RT Journal Article SR Electronic T1 Oxygen desaturation during a 6-min walk identifies a COPD phenotype with an increased risk of morbidity and mortality JF European Respiratory Journal JO Eur Respir J FD European Respiratory Society SP 1 OP 2 DO 10.1183/13993003.00884-2016 VO 48 IS 1 A1 Paul L. Enright YR 2016 UL http://erj.ersjournals.com/content/48/1/1.abstract AB