Surgery – Instruments – Cutting – puncturing or piercing
Reexamination Certificate
2001-09-21
2003-12-30
Truong, Kevin T. (Department: 3731)
Surgery
Instruments
Cutting, puncturing or piercing
Reexamination Certificate
active
06669709
ABSTRACT:
FIELD OF THE INVENTION
The present invention is concerned with improvements in catheter design and usage in-vivo; and is particularly directed to catheterization apparatus and methods for creating an arteriovenous fistula or a veno-venous fistula between adjacently positioned blood vessels.
BACKGROUND OF THE INVENTION
A catheter is a long flexible tube introduced into a blood vessel or a hollow organ for the purpose of introducing or removing fluids; implanting medical devices; or for performing diagnostic tests or therapeutic interventions. Catheters are conventionally known and frequently used; and a wide range and variety of catheters are available which are extremely diverse in shape, design and specific features.
Typically a catheter is a long thin tube of fixed axial length, with two discrete, unique ends. One end is designed and engineered to be inserted in the body; the other end generally remains outside the body, and is so designed. Most catheters have at least one internal lumen of a volume sufficient to allow for on-demand passage of a diverse range of wires, rods, liquids, gases, transmitting energy, fiber optics, and specifically designed medical instruments.
The fundamental principles and requirements for constructing a guiding flexible catheter exist as conventional knowledge in the relevant technical field; and all of the essential information is publicly known, widely disseminated, and published in a variety of authoritative texts. The medical and technical literature thus provides an in-depth knowledge and understanding of the diagnostic and therapeutic uses of conventional catheters and commonly used catheterization techniques. Merely representative of the diversity of publications now publicly available are the following, each of which is expressly incorporated by reference here:
Diagnostic And Therapeutic Cardiac Catheterization,
second edition (Pepine, Hill, and Lambert, editors), Williams & Wilkins, 1994 and the references cited therein; A Practical Guide To Cardiac Pacing, fourth edition (Moses et al., editors), Little, Brown, and Company, 1995 and the references cited therein:
Abrams Angiography,
third edition (H. L. Abrams, editor), Little, Brown & Co., 1983;
Dialysis Therapy,
second edition (Nissenson & Fine, editors), Hanley & Belfus Inc., 1992; and
Handbook of Dialysis,
second edition (Daugirdas & Ing, editors), Little, Brown and Co., 1994.
Thus, in accordance with established principles of conventional catheter construction, the axial length of the catheter may be composed of one single layer or of several layers in combination. In most multilayered constructions, one hollow tube is stretched over another tube to form a bond; and the components of the individual layers determine the overall characteristics for the catheter as a unitary construction. Many multilayered catheters comprise an inner tube of Teflon, over which is another layer of nylon, woven Dacron, or stainless steel braiding. A tube of polyethylene or polyurethane typically is then heated and extruded over the two inner layers to form a firm bond as the third external layer. Other catheter constructions may consist of a polyurethane inner core, covered by a layer of stainless steel braiding, and a third external jacket layer formed of polyurethane.
In addition, a number of dual-lumen catheters are known today which differ primarily in the size and spatial relationship between their individual lumens. Typically, a dual-lumen catheter can take many different forms such as: two co-axially positioned lumens where one small diameter tube extends axially through the internal volume of a larger diameter tube; or the catheter is a single large diameter tube and has a centrally disposed inner septum which divides the interior volume into two equal or unequal internal lumens; or where the material substance of the catheter tube contains two discrete bore holes of differing diameters which serve as two internal lumens of unequal volume lying in parallel over the axial length of the catheter. All of these variations present different dual-lumen constructions for catheters having a similar or identical overall diameter size.
Catheters are generally sized by external and internal diameter and length. The internal diameter is specified either by actual diameter (in thousandths of an inch or millimeters or French size). Many newer thin-walled catheter designs provide a much larger internal lumen volume to external diameter ratio than has been previously achieved; this has resulted in catheters which can accommodate much more volume and allow the passage of much larger sized articles through the internal lumen. External diameter is typically expressed in French sizes which are obtained by multiplying the actual diameter of the catheter in millimeters by a factor of 3.1415 (&pgr;). Conversely, by traditional habit, the actual size of any catheter in millimeters may be calculated by dividing its French size by a factor of &pgr;. As an illustration of size usage. French sizes from 4-8 are currently used for diagnostic angiography. In addition, because of the variation between standard, thin-walled, and super high-flow catheter construction designs, a wide variety of external and internal lumen diameter sizes exist today.
In order to perform effectively in specialized medical procedures and in particular anatomical areas, specific categories or classes of catheters have been developed. Among the presently known specific types of catheters are: peritoneal catheters employed for peritoneal dialysis and which provide dialysate inflow and outflow for the removal of the by-products of metabolism from the blood; acute and chronic urinary catheters introduced into the bladder, the urethra, or directly into the renal pelvis for the removal of urine; central venous catheters are designed for insertion into the internal jugular or subclavian vein; right heart catheters such as the Cournand and Swans-Ganz catheters designed specifically for right heart catheterization; transeptal catheters developed specifically for crossing from right to left atrium through the interatrial septum at the fossa ovalis; angiographic catheters which are used for right or left ventriculography and angiography in any of the major vessels; coronary angiographic catheters which include the different series of grouping including Sones, Judkins, Amplatz, multipurpose, and bypass graft catheters; as well as many others developed for specific purposes and medical conditions.
An illustrative and representative example of traditional catheter usage is provided by the medical specialty of hemodialysis—the process by which extra water and toxic metabolites are removed from the blood by a dialysis machine when the kidneys are impaired by illness or injury. A summary review therefore of renal insufficiency or failure, the techniques of hemodialysis, and the role of specialized catheters in machine dialysis will demonstrate and evidence conventional limitations.
A wide variety of pathological processes can affect the kidneys. Some result in rapid but transient cessation of renal function. In patients so affected, temporary artificial filtration of the blood is sometimes necessary. With time, renal function gradually improves and may approach normal; and dialysis is therefore usually required only for a short duration. The time required for the kidneys to recover will depend on the nature and severity of the injury which typically varies from a few days to several months Thus, if the acute condition lasts for more than three or four days, the patient will probably require hemodialysis at least once while awaiting return of renal function.
Other pathological conditions result in a gradual deterioration of renal function over months or years. These patients can go for quite some time before toxic concentrations of metabolites accumulate. Once they reach the stage where dialysis is necessary, however, it is usually required for the rest of their lives. Some of these patients retain low levels of renal filtration and can therefore be dialyzed a
Cohn William E.
Kim Ducksoo
Buyan Robert D.
Stout, Uxa Buyan & Mullins, LLP
TransVascular, Inc.
Truong Kevin T.
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