Feature Article

MANUFACTURING

The clinical problem

A urinary catheter is a hollow tube with a tip that is perforated with apertures/openings (Figure 1). Its use to drain the bladder of urine and/or instill fluids into the bladder is a common procedure: more than 12% of patients in hospital are catheterised¹ and 4% of patients on district nursing caseloads have a long-term catheter in situ.²

Studies have shown that urinary tract infections (UTIs) account for 23% of all hospital-acquired infections.³ Eighty per cent of these UTIs are associated with the presence of a urinary catheter,⁴ and 44% of hospitalised patients with indwelling catheters have been found to develop significant bacteriuria within 72 hours of catheterisation.¹ Other estimates show that approximately one quarter of hospital patients have a urinary catheter at sometime during their stay, and of these, an average of 5% (range is from 3–10%) will acquire a UTI every day. Thus, almost all patients will have an infection after approximately four weeks, which can extend a hospital stay by an extra three days. Patients with a UTI are also three times more likely to die; the fatality rate from urinary tract related bacteraemia is approximately 13%.⁵

Catheters are generally available in three lengths: standard or male, female and paediatric. Standard or male length catheters are on average 45 cm long to accommodate the male urethra. They are the only catheters that should be used for urethral catheterisation of adult men. Female catheters are on average 25 cm long and female patients may have advantages because the shorter the length of catheter external to the body reduces the possibility of compression, kinking and subsequent blockage.⁶

Most urinary catheters are routinely administered by insertion through the urethra and connected into the bladder as shown diagrammatically in Figure 2. Short-term catheters may remain in situ for up to 28 days; long-term catheters may remain in situ for up to 12 weeks.

Figure 2: The clinical use of urinary catheters. (click image to enlarge)

It is critical that the catheterisation process occurs with minimal trauma to the internal environment of the urinary tract. Damage to these tissues will compromise the patient’s safety and comfort, and significantly increase exposure to bacterial infections.

Importance of good manufacturing

Short-term indwelling catheters include poly(vinyl chloride) catheters that should not remain in situ for more than 14 days or according to the manufacturer’s instructions. Other short-term catheters include latex-based catheters coated with polytetrafluoroethylenene. Long-term catheters can be silicone-coated (elastomer) catheters or all-silicone catheters that could be left in situ for up to 12 weeks. These are still available and commonly used. More recent developments include hydrogel-coated latex and all-silicone catheters.

It is important that the surfaces of urinary catheters are perfectly smooth for two major reasons:

• Catheters with roughened surfaces can irritate and cause trauma to the urinary tract upon insertion.
• Catheters with roughened edges can provide “anchor sites” for bacteria to adhere to and thus create a focus for infection.

A particular cause for concern is the texture and shape of the apertures that are formed within the catheter wall. These apertures are required to allow drainage of urinary fluids and therefore they must be perfectly smooth and free from burrs. Most apertures are created by mechanical cutting or piercing/puncturing of the catheter body. These methods have limitations in that they cannot always reliably produce smooth apertures or guarantee the removal of any debris from the punctured or perforated catheter body.

An ultrasonic processing solution

Figure 3: Ultrasonically cut smoother apertures and chads. (click image to enlarge)

Using ultrasonic processing technology, specialised tooling has been developed that can be used to cut and form an aperture through a catheter body and thereby advance the production of smooth apertures. In addition, this technology has solved another problem inherent in the general manufacturing process, that is, the removal of the chad or debris that is generated when the aperture is cut (Figure 3).

Figure 4: Ultrasonic catheter cutter. (click image to enlarge)

In conventional manufacturing processes the chad can be left partially attached to the edge if the cut is not made cleanly or it can be pressed through into the hole and lost within the catheter bore. In both scenarios, unless the error is detected immediately, currently by visual inspection, the chad can still be in situ when the catheter is inserted into the patient’s urinary tract, which would cause trauma to the surrounding tissues and/or dislodge to cause blockages or other serious complications.

The ultrasonic technique combines a vacuum drawing system within the ultrasonic cutting tool so that when an aperture is cut, the vacuum simultaneously removes the chad and conveys it to an electronic counter. If a chad is not counted for each aperture that is cut, then the manufacturing process is automatically stopped and can only be restarted when the faulty catheter is physically removed and disposed of, which ensures 100% elimination of a problem with missing chads.

Figure 4 shows a catheter cutting station in which a catheter (that has been previously dipped in sterilising fluid) is about to be pushed onto an anvil. Two ultrasonic cutting horns would then be positioned on either side of the catheter body. Ultrasonic energy would then be applied and within a fraction of a second, apertures would be cut and the chads sucked through the horns into a counting device and waste reservoir.

L.G. Martini BSc(Hons), PhD MR(Pharm)S is Director Process Understanding and Control, World Wide Manufacturing Operations Science and Technology Pharmaceutical Development at GlaxoSmithKline, Third Avenue, Harlow CM19 5AW, UK, tel. +44 1279 64 3526 e-mail: luigi.gmartini@gsk.com www.gsk.com and A.L. Profit is Director and Founder at Rainbow Medical Engineering Ltd, Icknield Way, Letchworth Garden City SG 61RR, UK, tel. +44 1462 480 442, www.rainbow-medical.eu