Assessment of the mechanical properties of the lung and chest wall and evaluation of the efficiency of gas exchange in the lungs are clinically important. When abnormalities are revealed early, impairment may still be reversible or at least treatable. Pulmonary function testing is also helpful in elucidating the basis for breathlessness, a common symptom of pulmonary disease, as well as important in characterizing the pathophysiology and providing a measure of the severity of pulmonary diseases. Pulmonary function testing is also an excellent measure of general health and the risk of mortality from all causes. The range of pulmonary function tests, their accepted symbols, techniques of performance, and interpretation are summarized in Plates 3-1 and 3-2.
RESPIRATORY MUSCLES
The chest expands and the lungs are filled with air by the contraction of the inspiratory muscles that create a negative pressure within the chest cavity and a negative pressure gradient down the airways (see Plate 2-1
