Correlation of Six Minute Walk Test with Spirometry Indices in Chronic Obstructive Pulmonary Disease Patients

BACKGROUND Spirometry is the gold standard for accurate measurement of lung function. However, it is only one way of interpreting COPD disease severity and is effort dependent. Measurement of Peak Expiratory Flow Rate, 6-minute walk test (6-MWT) and quantitative assessment of symptoms like MMRC dyspnoea scale offers cheaper modes of assessing lung function. Six Minute Walk Test is the most commonly used test for assessing the functional capacity of persons with Chronic Obstructive Pulmonary Disease. It is a reliable, repeatable, reproducible and responsive test for measuring the functional exercise capacity of patients with Chronic Obstructive Pulmonary Disease. METHODS It is an observational study conducted in South Indian tertiary care hospital. All consecutive patients with confirmed diagnosis of chronic pulmonary disease attending the department of pulmonology, Sri Ramachandra Institute of Higher Education and Research, from January 2018 to January 2019, were included in the study. Six Minute Walk Test and Spirometry were performed as per American Thoracic Society guidelines. Correlation between Six Minute Walk Test and Spirometry was assessed using statistical software, Statistical Package for Social Sciences (SPSS) version 16.0. RESULTS The variables of Six Minute Walk test like six-minute walk distance and six-minute distance saturation both correlated positively with Spirometry parameters FVC, FEV1, FVC/FEV1 in COPD patients. In this study, we demonstrated that six minute walk test significantly correlated with absolute values of Spirometry. Six Minute Walk Test can replace spirometry in assessment of severity of Chronic Obstructive Pulmonary Disease. CONCLUSIONS Six Minute Walk Test significantly correlated with absolute spirometry values of FEV1/FVC, FVC, FEV1. Thus, we conclude that Six Minute Walk Test can replace spirometry in assessment of severity of Chronic Obstructive Pulmonary Disease. The variables of six-minute walk test varied as the severities of the disease varied. The six- minute walk distance and six-minute distance saturation both correlated with Spirometry parameters FVC/FEV1 (moderate positive correlation or weak positive correlation) in severe, very severe Chronic Obstructive Pulmonary Disease patients and SpO2 correlated with the scale. The predicted percent of FVC/FEV1 and FVC correlated with six-minute walk distance saturation in meters.