| Abstract |
Spirometry is the most common pulmonary function test (PFT) and it plays a central role in occupational respiratory disease surveillance programs. Accurate spirometry testing, interpretation, and follow-up are critical to effective screening and surveillance of workers exposed to respiratory hazards and to the management of patients in the clinical setting. Spirometry quality assurance includes examination of test values and evaluation of both the volume-time and flow-volume curves for evidence of technical errors. Technically poor spirometry may have little value and may even provide misleading information. When erroneous curves are detected, additional maneuvers are often needed. During testing, technicians should attempt to record a valid test, which is composed of at least 3 acceptable maneuvers with consistent ('repeatable') results for both FVC and FEV1. Achieving repeatability during testing means that the difference between the largest and second largest values for both FVC and for FEV1 are within 0 .15 l (150 ml). Additional maneuvers can be attempted, up to a maximum of 8, to meet these criteria for a valid test. Even tests that have 3 acceptable maneuvers of which at least 2 are repeatable may not represent an individual's maximum effort. Ideally, there should be 3 maximal effort curves with the same size and shape. This guide depicts common testing errors and shows how these errors can impact spirometry results. However, health professionals must bear in mind that, though the goal during testing is to obtain a valid test as described above, results from invalid tests may sometimes provide information that can be used to infer respiratory health status. In 1994, the American Thoracic Society* stated that tests should not be interpreted if fewer than 2 acceptable curves were recorded, reflecting the fact that useful information may be present even in tests that are not optimal. In fact, some medical conditions prevent workers and other test subjects from successfully recording valid tests, in spite of the best efforts of the technician and the subject to produce such results. Clinical judgment should be used to determine whether curves are so unacceptable that they would lead to a misinterpretation of respiratory health. |
