Open-lung ventilation and mechanical power in thoracic surgery

BACKGROUND: Individualisation of positive-end expiratory pressure (PEEP) is an open-lung ventilation strategy associated with better respiratory mechanics. Mechanical power has been associated with lung injury in critical care settings, but the interaction between optimisation of PEEP and mechanical power during one-lung ventilation (OLV) remains poorly understood. OBJECTIVE: This study aimed to determine the effect of individualisation of PEEP on mechanical power during OLV as well as to establish the association between mechanical power and postoperative pulmonary complications after thoracic surgery. DESIGN: This is a post hoc analysis of a multicentre randomised trial. SETTING: Operating rooms. PATIENTS: Thoracic surgery cases requiring OLV. INTERVENTION: Open-lung ventilation strategy (i.e. individualised PEEP titration based on respiratory compliance) versus standard PEEP. Mechanical power and its components were compared between both groups at five different time-points: two-lung ventilation (T0), baseline OLV (T1), 20 min after OLV (T2), end of OLV (T3) and before extubation (T4). MAIN OUTCOME MEASURES: Our primary outcome included a composite of postoperative pulmonary complications within 30 days after surgery. Multivariable mixed-effects logistic regressions were performed to assess associations between various thresholds of mechanical power and postoperative pulmonary complications. RESULTS: A total 1253 patients were included in this analysis, of which 635 received open-lung ventilation, and 618 received conventional ventilation. The median difference in mechanical power was higher in the open-lung ventilation group during OLV than in the control group at T2, T3 and T4: 1.39 [95% confidence interval (CI), 0.91 to 1.86] J min -1 , 1.27 (95% CI, 0.79 to 1.75) J min -1 and 2.12 (95% CI, 1.60 to 2.63) J min -1 , respectively. While the resistive component of mechanical power was associated with postoperative pulmonary complications [odds ratio (OR), 1.07 (95% CI, 1.01 to 1.13) per J min -1 ], the static component was protective [OR, 0.91 (95% CI, 0.85 to 0.98) per J min -1 ]. CONCLUSION: Individualisation of PEEP during OLV leads to nonclinically significant higher levels of mechanical power compared with standard PEEP. Each component of mechanical power seems to have different interactions with the occurrence of postoperative pulmonary complications. TRIAL REGISTRATION: NCT03182062.