BACKGROUND

Hemodialysis and other forms of extracorporeal blood treatment require the removal of blood from a patient by means of an arterial set, passing of the blood to a blood processing device such as a dialyzer, and returning of the blood to the patient again through a venous blood set.

Maintenance of a good blood set access is a major cost of dialysis, which is the most common extracorporeal blood treatment, although other types of blood treatment are also used, for example passing of the blood through an absorption bed for removal of toxins and the like, hemoperfusion, and other forms of blood treatment.

Beyond the initial cost of the surgical procedure to establish a fistula or graft in the patient, the keeping of adequate blood flow in an arterialized vein or synthetic arteriovenous graft of the patient frequently involves secondary surgical intervention for reconstruction of an old blood vessel site on the patient. Alternatively, it may be necessary to establish an entirely new fistula or graft at a new site if the old one fails.

Failure is evidenced typically by stenosis of the blood vessel, or blockage of an implanted catheter or other venous access site, with a consequent reduction in blood flow that eventually shuts down the site. Clotting is also a major cause of reduced blood flow.

If site failure is detected early enough, a less invasive technique such as balloon angioplasty can be employed to open the stenosis at a greatly reduced cost. Early detection of stenosis can be measured by change in pressure in the blood vessel or implant that reflects a restriction beginning to form. The technique described in Omachi U.S. Pat. No. 5,454,374 has been used to measure the baseline pressure access site for early detection of such a pressure change. Another method used by clinicians is to measure recirculation in the vessel during dialysis. As the flow is restricted in the access, the blood pumping rate indicated on the dialysis machine may exceed the flow rate of fresh blood coming into the vessel, so that some is recirculated from the venous access site to the arterial access site in the patient. This leads to inadequate dialysis since already cleansed blood is thus being reprocessed.

Various methods for measuring the degree of recirculation of this type are known. Another method described by Krivitsky determines blood flow in the access as a marker for stenosis. In this method blood set flow and recirculation are compared between arterial and venous flow in the normal orientation, and then with reversed flow between the arterial and venous access sites, which are typically fistula needles which enter the vein. In the prior art, clinicians typically accomplish this by stopping the flow of blood, clamping off all the lines, disconnecting the set or sets from the fistula needles, and then reconnecting the arterial line to the venous fistula while connecting the venous line to the arterial fistula.

Also regarding catheters (which are typically connected to larger veins or even the vena cava) it is known that catheter blockage may be relieved by reversing flow.

Catheters which are implanted in the venous system of a patient for dialysis access or the like may develop a “fibrin sheath” on the outside of the catheter within the blood vessel, for example the jugular or subclavian veins or the vena cava. This fibrin sheath coats the outside of the catheter and can extend over the end thereof.

At the outflow port, such a fibrin sheath is generally not too serious a problem since the outflowing blood forces the fibrin sheath open easily. However, at the inflow port of the catheter, the sheath can act as a one-way valve, collapsing with increasing negative pressure to seriously interfere with flow through the catheter.

Upon such an occurrence, a blood flow reversing valve may reverse the flow of blood through the catheter for continuation of a desired medical procedure such as hemodialysis application.

Referring toFIGS. 1A through 1E, a number of alternative designs for four-way valves have been developed for blood circuits. Referring toFIG. 1A, U.S. Pat. No. 5,894,011, discloses a valve that swaps the connections between pairs of lines905and906via a pair of rotatably connected disks901and902, each of which supports one of the pairs of lines905and906. The latter reference, for purposes of the US designation in the current PCT application, is hereby incorporated by reference in its entirety herein. A seal must be maintained between the disks901and902and between the respective lines. The device is intended to be operated manually. The parts are required to be rotated 180 degrees and must be rotated to a full lock before the seal and full patency are provided. Also, any indication of the two positions, such as a pointer and label, cannot be placed in a single location so that the position of the valve is indicated by looking at it. For example, if a pointer is positioned on the bottom and rotated 180 degrees from a forward to the reverse position, the pointer cannot be seen from one side as with the configuration of a valve like the quarter-turn type valve of U.S. Pat. No. 4,885,087 discussed below.

Referring toFIG. 1B, another four-way valve, disclosed in U.S. Pat. No. 5,605,630, which has been proposed for use in blood lines, has a rotating wheel910with channels911and912defined between the wheel910and the inside of a housing913. The latter reference, for purposes of the US designation in the current PCT application, is hereby incorporated by reference in its entirety herein. When the wheel is rotated, the channels911and912shift to join a different pair of lines. This device also has seals.

Referring toFIG. 1C, another arrangement is proposed in U.S. Pat. No. 6,177,049, which for purposes of the US designation in the current PCT application, is hereby incorporated by reference in its entirety herein. This device has a rotating component915with channels921and922defined within it. As the rotating component915is rotated, the channels defined between pairs of lines917and919change from parallel lines joining one set of corresponding lines to U-shaped channels joining a different set.

Referring toFIGS. 1D and 1E, a design, disclosed in U.S. Pat. No. 4,885,087, for purposes of the US designation in the current PCT application, hereby incorporated by reference in its entirety herein, is very similar to that ofFIG. 1B. This design has a rotator925that connects different pairs of lines depending on the position thereby defining two different sets of possible flow channels926and929or927and931.

Referring toFIG. 1E, another type of four-way valve is formed by interconnecting two tubes937and938with crossover lines935and936. This design is disclosed in U.S. Pat. No. 6,189,388 (Hereafter, “U.S. Pat. No. '388”), which for purposes of the US designation in the current PCT application, is hereby incorporated by reference in its entirety herein. Tube pinching actuators941-944are used to force fluid through different channels, depending on which actuators are closed. This device provides a hermetic seal and can be fairly inexpensive, but in a given configuration, significant no-flow areas are defined. These dead spaces can lead to the coagulation of blood, which is undesirable. Also, the interconnection of tubes in this does not lend itself to automated manufacturing.

Another type of four-way valve is based on the generally configuration ofFIGS. 1H through 1Lexcept that it is motor-actuated. A pinching mechanism achieves selection of opposite loop branches to switch flow paths by rotating a cam in the middle of the loop. The displacement of the cam can be less than 90 degrees between the two stop positions. This configuration is described in U.S. Pat. No. 8,002,727, which for purposes of the US designation in the current PCT application, is hereby incorporated by reference in its entirety herein.

Solutions known in the prior art include U.S. Pat. No. 6,177,049, for “Reversing Flow Blood Processing System,” which discloses a blood processing system having a reverse flow valve therein so that flow through the arterial and venous fistulas, or other equivalent patient connection equipment, can be reversed without reversing or stopping the blood pump. Another solution known in the prior art is U.S. Pat. No. 6,319,465 for “Reversing flow blood processing system having reduced clotting potential.” Referring toFIG. 1G, another type of flow reversing valve of simple construction is shown by U.S. Pat. No. 4,885,087 for “Apparatus for mass transfer involving biological/pharmaceutical media.” The valve described by the latter disclosure is of simple construction and is very intuitive and easy for a user to change the flow direction by rotating a lever. The general design of a lever and a cross-shaped set of tubes follows a manual reversing valve design used in plumbing systems as shown in the figure below.

Another very simple and inexpensive design uses a loop204from which four tubes205stem. The loop204can be made up of 4 T-shaped junctions fitted together so that the four tubes205extending radially from it. A double tube-pinching clamp202, is shown in side and top views at202A and202B respectively. The double tube-pinching clamp202is positioned as shown inFIG. 1Kto reverse (as shown inFIG. 1L) the flow between pairs of tubes. Although this configuration has a low cost of manufacture, some users may find it difficult to understand completely creating a training burden and concomitant risk. It will be observed that the routing of the tubes to make side-by-side sets of countercurrent flows is not apparent from the way the tubes stem from the loop204.

One feature of many of the prior art configuration is that they have tubes coming out of the flow switch that cross, when a first pair of tubes is extended toward the patient and a second pair of tubes is extended toward the treatment device. This can form a confusing arrangement. Although U.S. Pat. No. 6,319,465 does not have this drawback—the blood tubes extending to the patient extend from the same side and the blood tubes extending to the treatment device extend from an opposite side the configuration is complex and expensive to manufacture and can be unintuitive to use.

SUMMARY

The drawbacks of the prior art are overcome by providing a flat rotary switch type of valve as described in U.S. Pat. No. 4,885,087 without the drawbacks identified above and with additional benefits as herein described. First, the problem of crossing blood lines is resolved by providing an external support that routes the tubing in such a manner that the patient connection tubes extend from one end of the device and the treatment device tubes extend from the opposite end. The external support may provide guides that hold the tubing extending from the supported flat rotary switch type of valve so as to keep them from being pinch or kinked thereby ensuring free flow of blood. The flow switch is supported by the external support which can also support indicia indicating the switch position. The external support can include an enclosure. The enclosure may be of an ergonomic design that fits comfortably in the hand. In embodiments, the ergonomic design is asymmetrical to provide an indication or orientation.

Objects and advantages of embodiments of the disclosed subject matter will become apparent from the following description when considered in conjunction with the accompanying drawings.

