A NOVEL HOLLOW FIBER MEMBRANE

Abstract

The efficacy of a new polymethylpentene (PMP) hollow fiber membrane (inner diameter of 200μm and wall thickness of 90μm) was tested with an intravenous oxygenator and carbon dioxide removal prototype. The prototypes consisted of a polyurethane potted bundle of crimped hollow fibers with a membrane surface area of 0.38m2. The prototypes (two groups of n=3) gas transfer performance was tested using a buffered cristalloyd solution (pH=7.4) in a completely automated in vitro system. Each one was placed in a plexyglass chamber (inner diameter of 20mm) as host vessel. Oxygen and carbon dioxide transfer values (VO2, VCO2) were calculated and displayed continuosly at different liquid flow rates through the chamber (Qb=1; 2; 3; 5l/min) and gas flow rates (Qg=1; 3; 51/min). Permissive hypercapnia was modelized increasing venous CO2 partial pressure (pCO2=45; 60; 90mmHg). Liquid pressure drop in the chamber was also measured (ΔP mmHg). Gas transfer values were compared at the same conditions, with three other prototypes (with identical membrane surface area) made with polypropylene (PP) hollow fibers (inner diameter of 240μm and wall thickness of 30μm). Maximal and minimal gas transfer mean values are resumed in the following table:TableMaximal mean ΔP (for Qb= 5 l/min) for PP prototypes is 17.3±2.5mmHg and ΔP=28.71±6.1mmHg for those made with PMP. These results demonstrate a better performance of PMP fibers for O2 transfer. Besides, experiments showed an adequate capacity for CO2 transfer. Their smaller inner diameter and the higher hollow fiber densitiy in the chamber (derived from their bigger outer diameter) are effective ways to increase O2 transfer.