Ventilation and Perfusion in the Respiratory System

Respiratory failure occurs when the lung fails to perform one or both of its roles in gas exchange; oxygenation and/or ventilation. Presentations of respiratory failure can be mild requiring supplemental oxygen via nasal cannula to more severe requiring invasive mechanical ventilation as see in acute respiratory distress syndrome (ARDS).It is important to provide supportive care through noninvasive respiratory support devices but also to minimize risk associated with those supportive devices such as ventilator induced lung injury (VILI) and/or patient self-inflicted lung injury (P-SILI). Central to risk minimization is decreasing mechanical stress and strain and optimizing transpulmonary pressure or the distending pressure across the lung, minimizing overdistention and collapse. Patient positioning impacts ventilation/perfusion and transpulmonary pressure. Electrical impedance tomography (EIT) is an emerging technology that offers a noninvasive, real-time, radiation free method to assess distribution of ventilation at the bedside. The investigators plan to obtain observational data regarding distribution of ventilation during routine standard of care in the ICU, with special emphasis on postural changes and effects of neuromuscular blockade, to provide insight into ventilation/perfusion matching, lung mechanics in respiratory failure, other pulmonary pathological processes.