DEFINITION OF COPD
MD, FRCP (Lond), FAMS, DSc(Gul),
Emeritus Professor of Medicine,
Rajiv Gandhi University of Health Sciences
Chronic obstructive pulmonary disease (COPD) is a major public health problem associated with long-term exposure to toxic particles or gases, most often related to cigarette smoking. Even though there have been significant advances in the understanding and management of COPD the disease appears to be largely preventable, but remains marginally treatable.
COPD is a syndrome of persistent airflow limitation in the respiratory passages. The condition is usually progressive and it is associated with chronic inflammation in the airways and the lung parenchyma, often with systemic manifestations. It presents with chronic cough, excess sputum production and exertional breathlessness. With the progress of the disease, there is a gradual decline in lung functions and worsening of symptoms, exercise intolerance and decreased quality of life. Increasing severity of the disease leads to breathlessness at rest, decreased tension of oxygen in the arterial blood, and increased level of carbon dioxide in the arterial blood/ It will have deleterious effect on the lesser circulation in the body by causing raised blood pressure in the pulmonary circulation and enlargement of the right side of the heart and its failure to function properly. Thus the condition causes significant morbidity and mortality.
Tobacco smoking forms the single most important risk factor in the development of COPD. Exposure to smoke from biomass and solid fuel fires contributes to the development of COPD in some individuals in developing countries. However it is intriguing why only 18 to 20 per cent of chronic heavy smokers develop clinically significant COPD. There appears an individual susceptibility to smoking.
COPD is more common in men than women and it progresses after middle age and its natural history spans 20 to 40 years.
The term COPD is applied to diffuse obstruction involving structural and functional changes in the parenchyma and also in the large and small airways of the lungs. The airway obstruction is constant and makes slow progress, and exists without any specific causes in the airways. Asthma is not included in this, as airways hyper-reactivity leading to obstruction varies widely over time either spontaneously or in response to treatment.
COPD (synonyms: chronic obstructive lung disease, COLD; chronic obstructive airway disease, COAD; chronic airflow obstruction, CAO) includes those patho-physiologic processes contributing to the syndrome-chronic bronchitis (airway inflammation and fibrosis, bronchial mucous gland hyperplasia in the major airways, and increase in the number of mucus secreting goblet cells. mucus plugs in the lumen and increased airways resistance), emphysema (destruction of the gas-exchanging surfaces of the lung, loss of alveolar attachments, decreased elastic recoil) and small airways ( inflammation, fibrosis, smooth muscle hypertrophy, pigment deposition in the airways with goblet cell metaplasia and desquamation of the epithelium of the terminal bronchioles and inflammatory changes in the respiratory bronchioles lead to a marked increase in airflow resistance causing airflow obstruction) disease.
Though chronic bronchitis and emphysema differ morphologically and functionally in their pure form, often they coexist together to a greater or lesser extent in each patient; how ever, the relative contributions of which varies from person-to-person. These changes diminish the ability of the airways to remain open during expiration. Spirometry helps in the measurement of airflow limitation.
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