Fig. 1. Typical trend recording of transcutaneous carbon dioxide partial pressure (Ptcco2), pulse oximetry (Spo2), and heart rate (HR) during the apnea test in a brain-dead patient of the 20-min apnea test group. Arterial carbon dioxide partial pressure (Paco2) values are plotted for comparison to the simultaneous Ptcco2. Ptcco2was very close to Paco2for baseline measurement but exhibited a certain “delay” during the rapid increase of Paco2during apnea. After reconnection to the ventilator, Ptcco2became closer to Paco2as the rate of decrease in Paco2was reduced. This hemodynamically stable brain-dead patient did not present any complication during the 20 min of the apnea test.