Plastics extrusion: Medical device engineers look to bump tubing for catheters and more

The proliferation of minimally invasive procedures has prompted engineers and extruders alike to push the boundaries of medical tubing development. As a result, catheter diameters have shrunk dramatically to enable better navigation of the device through the narrow and tortuous anatomy of the body. But while decreasing the diameter at the distal end of a catheter is beneficial, it can be problematic at the proximal end of the tube, which must often accommodate luers, extension tubes, or other medical devices. To reconcile these varying size requirements at the proximal and distal ends of the catheter, engineers are increasingly turning to bump tubing as a design solution for peripherally inserted central catheters (PICCs) and other devices.

Benefits of the Bump "Prior to 2000, bump tubing was out there but only being done on a limited basis," comments Tim Steele, founder and CEO of Microspec Corp. (Peterborough, NH). "It has become more popular in the last 10 years. Practicality and design benefits for the user and the patient have fueled its growth."

Also known as a taper tube, bump tubing is characterized by a changing diameter along its length that typically transitions from a smaller-diameter distal end to a larger-diameter proximal end. This configuration allows catheter designers to minimize the diameter of the distal end to improve patient comfort while maximizing functionality of the proximal end and providing easier device access, according to Aubrey Sanders, medical market specialist for Zeus Inc. (Orangeburg, SC). It can also help to limit friction during the procedure, she adds, because there is less material at the distal tip.

While bump tubing enables a catheter to feature different diameters at either end, it also offers the added bonus of doing so in a single, continuous structure. "There's a huge advantage to that; the tube is functionally stronger and not going to break apart easily," Steele says. Non-bump methods of producing such a tube would require the use of multiple parts bonded together in some fashion.

And because it is extruded as a continuous piece, bump tubing can benefit medical device manufacturers as well in terms of time and cost savings. These designs, Steele notes, eliminate the need for added strain relief as well as associated welding and assembly costs. "Generally, if you're doing post-processing, you would also have to form the tube over some sort of mandrel," Sanders adds. "That can be very labor intensive and costly, and can generate a lot of scrap. If you do a bump tube with a supplier, it can be a cost reduction."

Find the rest of the article here at MPMN's website.