why does copd cause chest tightness

The primary cause of chronic obstructive pulmonary disease is cigarette smoking or exposure to tobacco smoke. It is estimated that 90% of the risk for development of chronic obstructive pulmonary disease is related to tobacco smoke. The smoke also can be secondhand smoke (tobacco smoke exhaled by a smoker and then breathed in by a non-smoker).

Other causes of chronic obstructive pulmonary disease are:

Prolonged exposure to air pollution, such as that seen with burning coal or wood and with industrial air pollutants
Infectious diseases: Infectious diseases that destroy lung tissue in patients with hyperactive airways or asthma also may contribute to causing this COPD.

Damage to the lung tissue over time causes physical changes in the tissues of the lungs and clogging of the airways with thick mucus. The tissue damage in the lungs leads to poor compliance (the elasticity, or ability of the lung tissue to expand). The decrease in elasticity of the lungs means that oxygen in the air cannot get by obstructions (for example, thick mucus plugs) to reach air spaces (alveoli) where oxygen and carbon dioxide exchange occurs in the lung. Consequently, the person exhibits a progressive difficulty, first coughing to remove obstructions like mucus, and then in breathing, especially with exertion.