An appreciation of the mechanical basis of pulmonary edema formation and the role of pleural pressure in modifying cardiac performance is important for managing patients with pulmonary edema. The role of hydrostatic forces in the development of lung edema may have magnified influence in acute lung injury and pulmonary edema formation. Although there is much to be learned, an understanding of the determinants of pulmonary blood volume is important to understand the hydrostatic forces that promote transvascular fluid filtration. Pulmonary blood volume is determined by the interaction of the compliant properties of the pulmonary circulation, downstream resistances, and the interaction of surface pressure, left atrial pressure, and pulmonary blood flow. Both cardiac output and left atrial pressure have important effects on lung, blood volume, and edema formation, Increasing pleural pressure will tend to reduce edema formation through a reduction in both cardiac output and pulmonary venous pressures. Cardiac output reduction will predominate when cardiac contractility is good, and left strial pressure reduction will predominate when contractility is poor. Overinflation of the lung, however, may lead to a net increase in pulmonary blood volume and obviate the beneficial effect of increasing pleural pressure.
ASJC Scopus subject areas
- Critical Care and Intensive Care Medicine