Individualised vs. fixed positive end‐expiratory pressure: a reply

We thank Song and Wu for their comments [1] on our study [2]. We agree that the individualised positive end-expiratory pressure strategy resulted in higher positive end-expiratory pressure levels than the fixed group. However, the intention of our study was not to compare predefined positive end-expiratory pressure levels, but to determine patient-specific optimal levels using electrical impedance tomography during one- and two-lung ventilation, and to maintain this throughout surgery. The positive end-expiratory pressure applied in the individualised group therefore reflects inter-individual variation in respiratory mechanics rather than systematic allocation to higher positive end-expiratory pressure. This approach mirrors clinical practice, where ventilatory settings are titrated according to physiological response rather than fixed protocols. In this context, individualised ventilation represents optimisation of the balance between alveolar collapse and overdistension, rather than escalation of positive end-expiratory pressure. Excessive positive end-expiratory pressure may also have haemodynamic consequences; two patients in our study were withdrawn due to high pressures during titration. We also agree that the composite endpoint of postoperative pulmonary complications comprise events with heterogeneous mechanisms. Postoperative pulmonary complications were selected because of their clinical relevance and widespread use in peri-operative trials [3]. Although certain components, such as prolonged air leak, are predominantly influenced by surgical and parenchymal factors, the composite endpoint captures the overall burden of pulmonary morbidity following thoracic surgery. No differences were observed in outcomes related more directly to ventilatory strategy, including atelectasis. Our findings suggest that improvements in intra-operative respiratory mechanics do not necessarily translate into reductions in clinically relevant postoperative outcomes. These findings are consistent with recent large randomised trials, which have similarly shown that optimisation of intra-operative ventilatory parameters alonemay be insufficient to improve postoperative outcomes [3, 4]. Future studies should refine endpoint selection and better target patient populations most likely to benefit from ventilatory optimisation.