Extracorporeal Membrane Oxygenation and Novel Modalities in Management of ARDS

Abstract

The lung has two essential, interdependent functions. One function is ventilation-perfusion matching to deliver oxygen to the body and to remove carbon dioxide that is produced by the body. The second function is host defense against the onslaught of airborne pathogens, chemicals, and particulates. These essential functions are emphasized through the gross, subgross, histologic, and ultrastructural determinants of respiratory gas exchange in the normal human lung. The lungs and the chest wall are elastic structures. Normally, no more than a thin layer of fluid is present between the lungs and the chest wall (intra-pleural space). The lungs slide easily on the chest wall, but resist being pulled away from it in the same way that two moist pieces of glass slide on each other but resist separation. The pressure in the “space” between the lungs and chest wall (intrapleural pressure) is subatmospheric. The lungs are stretched when they expand at birth, and at the end of quiet expiration their tendency to recoil from the chest wall is just balanced by the tendency of the chest wall to recoil in the opposite direction. ARDS is characterized by noncardiogenic pulmonary edema, lung inflammation, hypoxemia, and decreased lung compliance. The pathogenesis of ARDS remains elusive and there is no gold standard diagnostic test. The heterogeneity of the clinical conditions associated with ARDS would be consistent with the possibility that ARDS is in fact a collection of different diseases that have not yet been separately identified.