Strengths and limitations
RECRUITMENT, COMPLICATION, PNEUMOPERITONEUM
Our study is the largest investigation of LTVV during laparoscopic surgery. It analysed a pre-defined cohort of significance. It used an outcome that as assessed by observers blinded to the intervention. It adjusted findings in the laparoscopic group for any imbalances in relevant confounders. Moreover, it applied imputation analysis to test the robustness of its finding. Finally, it was the first to assess the effect of LTVV in isolation. In this regard, previous studies of patients undergoing laparoscopic surgeries have focused commonly on LTVV combined with differences in PEEP and recruitment manoeuvres, which have been proposed to oppose the physiological effects of the pneumoperitoneum [This study has several limitations. Importantly, this was a post-hoc analysis of a single centre study; therefore, it is subject to all the limitations intrinsic to such a study type. However, this study did include a diverse range of patients and laparoscopic procedures. In addition, blinding of clinical staff was not possible primarily due to the nature of the intervention. However, scoring of the clinical outcomes was determined by blinded observers. Unfortunately, due to limitations of the ventilators used in our centre at the time of our primary trial we were unable to measure plateau pressure and estimate driving pressure (as a surrogate of lung strain) during surgery. Notably, the respiratory management after the intraoperative intervention period was not protocolised. However, there are no current consensus guidelines to guide such management. Therefore, we designed this trial with a pragmatic approach. Furthermore, the use of the primary composite outcome implies equivalence of each of its components and the severity of the complication was not qualified in the results. However, this is consistent with the approach used in our overarching trial. This is also congruous with other major trials of intraoperative ventilation and PPCs [In conclusion, this post-hoc analysis of a large, randomised trial of LTVV during major laparoscopic found that LTVV was associated with a significantly reduced risk of PPCs compared to conventional tidal volume ventilation, when PEEP was applied equally between both groups. Given these results, further evaluation of the ideal ventilation strategy during laparoscopic surgery, is warranted.