The clinical significance of volume-adjusted maximal mid-expiratory flow (Iso-volume FEF25-75%) in assessing airway responsiveness to inhaled bronchodilator in asthmatics

Ann Allergy. 1982 Mar;48(3):139-42.


The clinical significance of Iso-volume FEF25-75% in assessing airway responsiveness to an inhaled bronchodilator was evaluated in 167 asthmatics who presented with variable degrees of airway dysfunction. Iso-volume FEF25-75% identified responsiveness in one patient (5%) out of 20 of the most dysfunctional asthmatics, in three (20%) out of 15 of the least dysfunctional asthmatics and over-all in four (8%) out of 47 asthmatics not showing significant responsiveness via the FEV1. Over-all, FEV1 identified significant responsiveness in more patients (68.6%) than did the Iso-volume FEF25-75% (61%). The authors conclude that the Iso-volume FEF25-75% adds little to the FEV1 in the assessment of obviously dysfunctional asthmatics, the FEF25-75% as conventionally measured is a relatively useless post-bronchodilator measurement and that the FEV1 remains the single best spirometric test with which to assess airway responsiveness in asthmatics.

MeSH terms

  • Administration, Intranasal
  • Adolescent
  • Adult
  • Aged
  • Airway Obstruction / diagnosis*
  • Amino Alcohols / therapeutic use*
  • Asthma / diagnosis*
  • Asthma / drug therapy
  • Bronchodilator Agents / administration & dosage
  • Bronchodilator Agents / therapeutic use*
  • Child
  • Forced Expiratory Volume
  • Humans
  • Isoetharine / administration & dosage
  • Isoetharine / therapeutic use*
  • Maximal Midexpiratory Flow Rate
  • Middle Aged
  • Vital Capacity


  • Amino Alcohols
  • Bronchodilator Agents
  • Isoetharine