Effect of Positive End-expiratory Pressure on Sevoflurane Washout Times from Anesthesia Workstations

This study examined the effect of positive end-expiratory pressure (PEEP) on sevoflurane washout from anesthesia workstations using a test lung model. Two workstations (Perseus A500 and Carestation 650) were tested with fresh gas flows (FGF) of 2-8 L / min at PEEP levels of 0 and 8 cmH2O. Washout time was the interval for sevoflurane concentration to fall from 8% to 0%. In the Perseus A500, PEEP prolonged washout at 2 L / min (2562 [92] s vs. 2266 [17] s, p = 0.027), 4 L / min (1397 [36] s vs. 1275 [32] s, p = 0.012), and 6 L / min (756 [8] s vs. 533 [34] s, p = 0.006), but not at 8 L / min (115 [2] s vs. 113 [2] s, p = 0.23). In the Carestation 650, washout was prolonged at 2 L / min (5254 [229] s vs. 4447 [113] s, p = 0.013), 4 L / min (3597 [101] s vs. 2911 [230] s, p = 0.022), and 6 L / min (1816 [94] s vs. 1492 [115] s, p = 0.021), but not at 8 L / min (252 [3] s vs. 212 [35] s, p = 0.187). Our findings indicated that PEEP delayed anesthetic washout most at lower FGFs, which warrants caution in low-flow anesthesia. J. Med. Invest. 73 : 111-115, February, 2026.