People with COPD have trouble breathing, primarily due to the narrowing of their airways. This is called airflow obstruction. Typical symptoms of COPD include: increasing breathlessness when active, a persistent cough with phlegm and frequent chest infections. The difference between COPD and asthma is that, in asthma the airflow obstruction is reversible. In COPD the obstruction is largely irreversible.

The main cause of COPD is smoking. The likelihood of developing COPD increases the more you smoke and the longer you’ve been smoking. This is because smoking irritates and inflames the lungs, which results in scarring. Over many years, the inflammation leads to permanent changes in the lung. The walls of the airways thicken and more mucus is produced. Damage to the delicate walls of the air sacs in the lungs causes emphysema and the lungs lose their normal elasticity. The smaller airways also become scarred and narrowed. These changes cause the symptoms of breathlessness, cough and phlegm associated with COPD. Rarely, cases of COPD are caused by fumes, dust, air pollution and genetic disorders.