To study 6MWT as a prognostic marker in stable COPD patients & its correlation with spirometry grading.

Abstract

6MWT is non invasive standardized exercise test that measures  global and integrated responses of all systems involved during exercises, including pulmonary and cardiovascular, systemic /peripheral circulation, muscle metabolism. Using desaturation during 6MWT in stable COPD patients we investigated various outcomes-frequency of exacerbations, hospitalizations,mortality & 6MWD correlating with GOLD Grading of spirometry. 

110 stable COPD cases were included & followed up for 1 year. Cases were characterized using spirometry grading,smoking profile. The study is designed to identify the relationship of desaturation at baseline using 6MWT with spirometry grading and clinical outcomes  of acute exacerbation, hospitalizations and mortality in stable COPD patients which is significantly noted in the study. Materials and Methods: One ten patients  with stable COPD diagnosed and staged as per the Global Initiative for Chronic Obstructive Lung Disease (GOLD) guidelines underwent 6MWT. A drop in standard pulse oximetry (SpO ₂ ) of ≥4% or nadir up to ≤88% was defined as desaturation. Based on Desaturation during 6MWT, two groups were formed: desaturated cases and nondesaturated cases.

Result: Out of 110 stable COPD patients, 36 patients desaturated during 6MWT (n = 36/110). Desaturation was significantly more in higher grades of spirometry (very severe , severe) compared to non desaturated cases. Smokers that too females were significantly more prone for desatuartion probably due to dual signergistic action of bio mass fuel exposure and smoking habits. Rate of hospitalization more frequent in very severe and severe grades with mortality of 5/110 of exclusive very severe grade.  Interpretation and Conclusion:  The 6MWT is a safe and sensitive test to access prognosis  in stable COPD patients. Desaturation during 6 minute walk test is found to be good predictor of hospitalization, exacerbations and mortality.