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COPD Pathophysiology (Pathophysiology (Mechanism of air trapping (Huether…

- - - - Mucous plugs and narrowed airways cause air trapping and hyperinflation of alveoli on expiration.
      - During inspiration the airways are pulled open allowing gas to flow past obstruction. During expiration decreased elastic recoil of the brochial walls results in collapse of the airways preventing normal expiratory airflow.
      - There is a ventilation- perfusion mismatch which leads to hypoxaemia. Airwyas collapse early in expiration leading to air becoming trapped dital to the obstruction.
      - Air trapping expands the thorax and places respiratory muscles at a disadvantage mechanically.
  - - - Inspired irritants cause inflammation of the airways. This leads to infiltration of neutrophils, macrophages and lymphocytes into the bronchial wall.
        
        Ongoing inflammation causes bronchial oedema and increases the size and number of mucous glands and goblet cells in the airway epithelium.
        
        This results in the production of thick mucous which can not be cleared due to the impairment of ciliary function.
      - Lungs defense mechanisms are compromised. Increasing susceptibility to pulmonary infection and injury
      - Initially only larger bronchi are affected but eventually all airways are involved.
        
        Thick mucous and enlarged bronchial smooth muscle constricts airways and leads to obstruction particularly during expiration.
- - - - Alveoli
- - - - Pulmonary Ventilation
        
        Physical movement of air into and out of the lungs
      - Gas diffusion
        
        Across respiratory membrane alveolar air spaces and alveolar capillaries and across capillary walls between blood and other tissues.
      - Transport of oxygen and carbon dioxide
        
        between alveolar capillaries and capillary beds in other tissues
- - - - Chronic bronchitis is the hypersecretion of mucous.