Introducing a new concept of extracorporeal gas exchange and first in vitro investigations

Hintergrund Oxygenators and gas exchangers in general are essential to thoracic surgery, as well as lung support modalities for patients suffering from pulmonary diseases. Here, a novel gas exchanger making use of dialysis capillary membranes, an impermeable layer, and an inversion of blood-gas flow patterns is introduced, and the findings of preliminary investigations are communicated.

Material und Methode Dialyzer modules have been coated with a silicone compound to create a thin film on the capillary membrane, capable of preventing plasma leakage without impeding gas diffusion. Using the above procedure two dialyzer modules with surface areas of 1,3 m² and 1,8 m² have been treated, and submitted to further testing. Coating quality was evaluated by building up pressure inside the fibers through gas inflation and monitoring its subsequent decline due to gas diffusion through the silicon layer. The fluid dynamic properties, as well as the gas exchange performance of both modules were assessed by means of an in vitro extracorporeal circuit using porcine blood, and compared to those of a commercial oxygenator (PMP hollow fibers, A_mem = 1,35 m²).

Ergebnis Coated dialyzers permitted gas to diffuse upon pressure build-up within the fibers, yet there was no plasma leakage into the gas side when primed with blood. Blood pressure drop in these modules was 170-210 mmHg at a blood flow rate, Q_B, of 1 L/min (hematocrit Hct. = 40%), whereas PMP 1,35 registered 69 mmHg under similar conditions. Oxygen transfer rate (OTR) ranged between 12,9-20,5 mL/min and 14,5-33,5 mL/min for the coated dialyzers and the PMP oxygenator respectively, at blood flow rates 200-500 mL/min (with constant sweep gas flow rate (Q_G = 5 L/min). Under these conditions, carbon dioxide transfer rate (CTR) values of 65-106 mL/min and 65-137 mL/min were attained by the coated dialyzer modules and the PMP gas exchanger respectively.

Schlussfolgerung As reported, the gas exchange capacity of coated dialysis membrane is equivalent to that of the PMP, particularly in terms of CTR. And since CO₂ removal applications don’t require high blood flow rates, these novel gas exchangers can be operated with a dialysis machine, thus avoiding excessive pressure drop and shear stress. Moreover, the implementation of affordable components and materials facilitates the production of efficient, hemocompatible gas exchangers. Further validation through animal trials is required.