Basic concepts of lung function and dysfunction: oxygenation, ventilation, and mechanics.

Acute respiratory failure is a complex disease process. However, it can be understood and appropriately managed if the key components of normal lung function are well understood and abnormalities are specifically identified. These components include oxygenation, ventilation, and respiratory mechanics. The abnormalities, which include hypoxia, hypercarbia, and altered compliance, can be present together or independent of each other. The optimum treatment modality will depend on which component predominates and on the factors producing changes from normal.