Acidic sweep gas with carbonic anhydrase coated hollow fiber membranes synergistically accelerates CO2 removal from blood

摘要

The use of extracorporeal carbon dioxide removal (ECCO2R) is well established as a therapy for patients suffering from acute respiratory failure. Development of next generation low blood flow (< 500 mL/min) ECCO2R devices necessitates more efficient gas exchange devices. Since over 90% of blood CO2 is transported as bicarbonate (HCO3⁻), we previously reported development of a carbonic anhydrase (CA) immobilized bioactive hollow fiber membrane (HFM) which significantly accelerates CO2 removal from blood in model gas exchange devices by converting bicarbonate to CO2 directly at the HFM surface. This present study tested the hypothesis that dilute sulfur dioxide (SO2) in oxygen sweep gas could further increase CO2 removal by creating an acidic microenvironment within the diffusional boundary layer adjacent to the HFM surface, facilitating dehydration of bicarbonate to CO2. CA was covalently immobilized onto poly (methyl pentene) (PMP) HFMs through glutaraldehyde activated chitosan spacers, potted in model gas exchange devices (0.0151m²) and tested for CO2 removal rate with oxygen (O2) sweep gas and a 2.2% SO2 in oxygen sweep gas mixture. Using pure O2 sweep gas, CA-PMP increased CO2 removal by 31% (258 mL/min/m²) compared to PMP (197 mL/min/m²) (P < 0.05). Using 2.2% SO2 acidic sweep gas increased PMP CO2 removal by 17% (230 mL/min/m²) compared to pure oxygen sweep gas control (P < 0.05); device outlet blood pH was 7.38 units. When employing both CA-PMP and 2.2% SO₂ sweep gas, CO₂ removal increased by 109% (411 mL/min/m²) (P < 0.05); device outlet blood pH was 7.35 units. Dilute acidic sweep gas increases CO₂ removal, and when used in combination with bioactive CA-HFMs has a synergistic effect to more than double CO₂ removal while maintaining physiologic pH. Through these technologies the next generation of intravascular and paracorporeal respiratory assist devices can remove more CO₂ with smaller blood contacting surface areas.