COPD is a type of obstructive lung disease in which chronic incompletely reversible poor airflow (airflow limitation) and inability to breathe out fully (air trapping) exist.
The poor airflow is the result of breakdown of lung tissue (known as emphysema) and small airways disease (known as obstructive bronchiolitis). The relative contributions of these two factors vary between people. Severe destruction of small airways can lead to the formation of large air pockets—known as bullae—that replace lung tissue. This form of disease is called bullous emphysema.

COPD develops as a significant and chronic inflammatory response to inhaled irritants. Chronic bacterial infections may also add to this inflammatory state. The inflammatory cells involved include neutrophil granulocytes and macrophages, two types of white blood cell. Those who smoke additionally have Tc1 lymphocyte involvement and some people with COPD have eosinophil involvement similar to that in asthma. Part of this cell response is brought on by inflammatory mediators such as chemotactic factors. Other processes involved with lung damage include oxidative stress produced by high concentrations of free radicals in tobacco smoke and released by inflammatory cells, and breakdown of the connective tissue of the lungs by proteases that are insufficiently inhibited by protease inhibitors. The destruction of the connective tissue of the lungs is what leads to emphysema, which then contributes to the poor airflow and, finally, poor absorption and release of respiratory gases.

COPD is characterized by long-term poor airflow. The main symptoms include shortness of breath and cough with sputum production. COPD typically worsens over time.
Chronic bronchitis and emphysema are older terms used for different types of COPD. The term "chronic bronchitis" is still used to define a productive cough that is present for at least three months each year for two years.

Tobacco smoking is the most common cause of COPD, with a number of other factors, such as air pollution and genetics, playing a smaller role. In the developing world, one of the common sources of air pollution is poorly vented heating and cooking fires.[

The diagnosis is based on poor airflow as measured by lung function tests. In contrast to asthma, the airflow reduction does not improve much with the use of a bronchodilator.

Most cases of COPD can be prevented by reducing exposure to risk factors: decreasing rates of smoking and improving indoor and outdoor air quality.
While treatment can slow down the worsening of symptoms, there is no cure.
COPD treatments include stopping smoking, vaccinations, respiratory rehabilitation, and inhaled bronchodilators and steroids. Some people may benefit from long-term oxygen therapy or lung transplantation. In those who have periods of acute worsening, increased use of medications and hospitalization may be required.

Adapted from Wikipedia, the free encyclopedia. Internet. Accessed on June 14, 2016.