Pulmonary Evaluation at Different Levels of PEEP: Ultrasonography Compared to Electrical Impedance Tomography (TIE) During Intraoperative Elective Surgeries

Patients submitted to general anesthesia and artificial ventilation almost always develop pulmonary atelectasis, which can determine adverse consequences both intraoperatively and postoperatively. It is recommended to use physiological tidal volume (6 - 8 mL / kg of ideal body weight) during the intraoperative period in order to minimize the risk of lung injury. To prevent the formation of atelectasis, minimizing the risk of complications, the use of PEEP has been recommended. At present, there is no way to make an optimal adjustment of PEEP to the needs of each patient, seeking a value that keeps the alveoli open without forming atelectasis and also without areas of hyperdistension.

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.

18 patients (> 18 years) of both sexes, submitted to general anesthesia, will be prospectively studied. All patients will receive, in addition to the usual monitoring, the monitoring with the electrical impedance tomography and chest ultrasonography, after being anesthetized and under neuromuscular block, being ventilated with an inspired fraction of 50% oxygen (or greater to maintain oxygen saturation > 96% ), Tidal volume of 6 mL / kg and respiratory rate to maintain expiratory tidal CO2 between 35-45 cmH2O.