Medical Plastic Data Service Magazine



Our 30th Year of Publication
Page  3 of 6

Cover Story

Medical Polymer Tubing : Applications & Extrusion Technology Highlights

Enhancing performance and design

Following are the various features incorporated in the catheter tubings to enhance performance depending on the applications :

• Braid/coil reinforcement for strength, rigidity and torque control along the length of the catheter to balance the need for flexibility and kink resistance to navigate tortuous pathways.
• Use of hydrophilic coatings delivers high lubricity to achieve low insertion force or a reduction in friction for a specific delivery application.
• Soft tip and multi-durometer segments along the length of the catheter provide atraumatic entry and maneuverability.
• Radiopaque contrast at the tip and key segments offer better visibility for the physician to visualize accurate anatomical placement.
• Steerability and deflection help attain optimal navigation.

Methods To Assess Tubing Properties :

Briefly . methods used to measure the effects of extrusion parameters on the final product and for comparison with the original polymer characteristics include : optical microscopy, tensile testing, rheometry testing, IR spectrophotometry, and enthalpy differential analysis.

Measuring Catheter Tubing Sizes

Problems can arise when the customer and catheter or tubing supplier are not using the same scale when discussing catheter tubing sizes.

French scale and gauge scale are the measures used to refer to the diameter of catheters and tubing. While each have certain advantages, misinterpreting these standards can lead to confusion. “OD” and “ID” are abbreviations for outer diameter and inner diameter, respectively, and are generally measured in inches or millimeters.

The catheter sizing classification most commonly used in the medical industry is the French (Fr) scale, also known as the “Charrière’s system.” The French scale is an easy method to use to describe the basic size of a catheter, because it specifies the most obvious component, the outer diameter. The French size = 3 times the diameter in millimeters. The disadvantage of the French scale is that it does not specify the inner diameter of the catheter or tubing. Thus, the French sizing used alone, is not specific enough to adequately describe small catheters, where internal diameter is critical. This scale is much more useful to specify larger catheter sizes.

A second method of sizing catheters is the gauge measurement. Gauge is a descending scale, opposite the French scale of measurement which ascends with corresponding size. The higher the gauge size the smaller the tubing.

Another less common method for sizing catheter tubing is the “PE” scale. It is specific to polyethylene and is an ascending scale used by some manufacturers to represent the OD and ID of the tubing, similar to French sizing.

The most definitive method to describe a catheter’s dimension is simply to state the exact measurements of both the outer and inner diameters. While it may seem a little more difficult to communicate, this method will actually give all the details necessary to the researcher or catheter manufacturer to properly size your specific catheter and catheter connections.

The Economics Of Extrusion

• Important elements of Expenses in the medical tubing extrusions are : Materials, Equipment, Direct Labour, Others ( includes : Power, Packaging, Insurance etc )
• In most of the cases , the largest cost is the material.
• Extrusion is usually a 24-hour continuous operation. Frequent starts and stops greatly increase production costs.

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