Author Contribution: Dr Marin had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: Marin, D. Nieto, Carrizo, Vicente.
Acquisition of data: Marin, Villar, Forner, D. Nieto, Carrizo, Vicente.
Analysis and interpretation: Marin, Agusti, Villar, Forner, Barbé, Wei, F.J. Nieto, Jelic.
Drafting of the manuscript: Marin, Agusti, F.J. Nieto.
Critical revision of the manuscript for important intellectual content: Marin, Agusti, Villar, Forner, D. Nieto, Carrizo, Barbé, Vicente, Wei, F.J. Nieto, Jelic.
Statistical analysis: Marin, Villar, Forner, D. Nieto, Wei, F.J. Nieto.
Obtained funding: Marin, Villar, Barbé, Vicente.
Administrative, technical, or material support: Marin, Villar, Forner.
Study supervision: Marin, Agusti, Carrizo, Vicente, Jelic.
Conflict of Interest Disclosures: All authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Jelic reported receiving grants/pending grants from the National Institutes of Health, National Heart, Lung, and Blood Institute (1R01HL106041-01A1). No other authors reported any financial disclosures.
Funding/Support: This work was supported by grants FISS PI04/1684 and FISS PS09/02449 from the Instituto Carlos III, Ministry of Health, Madrid, Spain, and SEPAR/2007 from the Spanish Society of Respiratory Medicine.
Role of the Sponsors: The funding sources had no role in the design and conduct of the study, in the collection, management, analysis, and interpretation of the data, or in the preparation, review, or approval of the manuscript.