Obesity, expiratory flow limitation and asthma symptoms

Sriram Mahadev, Claude S Farah, Gregory King, Cheryl M. Salome

Research output: Contribution to journalArticlepeer-review

38 Citations (Scopus)


Obesity is associated with poor asthma control, but the reason for this is unclear. Reduction in operating lung volume, as occurs in obesity, and bronchoconstriction, as occurs in asthma, can increase expiratory flow limitation during tidal breathing (EFLt), which may in turn increase respiratory symptoms. The aim of this study was to determine the effect of obesity on EFLt at baseline and after bronchoconstriction in non-asthmatic and asthmatic subjects, and to determine the association between EFLt, and respiratory symptoms. Data from previously published studies in non-asthmatic and asthmatic subjects were reanalyzed using an index of EFLt derived from respiratory system reactance measured by the forced oscillation technique. The analysis showed that during bronchoconstriction both non-asthmatic and asthmatic obese individuals were more likely to develop EFLt than non-obese subjects, despite similar changes in FEV1. Furthermore the index of EFLt was a significant determinant of the severity of breathlessness during challenge in non-asthmatic subjects, and of asthma symptom control in asthmatic subjects following anti-inflammatory treatment. These studies suggest that the combination of bronchoconstriction and low resting lung volume increase the risk of EFLt, and that this altered response to bronchoconstriction may increase the severity of symptoms and lead to worse asthma control.

Original languageEnglish
Pages (from-to)438-43
Number of pages6
JournalPulmonary Pharmacology and Therapeutics
Issue number4
Publication statusPublished - Aug 2013
Externally publishedYes


  • Adult
  • Anti-Inflammatory Agents
  • Asthma
  • Bronchoconstriction
  • Case-Control Studies
  • Forced Expiratory Volume
  • Humans
  • Maximal Expiratory Flow Rate
  • Middle Aged
  • Obesity
  • Retrospective Studies
  • Severity of Illness Index
  • Journal Article


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