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Elasticity of the lung tissue is lost, causing air to be trapped in the air sacs and impairing the exchange of oxygen and carbon dioxide. The result is that the small airways collapse during expiration, leading to an obstructive form of lung disease . Cigarette smoking is by far the most common cause of emphysema and is responsible for approximately 80-90% of deaths due to chronic obstructive pulmonary disease. However, the mechanisms by which exposure of the lung to smoke causes the destruction of the lung parenchyma are not known.
Signs and symptoms
The two most common symptoms of emphysema are shortness of breath and a reduced capacity for physical activity. As the disease progresses both of these symptoms are becoming worse.
Other signs and symptoms of emphysema include:
- Chronic, mild cough which sometimes may produce sputum or phlegm.
- Loss of appetite and weight loss. Emphysema can make eating more difficult because the act of eating can leave you out of breath. The result is that you simply may not feel like eating much of the time.
- Fatigue. The patients with emphysema are feeling tired all the time because it's more difficult to breathe and because your body is getting less oxygen.
Emphysema and chronic bronchitis frequently co-exist together to comprise chronic obstructive pulmonary disease.
Pathophysiology of the condition
When someone inhales, air travels to lungs through two major airways called bronchi. The bronchi divide into million smaller airways that finally end in clusters of tiny air sacs called alveoli. What happens in emphysema? In emphysema, inflammation destroys these fragile walls of the air sacs, causing them to lose their elasticity.
The result is clear- the bronchioles collapse, and air becomes trapped in the air sacs, causing them to overstretch. With time, this overstretching may cause several air sacs to rupture, forming one larger air space instead of many small ones.
Usually when someone is diagnosed with emphysema, many of those elastic fibers located in the lungs have already been destroyed, so the forced exhalation compresses many of the small airways, making expelling air even more difficult.
Possible causes of emphysema
The fact is that cigarette smoke is by far the most common cause of emphysema. The damage begins when tobacco smoke temporarily paralyzes the microscopic hairs called cilia that line bronchial air ways. What is the purpose of these hairs? Normally, these hairs sweep irritants and germs out of your airways, but when smoke interferes with this sweeping movement, irritants remain in your bronchial tubes and infiltrate the alveoli, inflaming the tissue and eventually breaking down elastic fibers. Oxidants present in the smoke itself or those generated by inflammatory cells in response to the particulate phase of the smoke, inactivate proteinase inhibitors and the increased inflammatory cells produce and release additional proteinases.
It is also proven that emphysema could results from low levels of a protein called alpha-1-antitrypsin. The purpose of this protein is to protect the elastic structures in lungs from the destructive effects of certain enzymes. It is easy to understand that a lack of this protein can lead to progressive lung damage which eventually results in emphysema. This deficiency is a hereditary condition that occurs when you inherit two defective genes, one from each parent. When will the first symptoms occur? People with two defective genes have a high likelihood of developing emphysema, usually between the ages of 30 and 40.