Six-minute walk, lung clearance index, and QOL in bronchiolitis obliterans and cystic fibrosis

IntroductionThe 6-min walk test (6MWT) predicts outcome in pulmonary hypertension. Recently, its use was reported in both cystic fibrosis (CF) and bronchiolitis obliterans (BO). While the 6MWT is a simple, non-invasive and inexpensive tool, lung clearance index (LCI) measurement requires expensive equipment and expertise. We aimed to evaluate 6MWT in BO and CF, and to compare to MBW (multiple breath washout), pulmonary function tests and quality of life (QOL). MethodsA prospective single center study assessing 6MWT, MBW, spirometry, whole-body plethysmography and QOL (SF-36 questionnaire) in BO and CF patients and correlations between them. ResultsThirty-three BO patients and 37 CF patients. LCI was significantly higher in BO (12.44.2 vs 10.5 +/- 3.4, P=0.044) while FEF 25-75% was significantly lower in BO (43.9 +/- 24.4 vs 60.8 +/- 30.8, P=0.014). 6MWD was 474.8 +/- 76.3 in BO and 506.6 +/- 70 in CF (P>0.05). There was no correlation between 6MWD and LCI in these small study groups There were few correlation between spirometry prameters and 6MWD. In CF, SF-36 scores correlated with pulmonary functions. ConclusionsThe 6MWT is an easy-to-perform test that may be helpful in chronic lung diseases in regions with limited resources. However,with the current limited data, 6MWT cannot replace LCI or spirometry as a marker of disease progression. Is is suggested that, together with QOL, the 6MWT may provide a global estimation of the physiological and general well-being of these patients. Further larger multi-center studies are warranted to evaluate the correlations of 6MWT with pulmonary physiology parameters in various chronic diseases.