Chronic Obstructive Pulmonary Disease is by far one of the worst chronic diseases to make this list and is a chronic disease Physicians see daily. The main cause of the chronic obstructive pulmonary disease is usually the cause of smoking tobacco like cigarettes. It can also be from individuals being exposed to fumes from burning fuel for cooking or even heating in poorly ventilated homes. Your lungs become affected due to the air traveling down your windpipe and into your lungs. Inside your lungs, the tubes are divided many times into smaller tubes that end in clusters of small air sacs. These air sacs do not have thick walls, so the oxygen you breathe in will pass through into these blood vessels and end up entering your bloodstream, while at the same time, the carbon dioxide which is a waste product of metabolism is then exhaled. Your lungs heavily rely on the elasticity of your bronchial tubes and air sacs to then force air out of the body, causing chronic obstructive pulmonary disease due to the elasticity and over-expanse dwindling and leaving air trapped in your lungs when you exhale.