There are probably as many possible combinations of variables to consider when planning a research and development extrusion trial as there are ideas for medical devices. This article will discuss key factors for meeting tubing specifications for medical devices. The first step is to ask the right questions: What are the mechanical requirements? Does the tube need to be stiff and rigid or soft and flexible. What amount of pressure or vacuum should the tube withstand? This could be critical in deciding whether material selection alone can meet the criteria or if reinforcement by braiding or multilayer extrusion is required. Reinforcement may be required to meet any torque requirements. Does the product need to be clear? How much tensile or tear strength will be needed? And, of course, what size constraints are needed? With medical devices being manufactured in ever smaller sizes to accommodate minimally invasive procedures, thinner walls and smaller diameter tubing with higher levels of performance are becoming the new norm.

Other factors to consider include determining whether the product will be single-use or reusable. If the product is to be single-use should the tubing be “disabled” if resterilized? For multiple-use products the material chosen and the tubing design should withstand repeated usage, repeated cleaning, and sterilization cycles. For products that are to be terminally sterilized, the method of sterilization will influence the material selection as some materials may not be capable of withstanding all sterilization methods.

Functional requirements may dictate the use of additives in the polymer material to provide for a clear image under X-ray or other imaging procedures. Color additives may be required for aesthetic purposes, brand identification, or color coding. Tubing lubricity may be modified by the use of specific chemicals in the polymer mix and other additives can provide for additional heat or UV stability. Early identification of these requirements, so they can be considered in early research and development extrusion trials, enables early stage device testing to cover the material composition that will ultimately be used in the production of the device, eliminating the need for duplication of laboratory testing.

If known, the manufacturing process that will be used to produce the finished medical device in which the tubing will be incorporated should be defined. This enables the selection of materials that are consistent with processing steps, bonding methods, marking systems, etc., which helps avoid repeat extrusion trials and the cost of additional tests associated with material changes.

Recently with the implementation of the REACH (European Union chemical regulation) requirements and the market emphasis on environmentally friendly or “green” products, additional criteria are being applied to the selection of polymers that fit these criteria in addition to all of the previously delineated medical device performance requirements.

Regulatory and commercial considerations should enter the planning process at the extrusion research and development stage. Polymers and additives should be selected that will meet all of the necessary FDA regulations required of the finished medical device. Arrangements to obtain the relevant regulatory information or permission to access data contained in a master file should be confirmed at this stage to avoid problems at later stages of the product development process. In addition, the commercial availability of the material must be confirmed: sufficient quantities are available at a reasonable price over the lifetime of the product.

After gathering all of the relevant information, one can look at the extrusion trial process itself. A design of experiments trial can be constructed to evaluate the effect of different materials or material grades (properties such as hardness) along with different concentrations of additives if used. Tooling design should be based upon the material considerations and the dimensional specifications allowing for some adjustment to sizes based upon product requirements. Consideration must be given to both the actual extrusion tooling as well as the downstream fixtures to assure a stable process yielding tubing meeting the specifications as defined for the device. Although process validation does not typically occur during the R&D trial phase, it is helpful to capture enough data to demonstrate stability and repeatability for additional process runs.

Once the performance of the tubing from the R&D trials has been evaluated during the development of the medical device under design controls, the information gathered should be used to develop formal tubing specifications for use in process validation of the extrusion process for the particular product. The combination of data from the medical device development process and the extrusion R&D trials can be reconciled into final tubing specifications. The extrusion process can then be validated to a formal protocol over multiple extrusion runs using multiple lots of raw material on actual production equipment, especially if the full-scale production is to be completed on equipment that differs from that used in the trials.

With all of the above completed, the specified tubing should be readily available in the production quantities required of the medical device manufacturing operations.

Autoclavable tubing offers options for sterilization

Flexelene 135C autoclavable tubing meets flexibility criteria for a wide range of life sciences, medical and biotech applications. Optional sterilization methods include gamma radiation, E-beam and ethylene oxide. The material is weldable, resistant to chemicals and shows a high potential for use in peristaltic pumps.

Properties:

• Ultra-low extractables / leachables
• No phthalate plasticizers or DEHP additives
• Temp. Range: -50° C to 135° C
• Withstands autoclave, gamma and EtO
• Soft - Shore A hardness 68
• Weldable
• Cleanroom manufactured
• ADF - animal derivative free
• Laser etched with tubing size and manufacture's ID (optional etching with material lot number is available)

Eldon James Corp, 626 W 66th St, Loveland, CO 80538, (970) 667-2728, www.info.hotims.com/25137-500