Abstract
BackgroundA higher slow vital capacity (VC) compared with forced vital capacity (FVC) indicates small airway collapse and air trapping. We hypothesized that a larger difference between VC and FVC (VC-FVC) would predict impaired exercise capacity in patients with chronic obstructive pulmonary disease (COPD).MethodsPulmonary function and incremental cardiopulmonary exercise responses were assessed in 97 COPD patients. Patients were then divided into two groups: one in which VC > FVC (n = 77) and the other in which VC ≤ FVC (n = 20).ResultsPatients with VC > FVC had lower FEV1 and peak oxygen uptake (VO2/kg) compared with patients with VC ≤ FVC. There was a significant inverse correlation for the entire group between VC-FVC and peak VO2/kg (r = -0.404; p < 0.001). There was also a direct correlation between FEV1% pred and peak VO2/kg (r = 0.418; p < 0.001). The results of the multivariate regression analysis with peak VO2/kg as the dependent variable showed that VC-FVC, FEV1(% pred) and age were all significant independent predictors of peak VO2/kg. The model explained 35.9% of the peak VO2/kg variance.ConclusionsThe difference between VC and FVC, easily measured by spirometry, can be used not only as an index of severity of airflow limitation, but also to predict exercise performance in COPD patients.
Highlights
A higher slow vital capacity (VC) compared with forced vital capacity (FVC) indicates small airway collapse and air trapping
Patients with VC > FVC had lower Forced expiratory volume in one second (FEV1) and peak Oxygen uptake (VO2)/kg compared with patients with VC ≤ FVC (Figure 1)
The peak work rate reached in the group of patients with VC > FVC was lower than in the patients with VC ≤ FVC, but without reaching statistical significance
Summary
Pulmonary function and incremental cardiopulmonary exercise responses were assessed in 97 COPD patients. There was a significant inverse correlation for the entire group between VC-FVC and peak VO2/kg (r = -0.404; p < 0.001). Conclusions: The difference between VC and FVC, measured by spirometry, can be used as an index of severity of airflow limitation, and to predict exercise performance in COPD patients. Subjects We recruited 97 patients with COPD who satisfied the following criteria: FEV1/FVC ratio < 0.7 and FEV1 of 30 to 80% predicted after inhalation of 400 ug albuterol [1] and in a stable condition for at least 6 weeks. Pulmonary function tests Spirometry, including VC, FVC and FEV1 was performed using MasterScreen system (MasterScreen Body, CareFusion, Hoechberg, Germany) before exercise testing in all subjects. VC maneuvers was performed before FVC maneuvers, each of which was performed 3 times, with the highest value of each selected
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