Emphysema is a condition of the lung characterized by abnormal permanent enlargement of airspaces distal to the terminal bronchiole, accompanied by destruction of their walls in the absence of obvious fibrosis. The cardinal physiologic defect in emphysema is a decrease in elastic recoil. This results in decreased maximum expiratory airflow, hyperinflation and air-trapping. Emphysema is usually the result of cigarette smoking, and it is a chronic progressive disorder that ultimately leads to disability and early death. It is estimated to be present in 2 million adults in the United States and along with other forms of chronic obstructive pulmonary disease (COPD) accounts for > 90,000 deaths annually.
Emphysema is characterized by loss of elasticity (increased pulmonary compliance) of the lung tissue caused by destruction of structures feeding the alveoli, in some cases owing to the action of alpha 1-antitrypsin deficiency. This causes the small airways to collapse during forced exhalation, as alveolar collapsibility has decreased. As a result, airflow is impeded and air becomes trapped in the lungs, in the same way as other obstructive lung diseases. Symptoms include shortness of breath on exertion, and an expanded chest. However, the constriction of air passages isn't always immediately deadly, and treatment is available.
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Image is of H&E (haematoxylin and eosin) stained lung tissue sample taken from an end-stage emphysema patient. Cell nuclei are blue-purple, red blood cells are red, other cell bodies and extracellular material are pink, and air spaces are white. Source: "T Cells Cause Lung Damage in Emphysema". PLoS Med 1(1): e25. |
Signs of emphysema include pursed-lipped breathing, central cyanosis and finger clubbing. The chest has hyper resonant percussion notes, particularly just above the liver, and a difficult to palpate apex beat, both due to hyperinflation. There may be decreased breath sounds and audible expiratory wheeze. In advanced disease, there are signs of fluid overload such as pitting peripheral edema. The face has a ruddy complexion if there is a secondary polycythemia. Sufferers who retain carbon dioxide have asterixis (metabolic flap) at the wrist.
Emphysema can be classified into primary and secondary. However, it is more commonly classified by location.
Emphysema can be subdivided into panacinary and centroacinary (or panacinar and centriacinar, or centrilobular and panlobular).
- Panacinary (or panlobular) emphysema is related to the destruction of alveoli, because of an inflammation or deficiency of alpha 1-antitrypsin. It is found more in young adults who do not have chronic bronchitis.
- Centroacinary (or centrilobular) emphysema is due to destruction of terminal bronchioli muchosis, due to chronic bronchitis. This is found mostly in elderly people with a long history of smoking or extreme cases of passive smoking.
Other types include distal acinar and irregular.
A special type is congenital lobar emphysema (CLE).
CLE is results in overexpansion of a pulmonary lobe and resultant compression of the remaining lobes of the ipsilateral lung, and possibly also the contralateral lung. There is bronchial narrowing because of weakened or absent bronchial cartilage.
There may be congenital extrinsic compression, commonly by an abnormally large pulmonary artery. This causes malformation of bronchial cartilage, making them soft and collapsible.
CLE is potentially reversible, yet possibly life-threatening, causing respiratory distress in the neonate.
Further Reading
Sourced and Abstracted from information found at Wikipedia (Creative Commons Attribution-ShareAlike License), CDC, NIH.
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