Chronic Obstructive Pulmonary Disease (COPD), which encompasses both chronic bronchitis and emphysema, is one of the commonest respiratory conditions of adults in the the developed world. Chronic Obstructive Pulmonary Disease poses an enormous burden to society both in terms of direct cost to healthcare services and indirect costs to society through loss of productivity. The exact prevalence of COPD is difficult to determine because of problems with definition and coding. Sometimes it is difficult to differentiate between COPD and chronic severe asthma, and patients with mild to moderate disease may not be identified as suffering from COPD.