Abstract

COPD is a preventable and treatable disease with some significant extra pulmonary effects that may contribute to its severity in individual patients. COPD is a significant cause of worldwide morbidity and mortality(1). Exercise tolerance is an important factor which affects quality of life in COPD patients. The 6MWT simple powerful tool in the evaluation of the global and integrated responses of all the systems involved during exercise, including the pulmonary and cardiovascular systems. Recently, several publications have established the value of the 6MWT in predicting morbidity and mortality from heart and lung disease. Spirometry is indicated primarily to detect abnormal lung function, to quantify the severity of disease and assess a patient’s treatment response. In this study we assessed the increased difference between slow vital capacity (SVC) and forced vital capacity (FVC) and its association with exercise tolerance 6MWT) in COPD patients. Methods: This is a hospital based observational cross-sectional study which included 100 patients who were all diagnosed and confirmed COPD patients attending the Department of Pulmonary Medicine, Gandhi hospital/Medical College. Results: In the present study, a total of 100 stable COPD patients were included. Out of 100 COPD patients in the study, patients with mild obstruction were 38%, moderate obstruction were 62%. Mean of SVC before 6 MWT in these patients is 2.08L and after 6 MWT is 1.96L. It indicates that SVC decreases after 6 MWT in these patients. Mean of FVC in mild obstruction before 6 MWT is 2.19L and after 6 MWT is 1.90L. It indicates that FVC also decreases after 6MWT. But the fall in FVC is 0.39 L which is more compared to fall in SVC that is 0.10L and the p value of both is statistically significant. In patients with mild obstruction the difference between SVC and FVC (SVC-FVC) after 6 MWT is 0.40 which is more than the difference before 6 MWT (0.21L). In moderate obstruction the difference in SVC and FVC before and after 6 MWT IS 0.21L and 0.25L respectively, both of which are statistically significant. The mean distance covered in mild obstruction patients was 408 ±15m and in moderate obstruction patients was 355.6 ±57m. Conclusion: We routinely use FEV1/FVC to diagnose COPD. This usually under diagnoses the patients of COPD especially in mild disease. Use of SVC to FVC difference may help in early identification of such patients and help in improved treatment outcomes. The difference between SVC and FVC can be used as a predictor of exercise tolerance and pulmonary rehabilitation can be planned accordingly. The degree of air trapping can also be identified but this warrants further investigation.

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