is shaped to define a filter chamber port; the flow indicating chamber is configured to thread onto the first side of the threaded ring; The filter chamber is configured to thread onto the second side of the threaded ring such that the inlet port or the outlet port is fluidly connected to the filter chamber port.

[0013] In some embodiments, the flow indicating chamber is further configured to hold a hemofilter therein.

[0014] In some embodiments, the device further comprises a valve configured to regulate the flow of blood through a port selected from a group of ports consisting of an inlet port and an outlet port.

[0015] In some embodiments, the valve comprises: a depressible element configured to penetrate a wall of the flow rate indicating chamber and cover the port when pressed into the flow rate indicating chamber; a spring coupled to the depressible element and to an inner wall of the flow-indicating chamber and configured to prevent the depressible element from covering the port in the absence of a pressing force applied to the depressible element.

[0016] In some embodiments, the spring comprises an extension spring.

[0017] According to some embodiments of the present invention, there is further provided a method comprising coupling an upstream end of a first conduit to a source blood vessel of a subject and coupling a downstream end of the first conduit to an inlet port of a shunt, the method further comprising coupling an upstream end of a second conduit to an outlet port of the shunt and coupling the downstream end of the second conduit to a sink blood vessel of the subject, such that blood flow from the source blood vessel through the shunt and into the sink blood vessel causes movement of one or more movable bodies disposed within the shunt, the movement being visible through a wall of the shunt.

[0018] In some embodiments, the shunt includes a flow rate indicating chamber including a movable body, and a filter chamber coupled to the flow rate indicating chamber and holding a blood filter therein.

[0019] According to some embodiments of the present invention, there is further provided a device including a chamber shaped to define a fluid port, a first appendage projecting from the chamber and shaped to define a first opening and a first row of one or more teeth, and a second appendage projecting from the chamber and shaped to define a second opening and a second row of one or more teeth parallel to the first row of teeth, the second row of teeth configured to mate with the first row of teeth at a plurality of different relative positions of the first and second appendages such that the second opening aligns with the first opening at different respective degrees of alignment and thus a tube carrying blood to or from the fluid port through the first and second openings is constricted at different respective degrees of constriction.

[0020] In some embodiments, the chamber is configured to hold a blood filter therein.

[0021] In some embodiments, the device further includes one or more movable bodies disposed within the chamber and configured to move in response to blood flow through the chamber, and at least a portion of the wall of the chamber is transparent to allow the movable bodies to be viewed.

[0022] In some embodiments, the first appendage and the second appendage are continuous with a wall of the chamber.

[0023] In some embodiments, the first and second attachments are configured to return to a default relative position in which the tube is not constricted when the first and second rows of teeth are released from each other.

[0024] In some embodiments, the first appendage includes a first rear arm projecting from the chamber and a first front arm angled relative to the first rear arm and shaped to define a first opening and a first row of teeth; A second appendage includes a second rear arm projecting from the chamber and a second front arm angled relative to the second rear arm and shaped to define a second opening and a second row of teeth.

[0025] In some embodiments, each of the teeth in the first and second rows of teeth are angled backwards such that the tube narrows as the first and second rows of teeth advance relative to one another.

[0026] In some embodiments, the tube does not completely constrict at any point.

[0027] According to some embodiments of the present invention, there is provided a method comprising: constricting a tube carrying blood to or from a fluid port of the chamber through the first and second openings by sliding a first appendage projecting from the chamber and shaped to define a first opening and a first row of one or more teeth across a second appendage projecting from the chamber and shaped to define a second opening and a second row of one or more teeth parallel to the first row of teeth, such that the second row of teeth engages with the first row of teeth in a relative position of the first appendage and the second appendage where the second opening is misaligned with the first opening. The method further comprises, after constricting the tube, releasing the first and second rows of teeth from each other to return the first and second appendages to their default relative positions where the tube is not constricted.

[0028] The present invention will be more fully understood from the following detailed description of the embodiments thereof taken in conjunction with the accompanying drawings, in which: [Brief explanation of the drawings]

[0029] [Figure 1] 1 is a schematic diagram of a device for shunting blood, according to some embodiments of the present invention. [Figure 2] 1 is a schematic diagram of a device for shunting blood, according to some embodiments of the present invention. [Figure 3] 1 is a schematic diagram of a device for shunting blood, according to some embodiments of the present invention. [Figure 4A] 1 is a schematic diagram of a tube constrictor according to some embodiments of the present invention. [Figure 4B] 1 is a schematic diagram of a tube constrictor according to some embodiments of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0030] overview In some cases, it may be necessary to shunt blood from one anatomical location to another. For example, during surgery to remove a blood clot from a subject's carotid artery, it may be necessary to shunt blood from the subject's carotid artery to a vein, such as the femoral vein. In such cases, a shunt device (or "shunt") is used to route blood between the two locations. However, there is a risk that blood flow through the shunt may slow or stop without the physician's knowledge.

[0031] To mitigate this risk, embodiments of the present invention provide a shunt that includes a flow-indicating chamber that includes one or more movable bodies configured to move in response to blood flow through the flow-indicating chamber. At least a portion of the wall of the flow-indicating chamber is transparent to allow the movable bodies to be viewed. For example, the wall can include a transparent window, with the movable bodies positioned behind the window. Thus, a physician can easily check whether blood is flowing properly through the shunt by observing the degree of movement of the movable bodies.

[0032] In some embodiments, the movable body comprises a plurality of beads suspended in the blood that rotate and / or change position when blood flows through them, hi other embodiments, the movable body comprises a wheel comprising a plurality of radial spokes that rotate when blood flows across the spokes.

[0033] Another challenge is that it may sometimes be necessary to slow or stop the flow of blood through the shunt, for example, to allow more blood to flow to the subject's brain through the carotid artery.

[0034] To address this issue, in some embodiments of the present invention, the shunt includes a valve configured to control the flow rate through the inlet or outlet port of the shunt. For example, the valve can include a pushable element that penetrates the wall of the flow rate indicating chamber described above, and a spring within the flow rate indicating chamber that couples the pushable element to the inner wall of the flow rate indicating chamber. In its resting state, the spring holds the pushable element away from the port so that blood can flow freely through the port. However, when sufficient pushing force is applied to overcome the force of the spring, the pushable element is pushed over the port, thereby slowing or stopping the flow of blood.

[0035] In another embodiment, the shunt includes a tube constrictor configured to constrict a tube carrying blood to or from a port. The tube constrictor includes a pair of parallel arms shaped to define respective openings and respective rows of teeth. The rows of teeth are configured to interlock with each other in a default position in which the openings are aligned with each other and in one or more other positions in which the openings are misaligned to varying degrees. Thus, by sliding the arms past each other while the tube is passing through the opening, the tube can be partially or completely constricted. After the tube is constricted, the rows of teeth can be released from each other, allowing the arms to return to their default positions to resume normal blood flow.

[0036] Device Description Reference is first made to Figure 1, which is a schematic illustration of a device 20 for shunting blood 22, according to some embodiments of the present invention. Insert 44 in Figure 1 shows a portion of the interior of device 20.

[0037] Device 20, which may be referred to as a "shunt," includes a flow indicator chamber 24 shaped to define an inlet port 26 and an outlet port 28. Blood 22 enters flow indicator chamber 24 through inlet port 26, flows through the flow indicator chamber, and exits the flow indicator chamber via outlet port 28.

[0038] In some embodiments, the inlet port 26 is configured to couple to an inlet tube 30 (or any other inlet conduit, such as a catheter) through which blood 22 flows into the device 20. For example, the inlet tube 30 can be snapped into the inlet port 26, or the inlet port can be snapped into the inlet tube.

[0039] In some embodiments, device 20 further includes a filter chamber 32 configured to couple to flow-indicating chamber 24 and hold a blood filter 34 therein. The blood filter 34 can be secured within the filter chamber using any suitable structural component, such as a plurality of ribs 86 as shown in FIG. 3, described below. Filter chamber 32 is shaped to define an inlet port 38 through which blood 22 enters the filter chamber and an outlet port 40 through which blood exits the filter chamber.

[0040] 1, the filter chamber can be coupled to the flow rate indicating chamber downstream thereof, such that blood flows through the flow rate indicating chamber before flowing through the filter chamber. (Optionally, a single common port can function as both outlet port 28 and inlet port 38.) In such an embodiment, outlet port 40 is configured to couple to outlet tubing 42 (or any other outlet conduit, such as a catheter) that carries blood from device 20.

[0041] Alternatively, the filter chamber can be coupled to the flow rate indicating chamber upstream of the flow rate indicating chamber. (Optionally, a single common port can function as both the outlet port 40 and the inlet port 26.) In such an embodiment, the inlet port 38 of the filter chamber is configured to couple to the inlet tube 30, and the outlet port 28 of the flow rate indicating chamber is configured to couple to the outlet tube 42.

[0042] In some embodiments, device 20 further includes a threaded ring 36. Flow rate indicating chamber 24 is configured to thread onto one side of threaded ring 36, and filter chamber 32 is configured to thread onto the other side of threaded ring 36 so that the two chambers are in fluid communication with each other. For example, as shown in FIG. 1 , the flow rate indicating chamber can be threaded onto the upstream side of ring 36, and the filter chamber can be threaded onto the downstream side of ring 36, allowing blood to flow directly from outlet port 28 to inlet port 38. Alternatively, the filter chamber can be threaded onto the upstream side of ring 36, and the flow rate indicating chamber can be threaded onto the downstream side of ring 36, allowing blood to flow directly from outlet port 40 to inlet port 26.

[0043] In another embodiment, the flow indicator chamber and the filter chamber are coupled to one another via a coupling tube 84, as shown in FIG.

[0044] In still other embodiments, the device 20 does not include a filter chamber 32. In such embodiments, the flow-indicating chamber 24 may be configured to hold a hemofilter 34 therein.

[0045] Device 20 can shunt blood 22 between any two suitable blood vessels in a human or animal subject. In other words, device 20 can shunt blood 22 from any suitable "source" blood vessel in the subject to any suitable "sink" blood vessel in the subject. For example, device 20 can shunt blood from an artery to a vein in the subject, with inlet tube 30 pumping blood from the artery and outlet tube 42 carrying blood to the vein. As a specific example, device 20 can shunt blood from a carotid artery to a femoral vein during surgery to remove a blood clot from the carotid artery. Alternatively, device 20 can shunt blood from a high-pressure artery to a low-pressure artery.

[0046] To deploy device 20, the upstream end of inlet tubing 30 is coupled (e.g., via a stopcock and / or any other suitable device) to a source blood vessel, and the downstream end of the inlet tubing is coupled to an inlet port of device 20 (e.g., inlet port 26 in embodiments where a flow rate indicating chamber is upstream of a filter chamber). Similarly, the upstream end of outlet tubing 42 is coupled to an outlet port of device 20 (e.g., outlet port 40 in embodiments where a flow rate indicating chamber is upstream of a filter chamber), and the downstream end of the outlet tubing is coupled (e.g., via a stopcock and / or any other suitable device) to a sink blood vessel. Blood then flows from the source blood vessel, through device 20, and into the sink blood vessel.

[0047] Blood Flow Indicator The device 20 further includes one or more movable bodies 46 disposed within the flow rate indicating chamber 24 and configured to move in response to the flow of blood 22 from the inlet port 26 to the outlet port 28. At least a portion of the wall 52 of the flow rate indicating chamber is transparent to allow the movable bodies 46 to be viewed. For example, as shown in FIG. 3 (described below), the wall 52 can be entirely transparent. Alternatively, as shown in FIG. 1, the wall can include at least one transparent window 50. Thus, a physician can easily check the rate of blood flow through the flow rate indicating chamber by observing the degree of movement of the movable bodies 46. In some embodiments, the transparent portion of the wall 52 includes a magnifying lens configured to magnify the movable bodies 46.

[0048] In some embodiments, the movable body 46 includes a plurality of beads 48 that rotate and / or change position when blood is flowing through them. Typically, the beads 48 have a density lower than that of the blood 22 so that the beads remain suspended in the blood. The beads 48 may include any suitable blood-compatible material, such as metal, plastic, wood, latex, synthetic rubber, or any combination thereof.

[0049] Generally, each bead can have any suitable shape. For example, beads 48 can include at least one spherical bead 48a. Alternatively or additionally, beads 48 can include at least one bead that includes multiple sides, which can exhibit greater movement in response to blood flow than spherical bead 48a due to the greater forces exerted on the bead by the blood. Examples of beads that include multiple sides include cubic bead 48b and pyramidal bead 48c.

[0050] Generally, larger beads can be more noticeable than smaller beads, and therefore in some embodiments, the Cartesian distance between any two points on the outer surface of the bead is greater than 0.1 cm for each bead 48. Alternatively or additionally, to allow for greater bead movement, the Cartesian distance between any two points on the outer surface of the bead can be less than 0.65 cm.

[0051] In some embodiments, each bead is coated with an anticoagulant such as heparin.

[0052] In some embodiments, to enhance visibility, the color of the beads contrasts with the color of the blood 22. Suitable contrasting colors include black, blue, and white. Alternatively, the beads can have any other color.

[0053] In some embodiments, outlet port 28 is covered with a filter configured to prevent the passage of beads. Alternatively or additionally, as described above, filter chamber 32 can be coupled to a flow rate indicating chamber downstream from the flow rate indicating chamber such that any beads that pass through outlet port 28 are filtered from the blood by filter 34.

[0054] Reference is now made to Figure 2, which is a schematic illustration of device 20 according to some embodiments of the present invention. Insert 58 in Figure 2 shows a portion of the interior of device 20.

[0055] In some embodiments, the movable body 46 includes a rotating member configured to rotate in response to a force exerted by the blood.

[0056] For example, the movable body 46 can include a wheel 54 including a plurality of spokes 56 (which may also be referred to as "radial members") configured to rotate in response to the blood 22 exerting a force on the spokes 56. To be easily noticeable, the length of each spoke 56 can be greater than 0.6 cm and / or the width of each spoke can be greater than 0.3 cm. Alternatively or additionally, to avoid the need for an excessively large flow-indicating chamber, the length of each spoke 56 can be less than 3.8 cm and / or the width of each spoke can be less than 1.3 cm.

[0057] Insert 58 uses two dashed lines to define the unobstructed path 60 of blood, i.e., the path the blood would follow from inlet port 26 to outlet port 28 in the absence of wheel 54. Typically, wheel 54 is positioned relative to the inlet and outlet ports so that each spoke intersects path 60 when it is perpendicular to path 60 at any point along the path. Thus, blood flow through the flow-indicating chamber generally causes the wheel to rotate in a single direction. For example, in FIG. 2, the wheel rotates clockwise as indicated by rotation indicator 55.

[0058] For example, if the end of a spoke closest to hub 62 is the proximal end of the spoke and the opposite end is the distal end of the spoke, the most proximal point on the spoke that intersects with path 60 can be located 50% to 80% of the length of the spoke from the proximal end of the spoke. (For example, if the spoke is 3 cm long, the most proximal point on the spoke that intersects with path 60 can be located 1.5 cm to 2.4 cm from the proximal end of the spoke.) This positioning of the wheel can advantageously increase the rotational forces experienced by the wheel.

[0059] In some embodiments, the inner wall 61 of the flow-indicating chamber 24 narrows the space within the chamber through which blood can flow, so that the blood follows the path 60 at a higher velocity and therefore exerts a greater force on the rotating member.

[0060] Typically, the wheel 54 is mounted on a shaft 64 (i.e., the shaft 64 passes through the hub 62) so that the wheel rotates about the shaft, as shown in cross section AA. The shaft 64 is coupled to the wall 52 at both ends.

[0061] The rotating member (eg, wheel 54) can be any suitable color, including a color that contrasts with the color of blood, as described above for beads 48 (FIG. 1).

[0062] In another embodiment, Doppler ultrasound is used to measure the rate of blood flow. For example, a fixture shaped to define a socket can be attached onto one of the tubes into which a standard Doppler ultrasound probe can be inserted.

[0063] Regulation of blood flow Referring again to FIG.

[0064] In some embodiments, device 20 further includes a valve 66 configured to regulate the flow of blood through the flow-indicating chamber, thus allowing a physician to control the rate at which blood is shunted.

[0065] In some embodiments, valve 66 includes a depressible element 68 that passes through wall 52 and is configured to cover inlet port 26 or outlet port 28 when pressed into the flow-indicating chamber. Typically, a (e.g., rubber) gasket 76 seals the opening in wall 52 through which the depressible element passes to prevent blood from leaking through the wall.

[0066] In such an embodiment, valve 66 further includes a spring 78 coupled to the depressible element (e.g., by being coupled to a ledge 82 coupled to the depressible element) and also coupled to an inner wall of the flow-indicating chamber (e.g., the inside of wall 52). Spring 78 is configured to prevent the depressible element from covering the inlet or outlet ports when no depressible force is being applied to the depressible element. Thus, to slow or stop blood flow, a physician must continually apply a depressible force that counters the force exerted by the spring, reminding the physician that blood flow is slowing or stopping.

[0067] Typically, spring 78 comprises a tension spring 80 as shown in Figure 1. Spring 80 is maximally compressed when there is no compressive force, such that the tension spring holds the compressible element in its outermost position.

[0068] In some embodiments, the pressable element 68 includes a neck 70 and a foot 72 that protrudes from the end of the neck 70 that resides within the flow indicator chamber. As the neck 70 is pressed further into the flow indicator chamber, the foot 72 covers a large portion of the inlet or outlet port, slowing the flow of blood. When the neck is pressed to its fullest extent, the foot 72 completely covers the port, stopping flow. Optionally, the opposite end of the neck 70 that resides outside the flow indicator chamber can terminate in a head 74 that is wider than the neck, thereby facilitating pressing the neck into the flow indicator chamber.

[0069] In other embodiments, valve 66 includes a pullable element that passes through wall 52 and is configured to cover inlet port 26 or outlet port 28 when pulled. (Note that valve 66 can also be combined with any other suitable embodiment of movable body 46, such as the embodiment of FIG. 2.)

[0070] Reference is now made to FIG. 3, which is a schematic illustration of an apparatus 20 according to some embodiments of the present invention.

[0071] In some embodiments, device 20 includes a tube constrictor 88, which may also be referred to as a "locking clip." Tube constrictor 88 includes a first appendage 90a shaped to define a first opening 92a and a second appendage 90b shaped to define a second opening 92b.

[0072] 4A-4B, tube constrictor 88 is configured to control the rate of blood flow through the tube passing through openings 92a and 92b by constricting the tube to various degrees of constriction. Thus, device 20 need not necessarily include valve 66 (FIG. 1).

[0073] For example, tube constrictor 88 may provide two degrees of constriction: no constriction (0%) and complete (100%) or partial (e.g., 80%-90%) constriction. Alternatively, tube constrictor 88 may provide three or more degrees of constriction. Examples of four degrees of constriction are 0%, 20%-40% (e.g., 33%), 60%-80% (e.g., 66%), and 90%-100%. (In the context of this application, including the claims, a tube may be considered to be x% constricted if the percentage of blood flow through the tube is x% of the percentage that would occur if the tube were not constricted at all.)

[0074] In some such embodiments, flow rate indicating chamber 24 is coupled to filter chamber 32 via connecting tube 84, and tube constrictor 88 is configured to constrict the connecting tube. For example, as shown in FIG. 3 , first appendage 90 a and second appendage 90 b can protrude upstream from filter chamber 32, i.e., the first and second appendages can protrude beyond inlet port 38, and connecting tube 84 can convey blood to inlet port 38 through the first and second openings. Alternatively, first and second appendages can protrude downstream from flow rate indicating chamber 24, i.e., the first and second appendages can protrude beyond outlet port 28, and connecting tube 84 can convey blood from outlet port 28 through the first and second openings.

[0075] In other such embodiments, tube constrictor 88 is configured to constrict inlet tube 30. In other words, first appendage 90a and second appendage 90b project upstream from flow rate indicating chamber 24, i.e., first appendage 90a and second appendage 90b project beyond inlet port 26, and inlet tube 30 conveys blood to inlet port 26 through first and second openings. (In this case, flow rate indicating chamber 24 can be coupled to filter chamber 32, as in FIGS. 1-2, or filter chamber 32 can be omitted.)

[0076] In yet another such embodiment, tube constrictor 88 is configured to constrict outlet tube 42. In other words, first appendage 90a and second appendage 90b project downstream from filter chamber 32, i.e., first appendage 90a and second appendage 90b project beyond outlet port 40, and outlet tube 42 conveys blood from outlet port 40 through first and second openings. (In this case, flow indicator chamber 24 can be coupled to filter chamber 32 as in FIGS. 1-2, or flow indicator chamber 24 can be omitted.)

[0077] In embodiments in which device 20 includes a flow rate indicating chamber 24, the flow rate indicating chamber can include any suitable movable body 46, such as a wheel 54 or a bead 48 (FIG. 1).

[0078] In some embodiments, the first and second appendages are continuous with the wall of the chamber from which they protrude, i.e., the wall extends beyond the chamber to define the appendages, while in other embodiments the appendages are bonded to the wall of the chamber, for example using any suitable adhesive.

[0079] Typically, each appendage includes a rear arm 100 that projects from the chamber and a front arm 102 that is angled (e.g., at about 90 degrees) relative to the rear arm 100 and shaped to define an opening through which the tube passes.

[0080] Reference is now made specifically to insert 110 in FIG. 3, which shows the rear surface of forearm 102 of first appendage 90a, i.e., the surface of the forearm facing second appendage 90b.

[0081] The first appendage 90a (e.g., the first appendage forearm 102) is shaped to define a first row 94a of one or more teeth 96, in addition to a first opening 92a. Similarly, as shown in FIGS. 4A-4B, the second appendage 90b (e.g., the second appendage forearm 102) is shaped to define a second row 94b of one or more teeth 96 parallel to the first row 94a. As further described below with reference to FIGS. 4A-4B, the second row 94b is configured to mate with the first row 94a in a number of different relative positions of the first and second appendages. In these different positions, the second opening 92b aligns with the first opening 92a to different degrees of alignment, thereby constricting the coupling tube 84 (or any other tube passing through the opening) to different degrees of constriction.

[0082] Reference is now made to Figures 4A-4B, which are schematic illustrations of a tube constrictor 88 according to some embodiments of the present invention.

[0083] In Figure 4A, the first and second appendages are in a first relative position in which the second opening 92b is aligned with the first opening 92a, thus not constricting the coupling tube 84. One or both of the appendages can then be moved to assume a second relative position in which the two openings are less aligned with one another, thus causing a majority of the tube 84 to be constricted, as shown in Figure 4B.

[0084] In some embodiments, as shown in FIGS. 4A-4B , each tooth 96 slopes backward (e.g., toward the rear arm 100 of the appendage) to include a long leading edge 104 and a short trailing edge 106. In such embodiments, the tube can be constricted by advancing the two rows of teeth toward each other, e.g., by pushing at least one front arm 102 toward the rear arm 100 of the other appendage. For example, the appendages can be pinched together using, e.g., an index finger placed on one rear arm 100 and a thumb placed on the other rear arm, as shown by pinch indicators 98 in FIG. 4A . As one or both rows of teeth advance, the leading edges 104 slide across each other until contact between the trailing edges 106 prevents the rows from sliding backward by interlocking at the next position.

[0085] In other embodiments, each tooth 96 slopes forward toward the tip of the appendage. In such embodiments, the tube can be constricted by moving at least one row of teeth rearward relative to the other row of teeth, for example, by pulling at least one front arm 102 away from the rear arm 100 of the other appendage.

[0086] In some embodiments, as shown in FIG. 4B by release indicators 108, the first and second appendages are configured to return to a default relative position when the first and second rows 94a, 94b are released from one another, without the tube being constricted. In other words, at least one of the appendages is resilient such that, upon movement from the default relative position, it stores elastic energy that returns the appendage to its default position when the rows are released from one another. Alternatively or additionally, upon release, elastic energy stored in the walls of the tube while the tube was constricted can return the first and second appendages to their default relative positions. (Note that the appendages can be shaped to define fewer teeth than those shown; for example, one appendage can be shaped to define a single tooth and the other appendage can be shaped to define N>2 teeth, so that N levels of constriction are provided.)

[0087] Typically, the tube does not fully constrict at any position where the teeth interlock. In other words, as shown in FIG. 4B, the tube can remain partially (e.g., 10% to 20%) unconstricted even in the most constricted interlocking position. Therefore, to remind the practitioner that flow has stopped, it is advantageous for the practitioner to continue to apply force to one or both appendages to fully constrict the tube. For example, in the scenario shown in FIG. 4B, continuous pinching of the appendages is required to fully constrict the tube. In the absence of pinching force, the appendages return to the most constricted interlocking position due to elastic energy stored in the appendages and / or the walls of the tube. (In embodiments with backward-tilted teeth, the most constricted interlocking position is when the front-most tooth of one appendage locks against the rear-most tooth of the other appendage. In embodiments with forward-tilted teeth, the most constricted interlocking position is when the front-most tooth of one appendage locks against the front-most tooth of the other appendage.)

[0088] Instead of tube constrictor 88, device 20 may include any other clamp configured to project from one chamber and constrict a tube in fluid communication with the chamber. The clamp may be continuous with or coupled to the wall of the chamber from which it projects.

[0089] Those skilled in the art will appreciate that the present invention is not limited to what has been specifically shown and described above. Rather, the scope of the embodiments of the present invention includes both combinations and subcombinations of the various features described hereinabove, as well as variations and modifications thereof that are not present in the prior art and that would occur to one skilled in the art upon reading the above description. Documents incorporated by reference into this patent application are to be considered an integral part of this application, except that to the extent that any term in these incorporated documents is defined in a manner that contradicts a definition expressly or implicitly given herein, only the definition in this specification shall be considered. The present invention may be embodied in the following manner. [1] a chamber shaped to define a fluid port; a first appendage projecting from the chamber and shaped to define a first opening and a first row of one or more teeth; a second appendage projecting from the chamber and shaped to define a second opening and a second row of one or more teeth parallel to the first row of teeth; wherein the second row of teeth is configured to mate with the first row of teeth at a plurality of different relative positions of the first appendage and the second appendage such that the second opening is aligned with the first opening at different respective degrees of alignment and thus a tube carrying blood to or from the fluid port through the first and second openings is constricted at different respective degrees of constriction. Device. [2] the chamber is configured to hold a blood filter therein; The device described in [1] above. [3] and one or more movable bodies disposed within the chamber and configured to move in response to the flow of blood through the chamber, wherein at least a portion of the chamber wall is transparent to allow the movable bodies to be viewed. The device described in [1] above. [4] the first appendage and the second appendage are continuous with a wall of the chamber; The device according to any one of [1] to [3] above. [5] the first and second attachments are configured to return to a default relative position in which the tube is not constricted when the first and second rows of teeth are released from each other. The device according to any one of [1] to [3] above. [6] the first appendage includes a first rear arm projecting from the chamber and a first front arm angled relative to the first rear arm and shaped to define the first opening and the first row of teeth; the second appendage includes a second rear arm projecting from the chamber and a second front arm angled relative to the second rear arm and shaped to define the second opening and the second row of teeth; The device according to any one of [1] to [3] above. [7] each of the teeth in the first and second rows of teeth inclines backward such that the tube is constricted by the first and second rows of teeth advancing relative to one another; The device according to any one of [1] to [3] above. [8] the tube is not completely constricted at any of the locations; The device according to any one of [1] to [3] above.

Claims

1. A device for shunting blood, comprising: a flow indicating chamber shaped to define an inlet port and an outlet port; a plurality of beads disposed within the flow-indicating chamber and configured to move in response to the flow of blood from the inlet port to the outlet port, each of the beads including a plurality of faces; and wherein at least a portion of the wall of the flow-indicating chamber is transparent to allow the beads to be viewed. Device.

2. each of said beads is coated with an anticoagulant; 10. The apparatus of claim 1.

3. a filter chamber configured to couple to the flow-indicating chamber and hold a blood filter therein; 3. The device according to claim 1 or 2.

4. Further comprising a threaded ring; the filter chamber is shaped to define a filter chamber port; the flow indicator chamber is configured to thread onto a first side of the threaded ring; the filter chamber is configured to thread onto the second side of the threaded ring such that the inlet port or the outlet port is fluidly connected to the filter chamber port.

4. The apparatus of claim 3.

5. the flow indicating chamber being further configured to hold a hemofilter therein.

3. The device according to claim 1 or 2.

6. further comprising a valve configured to regulate the flow of blood through a port selected from a group of ports consisting of the inlet port and the outlet port.

3. The device according to claim 1 or 2.

7. The valve is a depressible element configured to penetrate a wall of the flow rate indicating chamber and cover the port when pressed into the flow rate indicating chamber; a spring coupled to the depressible element and to an inner wall of the flow-indicating chamber, the spring configured to prevent the depressible element from covering the port in the absence of a pressing force applied to the depressible element; The apparatus of claim 6 , comprising:

8. the spring includes a tension spring; 8. The apparatus of claim 7.

9. 3. The apparatus of claim 1 or 2, wherein for each of said beads, the Cartesian distance between any two points on the outer surface of said bead is less than 0.65 cm.

10. 3. The device of claim 1, wherein the color of the beads contrasts with the color of the blood.

11. 11. The device of claim 10, wherein the color of the beads is selected from the group consisting of black, blue, and white.

12. A device for shunting blood, comprising: a flow indicating chamber shaped to define an inlet port and an outlet port; a plurality of beads disposed within the flow-indicating chamber and configured to move in response to the flow of blood from the inlet port to the outlet port; wherein at least a portion of the wall of the flow-indicating chamber is transparent to allow the beads to be viewed; for each of said beads, the Cartesian distance between any two points on the outer surface of said bead is less than 0.65 cm; Device.

13. The device of claim 12 , wherein the color of the beads contrasts with the color of the blood.

14. The device described in claim 13, wherein the color of the beads is selected from the group consisting of black, blue, and white.

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