National Center for Biotechnology Information NCBI NLM MEDLINE humans pubmed abstract nih national institutes of health national library of medicine research support non-u.s. gov't female male aged middle aged Comparative Study Cross-Sectional Studies severity of illness index lung / physiopathology* predictive value of tests principal component analysis pulmonary disease pmid:22500118 pmc3324996 doi:10.2147/copd.s29745 bruno mahut aurore caumont-prim christophe delclaux airway resistance* dyspnea / diagnosis dyspnea / etiology* dyspnea / physiopathology forced expiratory volume lung volume measurements oscillometry paris plethysmography whole body chronic obstructive / complications* chronic obstructive / diagnosis chronic obstructive / physiopathology respiration* spirometry vital capacity