title: Inspiratory fraction and exercise impairment in COPD patients GOLD stages II-III.
abstract: The inspiratory-to-total lung capacity ratio or "inspiratory fraction" (inspiratory capacity(IC)/total lung capacity (TLC)) may be functionally more representative than traditional indices of resting airflow limitation and lung hyperinflation in patients with chronic obstructive pulmonary disease (COPD). In the present retrospective study, a comparison was made of the individual performance of post-bronchodilator IC, IC/TLC and forced expiratory volume in one second (FEV(1)) in predicting a severely reduced peak oxygen uptake (V'(O(2)); <60% predicted) in 44 COPD patients Global Initiative for Chronic Obstructive Lung Disease stages II-III (post-bronchodilator FEV(1) ranging from 31-79% pred). Patients with lower IC/TLC values (<or=0.28) showed increased lung volumes and reduced exercise capacity as compared with other subjects. Following a multiple linear regression analysis, only IC/TLC and FEV(1) remained as independent predictors of V'(O(2)) (r(2) = 0.33). A receiver operating characteristic (ROC) curve analysis revealed that an IC/TLC <or=0.28 had the highest specificity (89.6%), positive predictive value (80%) and overall accuracy (86.3%) in identifying patients with V'(O(2)) <60% pred. In addition, the area under the ROC curve tended to be higher for IC/TLC than IC. In conclusion, post-bronchodilator total lung capacity-corrected inspiratory fraction provides useful information in addition to forced expiratory volume in one second and inspiratory capacity, to estimate the likelihood of chronic obstructive pulmonary disease patients to present with severely reduced maximal exercise capacity.
authors.affiliation: Pulmonary Function and Clinical Exercise Physiology Unit, Respiratory Division, Dept of Medicine, Federal University of Sao Paulo, Sao Paulo, Brazil.
authors.forename: A L P
authors.initials: AL
authors.lastname: Albuquerque
authors.forename: L E
authors.initials: LE
authors.lastname: Nery
authors.forename: D S
authors.initials: DS
authors.lastname: Villaça
authors.forename: T Y S
authors.initials: TY
authors.lastname: Machado
authors.forename: C C
authors.initials: CC
authors.lastname: Oliveira
authors.forename: A T
authors.initials: AT
authors.lastname: Paes
authors.forename: J A
authors.initials: JA
authors.lastname: Neder
mesh_terms: D000368:Aged; D001993:Bronchodilator Agents / Q000494:pharmacology*; D004417:Dyspnea / Q000503:physiopathology; D017079:Exercise Tolerance / Q000502:physiology*; D005260:Female; D005541:Forced Expiratory Volume / Q000502:physiology; D006801:Humans; D007320:Inspiratory Capacity / Q000502:physiology; D008297:Male; D008875:Middle Aged; D029424:Pulmonary Disease, Chronic Obstructive / Q000175:diagnosis / Q000503:physiopathology*; D012189:Retrospective Studies
chemical_list: D001993:Bronchodilator Agents