With emphysema, air gets trapped in your lungs.
Emphysema occurs when the tiny air sacs in your lungs — the alveoli — break down and become larger. With the destruction of the alveoli, your lungs are less able to get oxygen out of the air and less effective at getting rid of carbon dioxide.
The walls of the damaged air sacs are stretched and less flexible, so that air is trapped inside the lungs. When this happens the airways can become "flabby," and don't push out air as well. And because so much air is trapped in the lungs, your diaphragm (the muscle at the bottom of the lungs that acts like an accordion) can become shortened and unable to assist in breathing.
Damaged air sacs trap air inside your lungs. You might feel that it's hard to take a deep breath. Like old balloons, the tiny air sacs get stretched out of shape and break down. Old air gets trapped inside the air sacs so there is no room for new air to get in.