pathophysiology of respiratory diseases (COPD and pneumonia)

Question 1

what is COPD ?

Answer 1

• chronic obstructive pulmonary disease
• umbrella term used to describe patients with varying respiratory disease involving both chronic bronchitis and emphysema. COPD encompasses a long-term, progressive, and accelerated decline in respiratory function.

Question 2

how does smoking reduce respiratory function and lead to COPD ?

Answer 2

• 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 the smoke.
• 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) because the balance between proteases and anti-proteases is disrupted.
• 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 worsens the level of inflammation and long term damage to the airways and lungs
• The repeated and increasing respiratory inflammation discussed above drives the pathology within the airways and lungs that observed in COPD patients.

Question 3

what is chronic bronchitis ?

Answer 3

• long-term inflammation of the bronchi/airways
• characterised by chronic and excessive sputum production, coughing and airway obstruction.
• The coughing and mucus production is a consequence of inflammation (due to smoke exposure or infection) within the airway tissue, activating sensory neurons and stimulating mucus glands.
• Similar to asthma, chronic bronchitis involves impaired airflow through the airways due to reduced airway lumen radius and increased airway resistance. However whilst these changes are typically reversible in asthma, the changes in chronic bronchitis are generally progressive and irreversible.
• 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.

Question 4

what is emphysema ?

Answer 4

• describes pathological enlargement of alveolar airspaces due to destruction and degradation of lung tissue.
• This 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).

Question 5

what are the effects of chronic respiratory failure on the rest of the body ?

Answer 5

Question 6

give a summary of the functional changes that occur due to COPD and emphysema

Answer 6

Question 7

describe the mechanism of pneumonia

Answer 7

Weakening of host defence (e.g. following viral infection, damage to epithelium, or immune suppression)
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Colonisation of alveoli by pathogens
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Activation of macrophages and cytokine release (IL-6, IL-8, TNF-α)
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Recruitment of neutrophils into alveolar space, release of proteases & ROS
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Injury to alveolus and surrounding structures

Question 8

how does alveolar injury lead to impaired gas exchange and hypoxemia ?

Answer 8

Question 9

give a summary of all the respiratory diseases

Answer 9