Twenty-four-hour mechanical power variation rate is associated with mortality among critically ill patients with acute respiratory failure: a retrospective cohort study

Abstract

Objectives Defined as the energy applied to the respiratory system by ventilator, mechanical power (MP) of ventilation reflects the risk of ventilation-induced lung injury. This study aims to explore the relationship between dynamic changes in MP and prognosis in\xa0critically ill patients. Methods This was a single-centre retrospective cohort study. Patients receiving mechanical ventilation with acute respiratory failure (ARF) and MP\u2009>\u200910\xa0J/min on admission in the ICU were included. MP (J/min) was calculated as 0.098\u2009×\u2009minute ventilation (L/min)\u2009×\u2009[(peak inspiratory pressure\u2009+\u2009positive end-expiratory pressure)/2] and the MP variation rate (%) as ([baseline MP\u2009−\u200924-h MP]/baseline MP)\u2009×\u2009100. Patients were divided into two groups according to whether MP decreased 24\xa0h after admission (MP-improved group defined as 24-h MP variation rate\u2009>\u20090% vs. MP-worsened group defined as 24-h MP variation rate\u2009≤\u20090%). Results In total, 14,463 patients were screened between January 2015 and June 2020, and finally, a study cohort of 602 patients was obtained. The MP-improved group had a lower ICU mortality rate than the MP-worsened group (24% vs. 36%; p \u2009=\u20090.005). The 24-h MP variation rate was associated with ICU mortality after adjusting for confounders (odds ratio, 0.906 [95% CI 0.833–0.985]; p \u2009=\u20090.021), while baseline MP ( p \u2009=\u20090.909) and 24-h MP ( p \u2009=\u20090.059) were not. All MP components improved in the MP-improved group, while minute ventilation and positive end-expiratory pressure contributed to the increase in MP in the MP-worsened group. Conclusions The 24-h MP variation rate was an independent risk factor for ICU mortality among ARF patients with elevated MP. Early decreases in MP may provide prognostic benefits in this population.