Six-Minute Walk Test in Interstitial Lung Disease : various outcomes for various causes

Background: The six-minute walk test (6MWT) is commonly used in the assessment of sub-maximal exercise tolerance in patients with interstitial lung disease (ILD) that takes various clinical and functional forms. Aim: To assess the 6MWT outcomes in each form of ILD. Methods: A study including 195 patients with ILD divided into 4 groups (G1: 80 patients with sarcoidosis, G2: 56 patients with Idiopathic Pulmonary Fibrosis (IPF), G3: 35 patients with connectivitis and G4: 24 patients with hypersensitivity pneumonitis). All patients perfomed a 6MWT. The Physiological Cost Index (PCI)[1] was calculated. Result: Median age was 55 years in G1, 62,5 in G2, 60 in G3 and 56 in G4. Dyspnea (mMRC scale) was present among 80% of patients in G1, 91% in G2, 94% in G3 and 66% in G4. Mean 6-minute walk distance (6MWD) was 467±72m in G1, 427±96m in G2, 459±120m in G3 and 488±91m. Oxygen desaturation was present among 7% of patients in G1, 29% in G2, 19% in G3 and 25% in G4. Mean PCI was 0,33±0,15 in G1, 0,33±0,16 in G2, 0,29±0,11 in G3 and 0,36±0,15 in G4. IPF patients (G2) were significantly the most dyspneic (p=0.001), presented more frequent oxygen desaturation during 6MWT (p=0,001) and lower DM6 (p=0,02). In contrast, no significant difference in ICP were found. Conclusion: Comparing different etiologies of ILD, sub-maximal exercise tolerance appears to be more limited in IPF despite the similarity in energy cost of walking. Thus pulmonary rehabilitation should be recommended for these patients. [1] MacGregor J. The evaluation of patient performance using longterm ambulatory monitoring technique in the domiciliary environment. Physiotherapy 1981;67(2):30-3.