Comparative spallation performance of silicone versus Tygon extracorporeal circulation tubing

Objectives: Reports ranged from mixed to marginal tubing wear and spallation effects as a complication of roller pumps in cardiopulmonary bypass (CPB). Because the rollers constantly compress part of the tubing, we sought to determine whether circuit materials behave differently under a 3-h simulation of CPB.

Methods: Two different tubing materials (silicone and Tygon) were tested with a customized experimental circuit, designed to allow in vitro simulation of CPB with priming volumes, pressures, revolutions per minute and temperatures equivalent to the clinical scenario. Samples were analysed with optical and field-emission scanning electron microscopy. We collected 200-ml fluid samples at 4 different times: before starting the CPB (T0), when the predicted revolutions per minute corresponded to about 2 min of CPB (T1), at 90 min (T2) and at 180 min (T3). At the end of CPB, we harvested 2 samples of tubing. Lastly, optical investigations and field-emission scanning electron microscopy observations were used for qualitative and quantitative analysis of circulating fragments.

Results: T2 and T3 fluid samples showed more particles than T1 samples. Significant differences in terms of particle numbers were detected: silicone tubing released more fragments per millilitre than Tygon tubing, with both materials releasing particles from 5 to 500 µm. Silicone tubing was associated with a time-dependent increase in small particles released (P = 0.04), whereas this did not apply to large particles or to Tygon tubing. Yet, bootstrap estimates suggested that silicone tubing was associated with the release of more small particles whereas Tygon tubing released more large particles (both P < 0.01). Unlike silicone, Tygon samples taken from the portion of the circuit not subjected to the action of the roller pump did not show any erosion on their surfaces. Samples of both materials taken from the portion subjected to the compression of the roller pump showed signs of significant deterioration.

Conclusions: Silicone showed a worse spallation performance than Tygon, thus appearing less safe for more complex surgery of prolonged duration or for patients with a prior cerebral ischaemic event. Additional risk and cost-effectiveness comparisons to determine the potential benefits of one type of tubing material over the other are warranted to further expand our findings.