In this month's issue of Pediatric Critical Care Medicine, Proulx et al (1) present a sophisticated time-sequence analysis of the evolution of organ failure, gas exchange, ventilator settings, and lung mechanics in children with severe pediatric acute respiratory distress syndrome (PARDS). Their approach leverages over 12,000 hours of data during conventional mechanical ventilation in about 80 children with severe PARDS. They have confirmed the association amongst multiple organ failure, oxygenation deficits, and dead space with mortality in PARDS. Furthermore, they have found that an estimate for mechanical power, a composite variable reflecting the total energy given to the lungs during mechanical ventilation, which is associated with mortality in adults with acute respiratory distress syndrome (ARDS) (2), is also associated with mortality in severe PARDS.The authors should be commended for their work, as their approach has leveraged valuable data from the electronic health record to give us a deeper understanding of how these variables evolve over time among PARDS survivors and nonsurvivors. They have also highlighted that an often-ignored variable in ventilator management, the respiratory rate, may have prognostic relevance in severe PARDS. Respiratory rate is a particularly problematic variable for analysis in pediatrics, as it is age-dependent. The authors addressed this age dependence by normalizing respiratory rate using a z score method and identified that nonsurvivors had respiratory rates 2 z scores higher than survivors.Mechanical power is an attractive concept to characterize the degree of lung-protective ventilation because it is a composite metric representative of the energy delivered to the lung. It includes elastic static components, elastic dynamic components, and resistive components (3). Positive end-expiratory pressure (PEEP), inspiratory pressure (both peak inspiratory pressure and plateau pressure), tidal volume, flow, and respiratory rate contribute to mechanical power, to different extents (4). These individual variables are of course coupled with one another based on the elastance and resistance properties of the respiratory system, which has always made it difficult to understand the individual associations of these variables with outcomes in patients with PARDS, as, in most analyses, many of these variables are colinear with one another. This certainly increases the attractiveness of using mechanical power as an alternative approach to characterize the degree of lung-protective ventilation that is being used.