Friction reduction in co-axial catheter systems

The purpose of these experiments was to evaluate the effectiveness of treating manufactured catheters with radio-frequency induced plasma to obtain decreased static and dynamic friction between treated and non-treated catheters. This was accomplished by treating the catheters for 0, 5, 30, 120 and 300 seconds and inserting the treated catheter through the lumen of a larger diameter non-treated catheter, around a loop, and measuring the force required to initiate and maintain movement of the inner catheter through the secured outer catheter. Silicone rubber, polyethylene and two different polyurethanes were studied dry and in three different fluid media: wetted hydrate in a physiologically buffered saline, and in a 10 mg/ml albumin solution. X-ray photo-electron spectroscopy was performed on all dry catheters to determine surface chemical composition before and after radio frequency glow discharge treatment. Water contact angle were obtained on al dry catheters to determine the hydrophobic/hydrophilic nature of the catheters before and after treatment. Microscopic evaluation and infra-red absorption studies were also performed on some catheters to correlate results. A short in-vivo study was initiated to obtain qualitative results of the catheter treatments. No correlation between radio-frequency glow discharge treatment times and friction was observed. Earlier studies of this type showed some decrease in friction with radio frequency glow discharge treatment, although these previous test were performed on pure material and not on manufactured catheters as was done in these experiments. There was a definite correlation found between the fluid media used and the friction observed. These findings varied depending on the catheter material utilized. Further study is necessary to evaluate the basis behind these findings.