Chronic Obstructive Pulmonary Disease (COPD), also known as Chronic Obstructive Lung Disease (COLD) is a term used to refer to chronic respiratory diseases including chronic bronchitis and emphysema. In these conditions, there is obstruction to air flow in the airways of the lungs. This interferes with normal breathing.

In chronic bronchitis there is persistent inflammation of the airways (bronchi) of the lungs. In emphysema there is damage to the smaller airways (bronchioles) and air sacs (alveoli) of the lungs. Most people with COPD/COLD have a mix of both emphysema and bronchitis.