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Chapter: Medicine and surgery: Respiratory system

Acute bronchitis - Respiratory infections

An acute infectious condition of the lower respiratory tract.- Definition, Incidence, Aetiology, Pathophysiology, Clinical features, Complications, Investigations, Management, Prognosis.

Respiratory infections

Acute bronchitis




An acute infectious condition of the lower respiratory tract.




Very common.








= F



The primary cause is usually a respiratory virus, e.g. rhinovirus, influenza, parainfluenza and respiratory syncytial virus.




The virus enters via the airway by droplet inhalation and causes local inflammation, inducing secretions and impairing ciliary clearance.


Clinical features


Initially there is an irritating non-productive cough. The patient may feel short of breath, wheezy and complain of chest tightness and retrosternal discomfort. There is a low- or high-grade pyrexia. The cough then becomes wet and productive of yellow or green sputum. Discoloured sputum signifies infection, which may be of bacterial or viral origin. Streaky haemoptysis may occur. On auscultation wheezes and medium to coarse late or paninspiratory crackles may be heard.




The airway mucosa becomes red and oedematous, there is often an overlying mucopurulent exudate.




Secondary bacterial infection with Streptococcus pneu-moniae, Moraxella catarrhalis or Haemophilus influenzae may occur leading to bronchopneumonia, particularly in the elderly, smokers and individuals with underlying lung disease.




These are usually not required, there may be a mild neutrophil leucocytosis even in viral infections.




Antipyretic agents are used. Patients presenting with acute bronchitis during an influenza epidemic may benefit from treatment with a neuraminidase inhibitor if started in the first 48 hours. Only if secondary bacterial infection is suspected should a course of antibiotics be prescribed.




The illness usually lasts up to a week in healthy adults, prolonged symptoms may occur. Changes in the course of the illness or presence of bronchopneumonia suggest secondary bacterial infection.

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