Obstructive Airway Diseases Flashcards
What three entities is COPD an umbrella term for?
- Chronic bronchitis
- Emphysema
- Small airway disease - asthma
What two major groups do obstructive airway diseases fall into?
- Localised
- Diffuse
Describe the epidemiology of COPD.
- Principal cause is cigarette smoking
- Majority of COPD patients have emphysema (air space destruction) and chronic bronchitis (airway inflammation)
What is chronic bronchitis characterised by?
- Productive cough for at least 3 months for 2 consecutive years
- In absence of any other identifiable cause
Apart from smoking, what are some other causes of chronic bronchitis?
- Air pollutants
- Respiratory tract infections
- Toxic industrial inhalants
What are the clinical features of chronic bronchitis?
- Usually affects middle-aged men who smoke heavily
- EARLY SYMPTOMS - Prolonged, persistent, productive cough
- LATER STAGE - Dyspnea on exertion
Describe the pathogenesis of chronic bronchitis. PART 1
- Irritation by inhaled air pollutants
- Causes inflammation
- Infiltration by T lymphocytes, macrophages, neutrophils
Describe the pathogenesis of chronic bronchitis. PART 2
- Hyperplasia/hypertrophhy of submucosal glands in large airways - develop in response to inhaled irritants and proteases from neutrophils
Describe the pathogenesis of chronic bronchitis. PART 3
- Increase in goblet cells in airways - excess mucus production - inflammation and fibrosis of bronchial walls - leads to airway obstruction
What are the microscopic appearances of chronic bronchitis?
- Hyperplasia/hypertrophy of submucosal mucus-secreting glands
- Chronic inflammation of airways - infiltration by lymphocytes
- Increase in number of goblet cells
- Squamous metaplasia
- Narrowing of bronchioles - excess mucus production, inflammation, oedema and fibrosis
What are the main complications ffrom chronic bronchitis?
- Progress to COPD
- If prolonged, lead to cor pulmonale with cardiac failure
- Squamous metaplasia, dysplasia of respiratory epithelium - environment for cancerous transformation
Describe emphysema.
- Abnormal irreversible dilation of airspaces distal to terminal bronchioles
- Caused by destruction of airspace walls
What factors can lead to emphysema?
- Smoking and genetic predispositions
- Release of inflammatory mediators
- Alpha-1 antitrypsin deficiency leading to protease-antiprotease imbalance
- Oxidative stress
Describe the gross appearance of tissues affected by emphysema.
- Usually severely involves upper two thirds of lungs
- Voluminous lungs from advanced emphysema
- Bullae in irregular/distal acinar emphysema
Describe centriacinar emphysema.
- Most common type clinically
- Seen in smokers
- Usually more severe in upper lobes due to alpha1-antitrypsin deficiency
- Involvement of central part of acinus with sparing of alveoli
Describe panacinar emphysema.
- Involvement of entire acinus
- Seen with alpha1-antitrypsin deficiency
- More severe in lower lobes at base of lung (region more perfused - more distribution of neutrophils)
Describe distal acinar/paraseptal emphysema.
- Distal part of acinus affected - sparing of proximal part of acinus
- Seen in smokers
- Involvement of lung adjacent to pleura
- Associated with development of spontaenous pneumothorax
Describe irregular emphysema.
- Associated with fibrosis/scarring
- Most common type histologically
What would be seen under a microscope in emphysema?
- Abnormally large alveoli separated by thin septa
- Destruction of alveolar walls
- Loss of attachments of alveoli to outer wall of small airways
- Inflammatory changes
- Bullae in advanced emphysema
Describe bronchial asthma
- Characterised by reversible bronchoconstriction in response to various stimuli
Apart from bronchoconstriction, what can also occur in bronchial asthma?
- Inflammation of bronchial walls
- Mucus hypersecretion
How can bronchial asthma be classified?
- TYPE OF ANTIGEN - atopic (allergic) and non-atopic (without evidence of allergen sensitisation)
- TRIGGER (seasonal, occupational, exercise/drug/smoking induced)
Describe atopic asthma.
- Most common - begins in childhood
- Family history of asthma/allergies common
- IgE mediated hypersensitivity
- Triggered environmentally - e.g dust, pollen, food
- Skin test - exposure to allergen causes immediate wheal-and-flare reaction
Describe non-atopic asthma.
- Skin tests usually negative
- Family history less common
- No causative exogenous factors identified - no allergen sensitisation
- TRIGGERS - Respiratory infections due to viruses, inhaled pollutants
What occurs in sensitisation and inflammation during bronchial asthma?
- Genetically predisposed individuals - sensitised against multiple allergens
- Allergen taken by APCs - triggers hypersensitivity response.
- Promotes IgE production by B cells
What is the gross appearance in bronchial asthma?
- Airway occlusion by mucus
- Small areas of atelectasis and some distension of lungs (due to overinflation)
