1. Department of Pneumology, Galdakao-Usansolo Hospital, Galdakao, Bizkaia, Spain
2. Research Unit, Basurto University Hospital, Bilbao, Bizkaia, Spain
3. Research Unit, Galdakao-Usansolo Hospital, Galdakao, Bizkaia, Spain
4. Department of Pneumology, Basurto University Hospital, Bilbao, Bizkaia, Spain
5. Department of Pneumology, Alava University Hospital, Vitoria, Alava, Spain
6. Department of Pneumology, San Eloy Hospital, Barakaldo, Bizkaia, Spain