Intra-operative ventilator mechanical power as a predictor of postoperative pulmonary complications in surgical patients: A secondary analysis of a randomised clinical trial.

Abstract

BACKGROUNDStudies in critically ill patients suggest a relationship between mechanical power (an index of the energy delivered by the ventilator, which includes driving pressure, respiratory rate, tidal volume and inspiratory pressure) and complications.OBJECTIVEWe aimed to assess the association between intra-operative mechanical power and postoperative pulmonary complications (PPCs).DESIGNPost hoc analysis of a large randomised clinical trial.SETTINGUniversity-affiliated academic tertiary hospital in Melbourne, Australia, from February 2015 to February 2019.PATIENTSAdult patients undergoing major noncardiothoracic, nonintracranial surgery.INTERVENTIONDynamic mechanical power was calculated using the power equation adjusted by the respiratory system compliance (C RS). Multivariable models were used to assess the independent association between mechanical power and outcomes.MAIN OUTCOME MEASURESThe primary outcome was the incidence of PPCs within the first seven postoperative days. The secondary outcome was the incidence of acute respiratory failure.RESULTSWe studied 1156 patients (median age [IQR]: 64 [55 to 72] years, 59.5% men). Median mechanical power adjusted by C RS was 0.32 [0.22 to 0.51] (J min−1)/(ml cmH2O−1). A higher mechanical power was also independently associated with increased risk of PPCs [odds ratio (OR 1.34, 95% CI, 1.17 to 1.52); P < 0.001) and acute respiratory failure (OR 1.40, 95% CI, 1.21 to 1.61; P < 0.001).CONCLUSIONIn patients receiving ventilation during major noncardiothoracic, nonintracranial surgery, exposure to a higher mechanical power was independently associated with an increased risk of PPCs and acute respiratory failure.TRIAL REGISTRATIONAustralia and New Zealand Clinical Trials Registry no: 12614000790640.