Pulmonary Pathophysiology - Obstructive Lung Disease Flashcards
Mechanisms of airway obstruction
Secretions / fluid / foreign body within airway
Increased thickness of airway wall
Loss of radial traction of airway secondary to alveolar destruction
Examples of causes of increased airway thickness
Hypertrophy of smooth muscle
Chronic bronchitis
Example cause of alveolar destruction resulting in reduced airway radial traction
Emphysema
COPD components
Mixed picture of emphysema and chronic bronchitis
Emphysema definition
Enlargement of air spaces distal to the terminal bronchiole with destruction of their walls
Anatomical diagnosis
Distribution / types of emphysema
Centriacinar emphysema
Panacinar emphysema
Bullous emphysema
Paraseptal emphysema
Lower zone emphysema
Lower zone emphysema
Primarily lower lung zones affected by emphysema
Caused by alpha 1 antitrypsin deficiency
Possible pathogenesis of emphysema (as suggested by alpha 1 antitrypsin deficiency)
Imbalance of protease-antiprotease system
Cigarette smoking causes release of neutrophil elastase
Elastase attacks both elastin and collagen
Type IV collagen in blood gas barrier may be a critical structure
Why do neutrophils contain elastase
To break down bacteria
Chronic bronchitis definition
Excessive mucus production in the bronchial tree sufficient to cause excessive expectoration of sputum
Clinical diagnosis
Pathophysiology of chronic bronchitis
Increased mucus production by mucus glands in response to airway pollutant (cigarette smoke)
Mucus volume overwhelms mucociliary escalator
Changes in small airways in chronic bronchitis
Inflammation
Airway wall oedema
Narrowing
Cellular infiltration
Peri-bronchial fibrosis
Effect of single cigarette on airway conductance
Significantly reduces airway conductance for around 1 hour after single cigarette
Clinical presentations of COPD
Type A (Pink puffer)
Type B (Blue bloater)
Usually patients are a mix of type A and type B
Type A COPD presentation
‘Pink puffer’
SOB with high ventilation rate
Maintains relatively normal PaO2 and PaCO2
Type B COPD presentation
‘Blue bloater’
Severe chronic bronchitis
PaCO2 higher and lower PaO2
Pulmonary HTN + right heart failure