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Factors associated with improvement in breathing capacity during exercise in patients with chronic obstructive pulmonary disease
Author(s) -
ONG Kian Chung,
WANG Yee Tang
Publication year - 2003
Publication title -
respirology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 85
eISSN - 1440-1843
pISSN - 1323-7799
DOI - 10.1046/j.1440-1843.2003.00479.x
Subject(s) - medicine , pulmonary function testing , physical therapy , logistic regression , odds ratio , cardiology
Objectives: The aim of this study was to explore the relationship between resting pulmonary function indices and the ratio of minute ventilation at peak exercise to the maximal voluntary ventilation (V̇Emax/MVV) and to determine whether an improvement in breathing capacity during exercise (i.e. V̇Emax/MVV > 1) is associated with greater exercise capacity in patients with COPD. Methodology: The results of pulmonary function tests and incremental, symptom‐limited cardiopulmonary exercise testing in 84 patients with predominantly moderate to severe COPD were reviewed. Multiple linear regression analysis was applied to determine the relationship of V̇Emax/MVV with selected independent variables at rest. Multiple logistic regression was used to determine significant predictors of V̇Emax/MVV ≤ or > 1. Results: FEV 1 /FVC and inspiratory capacity (IC) were the only variables among resting pulmonary function indices that were significant independent determinants of V̇Emax/MVV and the stepwise analysis generated the following equation: V̇Emax/MVV = (−1.05E−02 × FEV 1 /FVC) + (0.15 × IC) + 1.28; r = 0.701, P < 0.001. Using multiple logistic regression with V̇Emax/MVV ≤ or > 1 as a dependent categorical variable, FEV 1 /FVC was the only significant predictor among resting pulmonary indices of a V̇Emax/MVV ratio of > 1 (Odds ratio 0.93, 95%CI 0.89, 0.97). There was a significant association between V̇Emax/MVV and peak oxygen uptake (V̇O 2 max) after adjusting for FEV 1 ( r = 0.66, P < 0.001). If the categorical variable of V̇Emax/MVV (≤ or > 1) was used instead of a continuous variable, a significant association with V̇O 2 max remained after adjusting for FEV 1 ( r = 0.60, P < 0.001). Conclusions: Among resting pulmonary function indices, the FEV 1 /FVC ratio is the best determinant of an improvement in breathing capacity during exercise in COPD patients. After adjusting for FEV 1 , an improvement in breathing capacity during exercise is associated with significantly higher exercise capacity.