Bronchiectasis

Bronchiectasis is a condition where the bronchi become permanently dilated due to recurrent inflammation, resulting in airway obstruction.

Pathophysiology

1. An initial trigger such as an infection leads to inflammation in the airways. Airway inflammation in bronchiectasis is mainly driven by neutrophils.
    
2. These neutrophils ultimately impair the function of the cilia and stimulate mucus hypersecretion which results in airway obstruction.
    
3. Due to the stagnant mucus which cannot be cleared by the now dysfunctional cilia, patients are prone to infection and colonisation of the mucus occurs by organisms such as staphylococcus aureus, Moraxella catarrhalis, pneumococcus, pseudomonas aeruginosa and haemophilus influenza.
    
4. In response to the presence of bacteria, further inflammation is triggered which recruits more neutrophils to the bronchi. These neutrophils release proteases such as elastase and matrix metalloproteinases leading to destruction of the bronchi and permanent dilation of the airways.
    
5. Chronic inflammation also leads to damage to mucosa and muscular layers, resulting in fibrosis and oedema.
    
6. These dilated airways further allow pooling of mucus and fluid, which begins the cycle of stagnant mucus, bacterial colonisation and inflammation – hence forming the basis of the bronchiectasis ‘vicious cycle’ theory.
    
7. With time, patients can become hypoxic due to mucus plugs lowering ventilation to parts of the lung. This ventilation-perfusion mismatch leads to vasoconstriction in the pulmonary vasculature to shunt blood to well ventilated parts of the lung. Through this, patients may develop cor pulmonale.

National Heart Lung and Blood Institute, Public domain, via Wikimedia Commons

Bronchiectasis Pathophysiology

Causes

Genetic

• Cystic Fibrosis: Due to mucus accumulating, which then becomes colonised by infectious agents thus triggering the vicious cycle
• Kartaganer’s Syndrome, or Primary Ciliary Dyskinesia
• Young’s syndrome: Azoospermia, rhinosinusitis and bronchiectasis

Infective

• Severe childhood respiratory infection e.g. pneumonia, whooping cough, tuberculosis
• Allergic bronchopulmonary aspergillosis: Fungal spores inhaled and trigger an immune response in the airways.

Connective Tissue Diseases

• Rheumatoid arthritis
• Vasculitis
• Marfan’s syndrome

Obstruction

• Bronchial obstruction e.g. by a tumour

Clinical Features

• Chronic productive cough: Patients will produce very large quantities of sputum
• Sputum may be foul smelling
• Dyspnoea
• Fatigue
• Haemoptysis: Due to mucosal inflammation, and can be massive
• Finger clubbing
• Coarse crackles on auscultation, which are typically in the bases
• Wheezing is possible due to obstructed airways

Investigations

Bedside

• Sputum culture

Imaging

• CXR: May show tramline and ring shadows
• High resolution CT: Will show dilated airways as well as extent of disease. Signet ring sign may be seen, which indicates a dilated bronchus with a pulmonary artery branch.

Special Tests

• Spirometry: Will show an obstructive pattern
• Aspergillus precipitins and total IgE
• Bronchoscopy: If bronchiectasis is restricted to a specific part of the lung, it may be due to a foreign body or other obstructive lesion, thus bronchoscopy could be done to rule this out

John S. To, MD, Public domain, via Wikimedia Commons

Signet Ring Sign

Management

A self-management plan is typically drawn up for patients. Airway clearance techniques are important to help drain mucus. Patients may require antibiotics during flare-ups, which is why sputum cultures are important in determining sensitivities. If patients are having frequent exacerbations, prophylactic antibiotics may also be needed.

Patients should also be encouraged to get an annual influenza vaccination, and a one-off pneumococcus vaccination. If there is massive haemoptysis or localised disease, surgery may also be indicated.

Infective Exacerbation

An infective exacerbation of bronchiectasis usually presents with a worsened cough, increased dyspnoea and increased sputum volume which may be darker. Patients who are very unwell e.g. cyanosed, tachypnoea, pyrexia of over 38 degrees or confused should be admitted to hospital.

For patients who do not require hospital admission, sputum culture and sensitivity should be performed, and a prophylactic antibiotic prescribed for 1-2 weeks. The patient may also benefit from a short-acting beta-2 agonist to help with dyspnoea.

References

https://www.blf.org.uk/support-for-you/bronchiectasis/treatment

https://cks.nice.org.uk/bronchiectasis#!scenario:1

https://bronchiectasis.com.au/bronchiectasis/bronchiectasis/pathophysiology

Gould's Pathophysiology for the Health Professions, 6th Edition

https://www.ncbi.nlm.nih.gov/books/NBK430810/