Fig. 2. Histograms showing supplemental oxygen required to keep SpO2at more than 90% in the postanesthesia care unit (PACU) and on postoperative day 1 (POD1). (A ) In the PACU 45 min after tracheal extubation for FIO20.3 versus FIO2more than 0.9 groups. (B ) On POD1 for FIO20.3 versus FIO2more than 0.9 groups. (C ) In the PACU 45 min after tracheal extubation for 0 cm H2O PEEP versus 3–5 cm H2O PEEP groups. (D ) On POD1 for 0 cm H2O PEEP versus 3–5 cm H2O PEEP groups. FIO2= fraction of inspired oxygen; IQR = interquartile range; Lpm = l/min; PACU = postanesthesia care unit; PEEP = positive end-expiratory pressure; POD1 = postoperative day 1.