Particle fragmentation generated in pump sets

Impact of mechanical stress on flexible tubing used for biomedical applications: Characterization of the damages and impact on the patient's health

Flexible tubing is a key part of a lot of medical devices used in hospital, but may be subjected to a lot of various mechanical stresses that can led to the failure or to complications for the patients. The nature and causes of these mechanical stresses were listed for peristaltic pump tubing, infusion set tubing and catheters. Their consequences in term of tubing damages and particular contamination were reported. The impact of the chemical nature of the tubing, of its size and also the impact of various parameters of the clinical acts were reviewed. Last the consequences for the patient's health were discussed.

Analysis of microembolic particles originating in extracorporeal circuits

Silicone tubing is utilised increasingly in extracorporeal circulation (ECC), particularly for prolonged bypass in cases of left ventricular failure following open heart surgery. We compared the spectrum of particle formation in the EC circuit, due to roller pump damage, resulting from wear of silicone tubing with that of polyvinyl chloride (PVC) tubing. The EC circuit was primed with plasmalyte solution for pump runs of up to 24 hours. Samples of the perfusate were taken from either system at prefixed times. Number and size of the particles were determined by means of a Coulter counter, while their chemical composition was analysed by X-ray dispersion (EDXA). The tubing was examined by scanning electron microscopy. When using PVC tubing, the amount of particles of all sizes rose above acceptable standards shortly after activating the roller pump. Following this early upsurge, the number of particles continued to increase for the remainder of the pump run, albeit at a more moderate rate. The silicone tubing continuously generated a marked quantity of particular matter at a steadily increasing rate. Electron microscopic examination of the silicone tubing revealed multiple particles emanating from the inner surface of the tube. The results suggest that filtration of the initial priming fluid may be advisable before connecting the patient to an EC circuit using PVC tubing. The multitude of particles liberated by the silicone tubing implies that its usage in ECC should be curtailed. Utilisation of noncrushing head pumps is recommended in ECC.

Spallation performance of extracorporeal membrane oxygenation tubing

During the prolonged roller pump use of extracorporeal membrane oxygenation (ECMO), tubing wear generates spallation. The spallation performance of Tygon S-65-HL was measured and compared with a potential new ECMO tubing, LVA (Portex 800-500-575). Spallation was measured by on-line laser diode particle counting (HIAC) during simulated ECMO. The effects of differing levels of occlusion and pump speed were examined, as was the effect of spallation over time. The spallation produced by Tygon S-65-HL was less than that seen with LVA during 24 h of simulated ECMO (p < 0.001), and after 72 h had fallen almost to zero. Spallation with Tygon tubing increases with increasing pump speed and decreases over time. There appears to be only a weak correlation with occlusion, which is surprising. The spallation performance of Tygon S-65-HL was variable and under some conditions exceeded that of LVA. Overall, however, Tygon S-65-HL produced less spallation than LVA. Therefore, LVA cannot be recommended for clinical ECMO use.

An in vitro study of silicone migration from intravenous fluid tubing

Migration of particulate matter from plastic tubing and solid plastic implants has been documented in a number of studies, including some with the use of cardiac bypass, haemodialysis, and pump-assisted intravenous infusions. In order to ascertain whether silicone embolisation occurs when children have an Ivac 560 pump-assisted IV infusion, we passed 180 ml of pumped fluid through a microfilter and compared the scanning electron micrographs of those filters with unused filters and with others through which a similar volume had been passed without using the pump. The particles on the filters were analysed for their elemental content using energy-dispersive X-ray analysis. In addition, the appearance of the silicone tubing used in the pump over 3 and 72 h was assessed and compared to that of flow-only and unused tubing. More particles were found on the microfilter when fluid had been delivered via the pump than on those through which non-pumped fluid had passed or that were unused. Elemental silicon-containing particles were only found on the filter when a pump had been attached to the IV line. The flow-only and unused tubing were found to have adherent particles on the inner surface that were not seen once the tubing had been used for 3 h in the Ivac 560 pump. Also, after 72 h use, the silicone tubing had a deformed inner layer. The clinical significance of these findings is yet to be determined, but it does appear that silicone embolisation occurs during pump-assisted infusions in children.

Surface alterations in dialysis roller pump inserts: a scanning electron microscopy study

Scanning electron microscopy has been used in a study of particle spalling from silicone and PVC elastomer inserts of dialysis roller pumps. In an experimental circuit using Isoton II, pump occlusion, pressure, pump revolutions and temperature were monitored. Scanning electron microscopy was performed on inserts exposed to 1-10 h of pumping using Silastic (medical grade) and a Watson-Marlow MHRE pump, with PVC and Pivipol, a polyurethane coated PVC (Bellco) using a Bellco BL705N pump. Changes included longitudinal splits (single and multiple), superficial cracks (random and orientated), deformations of normal surface pattern, holes, craters and detaching particles. There was an increase in these abnormalities with time for all types of pump insert, the changes being most marked for the Silastic/Watson-Marlow pump combination and least prevalent with the PVC/Bellco pump combination.

Particle spallation induced by blood pumps in hemodialysis tubing sets

The repeated flexion and compression of pump segments by the rollers of peristaltic pumps results in cracking and abrasion of the inner surfaces of the pump segment, leading to shedding of particles into the extracorporeal circuit. A series of studies to assess the rate of particle release from silicone rubber, polyvinyl chloride (PVC), and Pivipol, a coextruded polyurethane-coated PVC tubing, when these materials were used with blood pumps of the type found in hemodialysis units, was undertaken. The studies show that with all tubing/pump combinations there is an overall increase in the total number of particles released, but an analysis of the particle size distribution indicates that the majority of the particles are less than 16 micron in diameter. The rate of increase may be reduced, however, by decreasing the occlusion pressure.

Pathological findings in silicone spallation in vitro studies

Silicone pump head tubings were subjected to mechanical stress under conditions which simulated hemodialysis. Examination by scanning electron microscopy revealed evidence of abrasion on the internal surface of the tubing following 5 h of normal use. Damage was extensive after 20 h and large splits and lacerations were present on the internal surface after 96 h of pumping. Atomic absorption spectrometric analysis of the circulated blood provided confirmatory evidence of spallation, and concentrations of polydimethylsiloxane (silicone) rose in parallel with the duration of use. While spallation has previously been demonstrated from polyvinyl chloride, latex and silicone tubings during the faster flow rates of cardiopulmonary bypass, this report is the first to show silicone spallation at flow rates obtained during hemodialysis.

Microemboli observed in deaths following cardiopulmonary bypass surgery: silicone antifoam agents and polyvinyl chloride tubing as sources of emboli

Refractile foreign particles within clear vacuoles were observed in capillaries of 17 patients who underwent cardiopulmonary bypass surgery, died, and were autopsied at the George Washington University Hospital from December 1978 through April 1981. The postoperative survival time ranged from less than one day to more than eight months. The approximate maximal diameter of the individual particles was 10 micrometer and that of the vacuoles 60 micrometer. The particle-droplet complexes showed affinity for hydrophobic stains. In all 17 cases, the kidneys were involved in combination with several other organs. In two patients, the emboli were associated with microinfarcts in one or more organs. Scanning electron microscopy (SEM) of the polyvinyl chloride tubing used during four cardiopulmonary bypasses showed spallation and shredding of the luminal surface in the areas exposed to the roller pump heads. This suggested that fragments of polyvinyl chloride might be the particles in the emboli. Another possible source was the antifoam agent used in the bubble oxygenator. Scanning electron microscopy x-ray microprobe analysis of the foreign material within capillaries of several organs showed it to be strongly positive for silicon but not for chlorine. Therefore, it was concluded that the microemboli were droplets of antifoam agent, the refractile particles corresponding to the particulate silica component and the vacuoles corresponding to the dimethylpolysiloxane liquid component. Since x-ray microprobe analysis of the microemboli did not reveal a strong chloride peak, there is as yet no evidence that polyvinyl chloride fragments were involved in the microembolism. The morphologic findings reported here indicate that antifoam microembolization continues to complicate cardiopulmonary bypass surgery and must, therefore, be considered a potential cause of postoperative morbidity. The consequence of the fragments of polyvinyl chloride tubing released into the circulation remains to be established.