Fig. 1

Consolidated Standards of Reporting Trials (CONSORT) diagram for this trial. PEEP positive end-expiratory pressure, iPEEP individual PEEP, COPD chronic obstructive pulmonary disease, ICU intensive care unit, ASA American Society of Anesthesiologists classification, PaO2 partial pressure of arterial oxygen, FiO2 inspiratory fraction of inspired oxygen, EIT electrical impedance tomography, PPCs postoperative pulmonary complications