Asthma and Small Airways Dysfunction

Student thesis: Doctoral ThesisDoctor of Medicine


This thesis focused on examining the small airways dysfunction phenotype, determined by forced oscillation technique (FOT) on a variety of asthma outcome measures. The introduction provides a detailed summary of the pathophysiology of asthma in relation to small airways dysfunction (SAD) including different tools available to assess SAD in asthmatic patients. The impact of asthma treatments with conventional inhalers and biologic treatments on small airway asthma phenotype is also discussed comprehensively. In this thesis, FOT was used to investigate the impact of SAD in patients with asthma.

The first study presented in Chapter 3 is a cross-sectional study examining the use of two FOT devices namely impulse oscillometry (IOS) and airwave oscillometry (AOS) in patients with asthma and COPD. The two cross-sectional studies presented in Chapter 4 examine the relation of SAD to asthma control and type-2 inflammation. Chapter 5 describes two cross-sectional studies with the first study evaluating IOS defined bronchodilator response in relation to asthma control whereas the second study evaluating asthma control and lung function in relation to allergic status. Chapter 6 represents a prospective study to assess patient-reported outcomes after switching from fine to extra-fine particle inhaled corticosteroids (ICS) in persistent asthma.

The final study also known as the FOSTER1, is a randomised controlled study comparing two formulations of inhalers on respiratory impedance using IOS in asthmatic patients. The study was terminated prematurely by the Sponsor as the recruitment was hampered by COVID pandemic lockdown and lung function testing procedures including bronchial challenge were considered aerosol generation at that time. Moreover, the batch of bespoke investigational inhalers was due to expire and the cost to manufacture a new batch of inhalers proved to be prohibitive within the overall budget for the study. However, nine participants completed per protocol and the results are presented in Chapter 7 of this thesis.
Date of Award2023
Original languageEnglish
SupervisorBrian Lipworth (Supervisor) & Philip Short (Supervisor)


  • Asthma
  • Small airways dysfunction
  • oscillometry

Cite this