[Aex - the area under the expiratory flow-volume loop]

Pneumologie. 2015 Apr;69(4):199-206. doi: 10.1055/s-0034-1391401. Epub 2015 Apr 8.
[Article in German]


Preschool children often show total expiration times of less than one second in pulmonary function tests. Therefore, FEV1 cannot be used for evaluation of obstructive pulmonary diseases in small children. Aex, the area under the expiratory flow-volume loop, does not depend on the expiration time. The Aex value varies according to the convex or concave shape of the flow volume loop, can be quantified and is a valuable parameter in the diagnosis of obstructive airway diseases.In this study FEV1 und Aex values of 19882 flow-volume loops were measured and compared. The comparison shows a very high correlation coefficient of r = 0.99.The changes of both parameters in an individual after provocation or bronchospasmolysis also demonstrate a strong correlation. A 20 % change of FEV1 equals an Aex change of 36 %.We conclude that measuring Aex is a good alternative to measuring FEV1 especially if the FEV1 cannot be obtained due to short expiration times.

Publication types

  • English Abstract

MeSH terms

  • Adolescent
  • Algorithms
  • Area Under Curve
  • Asthma / diagnosis*
  • Asthma / physiopathology
  • Bronchial Provocation Tests / methods*
  • Child
  • Diagnosis, Computer-Assisted / methods*
  • Exhalation
  • Female
  • Forced Expiratory Volume*
  • Humans
  • Lung Volume Measurements / methods*
  • Male
  • Reproducibility of Results
  • Sensitivity and Specificity
  • Spirometry / methods*