Bioline-coated polymethylpentene (PMP) membrane oxygenators (MO) are used for extracorporeal membrane oxygenation (ECMO) to improve gas exchange in patients with severe acute respiratory distress syndrome (ARDS). However, in some patients, long-term durability is limited due to fibrous and cellular accumulations on the gas exchange surface which can increase resistance to blood flow and diffusion path. These surface deposits of PMP MO after removal were studied with scanning electron and fluorescence microscopy techniques. Three of 31 patients supported by a PMP MO in an ECMO setting required a replacement of the oxygenator after a mean support interval of 11 +/- 7 days due to an increase in flow resistance and an impairment of the gas exchange capacity. The membrane surface of the MO was covered with a fibrous network with imbedded platelets and red blood cells. A membranous structure composed of single cells and clusters of cells covered large areas of the PMP fibers. We assume that these cellular deposits lower the efficacy of ECMO. The identification of these cells could be a key for future therapeutic interventions and improvements in the development of MO.

Thrombosis is the most common technical complication with extracorporeal membrane oxygenation (ECMO). Accumulations of leukocytes on the gas exchange membranes within a membrane oxygenator (MO) may initiate thrombosis and influence outcome. MOs (n = 41) were removed routinely from adult patients on ECMO, preserved, and analyzed for their cellular deposits using nuclear (4',6-diamidino-2-phenylindole) and cell type-specific markers (CD45; von Willebrand factor, vWF). The extent of cellular colonization was correlated with patient data. Blood contact caused adhesion of leukocytes and accumulation of vWF. Six MOs contained "pseudomembranes" (PM). MOs with PM were from younger patients (median [interquartile range {IQR}]; age, 36 [30-47] vs. 61 [51-71] years; p = 0.040) and the leukocyte count before ECMO was on average higher (21 [16-24] vs. 15 [8-18] ×10 per L; p = 0.051) compared with PM-free MOs. The development of PMs did not influence pressure drop across the MO. Data indicating coagulation disorder within the MOs (d-dimers, fibrinogen, and platelets) were not significantly different between the groups. There was only one acute MO thrombosis in a PM-free MO. The support time of the analyzed MOs with PM tended to be longer when compared with PM-free MOs (11 [6-19] vs. 8 [5-11] days). Nevertheless, all patients with MOs with PMs were successfully weaned (6/6 vs. 17/35) and discharged from hospital (6/6 vs. 17/35; p = 0.027) compared with patients with PM-free MOs. In conclusion, elderly people on ECMO showed reduced PM formation that may reduce the risk of MO thrombosis. Younger patients had no negative effect.

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