Chronic obstructive pulmonary disease (COPD) is a group of lung diseases that cause swelling of the airways.  Emphysema and chronic bronchitis are the most common forms of COPD.

The leading cause of COPD is smoking. Between 15% and 20% of long-term smokers will develop COPD. Prolonged tobacco use causes lung inflammation and destroys air sacs in the lungs. (In rare cases, an enzyme deficiency called alpha-1 anti-trypsin deficiency can cause emphysema in non-smokers.)

Other risk factors for COPD are exposure to secondhand smoke, male gender, and working or living in a polluted environment.

• Shortness of breath (dyspnea) persisting for months to years
• Wheezing
• Decreased exercise tolerance
• Cough with or without phlegm

An examination often reveals increased work involved in breathing: nasal flaring may be evident during air intake, and the lips may be pursed (the shape lips make when you whistle) while exhaling.

During a flare of disease, chest inspection reveals contraction of the muscles between the ribs during inhalation (intercostal retraction) and the use of accessory breathing muscles. The respiratory rate (amount of breaths per minute) may be elevated, and wheezing may be heard through a stethoscope.

A chest X-ray can show an over-expanded lung (hyperinflation), and a chest CT scan may show emphysema.

A sample of blood taken from an artery (arterial blood gas) can show low levels of oxygen (hypoxemia) and high levels of carbon dioxide (respiratory acidosis). Pulmonary function tests show decreased airflow rates while exhaling and over-expanded lungs.