Fluid handling – Systems – Multiple inlet with multiple outlet
Reexamination Certificate
2000-03-10
2001-10-30
Fox, John (Department: 3753)
Fluid handling
Systems
Multiple inlet with multiple outlet
C251S331000, C604S006100
Reexamination Certificate
active
06308737
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a flow diverter for selectively changing a flow direction in a connected line, and particularly to systems for replacement of kidney function in patients with end stage renal disease (ESRD), and more particularly to the treatment of ESRD by means of hemodialysis. In hemodialysis systems, the current invention provides an apparatus for selectively controlling the direction of flow in a portion of a blood circuit of a patient undergoing hemodialysis. Specifically, in the blood circuit comprising the closed loop through the patient's vascular system and through the hemodialysis machine, this invention relates to changing the direction of flow on the patient side, that is, to and from the patient's vascular system, without altering flow through the hemodialysis apparatus.
BACKGROUND OF THE INVENTION
In present day medical practice, hemodialysis is the standard therapy for treating ESRD. This therapy involves dialyzing the patient's blood several times a week. During treatment, the patient's vascular system is connected to a hemodialysis machine for sessions lasting several hours. This connection forms a blood circuit whereby blood is drawn from the patient through a needle connected to a patient access, cycled through a hemodialysis machine that removes waste products including water, urea, and other impurities from the blood, and returned to the patient access via a second blood line and needle.
The functional interface between the patient and the extracorporeal circuit is the patient or vascular access, from which blood is withdrawn and to which the externally treated blood is returned. To facilitate removal and return of blood, the patient access may have specialized connections allowing mating of separate arterial and venous blood lines, or the access may be cannulated with a hollow needle which is then connected to arterial and venous blood lines. Vascular access has been called the “Achilles' heel of dialysis” because of the frequent morbidity associated with maintenance and utilization of the access. A malfunctioning vascular access is not trivial, as the access represents a conduit for the passage of blood to the artificial kidney. Without treatment via the external kidney, toxin accumulation in the body is rapid and can be deadly.
One of the difficulties that can arise in chronic hemodialysis is maintaining adequate blood flow during treatment sessions. When flow rates decrease significantly during a session, the attendant could in many cases restore adequate flow by switching the blood lines. In current practice, the attendant must usually turn off the hemodialysis machine. This process lengthens the dialysis session while the machine is primed and restarted. In addition, switching the blood lines involves disconnecting the lines, which can cause bleeding and allow air to enter the lines. Disconnecting the lines also breaks the microbe barrier, increasing the possibility of infection.
Another difficulty that often arises with chronic hemodialysis is the possibility that the patient will develop a thrombus or blood clot that partially or wholly occludes a vascular access created by a fistula or vascular graft. When a fistula or graft becomes blocked, surgery is frequently needed to restore the venous access to a useful condition or replace the access site. A balloon angioplasty may be used to enlarge the lumen of the fistula or graft and prevent the immediate formation of thrombosis, thereby extending the life of the access. When a site can no longer be restored, it must be replaced. Replacing an access is a serious matter because patients have only a limited number of access sites for A/V fistulas and PTFE grafts.
Accordingly, an object of the present invention is to provide for the easy and convenient selection of which needle or catheter will be used to draw blood from the access and which will be used to return blood to the access at any particular time during hemodialysis treatment sessions, wherein such flow reversal can be employed in assessing access maintenance. Another object of this invention is to have a device that is compatible with high rates of flow in dialysis methods which utilize catheters. Yet another object of this invention is to accomplish the flow reversal function while minimizing the amount of turbulence associated with blood flow through the device. Still another object of the invention is to provide a device enhances safe use. A further object of the invention is to minimize stagnant flow regions in the device. Still another object of this invention is to provide a device that is easily added to existing hemodialysis set ups and treatment programs. Still another object of this invention is to provide a low cost, easily manufactured, sterile disposable device compatible with the rest of the blood circuit.
SUMMARY OF THE INVENTION
The present invention provides for the ready and reversible redirection of flow through a circulating system. The present invention finds particular application in the field of access management and particularly to those systems employing dilution technology.
Specifically, it has been found that measurements of vascular access recirculation and vascular access flow during dialysis are possible with “Ultrasound Dilution.” Ultrasound Dilution uses changes that occur in the velocity of an ultrasound signal when blood is diluted with saline, instead of the traditional measurement of differences in temperature or dye concentration following an indicator infusion. Ultrasound travels through blood more quickly than it does through saline. Thus, when a bolus of saline is injected into the bloodstream, it dilutes the blood and reduces the velocity of the ultrasound signal. This reduction in the time it takes for the ultrasound signal to pass between sensors can be measured using ultrasound transit-time technology. By comparing the curves produced with the venous and arterial sensors after infusions of saline, it is possible to calculate recirculation, access flow and cardiac output. The disclosure of U.S. Pat. No. 5,685,989 naming Nikolai M. Krivitski and David R. MacGibbon as inventors, issuing Nov. 11, 1997 is hereby expressly incorporated by reference.
The determination of access flowing using this technology requires a reversal between the lines that draw blood and introduce blood to the access. That is, it is necessary to readily select which needle or catheter will be used to draw blood from the access and which will be used to return blood to the access at any particular time during hemodialysis treatment sessions. By allowing ready “reversal” of the blood flow, the present invention assists in access management including the determination of access flow, recirculation and cardiac output.
The present invention provides an apparatus for selectively diverting flow between ports of a common chamber so that flow through a needle or catheter in the patient access can effectively be reversed. In addition, the present invention may be manufactured at a sufficiently reduced cost to promote single use of the device, thereby reducing the risks associated with on-site sterilization techniques.
The present flow diverter includes a resilient deformable common chamber having a plurality of ports, wherein the chamber includes opposing interior surfaces that contact upon deformation of the chamber. Upon a sufficient deformation, the contacting surfaces form a fluid barrier within the chamber and thereby determine the permissible flow with respect to the ports. Preferably, the chamber is sufficiently deformable to contact opposing interior surfaces in a plurality of configurations to provide selective fluid communication between the ports.
In a preferred configuration, the flow diverter of the present invention can become an integral part of an extracorporeal circuit, allowing for blood passage to the artificial kidney (dialyzer) through the use of tubing similar to conventional arterial and venous blood lines.
The present invention further contemplates a me
Fox John
Harter Secrest & Emery LLP
Salai Esq. Stephen B.
Shaw Esq. Brian B.
Transonic Systems Inc.
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