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Location, location, location: studying anatomically comparable airways is highly relevant to understanding COPD
  1. Benjamin M Smith1,2,
  2. Eric A Hoffman3,
  3. Stephen Rennard4,
  4. R Graham Barr1,5
  1. 1 Department of Medicine, College of Physicians and Surgeons, Columbia University, New York, New York, USA
  2. 2 Department of Medicine, McGill University, Montreal, Quebec, Canada
  3. 3 Departments of Radiology, Medicine and Biomedical Engineering, University of Iowa, Iowa City, Iowa, USA
  4. 4 Department of Medicine, University of Nebraska Medical Center, Omaha, Nebraska, USA
  5. 5 Department 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}

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We have read with interest Nakano and colleague's thoughtful comments1 on Smith et al 2 and are pleased to offer the following observations.

We believe that a key strength of our paper is that it defines a rigorous sampling strategy to compare airways from matched hierarchical positions within the tracheobronchial tree with control for the known hierarchical gradient in airway dimensions.3 Nakano et al are correct to point out that hierarchical sampling by generation number results in grouping of airways from multiple anatomic locations (eg, segmental and lobar airways); conversely, hierarchical sampling by anatomic location results in grouping of airways from multiple generations.4 It is for this reason that we reported both sampling approaches (tables 2 …

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  • Correction notice This article has been corrected since it was published Online First. The competing interests statement has been corrected.

  • Acknowledgements We thank Professor Ewald R Weibel for graciously providing advice on the ideas expressed in this response to Nakano et al.

  • Contributors All authors contributed to the discussion, formulation and revising of this letter. BMS also conducted additional analyses and drafted the original letter.

  • Funding US Department of Health and Human Services-National Institutes of Health (HHSN268200900013C-HHSN268200900020C, N01-HC95159-HC95169, R01-HL075476, R01-HL077612, R01-HL093081), Fonds de Recherche du Québec—Santé (Clinician-researcher training award)

  • Competing interests EAF is a founder and share holder of VIDA Diagnostics, a company that is commercialising pulmonary image analysis software developed, in part, at the University of Iowa.

  • Provenance and peer review Not commissioned; internally peer reviewed.

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