Chronic obstructive pulmonary disease (COPD) is a major cause of disability and death all over the world.[1] Spirometry is the present gold standard for diagnosing COPD. FEV1/FVC ratio is used to define the presence or absence of airflow limitation and FEV1 is used to define the severity of the disease. FEV1 correlates weakly with dyspnea, accounting for 12% of the variability in dyspnea. Once FEV1 is reduced to 35% of predicted, there is a wide spectrum of ability; some patients are not limited in their activities, whereas others are confined to wheelchairs.[2]