Interpreting pulmonary function tests: recognize the pattern, and the diagnosis will follow.

When interpreting pulmonary function tests, one should first try to determine the pattern of abnormality: is it obstructive, restrictive, or normal? Pulmonary function tests cannot by themselves distinguish among the potential causes of abnormalities, and must be interpreted in light of the patient's history, physical examination, and ancillary studies. Once a pattern is recognized, the diagnosis will often follow.