Study of 2 Minute Walk Test in the Assessment of Functional Capacity in Patients with Stable Chronic Obstructive Pulmonary Disease

Abstract

Background: COPD is now one of the top three causes of death worldwide and 90% of these deaths occur in low and middle income country.Assessment of functional capacity is vital for appropriate therapy, standard rehabilitation program and also a strong predictor of survival in patients of chronic obstructive pulmonary disease. Field walking tests are simpler and cheaper, require less technical expertise and equipment. Incremental shuttle walking test and the widely practiced 6MWT is a good predictor of functional status for patients with COPD. 2MWT is more feasible in some settings as frail elderly patients were unable to complete a single trial of 6MWT but better able to tolerate 2MWT. So to find a cut off value of walking distance 2MWT and validity of the test this study is necessary. We search relation between 2MWT and airflow limitation of COPD patients. We also search relation of the test with 6MWT. Objective: To assess the usefulness of 2MWT as an assessment tool of functional capacity of stable COPD patients. Materials and Methods: This cross sectional study was conducted in the department of Respiratory Medicine of National Institute of Diseases of the Chest and Hospital (NIDCH) from February, 2022 to March, 2023. Eight five (85) stable COPD patients with mild to very severe airflow obstruction were enrolled in this study. Baseline data (FEV1, FEV1/FVC, resting pulse rate, respiratory rate and SpO2) were collected and then all the patients were subjected to perform 2 min walk Test (2MWT) and 6MWT under normal ambient conditions. Then pertinent post-exercise data (walking distance, pulse rate, respiratory rate, SpO2) were collected. The Statistical Package for Social Science (SPSS) v.23 was used for statistical analysisResults: Out of 85 patients, Majority 30(35.3%) patients had severe COPD, 27(31.8%) had very severe, 18(21.2%) had moderate and 10(11.8%) had mild COPD. Mean pulse, SpO2, respiratory rate - at the end of 2 minute walk test and 6 minute walk test were  statistically significant (p<0.05) compare with baseline. Mean distance walked was found 96.6±36.2 meter in the end of 2 minute and 250.3±91.8 meter in the end of 6 minute. Significant relationship was found between severity of COPD and 2MWT (p<0.001). Based on the receiver-operator characteristic (ROC) curves 2 minute walk test had area under curve 0.886.. Receiver-operator characteristic (ROC) was constructed by using 2 min walk test, which gave a cut off value d”95.7 meter, with 82.5% sensitivity and 85.7% specificity for prediction of severe FEV1. Based on the receiver-operator characteristic (ROC) curves 6 min walk test had area under curve 0.839. Receiver-operator characteristic (ROC) was constructed by using 6 min walk test, which gave a cut off value d”286.5 meter, with 89.4% sensitivity and 71.4% specificity for prediction of severe FEV1. The validity of 2 minute walk test vs 6 minute walk testevaluation for severity of airflow limitation of COPDwas correlated by calculating sensitivity (84.7%), specificity (96.2%), accuracy (88.2%), positive predictive value (98.0%) and negative predictive value (73.5%). Conclusion: This study concluded that the 2MWT is a reliable, valid, and sensitive test for the assessment of functional status in patients with stable COPD. It is practical, simple, quick, easy to administer, and well-tolerated by patients with stable COPD. Chest Heart J. 2024; 48(2) : 90-99