Screening tests for pulmonary function abnormality.

Simple tests based on a voluntary forced expiration can detect pulmonary impairment of occupational or environmental origin earlier than can be done using clinical or radiographic examination. These tests are easily performed and repeated, require little time and can be readily set up in the field. Flow impairment ("obstructive") has conventionally been measured by the forced expiratory volume--1 sec (FEV1); earlier changes, in the small airways are more likely to be detected by the maximal mid-expiratory flow (MMF) and the maximum expiratory flow-volume (MEFV) curve at low lung volumes. Volume impairment ("restrictive") is detected by the forced vital capacity (FVC) from which the preceding measurements are made.