Standardisation of lung function testing: the authors'replies to readers' comments

To the Editors: A few questions have been raised following the publication in 2005 of the joint American Thoracic Society (ATS)/European Respiratory Society (ERS) series of documents on standardising lung function testing and these are answered below. SPIROMETRY The following questions and answers pertain to the standardisation document for spirometry [1]. Start of test criteria Should blows be rejected solely on the basis of a poor back extrapolated volume (EV)? Reply Usually. The forced vital capacity (FVC) may be usable, but the forced expiratory volume in 1 s (FEV1) is likely to be falsely high or low. Rationale The acceptability criteria for spirometry were designed to help technologists improve the subject's technique in order to get the best and most reliable result. EV is important for determining that a fast start to the blow was achieved and this is crucial for getting the best values for FEV1 and peak expiratory flow (PEF).