FIELD OF THE INVENTION
The present invention relates to a method of producing a medical catheter. In particular, the invention relates to a method wherein a catheter is produced by solidifying a fluid catheter material in a mould.
BACKGROUND OF THE INVENTION
In general, medical catheters are used for draining bodily fluids such as blood and urine. A catheter for medical use is typically provided with a tubular oblong catheter body part made from a piece of flexible medical hose with an internal conduit, e.g. a PVC or PU hose having a substantially circular outer and inner cross-sectional shape. In an insertable end thereof, the catheter forms one or more openings through which fluid can drain from a bodily cavity and into the tubular body. In order to ease the insertion and to avoid injuring the bodily tissue when the catheter is inserted into a body opening and guided through a bodily canal, e.g. the urethra or a blood vessel, the insertable end is normally provided with a smoothly rounded tip. In the case of most catheters, the tip is formed by heating and melting an end part of the medical hose until its conduit seals. Even though the existing catheters are formed with a tip providing an acceptably safe and comfortable insertion, it is a desire to further shape a larger and more curved tip of the inserted part of the catheter since this may allow for an easier and safer insertion. However, the present technique of forming the tip of a medial hose does not support in making such a tip. As an alternative, some catheters are made from a medical hose with a glued-on catheter tip. This solution allows for a catheter with a larger and more curved tip, but the additional process step of providing a tip part and gluing the part to the medical hose implies additional production costs. Moreover, there is potential risk that the tip falls off during the catheterisation and thus remains inside the body cavity, e.g. in the bladder. For economical and for safety reasons, the on-glued catheter tip is therefore undesired.
When the tip has been formed, a number of draining holes are normally drilled or punched radially into the hose in the vicinity of the tip. In order to avoid that the holes damage the bodily tissue during the insertion of the catheter, the edges of the holes must be smoothly rounded. Accordingly, the process of making the holes is time-consuming and expensive.
At its opposite end, the oblong catheter body is formed with an opening allowing the fluid to drain out of the catheter and into an appropriate place of disposal. In this opposite end, most catheters are provided with a connector part. The connector part allows the catheter to be connected e.g. to a bag for collecting the fluid. The connector part is normally formed by adhesively bonding a funnel-shaped member to the medical hose. Once again, the additional process of gluing a separate member onto the hose is cost-inefficient and implies a larger percentage of defect products.
DESCRIPTION OF THE INVENTION
It is an object of the present invention to overcome the above described problems by providing a method of producing a catheter, said method comprising the steps of:
injecting a fluid catheter material into a mould formed to define an insertable catheter tip and a catheter body in one part, and subsequently
solidifying the material therein.
The injection may take place in a regular machine for injection moulding. Depending upon the size and length of the catheter, the injection pressure may be in the range of 500-1500 bar, such as 750-1250 bar such as in the size of 1000 bar.
The injection moulding process is in particular suitable for relatively short catheters, i.e. catheters which are in the range of 50-90 mm., such as in the range of 55-85 mm., such as in the range of 60-80 mm. such as with a length in the size of 70 mm. which length has been found to be a suitable insertable length for most female individuals. For male individuals, catheter sections may preferably be provided in a length in the range of 180-250 mm., such as in the range of 190-240 mm., such as in the range of 200-230 mm. such as in the size of 220 mm.
The catheter may further comprise connection means for connecting the proximal insertion section to a further catheter section or to a urinary collection bag. The connector part may be made from the same material as the proximal insertion section, whereby, at the step of forming the proximal insertion section, the proximal insertion section and the connector part may be formed substantially simultaneously. Alternatively, the connector part may be made from a material different from the material of the proximal insertion section, whereby the connector part and the proximal insertion section are formed in distinct process steps, for example in a multi-component injection moulding process.
The mould could be formed to define the body part as an oblong hollow, tubular part with an internal conduit of a size allowing bodily fluid to be drained through the catheter body. As an alterative, the body part could be provided in the form of an oblong solid kernel with one or more vanes extending radially from the kernel and along the entire length thereof. The vanes thus define a number of draining passages for draining urine between the kernel and a bodily draining passage, e.g. the urethra.
In order to allow the bodily fluid, e.g. urine from the bladder, to enter the hollow, tubular body part of the catheter, the mould could be formed to define at least one draining hole in the vicinity of the tip.
A connector part may be provided for connecting the catheter to a hose for extending the length of the catheter or for connecting the catheter to disposal means, e.g. to a urinary collection bag. The connector section could preferably be made in one part with the catheter body and the tip. The connector part may be made from the same material as the proximal insertion section and preferably substantially simultaneous therewith, e.g. during the same injection step. Alternatively, the connector part may be made from a material different from the material of the proximal insertion section. The connector part and the proximal insertion section are thus formed in distinct process steps, for example in a multi-component injection moulding process. The connector part may also be arranged as a separate component in the injection mould before the injection of the catheter material so that the connector part is moulded into engagement with the catheter body part during the injection moulding of the body part of the catheter. In a similar manner, a catheter tip may be arranged as a separate component in the mould and, during the injection moulding of the body part of the catheter, be moulded into the catheter. In a similar manner, additional components may be arranged in the mould prior to the injection moulding of the catheter body. As an example, one or more ring-shaped coloured members may be arranged for the purpose of visualizing a certain length of the catheter, e.g. for visualizing the intended insertable length. As another example, one or more objects made of a material, which improves the visualisation of the catheter in an x-ray or ultra-sound image may be arranged in the mould prior to the injection moulding of the catheter body.
In order to allow a user of the catheter to get a better grip, the catheter may be provided with means for attaching the catheter to peripheral articles such as a hand-grip for firmly gripping the catheter. The means for attaching the catheter to peripheral articles could be an out or inwardly extending bulge. As a further option, the catheter could be formed in one piece with means for handling the catheter during the insertion, e.g. a handle part which supports for a firm hand grip. As an example, the catheter could be provided in a diameter allowing for insertion into the urethra and with a catheter section not adapted for insertion and provided in a much larger diameter allowing a firm hand grip in the catheter.
Depending upon the type of catheterisation, the bodily fluid is typically drained either into a place of disposal e.g. into a toilet or into a reservoir or container for collecting the fluid. Accordingly, the mould could be formed to further define a reservoir for collecting the bodily fluids. The reservoir could be a plastic bag moulded in one piece with the catheter, e.g. by a combined injection and blow moulding process.
In order to fixate the catheter in the bodily passage, the catheter could be provided with a balloon in the vicinity of the inserted tip. The balloon could be moulded into one piece with the catheter.
Sometimes, it is desired that different parts of the catheter is provided with different characteristics. As an example, it may be desired for a urinary catheter that the insertable part is relatively soft and flexible so that the catheter can pass through the curved passage of the urethra. On the other hand, those parts of the catheter which is not adapted for insertion into the urethra may preferably be relatively less flexible, thus allowing an easier grip and allowing the inserted part of the catheter to be manipulated via the not inserted art.
Similarly, it may often be desired that the outer surface of the catheter is provided in a low-frictional material supporting an easier and more comfortable insertion of the catheter into the urinary canal. Accordingly, it may be desired to provide a surface layer of the catheter in a low-friction material such as FEP, PTFE or in a hydrophilic material such as polyvinylidone while the remaining part of the catheter is provided in a stronger and more durable material such as a thermoplastic elastomeric material, other thermoplastic materials, curable elastomeric materials, polyamide resins or elastomers or any mixture thereof, i.e. the group may comprise materials like, PVC, PU, PE, latex, and/or Kraton™. As an example, the mould may be coated with a hydrophilic material prior to the injection of a thermoplastic elastomeric material into the mould. As an alternative, series of injections of one or more types of thermoplastic elastomeric materials into the mould may take place. As an example, a hydrophilic material or a similar low frictional material such as siloxane, FEP etc. may firstly be injected to form an outer layer of the catheter. Subsequently, one or more types of materials, e.g. materials with different characteristics, are injected in one or more injection cycles in order to form the rest of the catheter.
As an advantage of the injection moulding process, the surface of the catheter may easily be provided with a surface roughness defining anchoring points for adhering a low frictional material to the surface of the catheter, e.g. anchoring points for bonding a FEP or PTFE (Teflon™) coating to the surface.
When injecting the material in more than one injection cycle, a catheter either comprising multiple layers or laminates or more individual sections in the length, is formed. Due to the laminated structure, the laminated structure may be more durable towards mechanical stress. Due to the individual sections in the length, a first part of the catheter, e.g. the part of the catheter which is intended to be inserted into the urethra or similar body canal, may be made in a softer material than the remaining catheter or it may be made in another colour or with another slipperiness, i.e. more slippery than the parts not intended to be inserted.
The different characeristics may relate to the softness of the material after solidification, the colour of the material, the strength of the material, the slipperiness of the material after solidification or to the ability of the solidified material to absorb liquid substances.
As an example, the part of the catheter which is adapted for insertion into the body canal, may be coloured in a colour different from the colour of the other parts of the catheter. In that way, the user can easily avoid touching the insertable part of the catheter.
In order to reduce the resistance against insertion into the body canal, the radial size of the tip may be larger than the radial size of the rest of the catheter. As an example, the tip may be formed into an onion-shaped or bulbous knob or the tip may be formed with a conical shape. Preferably, the tip is provided with a first end part, fronting the body canal opening during the insertion and provided with a narrow radial size. From this end part, the tip widens out in an intermediate part until the radial size exceeds the radial size of the catheter body part. Between the intermediate part of the tip and the catheter body part, the radial size slopes down in a second end part until the radial size of the catheter body part.
Inlet openings for draining bodily fluid from a body cavity and into the catheter may be provided either in the first end part, in the intermediate part or in the second end part or in more than one part or even en all of the parts. As an example, the tip may be formed in with a plurality of small holes in the tip.
According to a second aspect, the present invention relates to a catheter formed by the above described method and comprising the above described features.