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Thorax 69:987-996 doi:10.1136/thoraxjnl-2014-205160
  • Chronic obstructive pulmonary disease
  • Original article

Comparison of spatially matched airways reveals thinner airway walls in COPD. The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study and the Subpopulations and Intermediate Outcomes in COPD Study (SPIROMICS)

  1. R Graham Barr1,13
  1. 1Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, New York, USA
  2. 2Department of Medicine, McGill University, Montreal, Canada
  3. 3Departments of Radiology, Medicine and Biomedical Engineering, University of Iowa, Iowa City, Iowa, USA
  4. 4Department of Statistics, Columbia University, New York, New York, USA
  5. 5Department of Medicine, Wake Forest University, Winston-Salem, North Carolina, USA
  6. 6Department of Medicine, University of California San Francisco, San Francisco, California, USA
  7. 7Deparment of Biostatistics, University of North Carolina Chapel Hill, Chapel Hill, North Carolina, USA
  8. 8Department of Medicine, University of Michigan, Ann Arbor, Michigan, USA
  9. 9Department of Medicine, Johns Hopkins University, Baltimore, Maryland, USA
  10. 10Department of Medicine, University of Utah, Salt Lake City, Utah, USA
  11. 11Department of Medicine, David Geffen School of Medicine, University of California Los Angeles, Los Angeles, California, USA
  12. 12Department of Medicine, University of Nebraska Medical Center, Omaha, Nebraska, USA
  13. 13Department of Epidemiology, Mailman School of Public Health, Columbia University, New York, New York, USA
  1. Correspondence to Dr Benjamin M Smith, Presbyterian Hospital 9E Room 109, Columbia University Medical Center, 630 West 168th St, New York, NY 10032, USA; benjamin.m.smith{at}mcgill.ca
  • Received 22 January 2014
  • Revised 22 May 2014
  • Accepted 26 May 2014
  • Published Online First 13 June 2014

Abstract

Background COPD is characterised by reduced airway lumen dimensions and fewer peripheral airways. Most studies of airway properties sample airways based upon lumen dimension or at random, which may bias comparisons given reduced airway lumen dimensions and number in COPD. We sought to compare central airway wall dimensions on CT in COPD and controls using spatially matched airways, thereby avoiding selection bias of airways in the lung.

Methods The Multi-Ethnic Study of Atherosclerosis (MESA) COPD Study and Subpopulations and Intermediate Outcomes in COPD Study (SPIROMICS) recruited smokers with COPD and controls aged 50–79 years and 40–80 years, respectively. COPD was defined by current guidelines. Using CT image data, airway dimensions were measured for all central airway segments (generations 0–6) following 5 standardised paths into the lungs. Case-control airway comparisons were spatially matched by generation and adjusted for demographics, body size, smoking, CT dose, per cent emphysema, airway length and lung volume.

Results Among 311 MESA COPD participants, airway wall areas at generations 3–6 were smaller in COPD compared with controls (all p<0.001). Among 1248 SPIROMICS participants, airway wall areas at generations 1–6 were smaller (all p<0.001), and this reduction was monotonic with increasing COPD severity (p<0.001). In both studies, sampling airways by lumen diameter or randomly resulted in a comparison of more proximal airways in COPD to more peripheral airways in controls (p<0.001) resulting in the appearance of thicker walls in COPD (p<0.02).

Conclusions Airway walls are thinner in COPD when comparing spatially matched central airways. Other approaches to airway sampling result in comparisons of more proximal to more distal airways and potentially biased assessment of airway properties in COPD.