A device for oxygenating blood in an extracorporeal circuit includes a first structure suitable to delimit a portion of space-containing capillaries made of microporous membrane. The reference cell is programmed a predetermined amount, its program state is sensed relative to a prescribed cell on the same die, and the programming process continues until the reference cell fails a preselected read operation. The exhaust gases that are expelled from the first cylinder are routed through a first exhaust pipe.