The predefined ventilation zones*.
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SECONDARY
* Zones of ventilation adapted from: De Bie et al. [These definitions have been used in previous studies on automated ventilation and they reflect the quality of breathing with respect to important ventilator variables, using generally accepted safety zones.Abbreviations: etCO2: end–tidal carbon dioxide by mainstream capnography; FiO2: fraction of inspired oxygen; PBW, predicted body weight; SpO2: oxygen saturation by pulse oximetryWe had the following secondary endpoints: the proportion of breaths spent in the ‘acceptable’ and ‘critical’ zone in the first 3 hours of postoperative ventilation; the 