An in vitro technique to assess oxygenator potential for respiratory failure therapies

To assess microporous membrane oxygenators (MMO) for long-term respiratory support, an in vitro test of 4 days duration has been developed. The objective is to screen oxygenators before they undergo expensive animal trials. As a sensitive indicator of performance change, CO2 transfer rates (VCO2) are determined with fresh bovine blood at the start, after 48 hours and after 96 hours of perfusion. Blood is used only for gas exchange evaluation and is replaced with plasma in the intervening periods. Data are obtained at blood flow rates (QB) of 1.0, 1.5 and 2.0 l/min for gas: blood flow ratios (QG:QB) of 2:1 and 5:1. The test has been conducted on Bentley BOS-CM50 oxygenators (n = 10). With heated dry air ventilation there was no significant change in VCO2 with time for all QB and QG:QB combinations. Plasma leakage did not occur into the gas compartment of the MMO. Similar results were obtained with heated humidified air ventilation. The findings are in agreement with existing animal studies of 4-7 days duration.