Emphysema is a pulmonary condition with loss of elasticity in the alveoli and the interalveolar septa... the "meat-foam" and their interleaving sheaths that you fill up when you breathe.
Causes and Development
If a septum gets too stretched over time, several of the little sacs will coalesce together, decreasing the surface area for oxygen and carbon dioxide exchange. If enough of these sacs lose their separateness, like small soap bubbles joining to make a few larger ones, breathing gets harder because each breath accomplishes less interchange of gases, resulting in emphysema
Caused by years of bad asthma, tobacco smoking, chemical damage, and other chronic lung disorders, it can be halted but not reversed. The first breath you take defines forever the number of the alveolar bubbles: they cannot be regenerated if they coalesce together.