Chronic obstructive pulmonary disease (COPD) is a collective name, and includes conditions such as chronic bronchitis, emphysema and cystic fibrosis.
Chronic bronchitis refers to the inflammatory reaction in the small and large airway walls, while emphysema involves the delicate gas exchange part of the lung, the tiny sacs called alveoli. Destruction of these delicate structures leads to large non-functional spaces in the lungs known as bullae, which have a limited to non-existent capacity to take up oxygen, with subsequent severe exercise impairment in affected individuals.
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Chronic obstructive pulmonary disease, as the name suggests, is characterised by obstructive airflow into and out of the lungs, which can only be partially resolved with standard medication. The ongoing inflammatory response in the airways leads to mucus over-production and inflammatory swelling of the inner layers of the airways, with subsequent obstruction to airflow. Chronic inhalation of noxious particles and gases will stimulate this state of inflammation.
The cells involved in the inflammatory response are the normal white cells (neutrophils and macrophages), which should protect the body during infective challenges. The normal defence mechanism of the body, which is aimed primarily at mopping up the invasive substances, attacks normal lung tissue to the detriment of the respiratory system. Thickening of the bronchial walls, formation of scar tissue and eventual destruction of the minute alveoli, which are responsible for oxygen uptake, will not only impair airflow, but also the uptake of life-sustaining oxygen and removal of carbon dioxide. The inflammatory response will periodically flare up during attacks of influenza and bronchitis, during which period patients may become acutely ill and very short of breath.
A characteristic of the inflammatory response of COPD is that it is not responsive to long-term medication with drugs such as corticosteroids, which are used successfully for prevention of asthma. When the inflammatory response has, over a period of years, caused extensive damage to the small airways and alveoli, patients will present with respiratory failure due to lack of oxygenation, or right heart failure (See Symptoms and diagnosis of COPD).
The disease is not confined to the lungs; it has systemic (whole body) effects that result in, for example, weight and appetite loss, and particularly a decrease of muscle mass in the limbs in severely ill patients. This leads to a vicious circle, as weakened patients who are extremely short of breath tend to withdraw, become completely inactive and frequently die in isolation.
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