Mechanical Power Is Associated With Mortality in Pediatric Acute Respiratory Distress Syndrome

Abstract

Objectives: Mechanical power (MP) transferred from the ventilator to the lungs has been proposed as a summary variable that may impact mortality in children with acute respiratory distress syndrome (ARDS). To date, no study has shown an association between higher MP and mortality in children with ARDS. Design: Secondary analysis of a prospective observational study. Setting: Single-center, tertiary, academic PICU. Patients: Five hundred forty-six intubated children with ARDS enrolled between January 2013 and December 2019 receiving pressure-controlled ventilation. Interventions: None. Measurements and Main Results: Higher MP was associated with increased mortality (adjusted hazard ratio [HR] 1.34 per 1 sd increase, 95% CI 1.08–1.65; p = 0.007). When assessing the contribution of individual components of MP, only positive end-expiratory pressure (PEEP) was associated with mortality (HR 1.32; p = 0.007), whereas tidal volume, respiratory rate, and driving pressure (ΔP = [peak inspiratory pressure (PIP)–PEEP]) were not. Finally, we tested whether there remained an association when specific terms were removed from the MP equation by calculating MP from static strain (remove ΔP), MP from dynamic strain (remove PEEP), and mechanical energy (remove respiratory rate). MP from static strain (HR 1.44; p < 0.001), MP from dynamic strain (HR 1.25; p = 0.042), and mechanical energy (HR 1.29; p = 0.009) were all associated with mortality. MP was associated with ventilator-free days only when using MP normalized to predicted body weight, but not when using measured weight. Conclusions: Higher MP was associated with mortality in pediatric ARDS, and PEEP appears to be the component most consistently driving this association. As higher PEEP is used in sicker patients, the association between MP and mortality may reflect a marker of illness severity rather than MP itself being causal for mortality. However, our results support future trials testing different levels of PEEP in children with ARDS as a potential means to improve outcome.