Chronic obstructive pulmonary disease (COPD) is lung disease that makes it difficult to breathe. Most people with COPD have both emphysema and chronic bronchitis.

The leading cause of COPD is smoking. Between 15 - 20% of long-term smokers will develop COPD. Using tobacco for a long time causes lung inflammation and destroys air sacs in the lungs. (In rare cases, non-smokers who lack a protein called alpha-1 anti-trypsin can develop emphysema.)

Other risk factors for COPD are:

• Exposure to certain gases or fumes in the workplace
• Exposure to heavy amounts of secondhand smoke and pollution
• Frequent use of cooking gas without proper ventilation

• Cough
• Decreased exercise tolerance
• Shortness of breath (dyspnea) lasting for months to years
• Wheezing

Some people, even those with severe COPD, have few or no symptoms.

People with COPD may make wheezy air sounds, difficult-to-hear air sounds, or normal sounds when the doctor listens to them during an exam. In severe cases, a person with COPD can seem anxious and may breathe through pursed lips (the shape lips make when you whistle).

During a flare of the disease, the muscles between the ribs contract while the person is breathing in (intercostal retraction) and the person will use other muscles to breathe. The number of breaths per minute (respiratory rate) may be high.

A chest x-ray may show that the lung is expanding too much (hyperinflation). 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). The best test for COPD is lung function testing.