RELATION OF LUNG-FUNCTION, MAXIMAL INSPIRATORY PRESSURE, DYSPNEA, ANDQUALITY-OF-LIFE WITH EXERCISE CAPACITY IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

Background - Several studies have shown that both objective and subjec tive measurements are related to exercise capacity in patients with ch ronic obstructive pulmonary disease (COPD). In this study the relative contribution of lung function, maximal inspiratory pressure, dyspnoea , and quality of life to the performance in a walking distance test an d a bicycle ergometer test was investigated. Methods - Static lung vol umes, forced expiratory volume in one second (FEV(1)), inspiratory slo w vital capacity (IVC), transfer factor for carbon monoxide (TLCO) div ided by the alveolar volume (TLCO/VA), static compliance (Cst), and ma ximal inspiratory peak pressure (PImaxPOES) were measured in 40 patien ts with COPD with severe airways obstruction (mean FEV(1) 44% predicte d, mean FEV(1)/IVC 37% predicted). Quality of life was assessed by the Chronic Respiratory Questionnaire (CRQ) and dyspnoea by the Borg cate gory scale. Exercise capacity was measured by both a six minute walkin g distance (test) and a maximal work load of the bicycle ergometer tes t (Wmax). Results - Spirometric values and maximal inspiratory pressur e were modestly correlated with both the six minute walking test and W max, r values ranging from 0.50 to 0.58. The TLCO was strongly correla ted with the six minute walking test (r = 0.62) and with Wmax (r = 0.7 8). Quality of Life showed no correlation with exercise capacity, whil e there was a correlation between dyspnoea and the six minute walking test (r = -0.41). Backward linear regression analysis selected TLCO an d PImaxPOES as the most significant determinants for exercise performa nce. They explained 54% and 69% of the variance in the six minute walk ing test and Wmax, respectively. Conclusions - The results show that e xercise capacity in patients with COPD with severe airways obstruction is more strongly related to inspiratory muscle strength and lung func tion than to dyspnoea and quality of life. The significant correlation between dyspnoea and the six minute walking test suggests that subjec tive variables are more strongly related to walking tests than to bicy cle ergometer tests.