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In healthy people, both the airways and air sacs (alveoli) are expandable and elastic. When air is inhaled, the air bags fill as if they were small balloons. The balloons deflate when exhaling. In COPD, the airways and air sacs lose their shape and become soft.
In more advanced stages of the disease, and if there is emphysema, a destruction of the alveoli and tissue that supports them occurs and large air pockets are formed where there once was normal lung tissue. Air is trapped in the lungs due to lack of muscle tissue support, reducing oxygenation.
