Pulmonary function and the pathophysiology, diagnosis, and treatment of acute respiratory failure in critically ill and injured patients.

Ventilation The four main processes involved in gas exchange in the lungs include ventilation (the movement of air in and out of the lungs), distribution (the partitioning of the ventilated gases into the various lobes, segments and lobules), diffusion (the movement of gases back and forth between the alveoli and the plasma and red blood cells), and perfusion (the circulation of blood through the pulmonary capillaries).