Definition and Risk Factors of COPD

Definition of COPD
disease state that has airflow limitation that is not fully reversible. It is usually both progressive and associated with abnormal inflammatory response of the lungs to noxious particles or gases.

Risk Factors
Cigarette Smoking
- 90% of cases. Long-term exposure to toxic particles & gases.
- However, only 10-20% of smokers get COPD, indicating individual susceptibility.
- Development of COPD related to no. of cigarettes/day: risk of death from COPD with pt smoking 30 cigarettes/day is 20x a non-smoker.

How?
- infiltrated by neutrophil granulocytes in lumen of bronchial tree & small airways
- granulocytes can release elastases & proteases - may produce emphysema
- alpha-1 antitrypsin is a major serum antiprotease which can be inactivated by cigarette smoke
- hypertrophy of mucous glands in larger airways from persistent irritation
- smoke has adverse effect on surfactant = overdistention of lungs

Occupational Exposure. Air Pollution
Great increase found during periods of heavy atmospheric pollution. eg coal mining

Genetics- alpha-1 antitrypsin deficiency
- alpha-1 antitrypsin inhibitor is an antiproteinase inhibitor produced in the liver secreted into the blood - diffuses into lungs.
- functions as an antiprotease that inhibits neutrophil elastase, a proteolytic enz that destroys alveolar wall connective tissue
- more than 75 alleles of the gene has been described, 3 main phenotypes are MM(normal),MZ(heterozygous deficiency) & ZZ(homozygous)
- accounts for about 2% of emphysema cases

Infections
COPD patients cope badly with respiratory infections - often precipitating cause of acute exacerbations. however, role of infection in the development of progressive airway limitation is far less clear