ABSTRACT
Chronic obstructive pulmonary disease (COPD) is caused by two main mechanisms: chronic inflammation of the small airways and gradual destruction of the alveoli. The inflammation seen in COPD is different from that seen in asthma, and is driven by neutrophils. The mucus plugs block the terminal bronchioles, causing them to collapse and resulting in death of the alveoli. Excessive production of mucus in COPD causes clogging of the airways. Air becomes trapped in the distal airways, causing hyperinflation. This results in a reduction in tidal volume and an increase in dead space which, combined with narrowing of the airways and reduced gas exchange, leads to respiratory failure. The airways involved are predominantly peripheral, with parenchymal destruction. This is in contrast to asthma, where all of the airways are involved and there are no parenchymal effects.
