WO2014147620A1

WO2014147620A1 - A tearable endourethral catheter

Info

Publication number: WO2014147620A1
Application number: PCT/IL2014/050300
Authority: WO
Inventors: Ltd. Androphin; Ltd. Richampion; Shimon AMIT; Nir Bassa; Yitzchak ATLAS; David LIFSHITZ
Original assignee: Androphin Ltd; Richampion Ltd; Amit Shimon
Priority date: 2013-03-20
Filing date: 2014-03-19
Publication date: 2014-09-25
Also published as: WO2014147620A8

Abstract

The invention is an indwelling endourethral catheter, which is structurally similar to prior art Foley catheters with an additional feature that overcomes the common problem of significant damage to the patient caused by unsafely removing the catheter from the body before actively deflating the anchoring mechanism. The additional feature is a tear zone, which is a location at which the walls of the catheter are weaker than the rest of the catheter walls, is designed to at least cause a tear or rupture in at least one of the walls of the catheter tube when the catheter is pulled proximally with a force large enough to cause an inflated anchoring member to be pulled out of the bladder. Embodiments of the catheter of the invention additionally comprise a recoil limiting member disposed between the tear zone and the urethral orifice outside the patient's body to prevent part of the catheter tube from remaining inside the patient©s body after the tube tears at a tear zone.

Description

A TEARABLE ENDOURETHRAL CATHETER

Field of the Invention

The invention is from the field of medical devices. Specifically the invention is directed to indwelling endourethral catheters. Background of the Invention

Fig. 1 schematically shows a typical prior art Foley catheter. Catheter 10 includes an inflatable balloon 12 at the distal end of a catheter tube 14. The balloon 12 is deflated as the tube 14 is advanced up the urethra 16 towards the bladder 18. Once the balloon traverses the bladder sphincter, the balloon is inflated thus only preventing retrograde movement of the catheter within the urethra. The catheter tube 14 comprises two channels a central drainage channel, which is in fluid communication with the bladder, and a smaller diameter inflation channel, which is in fluid communication with the balloon. The proximal end of catheter tube 14, which is located outside of the patient, is bifurcated. One branch comprises the proximal section of the inflation channel and an inflation port 20 at its end that is adapted to engage a source of fluid, e.g. saline, sterile water, a gas, or a gel, for inflating the balloon in situ. The inflation port 20 can comprise a check valve and/or a relief valve. The other branch comprises the drainage channel and a drainage port 22 that is normally adapted to be attached to a receptacle for collection of the urine. Optionally, a plug or valve may be incorporated at drainage port 22 to stop the flow of urine. While the typical Foley catheter uses a balloon for retention, variations have incorporated alternative anchoring elements that are expandable and contractible within the bladder. These variations all require an additional lumen for passage of a control component for controlling the expansion or contraction of the alternative element within the bladder.

If the patient is confused or disoriented, suffering from dementia, Alzheimer, cognitive disorders, impairments in communication, or simply fails to remember to be cautious, he or she may forcibly pull out the catheter with the balloon fully inflated. Pulling out the catheter, with no medical or professional supervision and before the anchoring balloon is emptied, can also occur due to accidents in which the catheter's tube or other tubes and accessories that are connected to the catheter's tube are caught by an external object, while the patient moves or is moved in an opposite direction with respect to the object. In other cases, the external object moves, is moved or raised in an opposite direction with respect to the patient. An unintentional pull on the Foley Catheter while the balloon is inflated in the bladder is not uncommon and is extremely painful for the patient. The catheters are made of elastic materials which are highly resistant to stretching, pulling and pressure. They are much more resistant than the structure of the urethra and the urethra tissue. Since the inflation fluid is not compressible, if the catheter is pulled before the anchoring mechanism has been emptied the balloon will pass through the bladder neck and urethra uncompressed causing a serious tear of the bladder neck and the urethra. The urethra tissue may be severely damaged, traumatized and bleed. In many cases patients need several doses of blood transfusion as a result of pulling out the catheter unsafely.

A significant percentage of patients who use urinary catheters are severely injured, and suffer from severe trauma and bleeding as a result of pulling out the catheter before the anchoring mechanism has been emptied and reduced back to the diameter of the other parts of the catheter. Another problem associated with the typical Foley-type catheter is that the balloon or other retention element only prevents retrograde movement, or movement proximally towards the urethral orifice. The retention element typically does not prevent movement of the retention element (e.g., balloon) and the catheter deeper (distally) into the bladder. Obviously, excessive distal movement of the catheter may cause physical damage to the bladder. Irritation or abrading of the mucosa within the urethra may also result by continuous sliding back and forth of the catheter within the urethra. Moreover many catheters are made from elastomeric polymers exhibiting tensile strength of over 8 MPa, and elongation in the range of 200-300% elongation at failure. Catheters that tear without proper solutions to the recoil or the impact of the tearing on the inflation channel or on the balloon are known in the prior art. Stretching one of these catheters by from the proximal end until the tube tears or suddenly releasing the end before tearing, will result in recoil that may cause the catheter (or the distal part of it if it tears) to retract into the urethra. This may result in the need for surgical intervention to remove part of the catheter from the urethra. Even if the catheter tube does not tear, the balloon may burst and its contents released into the bladder on recoil. The fluids of the balloon or the residues of the balloon can cause an infection and their removal may require surgical operation.

It is therefore a purpose of the present invention to provide a urinary catheter that overcomes the problem of unsafely removing a catheter from the body without actively deflating the anchoring mechanism, which causes significant damage to the body.

It is another purpose of the present invention to provide a urinary catheter that is sensitive to and responds to abrupt pull and tear forces. It is another purpose of the present invention to provide a urinary catheter that protects the urethra, prostate (in males) and the bladder neck by using tear zones on the catheter that are activated to deflate or reduce in diameter the anchoring balloon before the tissue is damaged allowing the catheter to be safely removed from the body.

Further purposes and advantages of this invention will appear as the description proceeds. Summary of the Invention

As used herein, unless specifically defined differently, the following definitions are used for the following terms:

- An "anchoring element" is a reversibly inflatable structure, e.g. a balloon located at the distal end of a urethral catheter. Herein the term "balloon" is used to designate any form of reversibly inflatable anchoring device.

- An "inflation fluid" is any fluid - liquid, gas, or gel - that is used to inflate an anchoring element.

- The term "distal" as used in conjunction with a urethral catheter refers to the part of the catheter or any component of a catheter that is located farthest from the person inserting the catheter into the body of a patient. The anchoring element is located at the distal end of the catheter. In a patient the distal direction is the direction from the urethral orifice towards the bladder.

- The term "proximal" as used in conjunction with a urethral catheter refers to the part of the catheter or any component of a catheter that is located closest to the person inserting the catheter into the body of a patient. An inflation port is located at the proximal end of the catheter. In a patient the proximal direction is the direction from the bladder towards the urethral orifice. - The term "ductile" refers to materials that exhibit significant elongation before break and/or shear yielding in response to an applied stretching force or load.

- The term "tearable" and variations thereof such as "tear", and "torn", as used herein means that a portion of an internal or external wall of a catheter can be or has been ruptured or separated from another portion of the same wall by manual force.

- The term "tensile strength" refers to the maximum stress a material subjected to a stretching load can withstand without tearing.

- The term "tear zone" refers to a section of an internal or external wall of a catheter or component of a catheter is composed of material having a lower tensile strength than the material on either side of that section or made of a thinner material and that the wall can be torn at that section by manually exerting a stretching force that causes a stress greater than the strength of the material at the tear zone.

- The term "recoil" refers to the tendency of a catheter that is held at its distal end and has been stretched by pulling on its proximal end to spring back when it is released or for the distal portion to spring back if the catheter tears.

- The term "recoil limiting member" refers to an element that is integral with or added to an endourethral catheter to prevent recoil of a torn portion of the catheter back into the urethra of a patient.

The invention is an indwelling endourethral catheter comprising:

a. an elongated tube comprising a distal tip and a bifurcated proximal section at its proximal end;

b. at least one drainage channel inside the elongated tube, said drainage channel having an opening at its distal end that is in fluid communication with the exterior of the distal tip of the elongated tube and a drainage port at its proximal end which is located at the proximal end of one of the branches of the bifurcated proximal section of the elongated tube; and

c. at least one inflation channel having a distal end that is in fluid communication with the interior of a reversibly inflatable anchoring balloon that is located at the distal tip of the elongated tube and an inflation port at its proximal end which is located at the proximal end of one of the other of the branches of the bifurcated proximal section of the elongated tube. The invention is characterized in that the catheter comprises at least one tear zone comprising at least a portion of an internal wall of the elongated tube, the tear zone configured such that it can be ruptured or separated from another portion of the same wall by using manual force to pull on the proximal end of the catheter when the catheter is inserted into a bladder of a patient and the anchoring balloon is inflated; thereby allowing the anchoring balloon to be deflated or reducing its diameter before tissue damage occurs and allowing the catheter to be safely removed from the body of the patient. In embodiments of the catheter of the invention a tear zone comprises at least one of:

a. a section of an internal or external wall of the catheter made of a material having a lower tensile strength than the sections of wall on either side of it; and

b. a section of an internal or external wall of the catheter comprised of the same material but having a thinner thickness than the sections of wall on either side of it.

In embodiments of the catheter of the invention at least a part of the elongated tube that is proximal to the urethral opening when the catheter is inserted into the patient is comprised of two coaxial layers of material - an inner layer, which contains within it the drainage and inflation channels, made from a relatively weak material that will tear when subjected to a stretching/pulling force that exceeds a predetermined threshold value and a thin outer layer made from a material that will not tear if the stretching/pulling force is well above the predetermined threshold value. In these embodiments, after inserting the catheter into the body of the patient and inflating the anchoring balloon inside the bladder, the tear zone is created by slicing through at least part of the outer layer in a direction generally perpendicular to the longitudinal axis of the catheter at a location proximal to the urethra opening.

In embodiments of the catheter of the invention the tear zone has a tearing threshold that is determined as a function of the bladder neck tissue strength and the urethral tissue strength.

In embodiments of the catheter of the invention the tearing threshold is a function of the age of the subject, their gender, ethnicity, medical history and other parameters capable of affecting the resistance of the bladder neck to lacerations and tears resulting from the application of force.

Embodiments of the catheter of the invention comprise a tear zone located outside of the patient's body and a recoil limiting member disposed between the tear zone and the urethral orifice. The tear zone is configured to allow the catheter tube to separate into two parts when the catheter is pulled proximally with a force large enough to pull an inflated anchoring balloon out of the bladder.

In embodiments of the catheter of the invention the recoil limiting member comprises at least one of: an annular or partially annular projection created during manufacture at a location on the outer surface of the catheter tube and a sticker comprised of a piece of thin material comprising an adhesive on one side and a ridge on the other side.

In embodiments of the catheter of the invention the recoil limiting member comprises an inflatable balloon and the elongated tube comprises a side branch, which comprises a second inflation channel that is used to inflate the recoil limiting member, and the second inflation channel comprises unidirectional valve configured to allow inflation fluid to enter and inflate the balloon but not to escape the interior of the recoil limiting member.

Embodiments of the catheter of the invention comprise at least two tear zones spaced apart along its length and a sticker having a length long enough to cover any of the tear zone zones that are located inside the urethra and to locate the ridge on the sticker between a not covered tear zone outside of the body of the patient and the urethral opening when the anchoring balloon is inflated in the bladder. In these embodiments of the catheter of the invention the tensile strength of the catheter walls can increase between adjacent tear zones either from the proximal tear zone to the distal tear zone or from the distal tear zone to the proximal tear zone.

Embodiments of the catheter of the invention comprise:

a. a tear zone configured to allow the elongated tube of the catheter to be severed into two parts within the urethra of the patient when a sufficiently large stretching force is applied; and

b. a thin string or wire threaded throughout the length of the drainage channel and fixedly attached to the distal tip of the catheter and that is pulled proximally to safely remove the severed distal part of the catheter from the urethra after the anchoring balloon deflates. Embodiments of the catheter of the invention comprise a tear zone located within the urethra of the patient when the catheter is in place, the tear zone created on the internal wall of the catheter that separates the inflation channel and the drainage channel.

Embodiments of the catheter of the invention comprise tear zones constructed on the distal and proximal ends of the section of interior wall of the catheter that defines the part of the drainage channel that passes through the center of an annular anchoring balloon. The tear zones are configured such that, when they rupture, the anchoring balloon and a portion of the interior wall between the tear zones collapses into the volume formally occupied by the drainage channel allowing the catheter to be removed from the body safely without draining the inflation fluid from inside the anchoring balloon.

Embodiments of the catheter of the invention comprise a tear zone created in the interior wall between the inflation and drainage channels. The tear zone is configured such that, after it is ruptured, inflation fluid escapes from the interior of the anchoring balloon and drains down the drainage channel to the proximal end of the catheter. All the above and other characteristics and advantages of the invention will be further understood through the following illustrative and non-limitative description of embodiments thereof, with reference to the appended drawings. Brief Description of the Drawings

- Fig. 1 schematically shows a typical prior art Foley catheter;

- Fig. 2 schematically shows the main features of the endourethral catheter of the invention;

- Fig. 3A to Fig. 3C schematically illustrates the way in which the integral tear zone acts to prevent damage to the patient if the proximal end of the catheter is pulled proximally with the anchoring element inflated inside the bladder;

- Fig. 4A and Fig. 4B schematically shows the structure of the distal portion of the catheter of the invention in more detail;

- Fig. 5A to Fig. 5C schematically show an embodiment of the catheter of the invention comprising a balloon as a recoil limiting member;

- Fig. 6A and Fig. 6B schematically show an embodiment of the catheter of the invention comprising a sticker as a recoil limiting member;

- Fig. 7A and Fig. 7B schematically show an embodiment of the catheter of the invention in which the tear zone is located within the urethra of the patient when the catheter is in place;

- Fig. 8A and Fig. 8B schematically show another embodiment of the catheter of the invention in which the tear zone is located within the urethra of the patient when the catheter is in place;

- Fig. 9A and Fig. 9B schematically show an embodiment of the catheter of the invention in which the tear zone is configured in such a way that the anchoring balloon can be removed from the body safely without draining the inflation fluid from inside it; and

- Fig. 10A to Fig. IOC schematically show an embodiment of the catheter of the invention in which the tear zone is configured to rupture while maintaining the structural integrity of the catheter.

Detailed Description of Embodiments of the Invention

Fig. 2 schematically shows the main features of the tearable indwelling endourethral catheter 100 of the invention. Catheter 100 is structurally similar to the prior art catheter 10 shown in Fig. 1 but comprises an additional feature that overcomes the problems described herein above. The additional feature is a tear zone 24, which is a location at which the walls of the catheter have a lower tensile strength than the rest of the catheter walls. The tear zone 24 is designed to at least cause a rupture in the wall of the inflation channel to allow the inflation fluid to drain out of the anchoring element 12 when the catheter 100 is pulled proximally with a force that would cause an inflated anchoring member of a prior art catheter to be pulled out of the bladder. In the embodiment shown in Fig. 2, the tear zone 24 is created on the proximal portion of the catheter tube 14 outside of the body of the patient; however in other embodiments that will be described herein below, the tear zone 24 can be located at various locations inside the body. Embodiments of catheter 100 in which the tear zone 24 is located outside of the body of the patient additionally comprise a recoil limiting member 26 disposed between the tear zone and the urethral orifice outside the patient's body.

Fig. 3A to Fig. 3C schematically illustrate the way in which the integral tear zone 24 acts to prevent damage to the patient if the proximal end of the catheter is pulled proximally with the anchoring element inflated inside the bladder. As shown in Fig. 2 the catheter 100 is inserted through the urethra 16 and the balloon 12 is inflated inside the bladder 18. In this embodiment the integral tear zone is a weakening of the external and internal walls of the proximal section of the catheter tube 14 at a location between the urethral opening and the bifurcation of the catheter tube. If the proximal end is now pulled, the proximal part of the catheter tube separates from the part of the catheter inside the body at the tear zone 24 and inflation fluid - symbolically shown by drop 27 - begins to drain out through the torn inflation channel (Fig. 3A). As catheter 100 is pulled proximally before tearing it stretches and after tearing the part that is still in the body of the patient recoils distally. The recoil limiting member 26 prevents the recoiling part of the catheter from passing through the opening of the urethra (Fig. 3B). In a short time after the catheter has been torn the balloon 12 is completely deflated and the remaining part of the catheter can be safely withdrawn without causing any trauma to the patient (Fig. 3C). Fig. 4 A and Fig. 4B schematically shows the structure of the distal portion of the catheter of the invention in more detail. The catheter 100 comprises a long narrow tube 14 that has a distal tip 38 that is shaped to facilitate passage through the urethra and to minimize the potential for damage to the delicate tissues within the urethra as the catheter is inserted through the external urethral orifice, pushed up the length of the urethra 16, and enters the bladder 18 through the bladder sphincter. In embodiments of the invention the distal tip extends beyond the retention means, i.e. the balloon 12, by about 6-10 mm. In embodiments of the invention at least the tip of the catheter is radio-opaque or comprises radio-opaque markers for visibility by x-ray or other imaging methods to verify the position of the tip.

Two longitudinal channels pass throughout the length of tube 14. Drainage channel 30 has one or more openings 32 at its distal end that are in fluid communication with the interior of the bladder to allow urine to flow out of the bladder and through the proximal drainage branch 34 of the catheter to a collection vessel. A smaller diameter inflation channel 28 is in fluid communication with an anchoring mechanism, e.g. balloon 12, at the distal end of tube 14. The proximal end of inflation channel 28 passes through inflation branch 36 of the catheter and is in fluid communication, via appropriate check valves to a source of inflation fluid and means for withdrawing inflation fluid from the balloon. In an embodiment the balloon 12 has a torodial shape and, when deflated fits into a recess on the external wall of tube 14 as shown in Fig. 4A. When gas, liquid, or gel is introduced into the interior of the balloon it expands outward from the wall of the tube until its diameter is greater than that of the bladder sphincter, as shown schematically in Fig. 4B.

Catheter 100 typically has a length from its distal tip 38 to the fitting or drainage port at the proximal end of the drainage channel 30 that is sufficient to at least span the length of the urinary tract from the inside of the bladder adjacent the bladder sphincter to beyond the urethral orifice. The length of catheter 100 is typically such that the fitting or drainage port can be situated sufficiently beyond the end of the urethra to be readily accessible by medical personnel, such as for connecting the catheter to a suitable container for receiving urine (or other fluids) drained through the catheter. In embodiments of the invention, such as shown in Fig. 2, the catheter 100 is long enough to allow a length of tube 14 between the end of the urethra and the place at which the tube 14 bifurcates to be exposed to provide sites for creating at least one clearly visible (in other words, marked) tear zone 24 and anchoring a recoil limiting member 26.

In an embodiment, the catheter is provided in a single length that is known to accommodate the vast majority of patient anatomies. For example, the catheter can have a length of about 40 cm (16 inches). In another example, the catheter may be provided in several discrete lengths, with an appropriately sized catheter selected based on the patient's gender and anatomy. The proximal portion may constitute the majority of the length of the catheter, so the length of that portion measured from the fitting or distal drainage port may be between about 21cm and about 32 cm. In embodiments the entire length of the catheter that will be introduced into the patient's body comprises a radio-opaque coating, strip, or markings that will make it readily visible using external imaging.

The proximal portion of catheter 100 that is inserted into the body of the patient has an outer diameter - based on standard anatomical dimensions for the urethra - that allows it to fit snugly, but not tightly, within the urethra. Accordingly, the catheter of the invention may be provided in several diameters, ranging from about 12 French to about 30 French in 2 French increments, wherein each increment of French sizing Fr. = 0.33mm. Thus, the outer diameters for the selection of catheters of the invention can range, for example, from 4 mm to 10 mm. The diameter of the drainage channel 30 must be sufficient to allow adequate flow of urine through the catheter. In an embodiment, the catheter lumen can have an inner diameter of at least 3 mm. The diameter of channel 30 may, in certain embodiments, be the same regardless of the outer diameter dimension of the tubular portion. In other embodiments, to maintain flexibility, the wall thickness of the distal tubular portion (including the internal wall that defines the drainage channel and the inflation channel) is maintained generally constant regardless of outer diameter dimension. In an embodiment a wall thickness of 0.5 mm can provide an acceptable degree of flexibility to navigate turns, while retaining sufficient stiffness to avoid buckling of the distal tubular portion as the catheter is pushed up the urethra. A person skilled in the art would recognize that the wall of the urethra itself exerts an inward force that helps maintain the patency of the distal tubular portion as it is advanced distally. Thus, a thinner wall thickness of the distal tubular portion may be acceptable under certain circumstances.

The indwelling endourethral catheter of the invention can be formed, for example, from a medical grade ductile, biocompatible elastomer, e.g. Krayton™, latex, silicone, polyurethane, polyolefin elastomer, flexible polyvinyl chloride, ethylene vinyl acetate, ethylene methylacrylate, ethylene ethylacrylate, styrene butadiene styrene, and ethylene propylenediene rubber and may incorporate hydrogel or antibiotic impregnations.

The distal end of inflation channel 28 is in fluid communication with the interior chamber of an inflatable balloon 12 disposed at the distal end of the inflation lumen. Many arrangements are possible for attaching balloon 12 at the distal tip 38 of catheter 100. After inserting the distal tubular portion of the indwelling endourethral catheter of the invention through a patient's urethra to the desired location inflation fluid is delivered through the inflation channel to the balloon 12 through an inflation port at the end of inflation branch 36. The balloon 12 is constructed or attached to the distal tip of the catheter in such a way that, as the inflation fluid flows into it, it can expand radially while longitudinal inflation of the balloon is prevented, for example, by attaching it to the outside surface of the catheter or by stretching or bi-axial orientation processes during its manufacture.

In embodiments of the catheter 100 of the invention the inflation lumen can be, for example 40-50 cm in length, i.e. longer than the catheter lumen; however, other lengths are contemplated such that inflation lumen can be long enough to allow a health care professional to manipulate the inflation port away from the drainage port. In typical embodiments, the balloon holds between about 5 ml. to about 15 ml. of inflation fluid; however, capacity to hold more or less fluid is contemplated depending upon the physical characteristics of the patient. In embodiments of the invention, the inflation channel has a diameter of 0.9mm-1.0mm; however, other diameters are contemplated as long as the diameter is large enough to allow the selected inflation fluid to flow to the balloon.

A tear zone 24 in a catheter 100 of the invention can be created in many ways. For example the tear zone can be a weak zone in the lumen wall of the drainage channel 30, the inflation lumen 32, the outer wall of the catheter tube 14 or any combination of the three that is formed on the catheter during the production process, e.g. by thinning of the wall and/or locally varying the type and/or the composition of the material of which the catheter walls are made during polymerization or a molding or extrusion process. Most of the tear zones 24 are designed such that the external wall of the catheter has a smooth and surface; however, in embodiments of the invention the tear zone can be created by making a notch in the wall either during or after manufacture.

Another type of a tear zone, can be, created by manufacturing the catheter such that its entire length or at least a part of its length that is outside of the patient when inserted is comprised of two coaxial layers of material - an inner layer comprising the drainage and inflation channels and a relatively thin outer layer or skin. The inner layer is made of a relatively weak material that will tear when subjected to a stretching/pulling force exceeds a tearing threshold (defined herein below) and the skin is made of a material that will not tear even if the stretching/pulling force is well above the tearing threshold. After inserting this embodiment of catheter into the body of the patient and inflating the balloon a care giver cuts/slices the catheter's outer layer in a direction generally perpendicular to the longitudinal axis of the catheter at a location proximally to the urethra opening. The cut can be completely or only partially around the circumference of the catheter and should be deep enough to reach, but not penetrate the weaker inner layer. The cut can be made with a sharp instrument such as a scalpel or with a special device such as a "C" shaped clip made of a resilient material with sharp inner surfaces such that it can be stretched to fit over the catheter and when released the sharp edges will slice through the outer layer as the clip returns to its original dimensions.

In embodiments of the catheter of the invention the tear zones are clearly marked so that the person inserting the catheter will know where they are located relative to the anatomy of the patient and in this way can determine if the catheter is appropriate for use with the patient or if a different sized catheter should be selected. Similarly the tear zone can be labeled with other information that might be of interest such as the value of the threshold force needed to tear the zone or other parameters, e.g. the tensile strength at failure and elongation at break. The tear zones in the catheter of the invention are created such that minimum value, called herein the tearing threshold, of the stretching/pulling force that will cause tearing or rupture of the walls at the tear zone of a catheter of the invention that is anchored in the bladder by an inflated balloon is less than the force required to pull the inflated anchoring balloon out of the bladder. The tearing threshold will vary from patient to patient, according to the tissue strength. The tearing threshold can be determined as a function of the bladder neck tissue strength and the urethral tissue strength. The tearing threshold is a function of the age of the patient, their gender, ethnicity, medical history and other similar parameters capable of affecting the resistance of the bladder neck to lacerations and tears resulting from the application of force. A standard method for measuring tensile strength of a given material, which can be used herein, is defined by the American Society of Testing Materials in method number ASTM-D638. The tensile strength of the proximal tubular portion can be equal to or greater than about 9.0 MPa, for example, between 9.0 and about 35 MPa, or between about 10 MPa and about 30 MPa, specifically, between about 15 MPa and about 20 MPa. Likewise, the tensile strength of the distal tubular portion can be equal to or greater than 9.0 MPa for example, between 9.0 and about 35 MPa, or between about 10 MPa and about 30 MPa, specifically, between about 15 MPa and about 20 MPa. The tensile strength of the distal tubular portion can be the same or different from the tensile strength of the proximal tubular portion. Moreover, at a plurality of tear zone, such as used in embodiments described herein below, the tensile strength of the proximal tubular portion at the tear zone can be between about 10% and about 50% of the tensile strength of the section disposed proximally to each tear zone. In an embodiment, the tensile strength at each of the plurality of tear zones utilized in the tearable indwelling endourethral catheter described herein can be between about 10% and about 50% of the tensile strength of the section disposed proximally to each tear zone, for example, between about 10% and about 40%, or between about 10% and about 30%, specifically, between about 10% and about 20%, more specifically, between about 10% and about 15% of the tensile strength of the section disposed proximally to each tear zone. The tensile strength of the proximal tubular portion of the tearable indwelling endourethral catheter described herein can be the same or different between adjacent tear zones. The elongation-at-tear between adjacent tear zones in the proximal tubular portion of the tearable, indwelling endourethral catheter described herein can increase from the proximal tear zone to the distal tear zone or alternatively be the same. The term "elongation at tear" refers to the percentage that the material specified can stretch (extension) without breaking and is tested in accordance with the procedures of ASTM D412. The elongation at break of the proximal portion and/or the distal tubular portion of the tearable indwelling endourethral catheter described herein can advantageously be, for example, about 80%, or at least about 120%, specifically at least about 240%, or at least about 360%, more specifically about 2000%, or at most about 1000%, as measured by the procedures of ASTM D-412 and/or D-882. Conversely, the elongation-at-failure in the shear zone of the tearable indwelling endourethral catheter described herein can be a function of the tissue strength and can be a function of the age of the subject, their gender, ethnicity, medical history and other similar parameters capable of affecting the resistance of the bladder neck to lacerations and tears resulting from the application of force.

The elongation at break in a tear zone is manipulated, for example, during formation of the tear zones, by bi-axial orientation, increasing the crystallinity of the polymer and/or increasing cross-linking density, while, in certain embodiments, simultaneously reducing the wall thickness of the catheter lumen and the inflation lumen.

Recoil limiting members can be provided in many different embodiments. The simplest of these is to create at the time of manufacture an annular or partially annular projection at a location on the outer surface of the catheter tube that is certain to be beyond the urethra opening when the catheter is inserted into the bladder of the patient. Fig. 5A to Fig. 5C schematically shows an embodiment of the catheter of the invention comprising a balloon as a recoil limiting member in the proximal part of the catheter outside the urethra, in addition to the anchoring balloon 12 in the distal part. In this embodiment the proximal section of the elongated tube comprises a recoil limiting member 26, which is a balloon that in its deflated state fits into a recess on the external side of the wall of the catheter tube as shown in Fig. 5A. The recoil limiting member/balloon 26 is located on the elongated tube at a location that will be distal to the urethral opening of the patient when the catheter is correctly inserted. A tear zone 24, which in this embodiment is a weakening of the external and internal walls of the catheter tube, is located proximally and close to recoil limiting member/balloon 26. The elongated tube comprises a side branch 40, which comprises a second inflation channel 28' that can be used to inflate recoil limiting member/balloon 26 after the distal tip of the catheter has been inserted into the bladder of the patient and balloon 12 inflated as shown in Fig. 5B. A unidirectional valve 42 at the location at which the distal end of second inflation channel 28' is in fluid communication with the interior of recoil limiting member/balloon 26, allows inflation fluid to enter and inflate the balloon but not to escape. If, with the catheter is inserted into the patient as shown in Fig. 5B, its proximal end is pulled with sufficient force, the tube will stretch and separate into two portions at tear zone 24 and inflation fluid (indicated by drop 27) will drain out through the severed inflation channel 28 allowing balloon 12 to deflate (Fig. 5C). The recoil limiting member/balloon 26 will remain inflated and prevent recoil of the catheter tube into the urethra. Balloon 26 and balloon 12 can be of different colors. Thus, when the catheter is inserted into the body it would be easier to see that balloon 26 is inflated outside the urethra and remains outside the body.

Fig. 6A and Fig. 6B schematically show an embodiment of the catheter of the invention comprising a sticker as a recoil limiting member. The recoil limiting member/sticker 26 is a piece of thin material, e.g. a piece of medical grade biocompatible elastomer comprising an adhesive on one side and a ridge on the other side. If the tear zone 24 is located proximally to the urethral opening then, after the tip of the catheter is inserted into the bladder of the patient, the recoil limiting member/sticker 26 is attached by means of the adhesive to the surface of the catheter at a location between tear zone 24 and the urethra opening as shown in Fig. 6A. The ridge on recoil limiting member/sticker 26 will prevent the severed distal end of the catheter tube from recoiling into the urethra of the patient when the tensile strength of the tear zone is exceeded.

Fig. 6B illustrates an embodiment of the catheter of the invention that comprises a sticker that functions both as a recoil limiting member and to allow the location of the tear zone to be determined according to the length of the urethra of the patient by strengthening and thereby neutralizing the tear zones it covers. In this embodiment a number of tear zones, e.g. 24a, 24b, and 24c, are created in the catheter tube. The health care provider inserts the catheter into the urethra of the patient and observes that, for example tear zone 24c is located distally of the urethral opening and that tear zones 24b and 24c are visible. She/he then retracts the catheter and attaches recoil limiting member /sticker 26 to the catheter tube such that the sticker covers tear zone 24c strengthening the catheter wall at that location and the ridge of recoil limiting member /sticker 26 is between tear zones 24c and 24b. The catheter is then reinserted in the patient and balloon 12 inflated in the bladder. If the proximal end of the catheter is now pulled, the catheter will be severed at either tear zone 24b or 24a and the ridge on the recoil limiting member/sticker 26 will prevent recoil into the urethra. The exact location at which the catheter will be severed, i. e. at tear zone 24b or 24a, can be controlled by creating each of the tear zones with different tensile strengths. In this way, if tear zone 24a has a higher tensile strength than tear zone 24b, the catheter will tear at tear zone 24b and vice versa.

A series of tear zones can be created by changing the wall thickness of the catheter lumen. The wall thickness of the catheter lumen can decrease from the proximal end to the distal end or from the distal end to the proximal end.

Fig. 7A and Fig. 7B schematically show an embodiment of the catheter of the invention in which the tear zone is located within the urethra of the patient when the catheter is in place. In this embodiment the tear zone 24 is constructed so that all of the interior walls of the catheter tube will be severed when a sufficiently large stretching force is applied. A thin string (or wire) 44 is threaded throughout the length of the drainage channel and is fixedly attached to the distal tip of the catheter (Fig. 7A). When the catheter is torn into two parts, the distal part remains inside the urethra and the proximal part can be removed pulling the sting 44 out through the drainage channel leaving a loose end outside of the urethral opening. When the catheter tears at the tear zone, inflation fluid drains out of balloon 12 and through the severed end of the inflation channel into the urethra (Fig. 7B). When balloon 12 is completely deflated the distal part of the catheter can be removed from the urethra by pulling proximally on string 44. In this embodiment a recoil limiting member is not needed. Fig. 8A and Fig. 8B schematically show another embodiment of the catheter of the invention in which the tear zone is located within the urethra of the patient when the catheter is in place. In this embodiment, as shown in Fig. 8A, the tear zone 24 is created on the internal wall of the catheter that separates the inflation channel 28 and the drainage channel 30. When this wall is ruptured, as shown in Fig. 8B, inflation fluid drains out of balloon 12 down the inflation channel till the rupture and then into the larger diameter drainage channel to the proximal end of the catheter. In this embodiment the catheter is left intact after the tear zone has ruptured. Therefore it can be removed from the patient by pulling proximally after the balloon in the bladder has emptied and a recoil limiting member is not needed.

Fig. 9A and Fig. 9B schematically show an embodiment of the catheter of the invention in which the tear zones are configured in such a way that the catheter can be removed from the body safely without draining the inflation fluid from inside the anchoring balloon. In this embodiment tear zones 24 are constructed at the distal and proximal ends of the section of the interior wall of the catheter that defines the part of the drainage channel that passes through the center of the annular balloon 12 Fig. 9A). When these tear zones 24 rupture (Fig. 9B) the balloon 12 and the portion of the interior wall between the tear zones collapses into the volume formally occupied by the drainage channel. Even if the volume made available after rupture of the tear zones is not large enough to accommodate all of the volume of the filled balloon, the resilient nature of the walls of the balloon and the fluid within it allows the configuration of the balloon to change making it longer and narrower so that its external radius is reduced such that it can be pulled through the bladder sphincter and urethra without causing trauma to the tissue or pain to the patient. In this embodiment the catheter is left intact after the tear zone has ruptured. Therefore it can be removed from the patient by pulling proximally after the bladder has emptied and a recoil limiting member is not needed.

Fig. 10A to Fig. IOC schematically shows an embodiment of the catheter of the invention in which the tear zone is configured to rupture while maintaining the structural integrity of the catheter. Fig. 10A shows the catheter with balloon 12 in its collapsed configuration as the catheter would be introduced into the body of the patient. The tear zone 24 in this embodiment is in the interior wall between the inflation and drainage channels. Fig. 10B shows the catheter as it would be with the balloon 12 inflated inside the bladder of the patient. Fig. IOC shows that after tear zone 24 collapses, inflation fluid can escape from the interior of the balloon 12 and drain down the drainage channel to the proximal end of the catheter. In this embodiment, depending on the type of inflation fluid used, a one way valve should be installed in the distal tip to allow urine to exit the bladder while preventing the inflation fluid that leaks out of the ruptured balloon from entering the bladder. Also in this embodiment the catheter is left intact after the tear zone has ruptured and can be removed from the patient by pulling proximally after the bladder has emptied. A recoil limiting member is not required.

Embodiments, such as those shown in Fig. 8A to Fig. IOC in which the catheter remains intact and in place the patient's urethra - but not necessarily in the bladder - after collapse of the tear zone, can be configured to provide an alert, for example releasing a dye, to indicate to the medical staff that the balloon has been emptied.

Although embodiments of the invention have been described by way of illustration, it will be understood that the invention may be carried out with many variations, modifications, and adaptations, without exceeding the scope of the claims.

Claims

1. An indwelling endourethral catheter comprising:

c. at least one inflation channel having a distal end that is in fluid communication with the interior of a reversibly inflatable anchoring balloon that is located at the distal tip of the elongated tube and an inflation port at its proximal end which is located at the proximal end of one of the other of the branches of the bifurcated proximal section of the elongated tube;

characterized in that the catheter comprises at least one tear zone comprising at least a portion of an internal wall of the elongated tube, the tear zone configured such that it can be ruptured or separated from another portion of the same wall by using manual force to pull on the proximal end of the catheter when the catheter is inserted into a bladder of a patient and the anchoring balloon is inflated, thereby allowing the anchoring balloon to be deflated or reducing its diameter before tissue damage occurs and allowing the catheter to be safely removed from the body of the patient.

2. The catheter of claim 1, wherein a tear zone comprises at least one of: a. a section of an internal or external wall of the catheter made of a material having a lower tensile strength than the sections of wall on either side of it; and b. a section of an internal or external wall of the catheter comprised of the same material but having a thinner thickness than the sections of wall on either side of it.

The catheter of claim 1, wherein at least a part of the elongated tube that is proximal to the urethral opening when the catheter is inserted into the patient comprised of two coaxial layers of material - an inner layer, which contains within it the drainage and inflation channels, made from a relatively weak material that will tear when subjected to a stretching/pulling force that exceeds a predetermined threshold value and a thin outer layer made from a material that will not tear if the stretching/pulling force is well above the predetermined threshold value, wherein, after inserting the catheter into the body of the patient and inflating the anchoring balloon inside the bladder, the tear zone is created by slicing through at least part of the outer layer in a direction generally perpendicular to the longitudinal axis of the catheter at a location proximal to the urethra opening.

The catheter of claim 1, wherein the tear zone has a tearing threshold that is determined as a function of the bladder neck tissue strength and the urethral tissue strength.

The catheter of claim 4, wherein the tearing threshold is a function of the age of the subject, their gender, ethnicity, medical history and other parameters capable of affecting the resistance of the bladder neck to lacerations and tears resulting from the application of force.

The catheter of claim 1, comprising a tear zone located outside of the patient's body and a recoil limiting member disposed between the tear zone and the urethral orifice, the tear zone configured to allow the catheter tube to separate into two parts when the catheter is pulled proximally with a force large enough to pull an inflated anchoring balloon out of the bladder.

7. The catheter of claim 6, wherein the recoil limiting member comprises at least one of: an annular or partially annular projection created during manufacture at a location on the outer surface of the catheter tube and a sticker comprised of a piece of thin material comprising an adhesive on one side and a ridge on the other side.

8. The catheter of claim 6, wherein the recoil limiting member comprises an inflatable balloon and the elongated tube comprises a side branch, which comprises a second inflation channel that is used to inflate the recoil limiting member, and the second inflation channel comprises a unidirectional valve configured to allow inflation fluid to enter and inflate the balloon but not to escape the interior of the recoil limiting member.

9. The catheter of claim 7, comprising at least two tear zones spaced apart along its length and a sticker having a length long enough to cover any of the tear zone zones that are located inside the urethra and to locate the ridge on the sticker between a not covered tear zone outside of the body of the patient and the urethral opening when the anchoring balloon is inflated in the bladder.

10. The catheter of claim 9, wherein the tensile strength of the catheter walls increases between adjacent tear zones either from the proximal tear zone to the distal tear zone or from the distal tear zone to the proximal tear zone.

11. The catheter of claim 1, comprising: a. a tear zone configured to allow the elongated tube of the catheter to be severed into two parts within the urethra of the patient when a sufficiently large stretching force is applied; and

b. a thin string or wire threaded throughout the length of the drainage channel and fixedly attached to the distal tip of the catheter and that is pulled proximally to safely remove the severed distal part of the catheter from the urethra after the anchoring balloon deflates.

12. The catheter of claim 1 comprising a tear zone located within the urethra of the patient when the catheter is in place, the tear zone created on the internal wall of the catheter that separates the inflation channel and the drainage channel.

13. The catheter of claim 1 comprising tear zones constructed on the distal and proximal ends of the section of interior wall of the catheter that defines the part of the drainage channel that passes through the center of an annular anchoring balloon, the tear zones are configured such that when they rupture the anchoring balloon and at least a portion of the interior wall between the tear zones collapses into the volume formally occupied by the drainage channel allowing the catheter to be removed from the body safely without draining the inflation fluid from inside the anchoring balloon.

14. The catheter of claim 1 comprising a tear zone created in the interior wall between the inflation and drainage channels and configured such that, after the tear zone is ruptured, inflation fluid escapes from the interior of the anchoring balloon and drains down the drainage channel to the proximal end of the catheter.