Specific Aim 2: To demonstrate the efficacy of a PEEP titration strategy to increase distribution of ventilation and improve oxygenation in children with ARDS utilizing an EIT guided protocol within two standards of care. (Hypothesis: EIT guided titration of PEEP will lead to a more homogeneous distribution of ventilation, improved lung compliance and improved ventilation and oxygenation.) Background and Significance Lung units participating in gas exchange are known as 'recruited' lung. Patients with lung injury suffer from a proportion of lung units which not participating in gas exchange (i.e. the derecruited state), at times resulting in impaired gas exchange. Derecruitment of alveoli may also cause intrapulmonary shunting and worsen lung injury through atelectotrauma. Outcomes in ARDS have improved significantly since clinicians have begun to employ lung protective strategies, including low-tidal volume ventilation and permissive hypercapnea. However, low-tidal volume ventilation has been recognized to decrease recruited lung volume, a phenomenon that persists despite the aggressive positive end-expiratory pressure (PEEP) strategy employed in ARDSNet studies. Atelectasis associated with low-tidal volume ventilation is relieved through the use of so-called sigh breaths, higher levels of PEEP or recruitment maneuverers. Further, the proportion of lung remaining in the derecruited state may contribute to the morbidity and mortality associated with ARDS. In adults, several strategies have been utilized to recruit the lung: sustained inflation (SI) and the maximal recruitment strategy. The so-called open lung approach (OLA) includes an SI followed by the setting of PEEP to the measured lower inflection point of the PV curve. An alternative approach to setting PEEP is a decremental PEEP titration, which includes the sequential lowering of PEEP until a predetermined decrement in PaO2 or SaO2 occurs.