Discussion
atelectasis
RECRUITMENT, ATELECTASIS, PNEUMOPERITONEUM
In this randomized controlled study we found that lung protective ventilation, applied during elective robotic-assisted laparoscopy surgery with steep Trendelenburg position, improved ventilation distribution recorded by EIT and reduced driving pressure.To our knowledge, this is the first randomized controlled study evaluating the use of EIT to monitor protective ventilation during robotic-assisted laparoscopy surgery with a steep Trendelenburg position. Several studies suggested that pneumoperitoneum and Trendelenburg position can adversely affect lung function and ventilationOur study sustained the evidence that protective mechanical ventilation with an adequate PEEP level improved the distribution of ventilation evaluated by the EIT during general anesthesia. Even if a drop in tidal volume distribution was seen in both groups after induction and anesthesia, the protective ventilation group had a homogeneous distribution of ventilation from the beginning of the Trendelenburg position to come back in supine position. Therefore, the protective ventilation group showed a better ventilation distribution also at the extubation and follow-up. Indeed, only after the extubation we found that EIT-derived parameters and driving pressure came back to the pre-anesthesia levels suggesting that persistent atelectasis and a ventilation–perfusion mismatch were present until the end of general anesthesia.We did not use zero PEEP as a control group to minimize the negative effects of anesthesia and pneumoperitoneum and Trendelenburg position on lung functionThis study had several strengths. First, this is the first randomized controlled study evaluating the use of EIT during elective robotic-assisted laparoscopy surgery with steep Trendelenburg position. Second, the recruitment of 40 patients exceeds the estimated sample size (24 patients), thus the study is adequately powered. Third, this study may be a proof of concept that EIT may be used as respiratory monitoring in operation room.This study had also several limitations. First, the electrical interferences caused by the use of the electrocautery affected EIT measurements and impaired their interpretation, making it necessary to exclude these breaths. Second, EIT belt positioning was a key factor in measurement consistency, since its position was not standardized. Third, the possible clinical impact of our intervention was not evaluated since was not an aim of this study protocol.