Q: What is the purpose of braided tubing?
A: Braided tubing is used for a broad range of medical applications. Stent and valve delivery sheaths, guiding catheter sheaths, valved vascular access sheaths and contrast media injection. Braided tubing is designed to withstand the internal pressure from the air or fluid passing inside it. For catheters, high-pressure braided tubing is used significantly in the administration of contrast media injection. Contrast media is an agent required to make even the smallest branches of the blood vessels visible during angiography procedures. Angiography is the process of taking an X-ray of blood or lymph vessels, carried out after introduction of a radiopaque substance. Depending upon the materials and construction, tubing can be designed to withstand low pressure situations (of around 500 psi) and high pressure situations (around 1,500 psi). To manufacture a braided tube, a central core is initially extruded. That core is then braided with a Nylon, Kevlar, stainless steel or even Nitinol wire. The type of braid and the complexity of the pitch are dependent upon the overall strength and properties needed within the tube. Once the entire length of tubing has been braided, that same length of tubing is again extruded. This encapsulates the braid within the wall of the outer tube. The braided section acts as a structural support to maintain the wall geometry and resist swelling formed due to the pressurized material moving within the I.D. Typically once a material expands and swells it is not likely to return to its normal shape and is at risk of rupturing. The objective is to prevent this from occurring. If a tube were to break during a procedure it could be quite dangerous and costly to the hospital and the patient. Reinforced tubing reinforcing provides added kink resistance, column strength (to make it more pushable), and it also increases torque transmission when compared to non-reinforced tubing. Typical braiding capabilities range from .75 French (Fr) Outside Diameter (OD) to 32Fr, with wall thickness as low as 0.005”.