Pathophysiology of COPD Flashcards
What is COPD?
Chronic obstructive pulmonary disease (COPD) is an umbrella term used to describe patients with varying respiratory disease involving both chronic bronchitis and emphysema.
What are the main causes for COPD?
Smoking (90%of cases)
Exposure to pollution and chemicals
Genetic disorders such as alpha-1-antitrypsin deficiency
What effect does tobacco have?
Tobacco smoke smoke contains many harmful chemicals which cause acute damage to respiratory tissue, generating an inflammatory response. With repeated and long-term exposure, this inflammation becomes chronic, pathological, and generates irreversible injury and dysfunction.
What effect does the inflammation have on the tissue?
Immune cells, such as neutrophils and macrophages, are attracted to tissues damaged by tobacco smoke due to acute local inflammation caused by the chemicals in tobacco smoke. When immune cells infiltrate the affected areas, they attempt to resolve the inflammation and repair damaged tissue.
What happens when the inflammation becomes pathological?
However these mechanisms become pathological with chronic smoke exposure, due to the constant cycles of damage and incomplete or faulty tissue repair (e.g. fibrosis), and because the balance between proteases (enzymes which break down proteins) and anti-proteases (enzymes which inhibit proteases) is disrupted.
What is chronic bronchitis?
Long-term inflammation of the bronchi/airways is characterised by chronic and excessive sputum production, coughing and airway obstruction.
What is the coughing and mucus production a consequence of in chronic bronchitis?
It is a consequence of inflammation within the airway tissue activating sensory neurones and stimulating mucus glands.
What effect does chronic bronchitis have on the airway lumen?
Airway lumen is reduced due to excessive mucus secretion, tissue swelling and degradation of the overall airway structure, increasing airway resistance.
What is the difference between asthma and chronic bronchitis
Asthma is reversible because it is caused by smooth muscle contraction.
Chronic bronchitis is irreversible because it is caused by excessive mucus secretion, tissue swelling and degradation of the overall airway structure
Therefore beta 2 agonist bronchodilators less effective in COPD than asthma.
What is emphysema?
Enlargement of alveolar airspaces due to destruction and degradation of lung tissue.
Results in loss of structural fibres such as elastin (increasing compliance) as well as reduced surface area and damage to the pulmonary vasculature (decreasing perfusion), decreasing gas exchange.
What does COPD eventually result in?
Decreased airflow, ventilation and gas exchange due to a combination of the pathological features involved in chronic bronchitis and emphysema, eventually causing chronic respiratory failure.
Give effects of respiratory failure on cardiovascular system.
Causes pulmonary heart disease (cor pulmonale)
Chronic hypoventilation of alveoli results in hypoxic vasoconstriction of pulmonary vasculature, increasing vascular resistance and causing pulmonary hypertension
This requires the heart to work harder to maintain normal blood flow against increased resistance, resulting in right heart hypertrophy
Eventually, heart is unable to cope with increasing demands and results in heart failure, increased venous pressure and right ventricular afterload
Increases risk of myocardial infarction, a common cause of death in COPD patients.
What is smoking cessation
Most effective method of slowing down decline of FEV1 and at preventing COPD.
Lung function doesn’t regenerate and decline does continue, just not as rapidly
