Lower respiratory tract infection

Lower respiratory tract infections (LRTI) affect the airways below the level of the larynx, primarily the bronchi and lungs.

• Bronchitis: Infection of the bronchi.
• Pneumonia: Infection of the lung parenchyma.
• Bronchiolitis: Infection of the bronchioles, typically seen in infants.

• Bacteria: *Streptococcus pneumoniae*, *Haemophilus influenzae*, *Mycoplasma pneumoniae*.
• Viruses: Influenza, respiratory syncytial virus (RSV), adenovirus.

• Persistent cough, sometimes productive.
• Fever and malaise.
• Chest discomfort or pain.
• Dyspnoea and tachypnoea.
• Crackles on auscultation in pneumonia.

• Chest X-ray: Consolidation suggests pneumonia.
• Sputum culture: Identifies causative organism.
• Full blood count: Raised white cell count suggests bacterial infection.
• Arterial blood gases if severe.

• Antibiotics: Choice depends on suspected pathogen. Amoxicillin or doxycycline are often used as first-line for community-acquired pneumonia in adults.
• Supportive: Analgesia, antipyretics, and hydration.
• Oxygen therapy for hypoxic patients.
• Viral bronchitis often requires only supportive care.

• Empyema: Pus in the pleural space.
• Respiratory failure.
• Septic shock.
• Lung abscess.

• Vaccination, e.g., pneumococcal vaccine, influenza vaccine.
• Hand hygiene and respiratory precautions.

• Lower respiratory tract infections (LRTI) include bronchitis, pneumonia and bronchiolitis. 
• Often presents with lung features like persistent cough and chest pain, as well as general fever and malaise.
• Early recognition and intervention are crucial to prevent complications like respiratory failure and septic shock.
• Investigation consists of chest X-ray, sputum culture and blood tests to detect infection and identify causative organism.
• Management is dependent on suspected pathogen and is followed up with supportive care.