Applying spirometry in industrial surveillance programs is reviewed. Proper spirometry requires standardized methodology for test performance and calculation, technician competence, and minimum standards for instrument performance. Pulmonary anatomy and physiology are discussed to identify critical parameters measured by spirometry. These include forced expiratory volume in 1 second (FEV1), a measure of the degree of airway obstruction, and forced vital capacity (FVC), a measure of the elastic recoil pressure and compliance of the airway. The importance of training and skills for competent spirometry technicians is discussed; necessary techniques include subject preparation, test performance, and spirogram assessment. A valid spirogram must be free from cough, early termination of expiration, inconsistent effort, and excessive variability. Spirometric indices calculated from the spirogram time volume tracing are FVC, FEV1, FEV1 as a percent of the total FVC (FEV1/FVC percent) and the mean forced expiratory flow (FEF) during the middle half of the FVC. The method for calculating indices and their importance are discussed. The FEV1/FVC percent index is used to detect severe restrictive pulmonary disease, where a reduction in FEV1 may falsely suggest airway obstruction. The FEF 25 to 75 percent index is a sensitive detector of early airway obstruction in small bronchi and bronchioles. Body temperature, ambient pressure, and saturation with water vapor are factors needed to correct spirometric test results to incorporate results in the patient's permanent record. Calculations of changes in follow up spirograms are discussed. Respiratory surveillance program components include medical history, occupational history, physical examination, chest roentgenogram, and pulmonary function tests in accordance with the American Thoracic Society Standards. Instrument specifications and equipment standards are examined.
Division of Training and Manpower Development, NIOSH, U.S. Department of Health and Human Services, Cincinnati, Ohio