Obstructive Pulmonary Disease
Author(s): Osman El-Koubani
Learning objectives
- Revise the anatomy of the lungs
- Describe the causes of localised and diffuse airways obstruction
- Describe the clinical and pathological features of asthma
- Define the terms chronic bronchitis and emphysema
- Describe the clinical and pathological features of chronic obstructive pulmonary disease
- Describe the causes, clinical and pathological features of bronchiectasis
- Review of causes, clinical and pathological features cystic fibrosis
Anatomy of the lungs questions Part 1 of 17
There are two lobes in the left lung, and three lobes in the right lung.
Localised Airway Obstruction Part 2 of 17
Obstruction that affects single bronchus/bronchiole.
Causes of localised airway obstruction
- Extrinsic / outside the wall of bronchus – e.g. large lymph node/neoplasm.
- Intrinsic / within the wall or lumen of bronchus – e.g. neoplasm or foreign body.
Obstruction usually results in distal lobe collapse, which can lead to:
- Wheeze
- Stridor
- Distal infective pneumonia
- Bronchiectasis – from prolonged exposure
Diffuse Airway Obstruction Part 3 of 17
Diffuse airway obstruction is obstruction that affects many airways through the lung.
Pulmonary function tests will show an obstructive picture:
Causes of Diffuse Airway Obstruction
- Asthma – reversible and intermittent
- Chronic Obstructive Pulmonary Disease – irreversible and persistent
Asthma Part 4 of 17
Definition
Breathing that is periodically rendered difficult by widespread narrowing of the airways, which change in severity over short periods of time.
It is reversible and intermittent.
Pathophysiology
Clinical Features
- Paroxysmal wheeze
- Shortness of breath
- Diurnal cough and peak expiratory flow rate (PEFR) – worse in the morning, better in the evening
- Susceptible to recurrent chest infections – known as acute exacerbation of asthma
Subtypes of asthma Part 5 of 17
There are 5 main aetiological caterogies which can cause asthma:
Histology of asthma Part 6 of 17
Macroscopic Appearance of Asthmatic
Microscopic Appearance of Asthmatic
Chronic Obstructive Pulmonary Disease Part 7 of 17
Definition
The spectrum of co-existence of chronic bronchitis and emphysema – therefore affects both the airways and the alveolar parenchyma.
It is irreversible and persistent.
Epidemiology
Typically seen in – middle-aged patients who have an extensive smoking history or occupational/environmental exposure to pollution e.g. coal miners
2% of the UK population (1.2 million) are estimated to have COPD. It is a common cause for hospital admissions and has a large burden on healthcare, especially during winter. It is the 3rd leading cause of death globally.
Chronic Bronchitis Part 8 of 17
Definition
Chronic productive cough which occurs most days for at least 3 months over 2 consecutive years.
It is a clinical diagnosis – meaning no special tests are required, as long as the patient fulfils the above criteria.
Clinical Features
Histology of chronic bronchitis Part 9 of 17
Emphysema Part 10 of 17
Definition
Permanent loss of alveolar parenchyma distal to the terminal bronchiole.
Aetiology
- Smoking – usually older patients as emphysema develops slower
- Alpha-1 antitrypsin deficiency – usually younger patients as emphysema develops quickly
- Rarely – connective tissue diseases e.g. Marfan’s
Clinical features
Types of emphysema Part 11 of 17
1. Centrilobular – affects respiratory bronchioles
Most common type, typically found in upper zones of the lung in a patchy distribution.
Strongly associated with smoking, and also seen with pneumoconiosis.
Respiratory bronchiolitis is often present.
2. Panlobular – affects respiratory bronchioles and alveoli
Typically found in lower lobes.
Associated with alpha-1 antitrypsin deficiency.
Pathophysiology
Please see interstitial lung disease lecture for more information about pneumoconiosis and respiratory bronchiolitis.
Histology of emphysema Part 12 of 17
Chronic bronchitis vs emphysema Part 13 of 17
| Chronic Bronchitis | Emphysema | |
|---|---|---|
| Area affected | Larger airways | Alveoli |
| Clinical description | Blue bloater - Low RR, low O2, high CO2 | Pink puffer - high RR, normal O2, low CO2 |
| Histology | Dilatation of airways Mucous gland hypertrophy Goblet cell hyperplasia Chronic inflammation | Bullae Airspace enlargement Breakdown of alveolar wall Inflammation |
| Specific Complications | Chronic infection Risk of squamous cell carcinoma | Pneumothorax from ruptured bullae |
| Subtypes | Nil | Centrilobular Panlobular |
Bronchiectasis Part 14 of 17
Definition
Permanent abnormal dilatation of bronchi.
Aetiology
- Post-infectious – especially in children prone to infection e.g.
- Primary cause: Cystic fibrosis or ciliary dyskinesia
- Secondary cause: Chemotherapy, measles
- Obstruction – intrinsic or extrinsic local obstruction
- Asthma
- Systemic disease – connective tissue disease
Clinical features
- Chronic productive cough with copious sputum
- Finger clubbing
- Recurrent infections
- Pulmonary hypertension and right heart failure
Histology of Bronchiectasis Part 15 of 17
Brief Overview of Cystic Fibrosis Part 16 of 17
Pathophysiology
Mutation of the CFTR gene on Chromosome 7q3.
This leads to increased secretions of various organs and can affect:
- Lungs
- Pancreas
- Sweat glands
- Liver
- Kidneys
- Gonads
Clinical Features
- Failure to thrive in early development
- Chronic chest infections – especially Staphylococcus aureus and Pseudomonas aeruginosa
- Bronchiectasis
- Fatty stools
- Increase sodium and chlorine in sweat – this leads to metabolic alkalosis
- Infertility – absent vas deferens
- Clubbing of fingers
- Meconium ileus as a neonate
Investigation
Sweat test positive due to raised secretions of sodium and chlorine