Tubes – Versatile and indispensable

Thin or thick, colored or clear, single or multi-lumen – medical tubing is very versatile. Its application is just as multifaceted. Whether it is for endoscopies, infusions or in heart-lung machines – tubes transport various substances or make minimally invasive surgeries possible. Yet how and what are they actually made of?


Photo: Infusion

It is extremely important that infusion tubes do not bend; © chatchawin jampapha

The most common manufacturing technique is the extrusion process. The machine needed for this, the so-called extruder is reminiscent of a meat grinder. In this process, the material is fed in at the top end, then crushed and plastified into a homogeneous mass using a spiral conveyor, which is heated with cylinders and then recooled. The tool that gives the melted material the necessary form is located at the end of the cylinder. The strand that is squeezed out of the form is being cooled, hardened and the tube is ready to go!

The tube on its own however is not enough. You need suitable ends and applications to integrate it into a medical system. These are often manufactured using an injection molding process: the typically hot material is injected into a mold, cooled down again and a catheter tip is completed for example. The injection-molded parts can then be connected with the tube using a so-called overmolding or insert molding process, that being injection and coating. These methods are an alternative to adhering molded parts.

A clean production

Hygiene is already extremely important during the manufacturing process. This is why medical tubing is produced in cleanrooms where the concentration of airborne particles is kept as low as possible. The traceability of the final product is also very important. This is why many manufacturers offer turnkey service – from raw material all the way to certified medical tubing in sterile packaging.

Photo: Dialysis machine

Medical tubes transporting various substances such as oxygen or blood; © Pfannenschmidt

Silicone is perfectly suited for manufacturing medical tubing. This biocompatible material is characterized by a high level of purity. Silicone is also well suited for tubing with very small diameters. The material makes it possible to produce highest quality medical tubing with diameters of up to 0.2 millimeters. Such tubes are used in microfluidics or with microcatheters and in pediatrics for example.

PVC application still questionable

Plasticized PVC is great to connect with other materials, which also qualifies it as a material for tube manufacturing processes. This plastic can be controlled and processed in many different ways. Even though manufacturers state that they swap out the critical substances, which can be carcinogenic, plasticized PVC, is nevertheless a plastic material, whose application is questionable in medicine in any case.

Thermoplastic elastomers can be melted repeatedly at high temperatures. At room temperature on the other hand, they exhibit a rubber elastic response. This material is particularly interesting for use with hard-soft combinations, which also makes it ideal for medical purposes, for instance in fasteners or syringes.

From single to multi lumen tubing, from double or triple fused tubing – depending on the application, the versatile piping systems can also have different shapes, since they transport different substances such as gases, liquid medicines or food. From infusion to endoscopy, urology and dialysis all the way to hearing aid devices – tubes in their extensive variety are indispensible in medical technology. Without them, it would not be possible to perform both complicated surgeries and simple tasks like drawing blood. Now it has become clear – tubes save lives. At the very least, they help assist with it.
Photo: Michalina Chrzanowska; Copyright: B. Frommann

© B. Frommann

Michalina Chrzanowska