The increased pressure of the trapped air, over time, will shorten and flatten the diaphragm. This change in the shape of the diaphragm makes it much harder for the diaphragm to play its part in moving air in and out of the lungs. The diaphragm muscle becomes weak and fatigued.
An additional result of the trapped air is that the chest cavity becomes larger (barrel chest) and the muscles in between the ribs become stretched out.
The change in the muscles of breathing significantly increase the work of breathing. Normally, the muscles of breathing require a low level of oxygen at rest (1 to 3%) but when you have COPD, the needed oxygen increases to as high as 25%.
COPD has no cure, yet there are treatments (see Treatment), along with the removal of irritants that will decrease the effects of COPD.