Pulmonary function testing in the screening of workers: guidelines for instrumentation, performance, and interpretation.
A condensed guide for the medical surveillance of occupational respiratory diseases is presented. According to the National Institute for Occupational Safety and Health (NIOSH) Manual of Spirometry in Occupational Medicine, the four major objectives of occupational surveillance are to: identify the job applicant with preexisting functional impairment and facilitate proper placement; detect both occupational and nonoccupational disease in an early stage when corrective measures are most likely to be beneficial; identify hazardous working conditions and underscore the need for improvements in industrial hygiene; and reduce the human and economic toll of occupational disease. Procedures to use for surveillance, techniques for interpreting test results, and a study of normal reference values are given. The first stage in the establishment of a surveillance program for respiratory diseases is the determination of an acceptable method of pulmonary function testing. According to the author, pulmonary function testing has a threefold purpose: to identify preexisting pulmonary disorders for proper job placement, to detect early changes in pulmonary function in workers while intervention may still be effective, and to accumulate data to evaluate how well the exposure controls are working. Spirometry is accepted as the most appropriate pulmonary function test for medical surveillance. Spirometry tests should be carried out according to the recommended spirometry standards of the ATS and NIOSH which establish minimum equipment requirements as well as the procedure to use in administering the tests. Also essential to effective spirometry testing is the accurate interpretation of test results. Evaluation of changes in lung function baseline or at a given point of time, evaluation of changes in lung function during a work shift with exposure to hazardous substances, and evaluation of longitudinal changes in lung function are the three methods for interpreting spirometry results in a surveillance program. In addition, a detailed discussion of the two basic methods for comparing a subject's observed value with predicted normal values is given. A lengthy bibliography is given at the conclusion of the article to aid in the establishment of a respiratory medical surveillance program.