The aim of this study was to evaluate the agreement between the ultrasound and the electrical impedance tomography - Timpel® (TIE) to detect the beginning of the formation of areas of atelectasis after pulmonary recruitment, with decreasing PEEP values. In addition, the lung ultrasound will be validated for intraoperative use for both adequacy of PEEP, as well as quantitative analyzes of ultrasound images to assess atelectasis.