Surgery – Blood drawn and replaced or treated and returned to body – Body inserted tubular conduit structure
Reexamination Certificate
2002-01-18
2004-02-24
Bianco, Patricia (Department: 3762)
Surgery
Blood drawn and replaced or treated and returned to body
Body inserted tubular conduit structure
C604S004010, C604S006100, C422S044000, C210S646000
Reexamination Certificate
active
06695807
ABSTRACT:
BACKGROUND OF THE INVENTION
As discussed in Schnell, et al., U.S. Pat. No. 6,319,465 and elsewhere, hemodialysis and other forms of extracorporeal blood treatment require the removal of blood from a patient by means of an arterial tube set, the passing of the blood to a blood processing device such as a dialyzer, and the subsequent returning of the blood to the patient again through a venous tube set.
Maintenance of good blood set access is a major cost and problem of dialysis, which is the most common extracorporeal blood treatment, although other types of blood treatment are also known, for example, passing of the blood through an absorption bed for removal of toxins or 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.
Such 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 a 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 this recirculation are known. A method described by Krivitski 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 accomplished this by stopping the flow of blood, clamping 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. This of course is inconvenient and undesirable in that blood spillage and infection becomes a possibility. Accordingly, various other solutions relating to obtaining a reverse flow of blood in an extracorporeal blood circuit have been proposed, for example, Schnell, et al., U.S. Pat. Nos. 6,177,049 and 6,319,465, Krivitski, U.S. Pat. No. 6,308,737, Prosl, et al., U.S. Pat. No. 5,894,011 and Schneditz U.S. Pat. No. 5,830,365.
Also, regarding permanently implanted 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 through the catheter and thus extending its useful life.
Accordingly, there are several reasons for why it is desirable to have an easily controlled flow reversal system in extracorporeal blood treatment.
By this invention, a flow reversal system is provided, free of slidably moving parts, and simply comprising connected flexible tubing, which has long been used in blood handling. The flow reversal system of this invention is quite inexpensive and easy to manufacture, utilizing generally conventional components, which have had long use, testing, and reliability, to obtain with ease the desired flow reversal when it is needed, with a minimal increase in the blood volume of the system because of the presence of the flow reversal apparatus, and generally free of stagnant flow areas.
DESCRIPTION OF THE INVENTION
By this invention, a tubular set portion is provided for circulating blood between a patient and an extracorporeal blood treatment device. This tubular set portion may be an integral part of joined arterial and venous blood flow sets, and/or fistula sets, which may otherwise be generally conventional in nature, apart from the improvement of this invention. Alternatively, the tubular set portion may be a separate set portion, which may be connected to any kind of conventional arterial and venous blood flow sets, and/or fistula sets and also connected to fistula needles, or percutaneous catheters to provide a complete flow circuit between the patient and an extracorporeal blood treatment device such as a dialyzer.
By this invention, the set portion comprises: an arterial tube for conveying blood from a patient toward the blood treatment device; a venous tube for conveying blood from the blood treatment device back toward the patient; and a pair of spaced, transverse tubes that each connect between the arterial tube and the venous tube. Each of the transverse tubes are capable of being sealed by a clamp (for clamp sealing by the usual collapse of a tube). Furthermore, the arterial and venous tubes are clamp sealable at a position between the spaced, transverse tubes.
Preferably, the wall-to-wall spacing between the transverse tubes is substantially equal to the wall-to-wall spacing of the arterial and venous tubes at a position between the transverse tubes. Furthermore, it is preferred for this wall-to-wall spacing, especially between the transverse tubes, to be so that both of the transverse tubes may be substantially completely sealed by the closure of one or two hemostat clamps or the like of a width to provide minimal residual blood volume left in the transverse tube. This is desirable since a significant residual blood volume in the clamped tubes may comprise a stagnant area for blood, as the blood flows through the arterial tube and the venous tube. Such stagnant areas for blood are likely to clot, which of course is undesirable. Such a substantially complete seal of a length of the transverse blood tubing as defined herein, or other blood tubing, is defined to comprise enough sealing closure of the tube to eliminate stagnant areas that can clot in normal operation.
Similarly, the wall-to-wall spacing between the sections of the arterial and venous tubes which are between the spaced, transverse tubes should be proportioned so that those sections of the arterial and venous tubes may be substantially completely sealed by the closure of the one or two hemostat clamps, or the like, to similarly provide a minimal residual blood volume, and essentially no clotting while at the same time not significantly collapsing the transverse tubes or other portions of the arterial and venous tubes.
Thus, a variable flow path maybe provided through the section which comprises the transverse tubes and adjacent arterial and venous tubes. The hemostat may close off the two transverse tubes in one flow position, causing blood flow to take place first through the arterial tube from the patient toward the blood treatment device, and then for the blood to pass through the venous tube away from the blood treatment device back toward the patient. However, when the hemostat closes off those portions of the arterial and venous tubes which are between the transverse tubes, the flow of the blood path is entirely different. The return blood from the treatment device passes from a first portion of the venous tube into a portion of the former arterial tube and then back to the patient
Bell David
Schnell William J.
Utterberg David S.
Bianco Patricia
DSU Medical, Inc.
Garrettson Ellis Seyfarth Shaw LLP
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