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Table 1 Overview of intermittent high fresh gas episodes and ensuing sevoflurane spikes

From: Agent consumption with the Zeus® in the automated closed circuit anesthesia mode with O2/air mixtures

   High FGF episodes Sevoflurane spikes   
Etiology Message Time Av FGF Composition Duration Volume wasted Vsevoprior to spike Vsevoduring spike Duration Sevo waste % of average usage 1–60 min (5.44 mL) Pt
   min L/min % O2 sec L mL/h mL/h sec mL   #
FAsevo overshoot + Autoflush 2 6.4 21 36 3.86 part of washin after overshoot, N/A   1
CO2 sampling issue Autoflush 7 2.1 100 31 1.10 followed by sampling issue N/A   1
During calibration Calibration 27 2.0 33 19 0.65   no change   N/A   2
Pressure on abdomen Bag filling 14 14.0 38 7 1.64 7 84-198 7 0.15-0.39* 3-7 5
  Bag filling 20 13.8 100 7 1.61 8 79-165 7 0.14-0.32 * 3-6 4
  Bag filling 25 13.3 99 6 1.33 6 58-131 11 0.16-0.40* 3-7 5
  Bag filling 25 13.2 21 6 1.32 4 72-172 8 0.15-0.38* 3-7 2
  Bag filling 33 16.6 100 6 1.66 4 89 6 0.14 3 3
  Bag filling 34 16.9 98 6 1.69 4 100-300 6 0.16-0.49* 3-9 3
FIO2 < 50% Autoflush 45 1.9 100 27 0.87 5 6 209 0.08 2 6
  Autoflush 51 2.3 100 26 0.98 7 21 20 0.08 1 4
  Autoflush 52 1.9 100 33 1.07 5 7 311 0.19 3 7
  Autoflush 55 1.7 100 37 1.04 2 4 254 0.16 3 1
Pressure on abdomen + FIO2 < 50% Bag filling, then autoflush 36 3.1 60 32 1.68 4 13 60 0.15 3 3
  1. FAsevo = end-expired sevoflurane %; FGF = fresh gas flow; Av = average; Vsevo = sevoflurane usage; Pt = patient; N/A = not applicable.
  2. *Sevoflurane injection rate at least temporarily > 100 mL/h, thus a range is given. See text for details.