POLYURETHANE BLEND MEMBRANES FOR BLOOD OXYGENATION

Objectives: Extracorporeal Membrane Oxygenation (ECMO) is essential in critical care for the management of severe respiratory and cardiac failure. Responsible for maintaining O2 and CO2 levels in the blood, the membrane blood oxygenator (BO) is considered the most important part of the ECMO circuit. Despite the considerable progress during the last decades, efficient BOs for prolonged ECMO do not exist, contributing to the higher rates of thrombosis seen in patients supported by ECMO. To improve the O2 permeability our research group have been focused on the development of new blend polyurethane-based (PUR) membranes, using polyether and polyester-based segmented PURs, which exhibit enhanced hemocompatibility, in association with a good flex-life and mechanical strength. Methods: In this work, two groups of dense symmetric membranes were prepared by the solvent evaporation technique: pure polyurethane (PU) membranes and polyurethane blend membranes using different total polymer/solvent and polyurethane/second reagent weight ratios. The mechanical properties of the membranes were studied through tensile tests. Single gas, O2 and CO2 permeation studies were carried out by the constant volume method at 37°C in an in-house built experimental set-up. Results: The permeability coefficients obtained from the permeation curves ranged from 239 to 347 Barrer for CO2 and 26 to 30 Barrer for O2. The ranges obtained for the diffusion coefficients by the time-lag method were between 1.4 and 3.0 x 10-6 cm2/s for CO2 and between 2.0 and 2.5x10-6 cm2/s for O2. The solubility coefficients varied between 116 and 186 x 10-4 cm3/cm3.cmHg for CO2, and between 11 and 13 x 10-4 cm3/cm3.cmHg for O2. Conclusions: Our data suggests that the introduction of a second component affected not only the mechanical properties by increasing the molecular mobility, thus reducing stiffness but also, that the higher degree of mixing between hard and soft segments leads to higher CO2 and O2 permeation rates.