Physiological Effects of Lung Recruitment During General Anesthesia and Low-tidal Volume Ventilation

Fluid administration or amine administration if deemed necessary by the attending physician. Haemodynamics will be monitored through noninvasive cardiac output assessment by arterial pulse contour analysis

Total intravenous anesthesia with a standard protocol

3-5 ml/kg of balanced crystalloids will be administered throughout the whole surgical procedure

Volume-control ventilation with tidal volume=7 ml/kg of predicted body weight for the entire surgical procedure. Respiratory rate will be set to maintain EtCO2 within a physiological range and kept unchanged for the entire duration of the study

Pressure-control ventilation inspiratory pressure=10 cmH2O. Steplike 5-cmH2O-PEEP increase every 30 seconds to achieve a peep of 35 cmH2O, followed by 5-cmH2O-PEEP reduction every 30 seconds to set PEEP