3. Electrical Impedance Tomography (EIT) Electrical impedance tomography capitalizes on changes in impendence in air-filled versus tissue-filled spaces to characterize and quantify regional distribution of lung volume at the bedside. Significant work has been done in the past decade to validate the technology in animals25 and in humans26, 27. The technology utilizes a series of 16 electrodes placed across the patient's chest (Figure 6). As small currents are passed between the electrodes, impedance is measured between and amongst the series. Through a complex interrogation and manipulation of these impedance values, a two-dimensional image is formed (Figure 7), and has been shown to correlate with clinical and radiographic changes in patients27. In ten mechanically ventilated adults with ARDS, end-expiratory lung volume as determined by nitrogen washout correlated well with end-expiratory lung impedance with an r2 of 0.95.26 The ability to estimate lung volume non-invasively and in real time may significantly improve outcomes in patients with lung injury. Specifically, the ability to determine a patient's ideal functional residual capacity and ventilate them towards that goal may improve oxygen delivery by maximizing pulmonary compliance and minimizing pulmonary vascular resistance. This study seeks to utilize varying levels of PEEP to alter end-expiratory volume, using EIT and other surrogate measures to confirm efficacy, measuring oxygenation and shunt fraction as the clinical end points. Should this study demonstrate the ability to effectively recruit lung and minimize shunt fractions using an aggressive PEEP strategy, further studies of clinical benefit from this will be warranted.