Acute Respiratory Distress Syndrome

ACCP Critical Care Board Review 2003 T acute respiratory distress syndrome (ARDS) and the related acute lung injury (ALI) syndromes are forms of Type I or acute hypoxemic respiratory failure (AHRF). This form of lung dysfunction rises from diseases causing collapse and/or filling of alveoli with the result that a substantial fraction of mixed venous blood traverses nonventilated airspaces, effecting a right-to-left intrapulmonary shunt (Figure 1, panel b). In addition to the adverse consequences upon gas exchange, interstitial and alveolar fluid accumulation result in an increase in lung stiffness, imposing a mechanical load with a resulting increase in the work of breathing (Figure 1, panel a). Uncorrected, the gas exchange and lung mechanical abnormalities may eventuate in tissue hypoxia, respiratory arrest, and death (see Figure 2). When this form of respiratory failure arises from acute lung injury with diffuse alveolar damage and flooding, it is termed ARDS.