Application of smaller ventilation volumes requires extracorporeal carbon dioxide removal, using a device similar to a dialysis to remove carbon dioxide directly from the blood. One such device in the Prismalung, it removes blood through a catheter, much like a dialysis catheter, pumps it through a gas exchange cartridge which removes carbon dioxide. The gas exchange cartridge functions in a similar way to a dialysis filter, except it allow gases to pass through, unlike dialysis filters which allow passage of fluid and small molecules.