The Solution

An oversized proof-of-conceptmodel of the Dialysflexhemodialysis catheter

While other medical catheters exist that allow for the exchange of a sharpened steel needle (used to puncture the skin) for a soft and flexible Teflon sleeve, hemodialysis patients face a special set of problems when it comes to gaining access to a usable dialysis therapysite. As Dr. Nguyen pointed out in his video, access sites for hemodialysis patients are specially made areas of high volume, high pressure blood flow that are created surgically just beneath the surface of the skin. These special areas, called AV fistula sites (or graft sites) are perfectly suited for the kind of high volume, highflow exchange that is needed during the course of hemodialysis therapy. But gaining access to these high pressure puncture sites creates a special set of problems for the dialysis patient that until now, has not been adequately addressed.

In contrast to the use of a more common type of medical catheter such as the intravenous (IV) catheter, which operates under a normal venous pressure of about 2 to 6 mm/hg, a hemodialysis catheter must function under AV fistula pressures of approximately 18 to 28 mm/hg. Comparing thesemean pressures (4mm/hg to 23 mm/hg), wesee that a hemodialysis catheter must function under pressures about 5 to 6 times greater than that of any ordinary intravenous catheter. This makes the exchange of a sharpened steel needle for a soft and flexible Teflon sleeve much more complicated for hemodialysis therapy.

The normal procedure for placing a low pressureintravenous catheter within the hollow interior (lumen) of a blood vessel involves first puncturing the patents skin with a sharpened steel needle. This must be done in order to gain access to the IV therapy site. As one can see from the followingphotos, the(low pressure)intravenous catheter consists of a sharpened steel needle surrounded by a blunted Teflon sleeve. This is in contrast to the (high pressure) AV fistula access catheter used for hemodialysis therapy, which consists of nothing more than a sharpened stainless steel needle and its attached extension tubing. With theAV fistula catheter there is no Teflon sleeve included for use.

A high pressure AV fistula catheter

A set of low pressure intravenous catheters

The hollow Teflon sleeve of the low pressure intravenous catheterwraps snugly around the barrel of its steel puncture needle, and it follows the course of the needletip as theIVis threaded into proper position within a suitable vein. Once in position, the blunted Teflon sleeve of the IV catheter is left in place within the blood vessel and the sharpened steel needle portion of the assembly is removed. This leaves the soft and flexible Teflon cannula in place within the intravenous access site instead of a sharpened steel needle, and therefore it reduces damage to the interior walls of a vein during the course of intravenous therapy.This is also much more comfortable for the patient to use than an access catheter with a sharpened steel needle tip. The arrangement allows for greater freedom of movement without the fear of a sharpened needle tip scraping up against the walls of the blood vessel and causing pain.

As Dr. Nguyen pointed out in his video, it would be an advantage to have such a system available for patients receiving hemodialysis therapy. Butthere is a good reason why the Teflon sleeve is not available for use with an AV fistula catheter. The problem is illustrated as follows.

During the time that the needle assembly is withdrawn from the housing of a (low pressure) intravenous catheter and before the catheter is coupled to its connection tubing, the open end of the intravenous catheter is exposed to room air at normal atmospheric pressure. The greater pressures within the venous circulatory system will cause a small amount of blood to trickle out from the open end of the intravenous access catheter. Blood simply follows a course from higher to lower pressure, as all fluids do.

Because pressures within the venous circulatory system are relatively low, not much blood is lost in this way. It is a common practice to exert a bit of pressure from a gloved finger placed just above the site where blood flows through the lumen of an intravenous catheter. This point of resistance stops the trickle of blood from leaving the open end of the catheter until a set of IV tubing can be connected tothe device.

However, this method will not work when placing a hemodialysis catheter. The higher pressures encountered with the use of a hemodialysis access site (5 to 6 times greater than that of an intravenous access site) will cause blood to rush out from the open end of the dialysis catheter at high speed. This would obviously lead to an unacceptable amount of blood loss for patients receiving multiple sessions of hemodialysis therapy. It would also create a hazard for healthcare workers, exposing them unnecessarily to the patient's blood and to possible blood-borne pathogens.

It should also be mentioned that physicians such as Dr. Nguyen are averse to having any sort of pressure or occlusion placed over these surgically created AV fistula access sites. Access sites for hemodialysis therapy are artificially made avenues of high pressure blood flow, and as such they are far more prone to clotting (and therefore to ruin) than any naturally formed blood vessel. Any occlusion or pressure placed over these specially made access areas for any reason is always discouraged. Because of this, the practice of holding hard pressure over an AV fistula site is always to be avoided.

The Dialysflex hemodialysis catheter solves this set of problems simply and efficiently. It allows for the exchange of a sharpened steel needle used to gain access to an AV fistula site for a blunt and flexible Teflon sleeve without the risk of excessive blood loss or the needless exposure of healthcare workers to blood-borne pathogens. The device can be used without applying unnecessary pressure to the dialysis access site, and it avoids damage to the AV fistula during the course of hemodialysis therapy.

The new Dialysflex catheter consists of three major components:

1.The Catheter Housing:

2.The Needle Assembly :

3.The Extension Tubing :

The catheter housing includes aflexible Teflon sleeve, which remains in place within the confines of a high pressure AV fistula or graft access site during the course of hemodialysis therapy. The invention arrives from the manufacturer with its needle assembly securely in place within the hollow body of acatheter housing, just as a low pressure intravenous catheter does.

The sharpened steel tip of the needle extends just beyond the length of the flexible Teflon catheter lead. The Teflon catheter lead surrounds the exterior of the shaft of the needle assembly as a smooth, close fitting cannula or sleeve wrapped snugly around the barrel of the needle shaft. The back portion of the needle assembly includes a needle grip. The needle grip is wide and flat, and allows for a generous amount of control surface for finger placement. This is needed for the delicate task of threading the tip of the needle into the (relatively narrow) confines of a dialysis access site.

The front portion of the needle grip arches over the top of the catheter housing (see the illustration below). This arched portion then forks into two distinct and separate prongs. These hard plastic prongs allow for the devices flexible anchoring wings, (attached to each side of the main body of the catheter housing) to fold vertically and be tucked into a holding slot which is situated between them. The configuration allows for good visualization from both sides of the catheter during the delicate process of engagement and cannulation of an access site.

Anchoring wings folded and unfolded

After engagement of an access site, the needle assembly is withdrawn from the body of the catheter housing and the anchoring wings unfold from each side. These anchoring wings are then used to secure the dialysis catheter to the patients body, such as taping it or bandaging it to an arm.

On the farthest end of the catheters needle assembly and continuous with the hollow interior shaft of the steel needle there is a clear plastic visual flashback chamber. On the very end of this visual flashback chamber there is a thin semipermeable membrane such as a porous cotton weave stretched across the otherwise open end of the barrel. This semipermeable membrane allows air, but not blood to rush out from the hollow interior of the needle shaft and toturn the flashback chamber red, just as occurs with the use of a low pressure intravenous catheter. As the needle tip pierces the skin and engages the high pressure confines of a hemodialysis access site, blood rushes up into the hollow steel shaft portion of the needle assembly. When this blood reaches the flashback on the opposite end of the shaft it begins to fill the clear plastic portion of the flashback chamber. This can then be seen by healthcare workers as an indication of the successful engagement of a hemodialysis access site.

On the body of the main catheter housing itself are placed two opposing tension clips. These clips are molded from the same material as the hard plastic housing of the catheter, and are disposed for lateral motion at right angles to one another (see photograph below). Secured to each end of the hollow interior of the catheters housing and placed directly between these two tension clips is a compressible plastic tubing (not shown). Adequate space is given within the interior of the body of the catheter for these tension clips to move, and for the compressible plastic tubing to collapse and re-expand.

The shaft of the needle assembly rests within the interior space of the catheters collapsible plastic tubing, pushing the tension clips apart and keeping the device open to flow. For so long as the needle assembly is in place within the body of the dialysis catheter housing, blood is allowed to flow unobstructed within the cylindrical interior of the catheter body.

After piercing the wall of an AV fistula blood rushes from the needle tip and passes through the hollow interior of the needle shaft without obstruction, filling the visual flashback chamber and confirming the successful engagement of an access site. After proper placement of the device has been confirmed, the needle assembly is withdrawn from the main body of the catheter housing. The tension clips now press up against the walls of the collapsible plastic tubing from both sides, closing the open center of the catheters interior lumen and arresting all blood flow. The mechanism of action is smooth and automatic. The tension clips are designed to withstand a pressure of up to 75 mm/hg without leaking. The catheter isnow resting in place with its flexible Teflon cannula securely positioned within the confines of a hemodialysis access site. The flow of blood from the high pressure access site is safely arrested.

The final component of the new catheter (the extension tubing component) includes a hollow metal sleeve extending from the front of a barrel shaped connection hub. To reestablish the flow of blood through the device,a healthcare worker simply threads the hollow metal sleeve through the center of the housing of the catheter body. The leading edge of the metal extension sleeve is blunted and smooth. As the extension sleeve passes through the interior of the compressible plastic tubing, it forces the two opposing tension clips pressing against the outer walls of the tubing to reopen (see illustration below). This restores blood flow through the body of the dialysis catheter. The extension tubing assembly is then secured to the catheter housing by means of a rotating barrel lock.

With the extension tubing assembly securely in place and the tension clips open, all further regulation of blood flow through the catheter is achieved by use of a simple mechanical occlusion clamp located on the exterior surface of the tubing set.

The advantages of this design are in the simple mechanics of the tension clip and extension sleeve combination. It has few moving parts, and the opening and closing of the tension clips which control blood flow are automatic. The simplicity of the design allows the device to be stored for prolonged periods of time with very little concern for possible malfunction. It is a simple device that solves a complicated problem, and as such it reflects the very best kind of an invention.

The patent application for this new catheter was filed in 2011 and a patent #8926571 was granted on January 6, 2015. Patent negotiations and prototype building are very expensive. Dialysflex INC. was established in order to raise money for the project by the sale of membership units to potential investors. Each unit of membership reflects an equal portion of the profits from royalties to be gained by licensing the invention to a manufacturer/distributer. The company itself has no interest in manufacturing the new invention. Dialysflex INC. simply exists in order to develop the device and to manage the intellectual property.

The manufacturers of the current design of hemodialysis catheters know that there is a problem with their product. They have taken to Teflon coating the exterior portion of the steel needle of their catheters in order to lessen the amount of damage done to a dialysis access site during hemodialysis therapy. It is a half-hearted solution at best. There is a better answer to the problem. The Dialysflex catheter was created in order to pursue it.

To those who are interested in investing in this project, the inventor would direct your attention to the Investor Relations tab of this website. It will explain how you can become a member of Dialysflex INC. To those who are not interested in investing, the inventor would still like to thank you for reading this presentation and for taking an interest in the project. It is a worthyendeavor intended to make the dialysis experience more comfortable for the patient, and to reduce the frequency of access related complications of hemodialysis therapy.

Hemodialysis patients depend on these specially created access sites for their very lives. Without them they cannot participate in dialysis therapy, and without dialysis therapy they cannot survive. It is the greatest hope of this inventor that use of the new catheter will result in a decrease in the mortality rate for patients undergoing hemodialysis therapy.

My special thanks to Dr. Vo Nguyen of Memorial Nephology associates for his input into the Dialysflex project. Without his help the new dialysis catheter would simply not exist.