The goal of this study is to evaluate the sensitivity and specificity of Electrical Impedance Tomography (EIT) as a bedside diagnostic tool for lung pathologies in patients who are mechanically ventilated. In electrical impedance tomography low amplitude, low frequency current is applied on electrodes, and the resulting voltage is measured and used to computed the electrical properties of the interior of the chest as they change in time. The computed properties are used to form an image, which can then be used for monitoring and diagnosis.