Discriminating measures and normal values for expiratory obstruction

Chest. 2006 Feb;129(2):369-377. doi: 10.1378/chest.129.2.369.


Objectives: To develop mean and 95% confidence limits for the lower limit of normal (LLN) values for forced expiratory volume in 3 s (FEV3)/FVC ratio for Latin, black, and white adults; to ascertain comparative variability of the FEV1/FVC ratio, the FEV3/FVC ratio, and forced expiratory flow, midexpiratory phase (FEF(25-75)) in never-smoking adults; to evaluate their utility in measuring the effect of smoking on airflow limitation; and to develop and use the fraction of the FVC that had not been expired during the first 3 s of the FVC (1 - FEV3/FVC) to identify the growing fraction of long-time-constant lung units.

Design: Analysis of the Third National Health and Nutrition Examination Survey (NHANES III) database of never-smokers and current smokers.

Participants: A total of 5,938 adult never-smokers and 3,570 current smokers from NHANES III with spirometric data meeting American Thoracic Society standards.

Measurements and results: After establishing new databases for never-smokers and current smokers, we quantified the mean and LLN values of FEV3/FVC in never-smokers, and identified spirometric abnormalities in current smokers. When associated with older age, FEV3/FVC decreases and 1 - FEV3/FVC increases as FEV1/FVC decreases. On average, using these measurements, the condition of current smokers worsened about 20 years faster than that of never-smokers by middle age. If < 80% of the mean predicted FEF(25-75) was used to identify abnormality, over one quarter of all never-smokers would have been falsely identified as being abnormal. Using 95% confidence limits, 42% of 683 smokers with reduced FEV1/FVC and/or FEV3/FVC would have been judged as normal by FEF(25-75).

Conclusions: FEV1/FVC, FEV3/FVC, and 1 - FEV3/FVC characterize expiratory obstruction well. In contrast, FEF(25-75) measurements can be misleading and can cause an unacceptably large number of probable false-negative results and probable false-positive results.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Female
  • Forced Expiratory Volume
  • Humans
  • Male
  • Maximal Midexpiratory Flow Rate
  • Middle Aged
  • Pulmonary Ventilation*
  • Reference Values
  • Smoking / physiopathology*
  • Spirometry
  • Vital Capacity