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Case Study 1: Catheter Hole Formation

Case study number 1 exemplified in Figure 1, shows that it is possible to precisely cut/core a wide variety of shapes through hollow flexible plastic tubing, in this case an ovoid aperture was precisely punctured through a catheter. In addition, the application of a vacuum through the hollow sonotrode would allow the plastic debris, which has been cut, to be extracted and accounted for within a waste reservoir. The consequences of unaccounted for shard of plastic, remaining within a catheter, could have drastic clinical implications. Other applications include the cutting of semi-solid materials such as creams, ointments, polymeric films and even foodstuffs.

Figure 1 - Ultrasonically cut apertures within a catheter

Problem one

A leading medical company needed to reduce the incidence of “hospital acquired infection” and consequent patient deaths caused by urinary catheters.

The general manufacturing process of cutting eyes / holes in urinary catheters is mechanical pressure which produces eyes with surfaces that are less than perfectly smooth. A rough upper surface can cause tissue damage when inserted and removed and the damaged area can become a site of infection. Similarly a rough lower surface can become encrusted by particles, bacteria etc. and also become a site of infection.

Solution one

By developing highly specialised tooling and cutting the eyes ultrasonically, Rainbow Medical has provided a manufacturing process that is a measurable step forward in edge/ surface smoothness.

Problem two

Rainbow Medical’s process also resolves the problem of the hanging or lost chad / slug i.e. the waste material produced when the eye / hole is cut.

In the general manufacturing process the chad can either be left partially attached to the edge if the cut is not made completely (hanging) or pressed into the hole (lost). In either situation, unless the error is detected, currently by inspection, the chad can still be in situ when the catheter is inserted into the patient, where it can dislodge and cause a blockage and other serious problems.

Solution two

Rainbow Medical’s process also includes cutting the eyes in a vacuum which draws the chad through an electronic counter. Should the count not tally the manufacturing process is automatically stopped and can only be re-started when the faulty catheter is physically inserted into a disposal point in the machine, ensuring 100% elimination of the hanging or lost chad problem.

© Rainbow Medical Engineering, Shaftesbury Industrial Centre, Icknield Way,  Letchworth Garden City, Hertfordshire SG6 1RR