Apnea testing by artificial CO2 augmentation

We used artificial augmentation of CO2 at a rate of 1 l/min after preoxygenation with 100% O2 to test for apnea in 34 patients with suspected brain death. Observation time was markedly reduced compared with conventional apneic oxygenation, allowing PaCO2 levels > or = 60 mm Hg to be reached within 2 minutes. Properly administered, CO2-supported apnea testing is quick, requires only simple technical equipment, and does not unduly lower PaO2 or pH. It seems to be a useful alternative in cases where reduction of ventilatory volume is not wanted.