Chronic obstructive pulmonary disease (COPD) is one of the commonest lung disorders that is associated with smoking. It is typically characterized by chronic airflow obstruction and difficulty in breathing.
Along with difficulty in breathing there are several pathological changes in the lung (pulmonary) as well as some significant effects on the whole body (extra-pulmonary effects) and presence of co-existing ailments. These all contribute to the severity of the disease in individual patients.
Definition of COPD
According to the World Health Organization, “Chronic Obstructive Pulmonary Disease (COPD) is a preventable and treatable disease with some significant extra-pulmonary effects that may contribute to the severity in individual patients.”
The definition suggests that the airway obstruction is not fully reversible. There is a progressive damage to the airflow due to inflammation in the airways.
Local pathology of COPD
Smoking is the most important causative factor associated with COPD. At least four out of five people with COPD have a history of being smokers in the past or are smokers at present.
Cigarette smoke contains harmful chemicals that cause irritation in the inner lining and walls of the airways. This leads to inflammation of the walls. The inflammation and damage leads to scarring and deformities of the air sacs and narrow air passages. This is called emphysema and leads to loss of elasticity of the lung tissues that is essential for breathing and oxygen extraction from the inhaled air. This damage caused to the airways by cigarette smoke cannot be reversed and smokers even after quitting continue to have a higher risk of developing COPD.
Around 10-25% of smokers develop COPD. Approximately 80 to 90 percent of COPD deaths are caused by smoking. Female smokers are nearly 13 times as likely to die from COPD as women who have never smoked. On the other hand male smokers are nearly 12 times as likely to die from COPD as males who have never smoked.
Airway obstruction pathology in COPD
The airway obstruction that is characteristic of COPD is caused by a mixture of small airway disease called obstructive bronchiolitis as well as due to damage and destruction of the lung tissues or lung parenchyma in a process called emphysema. The relative proportions of these two pathologies are different in different individuals.
Destruction of the lung parenchyma caused due to inflammation also leads to loss of alveolar attachments to the smaller airways that reduces the elasticity of the lung tissues, this prevents the airways from remaining open while breathing out. Airflow limitation is best measured by spirometry.
Chronic bronchitis refers to the presence of cough and sputum production for at least 3 months in two consecutive years. It forms a part of COPD diagnosis along with emphysema.
COPD and other ailments
COPD may often co-exist with other ailments. This may be because most COPD patients are long term smokers in their middle ages. They may thus have other diseases associated with smoking and aging as well.
Studies have shown that up to 25% of the population 65 years and older may develop at least two co-existing ailments and up to 17% have three coexisting ailments along with COPD.
Some of the common associated diseases that may be seen among COPD patients include:-
- Respiratory infections that may be frequent and recurrent
- Heart attacks or myocardial infarction
- Angina or chest pain during exertion
- Osteoporosis or brittle bones leading to easy fractures
- Sleep disorders
- Glaucoma of the eyes
- Lung cancer
Some of the common problems that that may be seen among COPD patients include:-
- Nutritional deficiencies
- Weight loss
- Muscle weakness
Development of COPD
COPD is generally a progressive disease especially if the patient continues to be exposed to cigarette smoke and other noxious fumes.
Stopping exposure to these agents may result in some improvement in lung function and slow the progression of the disease.
Reviewed by April Cashin-Garbutt, BA Hons (Cantab)