Electrical impedance tomography (EIT) is a non invasive monitoring technique that allows to evaluate the regional distribution of ventilation. EIT has been used in different contexts, such as acute respiratory failure or intraoperative ventilation settings. Obesity, by increasing intrabdominal pressure, may reduce functional residual capacity after anesthesia and therefore require a more aggressive intraoperative ventilatory setting. In addition, laparoscopy, by increasing the volume of the abdomen, further pushes the diaphragm and increase the probability of lung collapse.~The aim of the current study is to describe the effect of 1) anesthesia and of 2) laparoscopy and trendelenburg position on regional ventilation distribution. Moreover, the investigators will evaluate if the best ventilatory parameters set after anesthesia induction are confirmed also when the condition changes (i.e. during pneumoperitoneum and trendellenburg).~Finally, the investigators will explore if the different parameters which can be provided by EIT agree in suggesting the best level of positive-end expiratory pressure in both moments of surgery.
This study will evaluate what is the impact of laparoscopy and Trendelenburg position on lung regional ventilation distribution in obese patients, focusing on the differences between the different phases of surgery.