This study is a Phase II controlled clinical trial that will obtain comprehensive, serial assessments of respiratory muscle strength and architecture to understand the evolution of ventilator-induced respiratory muscle weakness in critically ill children, and test whether a novel computer-based approach (Real-time Effort Driven ventilator management (REDvent)) can preserve respiratory muscle strength and reduce time on MV. REDvent offers systematic recommendations to reduce controlled ventilation during the acute phase of MV, and uses real-time measures from esophageal manometry to adjust supported ventilator pressures such that patient effort of breathing remains in a normal range during the ventilator weaning phase. This phase II clinical trial is expected to enroll 300 children with pulmonary parenchymal disease, anticipated to be ventilated > 48 hrs. Patients will be randomized to REDvent-acute vs. usual care for the acute phase of MV (interval from intubation to first spontaneous breathing trial (SBT)). Patients in either group who fail their first Spontaneous Breathing Trial (SBT), will also be randomized to REDvent-weaning vs. usual care for the weaning phase of MV (interval from first SBT to passing SBT). The primary clinical outcome is length of weaning (time from first SBT until successful passage of an SBT or extubation (whichever comes first)). Mechanistic outcomes surround multi-modal serial measures of respiratory muscle capacity (PiMax), load (resistance, compliance), effort (esophageal manometry), and architecture (ultrasound) throughout the course of MV. Upon completion, this study will provide important information on the pathogenesis and timing of respiratory muscle weakness during MV in children and whether this weakness can be mitigated by promoting more normal patient effort during MV via the use of REDvent. This will form the basis for a larger, Phase III multi-center study, powered for key clinical outcomes such as 28-day Ventilator Free Days.