Pathology of pulmonary airways disease Flashcards
What are the host defences?
- Cough reflex
- Cilia
- Mucus
- Antibody deficiency (IgA)
- Immunosuppression- disease, drugs
- Macrophage dysfunction
- Pulmonary oedema
Describe the organisation of the respiratory tree
-Trachea
-Bronchus (cartilage)
-Terminal bronchiole
=Respiratory bronchiole
=Alveolar duct
=Alveolar sac
=Alveolus
All = is acinus
Describe Acute Bronchitis
- Inflammation of bronchi
- Often viral
- May be bacterial (H. influenzae)
- May also involve larynx and trachea= laryngotracheobronchitis
- Acute exacerbations of ‘chronic bronchitis’ are common
Describe Bronchiolitis
- Inflammation of bronchioles
- A feature of chronic bronchitis
- Primary bronchiolitis= usually in children/ respiratory syncytial virus (RSV)/ tachypnoea and dyspnoea
- Rare types= follicular bronchiolitis, bronchiolitis obliterans
Describe Localised Airway Obstruction
- Airway obstruction= lesion outside the wall (large lymph node), lesion in the wall (tumour), lesion in the lumen (foreign body)
- Causes distal collapse or over-inflation
- May be distal lipid or infective pneumonia
- Normal pulmonary function tests
Describe Diffuse Obstructive Airways Disease
-Reversible and intermittent OR Irreversible and persistent
-Centred on bronchi and bronchioles
-Diffuse disease as many airways involved
Pulmonary function tests ‘obstructive’= reduced vital capacity (VC), Reduced FEV1/FVC ratio, Reduced peak expiratory flow rate
What clinico-pathological entities does Diffuse Obstructive Airways Disease encompass?
- Chronic bronchitis
- Emphysema
- Asthma
- Bronchiectasis
- COPD (spectrum of co-existence of chronic bronchitis and emphysema)
What is the clinical definition of Chronic Bronchitis?
- Cough and sputum for 3 months in 2 consecutive years
- Aetiology- pollution, smoking
- Middle-aged heavy smokers, recurrent low-grade bronchial infections (exacerbations), H. influenzae, S. pneumoniae, viruses, airway obstruction may be partially reversible
Describe the progression of chronic bronchitis
- Hypercapnia
- Hypoxia
- Pulmonary hypertension
- ‘Cor pulmonale’- right ventricular failure
- Blue bloater
Describe the pathology of chronic bronchitis
- Respiratory bronchiolitis (<2mm diameter)
- Can lead to centrilobular emphysema
- Mucus hypersecretion (mucous gland hypertrophy)
- Chronic bronchial inflammation (squamous metaplasia, increased risk of malignancy)
What is the anatomical definition of emphysema?
- Irreversible dilation of alveolar spaces with destruction of walls
- Associated with loss of surface area for gas exchange
What are the classifications of emphysema?
- Centrilobular
- Panlobular
- Paraseptal
- Irregular
- Others
Describe Centrilobular emphysema
- Strongly associated with smoking
- Seen in some with pneumoconiosis, particularly coal-workers
- Most commonly in upper lobes
- Respiratory bronchiolitis often present
Describe Panlobular emphysema
- Usually lower lobes
- Lungs overdistended
- Associated with alpha-1-antitrypsin deficiency
- Markedly accelerated in smokers with this disorder
Describe Paraseptal emphysema
- Distension adjacent to pleural surfaces
- May be associated with scarring
Describe Irregular emphysema
Associated with scarring
-Overlap with Paraseptal emphysema
Describe other emphysema classifications
- Bullous: distended greater than 10mm
- Interstitial
What are the clinical features of emphysema?
- Hyperventilation
- Normal pO2, pCO2
- ‘Pink puffer’
- Weight loss
- Right ventricular failure
- Often co-existing chronic bronchitis, in which case clinical features are mixed
What is asthma?
- Reversible wheezy dyspnoea’
- Increased irritability of the bronchial tree with paroxysmal airway narrowing
What are the 5 aetiological categories?
- Atopic
- Non-atopic
- Aspirin-induced
- Occupational
- Allergic bronchopulmonary aspergillosis (ABPA)
How can asthma lead to sudden death?
Mucus plugging
Describe Atopic asthma
- Associated with allergy
- Triggered by a variety of factors (dust, pollen, house dust mites)
- Often associated with eczema and hay fever
- Bronchoconstriction mediated by a type 1 hypersensitivity reaction
What does the hypersensitivity reaction lead to in atopic asthma?
- Bronchial obstruction with distal over inflation or collapse
- Mucus plugging of bronchi
- Bronchial inflammation
- Mucous gland hypertrophy
- Bronchial wall smooth muscle hypertrophy
- Thickening of bronchial basement membranes
Describe Non-atopic asthma
- Associated with recurrent infections
- Not immunologically mediated
- Skin testing negative
Describe aspirin-induced asthma
- Associated with recurrent rhinitis, nasal polyps and urticaria
- Mechanism of asthma unclear (prostaglandins/ leukotrienes)
Describe occupational asthma
- Hypersensitivity to an inhaled antigen
- May be non-specific in those with hyper-reactive airways
- May be a specific allergic response
Describe Allergic Bronchopulmonary Aspergillosis
- Specific allergic response to the stories of Aspergillus fumigatus
- Mixed type 1 and type 3 hypersensitivity reaction
- Mucous plugs common
- Associated with bronchiectasis
- Not to be confused with an aspergilloma, which a=is a fungal ball, usually colonising a pre-existing cavity in the lung (often tuberculous)
What is Bronchiectasis?
- Permanent dilation of bronchi and bronchioles
- Due to a combination of obstruction and inflammation (usually infection)
- May be localised or diffuse, depending on cause
- Historically seen in patients with pulmonary tuberculosis involving hilar lymph nodes
- Classically associated with childhood infections, particularly measles and whooping cough
- Diffuse bronchiectasis seen in patients with cystic fibrosis
What does Bronchiectasis cause?
Bronchial dilation
Acute and chronic inflammation
Fibrosis
What are the clinical features of bronchiectasis?
- Chronic cough productive of copious sputum
- Finger clubbing
What are the complications of bronchiectasis?
- Spread of infection (pneumonia, empyema, septicaemia, meningitis, metastatic abscesses e.g. brain)
- Amyloidosis
- Respiratory failure
