2.3. Randomization and Blinding
LUNG, BLIND
The patients were divided into two groups with the closed envelope method to undergo either volume-controlled ventilation (Group V) or pressure-controlled volume-guaranteed ventilation (Group PV). Opaque envelopes with sequential numbers were created by an individual who was not involved in the study. These envelopes were opened by an independent party who was also not involved in the study or the preparation of the envelopes. Intraoperative hemodynamic data and ventilation parameters, predetermined in the study protocol, were recorded on patient monitors and subsequently transcribed onto paper case report forms by an anesthesia assistant who was blinded to the protocol and hypothesis of the study and group assignments. Lung ultrasonography was performed by an anesthesiologist who was blind to the study groups and experienced in lung ultrasonography.