The American Thoracic Society/European Respiratory Society 2019 Spirometry Statement and Occupational Spirometry Testing in the United States

To the Editor:

U.S. occupational settings, in which hundreds of thousands of workers are tested each year, have scrupulously adhered to American Thoracic Society (ATS) statements since the first Spirometry Statement was written in 1979. However, although the testing recommendations of the 2019 ATS/European Respiratory Society document (1) clearly apply to clinical and research testing, separate practices may apply in workplaces (2–4). I am requesting clarification on two aspects of the current statement that may be problematic for occupational testing.

First, there are differences between the clinical pulmonary function testing laboratory setting and most occupational settings in the training and depth of respiratory background of operators who perform the testing (e.g., inspiratory loops have never been part of standard occupational testing) and in the varieties of spirometers in use in the two settings. These differences may affect how useful a final inspiratory loop may be, as well as how this added step may affect the measured FVC.

To check the initial inspiration, the inspiratory loop in all settings must be performed accurately. It must commence after recording the FVC plateau, and it must be a maximal inspiration that is forced. If the inspiration begins before the plateau is fully recorded, the FVC may be underrecorded, as can occur if technicians focus more on initiating the inspiration at the earliest possible moment, rather than on fully recording the FVC plateau. In all settings, if not well-trained in the reasons for procedural details, the technician may not elicit a maximal inhalation, in which case the forced inspiratory vital capacity cannot give information about the adequacy of the previous inspiration. If not performed maximally, the loop cannot accurately evaluate the presence of upper airway obstruction and may even falsely suggest that it exists.

Occupational spirometry is governed not only by ATS recommendations but also by regulations from the Occupational Safety and Health Administration, National Institute of Occupational Safety and Health, and other agencies, and consistency of testing technique is crucial when test results are evaluated over long periods of employment. For all of these reasons, the U.S. occupational setting probably will not require performance of the final inspiratory loop as recommended by the ATS/European Respiratory Society in the 2019 Spirometry Statement, although the goal of occupational testing still remains the recording of accurate maximal FEV₁ and FVC. If occupational testing is performed in a pulmonary function testing laboratory by trained respiratory personnel (registered respiratory technician, certified pulmonary function technician, or registered pulmonary function technician), such loops may be performed if desired. However, inspiratory loops are not required for general occupational testing that is performed under regulations promulgated by the Occupational Safety and Health Administration, National Institute of Occupational Safety and Health, and others, and these regulations are unlikely to change. In such testing, adequacy of the inspirations is evaluated by assessing the consistency of the FVCs and the plateaus. The Official Statement from the American College of Occupational and Environmental Medicine is being updated to reflect these recommendations.

In light of this testing protocol, could the statement wording on page e77 be modified from “For spirometers measuring expiration only” to “For spirometers measuring expiration only, or for settings where only expirations are required”? And similarly, in Table 6 on page e78, could “Perform maneuver (expiration-only devices)” be changed to “Perform maneuver (for expiration-only testing protocols or devices)”?

Finally, as specified in regulations and in numerous ATS statements (5, 6), the National Health and Nutrition Examination Survey, Round III (NHANES III) reference values will continue to be recommended for occupational testing in the United States. This follows the 1991 ATS directive to select a reference group that is similar to the participants being tested (i.e., the American workforce), and the recommendation that “NHANES III reference values remain appropriate where maintaining continuity is important” (6). Maintaining these NHANES III reference values will permit consistent evaluation of the FEV₁% predicted over time, as recommended for occupational testing (3).