What is the definition of COPD?
- Progressive airflow obstruction that is not fully reversible and does not change markedly over several months
What are the common causes of COPD?
- Alpha 1 antitrypsin deficiency
What is the pathogenesis of COPD?
- Loss of elasticity and alveolar attachements due to emphysema (airways collapse on expiration causing air trapping, hyperinflation, increased work of breathing and SOB)
- Goblet cell metaplasia with mucus plyggung of lumen
- Inflammation of the airway wall
- Thickening of bronchiolar wall (smooth muscle hypertrophy and peribronchial fibrosis)
What is chronic bronchitis?
- Production of sputum on most days for at least 2 months in at least 2 years
- Larger airways >4mm in diameter
- Develop airway inflammation (predominantly neutrophilic with CD8 cytotoxic lymphocytes and some eosinophils which leads to scarring and thickening of the airways)
- Inflammatory mediators include TNF, IL-8, neutrophil elastase, proteinase 3, cathespin G, elastase and MMPs from macrophages and ROS
- Squamous metaplasia and as tissue is destroyed you lose the interstitial support of the tissue around the bronchioles making them more collapsible
What is emphysema?
- Abnormal, permanent enlargement of the airspaces distal to the terminal bronchioles
- Four general types but centri-acinar (damage around respiratory bronchioles) and pan-acinar (uniformly enlarged from the level of terminal bronchiole distally) are most important
What are the stages of COPD?
- 1) Mild - FEV1 80%
- 2) Moderate - FEV1 50-79%
- 3) Severe - FEV1 30-49%
- 4) Very severe - FEV1 <30% or <50% with respiratory failure
What does type 1 respiratory failure look like?
- Pink puffer
- High respiratory drive
- ↓PaO2, ↓PaCO2
- Signs and symptoms include desaturation on exercise, pursed lip breathing, use of accessory muscles, wheeze, indrawing of intercostals and tachypnoea
What does type 2 respiratory failure look like?
- Low respiratory drive
- Type 2 respiratory failure
- ↓PaO2, ↑PaCO2
- Signs and symptoms include cyanosis, warm peripheries, bounding pulse, flapping tremor, confusion, drowsiness, right heart failure, oedema and raised JVP
What are the processes in asthmatic airway inflammation?
- CD4+ lymphocytes
- T lymphocytes
What are the processes involved in COPD airway inflammation?
- T lymphocytes
Why does cigarette smoking cause COPD?
- Cigarette smoking leads to reduced cilial motility, neutrophilic inflammation, mucus hypertrophy and Goblet cells, increased protease activity against anti-protease inhibition leading to more damage to tissues in the lungs (i.e. α1 antitrypsin is one of the main anti-proteases) and oxidative stress. Furthermore it can lead to squamous metaplasia.
How is COPD treated?
- Inhaled bronchodilators (salbutamol, salmeterol)
- Inhaled corticosteroids (budenoside, fluticasone)
- Oral theophyllines
- Mucolytics (carbocysteine)
- Nebulised therapy