Lower Respiratory Tract Infection

Definition/diagnostic criteria Lower respiratory tract infection (LRTI) encompasses infections below the vocal cords, including bronchitis and pneumonia. LRTIs are typically characterised by cough, dyspnoea, sputum production and often fever. They may be divided into:

• Acute bronchitis (NICE defines this as ‘a lower respiratory tract infection which causes inflammation in the bronchial airways’, which translates into ‘a clinical diagnosis characterised by cough resulting from acute inflammation of the trachea and large airways but with no evidence of pneumonia’ which is usually viral and self-limiting).
• Pneumonia (defined by NICE as ‘an infection of the lung tissue in which the air sacs in the lungs become filled with microorganisms, fluid and inflammatory cells, affecting the function of the lungs’, which is often bacterial and potentially more serious than acute bronchitis).

Epidemiology LRTIs are a significant health concern in the UK, with acute bronchitis being one of the most common conditions seen in primary care. Pneumonia accounts for considerable morbidity and mortality, especially in the elderly and those with comorbidities. The incidence of pneumonia is highest during winter and in populations with higher rates of smoking and chronic health conditions.

Diagnosis
Clinical features: LRTIs typically present with a persistent cough, sputum production, dyspnoea and potentially fever. Bronchitis is usually characterised by a cough lasting 1-3 weeks. Pneumonia may present with these symptoms plus signs of systemic infection and sometimes pleuritic chest pain. Distinguishing between viral and bacterial infections based on clinical features alone can be challenging.

Investigations: In many cases in primary care, no investigations are required or practical. If required urgently then the patient would need hospital assessment.

• Investigations include chest radiography to confirm pneumonia, which typically shows localised opacities.
• Blood tests, including CRP and WBC count, may assist in assessing severity and the need for antibiotics.
• Sputum culture is recommended in some cases.

Treatment The treatment of LRTIs is primarily empirical.

• For bronchitis, management is largely supportive, focusing on symptom relief. Antibiotics are not routinely recommended due to the predominantly viral aetiology – although they might be considered depending on the clinical picture, age of the patient, and risk factors.
• Community-acquired pneumonia (CAP) requires antibiotics. The choice of antibiotic should be guided by the severity of the infection (the CRB-65 score can provide guidance here), patient’s age, comorbidities, and local resistance patterns. Common choices include amoxicillin, doxycycline, or clarithromycin. Treatment duration typically ranges from 5-7 days.

Prognosis The prognosis for acute bronchitis is generally excellent, with most individuals recovering within a few weeks. However, persistent cough can linger. The prognosis for pneumonia varies depending on the severity at presentation, the causative organism, and the patient’s underlying health. Elderly patients and those with significant comorbidities have a higher risk of complications and mortality. Early diagnosis and appropriate treatment are crucial for improving outcomes in pneumonia.