PURPOSE: It's still uncertain the role of some functional indices, other than FEV1, as tools which reflect the quality of life and define the exercise tolerance in Chronic Obstructive Pulmonary Disease (COPD). The present study is designed to assess during exercise the role of these functional parameters which are related to the behaviour of small airways when expiratory flow-limitation is present.
METHODS: We studied fifty-three patients selected at rest and during severe exercise (cardiopulmonary exercise testing), by spirometry, diffusing lung capacity (Dlco), tidal exercise flow-volume loops, blood and expiratory gas analysis and alveolar-arterial oxygen differences (A-aDO2).
RESULTS: The patients showed on average airflow obstruction (FEV1 56±17% of predicted), pulmonary hyperinflation (IC/TLC=0.38±0.8; FRC/TLC=0.62±0.8) and impaired gas exchange (DLco 67±20% predicted; A-aDO2 30+8 mmHg). Expiratory flow-limitation at rest and dynamic hyperinflation were exhibited by 89% and 54% of patients, respectively. Significant correlations were observed between IC/TLC and exercise ventilatory efficiency parameters (r.64; p<.0001, VD/VT peak). Dynamic hyperinflation was significantly linked to indices of small airways activity as FEF 50% and MEF 25-75% (p<.0001), suggesting some role in limiting ventilatory performance (p.0002, VD/VT peak). A significant correlation was found between impaired ventilatory efficiency variables and both metabolic (r.71; p<.0001, VO2max % predicted) and cardiocirculatory (r.74; p<.0001, VO2/HR peak) exercise response levels. A good correlation, ultimately, was found between DLco and VO2max % predicted (r.63; p<.0001), VD/VT peak (r.51; p.0006) and VO2/HR peak (r.48; p.001).
CONCLUSION: It's confirmed that dynamic hyperinflation limits the exercise tolerance in COPD and it appears better evaluated by inspiratory capacity (IC) and small airways indices. At the same time, DLco, yet, appeared to predict exercise tolerance much better than FEV1.
CLINICAL IMPLICATIONS: These parameters showed a potential role in monitoring the effectiveness of therapy on the life quality of COPD patients.
DISCLOSURE: Giosuè Catapano, No Financial Disclosure Information; No Product/Research Disclosure Information