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Original article
Greater parallel heterogeneity of airway narrowing and airway closure in asthma measured by high-resolution CT
  1. J R Dame Carroll1,2,3,
  2. J S Magnussen4,
  3. N Berend1,2,3,5,
  4. C M Salome1,2,3,
  5. G G King1,2,3,6
  1. 1The Woolcock Institute of Medical Research, Glebe, New South Wales, Australia
  2. 2The Northern and Central Clinical Schools, The University of Sydney, Sydney, New South Wales, Australia
  3. 3Cooperative Research Centre for Asthma and Airways, Glebe, New South Wales, Australia
  4. 4Macquarie University Hospital, Macquarie University, North Ryde, New South Wales, Australia
  5. 5The George Institute for Global Health, Sydney, New South Wales, Australia
  6. 6Department of Respiratory Medicine, Royal North Shore Hospital, St Leonards, New South Wales, Australia
  1. Correspondence to Dr Gregory G King, Department of Respiratory Medicine, Royal North Shore Hospital, St Leonards, NSW 2065, Australia; gregory.king{at}sydney.edu.au

Abstract

Background Heterogeneous airway narrowing and closure are characteristics of asthma. However, they have never been quantified by direct measurements of parallel sister airways obtained from image data, and the anatomical basis of these processes remains unknown.

Methods Seven normal and nine asthmatic subjects underwent high-resolution CT, before and after methacholine challenge. Mean lumen areas of the entire airways were measured in 28 and 24 parallel sister airway pairs (a pair of airways arising from the same bifurcation) respectively (range 1.0–8.7 mm diameter). Heterogeneous narrowing was defined as the median difference in percentage narrowing between parallel sister airways. Forced oscillatory respiratory resistance (Rrs) and spirometry were measured before and after methacholine challenge conducted while supine.

Results The airways of asthmatics were smaller at baseline, and following bronchoconstriction there were similar decreases in FEV1, increases in Rrs and mean narrowing of airways for asthmatic and non-asthmatic groups. Non-asthmatics required higher doses of methacholine than asthmatics to achieve the same changes. However, parallel heterogeneity (median (IQR) 33% (27–53%) vs 11% (9–18%), p<0.001) and airway closure (24.1% and 7.7%, p=0.001, χ2) were greater in asthmatics versus non-asthmatics.

Conclusion We found clear evidence of differences in airway behaviour in the asthmatic group. Asthmatic airways were narrower at baseline and responded to inhaled methacholine by more heterogeneous narrowing of parallel sister airways and greater airway closure.

  • Asthma
  • Imaging/CT MRI etc
  • Lung Physiology
  • Asthma Mechanisms

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