CHRONIC OBSTRUCTIVE PULMONARY DISEASE
Posted by admin on May 12th, 2010A group of diseases, including chronic bronchitis, emphysema, small airway disease, asthma, and bronchiectasis, characterized by chronic airflow obstruction with reversible andlor irreversible components. Airflow obstruction is a reduction in Ihe ratio of forced expiratory volume in the first second to forced vilal capaciiy (FEWFVC). Although each type of chronic obstructive pulmonary disease (COPD) is a distinct clinical entity, patients commonly have two or more types. In clinical practice, COPD usually refers to some combination of chronic bronchitis, emphysema, and small airway disease, while asthma and bronchiectasis arc usually considered separate entities.
Chronic bronchitis is characterized by a chronic, productive cough occurring most days of the month for at least 3 mo of the year for two consecutive years. Mucous-gland hyperplasia occurs in the airways. Emphysema is characterized by its morphologic abnormalities, including enlarged alveolar spaces and destructive changes in the alveolar walls, which reduce the surface area for gas exchange. Small airway disease is characterized by physiologic test abnormalities compatible wilh dysfunction of airways – 2 mm in diameter. Asthma is characterized by increased bronchial and bronehiolar responsiveness to various stimuli resulting in widespread airway narrowing. Changes in severily may occur spontaneously or as a result of therapy. Bronchiectasis, a permanenl dilatation of one or more bronchi, is characterized clinically by production of copious sputum that separates into distinct layers.
Incidence and Etiology
In the USA, COPD ranks among Ihc ten leading causes of death. Over the last 1? yr, the incidence of COPD has risen more rapidly than that of any of the other nine leading causes of death. As a cause of Social Security-compensated disability, COPD ranks second only to coronary artery disease.
About 3% of the US population has chronic bronchitis, which is 1.2 to 2.3 times more prevalent in older persons than in younger persons: about 1% of the US population has emphysema. However, only 5% of those with chronic bronchitis and about 40% of those with emphysema have clinically significant airway obstruction. Asthma beginning in old age is uncommon.
A combination oogenetic predisposition and environmental exposure leads to COPD. Cigarette smoking, the most common environmental risk factor, is believed to contribute to COPD in > 80% of cases. Smoking contributes to airway obstruction by causing an inflammatory reaction with or without mucus production in the airways; by promoting the influx of polymorphonuclear leukocytes, which release inflammatory mediators and elastases that break down lung elaslin, leading lo emphysema; and by inhibiting the body’s endogenous elastases. Pollution, occupational contacts, and other environmental exposures are less important contributors to airway obstruction. Other risk factors for COPD include being male, having a low socioeconomic status, and having had a childhood respiratory illness.
Tags: CHRONIC
