Pathophysiology of COPD Flashcards
What is COPD (chronic obstruction pulmonary disease) used to describe?
Chronic obstructive pulmonary disease (COPD) is used to describe patients with varies respiratory diseases involving chronic bronchitis and emphysema. A long term, decline in respiratory function
What are the causes of COPD?
The main causes are people who smoke tobacco and the remaining population is due to exposure to chemicals/pollution or genetic disorders such as alpha-1-antitrypsin deficiency.
Why is exposure to tobacco smoke dangerous?
Dangerous as the 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 happens when immune cells such as macrophages and neutrophils are attracted to tissue damage by tobacco smoke due to local inflammation caused by the chemicals?
When immune cells infiltrate the affected areas, they attempt to resolve the inflammation and repair damaged tissue (by releasing proteolytic enzymes that breakdown dead cells and kill invading organisms). 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.
Furthermore the damage to airway tissue also impairs host defence against invading organisms as mucociliary clearance in impaired due to increased mucus secretion and damage to cilia. This further exacerbates the level of inflammation and long term damage to the airways and lungs:
Describe the tobacco smoke pathway
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What is chronic bronchitis and what is it characterised by?
Chronic bronchitis is long term inflammation of the bronchi.
It is characterised by chronic and excessive sputum production, coughing and airway obstruction.
What is a consequence of inflammation within the tissue activating mucus glands?
Coughing and mucus production
Is there reduced airflow in chronic bronchitis and why?
It involves impaired airflow through the airways due to reduced airway lumen radius and increased airway resistance. These changes are progressive and chronic.
How does chronic bronchitis differ from asthma?
The primary cause of the dysfunction also differs: in chronic bronchitis airway lumen size is reduced by excessive mucus secretion, tissue swelling, and degradation of the overall airway structure (resulting in the airway simply collapsing entirely when placed under excessive pressure), rather than being primarily caused by airway smooth muscle contraction, as in asthma. This has implications for the efficacy of specific therapies, as treatments such as beta-2 agonist bronchodilators, which act by relaxing airway smooth muscle, are less effective in COPD than asthma for this reason (this is discussed further in subsequent sections).
Give an overview of the pathological features of chronic bronchitis?
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What is emphysema?
This describes pathological enlargement of alveolar airspaces due to destruction and degradation of lung tissue.
What are the consequences of emphysema?
Results in loss of structural fibres such as elastin (increasing compliance) as well as reduced surface area and damage to the pulmonary vasculature (decreasing gas exchange)
The main effects of this are ventilation and gas exchange become severely reduced, resulting in respiratory failure and the symptoms of COPD observed in patients.
What can Chronic Bronchitis and emphysema eventually result in and what does it cause?
Respiratory failure
Respiratory function declines in a progressive irreversible manner, causing hypoxaemia and acidosis.
What will patients experience by a declining respiratory function
Patients experience acute exacerbations by a temporary but drastic decline in symptoms and respiratory function caused by the acute inflammation brought about by infection.
How does hypoxic vasoconstriction impact on the respiratory system?
Constriction of the pulmonary vasculature increases vascular resistance, in turn increasing the force required to pump blood through the system and the pressure of blood within it (pulmonary hypertension). This requires the heart to work harder to maintain normal blood flow against increased resistance, resulting in right heart hypertrophy and worsening efficiency.
This results in heart failure, increased venous pressure and right ventricular afterload. Can lead to myocardial infarction
