Estimation of Critical Surface Tension Threshold for Plasma Leakage in Hollow Fiber Membrane Oxygenators: A Proof-of-Concept Pilot Study Using a Surfactant Model

Source abstract

Background: Extracorporeal membrane oxygenation (ECMO) is essential for life support in patients with severe respiratory and circulatory failure. However, plasma leakage remains a major complication. Membrane wetting is known, but the specific physicochemical conditions (surface tension) required to disrupt the barrier function of modern high-performance membranes are unclear. This exploratory pilot study aimed to estimate the critical surface tension threshold for leakage in polymethylpentene (PMP) and silicone-coated polypropylene (PP+Si) membranes and preliminarily evaluate the utility of gas inlet pressure monitoring for early detection. Methods: Two types of adult membrane oxygenators were used: Capiox LX (PMP) and Excelung NHP (PP + Si). In vitro closed-loop circulation was established, and the surface tension of the circulating fluid was reduced stepwise (0–0.15%) by adding sodium dodecyl sulfate (SDS). Water volume loss was quantified over 60 min using a closed-system volumetric method with a metered-dose infusion set to exclude evaporation effects. Water loss in the 0% SDS group was defined as membrane-specific insensible water loss, and any loss exceeding this value was defined as leakage. The inlet pressure of the oxygenator gas was continuously monitored under leakage conditions (0.2% SDS). Results: For both membranes, the barrier function was maintained with a surface tensions >37.2 mN/m. However, at 33.9 mN/m (0.15% SDS), the Excelung NHP showed significant water loss of 23.7±1.2 mL (p<0.0125). The Capiox LX showed an increasing but nonsignificant trend (12.3±1.7 mL). The gas inlet pressure increased significantly within 3 min of circulation onset under leakage conditions. Conclusions: In this surfactant model, the estimated critical threshold for plasma leakage was 33.9–37.2 mN/m. Significant leakage was confirmed in the PP+Si membrane, while leakage in the PMP membrane was increasing. These results suggest that an increase in the gas inlet pressure may be an early warning sign of leakage.