Shortness of breath is a symptom of chronic obstructive pulmonary disease that develops because oxygen flow through the airways is restricted, explains the National Heart, Lung, and Blood Institute. COPD causes tissue damage, inflammation and loss of elasticity in the air sacs and pathways of the respiratory system, and the excessive buildup of mucus leads to further airway obstruction. Long-term breathing impairment gradually interferes with routine activities, such as walking.
Emphysema and chronic bronchitis are the two major forms of COPD, and many people have both conditions, notes the National Heart, Lung, and Blood Institute. The bronchial tubes and bronchioles are branching pathways that lead to tiny air sacs, or alveoli, which are lined with blood vessels. The alveoli transfer oxygen to the bloodstream through the capillaries while collecting carbon dioxide to remove it from the body. Emphysema develops when the alveoli walls deteriorate and become too large and misshapen to move air in and out of the lungs properly. Chronic bronchitis occurs when ongoing inflammation causes the lining of the airways to thicken and overproduce mucus.
COPD is most often caused by smoking, including secondhand exposure, but it is also linked to air pollution and chemical inhalation, according to WebMD. The disease develops slowly over a lengthy time period and is most common in people over age 60. Other symptoms of COPD include chronic cough and mucus-producing cough.