Community-Acquired Pneumonia
Infection filling the alveoli with inflammatory exudate outside a hospital setting, so the alveolar space (not the airway) is consolidated, producing focal signs of consolidation, hypoxia and a systemic inflammatory response whose severity must be scored to guide urgent treatment.
In a nutshell
Infection floods the alveoli with inflammatory exudate, producing consolidation rather than airway obstruction. Consolidated but perfused alveoli cause ventilation-perfusion mismatch and hypoxaemia, while systemic cytokine release drives fever and, in severe cases, sepsis: hence CURB-65 translates this physiology into a mortality-guided treatment decision.
Classic presentation
Acute fever, productive cough and pleuritic chest pain with focal dullness, bronchial breathing and crackles, and new consolidation on chest X-ray.
Key points
- Consolidation is alveolar filling with exudate, not airway narrowing: this is why signs are focal (dullness, bronchial breathing) rather than the diffuse wheeze of obstructive disease.
- Sound and vibration travel better through fluid-filled lung, explaining increased vocal resonance and tactile fremitus over consolidation.
- Hypoxaemia arises from ventilation-perfusion mismatch: consolidated alveoli are still perfused but no longer ventilated.
- CURB-65 converts decompensation markers (confusion, urea, respiratory rate, blood pressure, age) into a mortality estimate that determines site of care.
- Antibiotics should be started promptly once severity is assessed, with intravenous and broader-spectrum therapy reserved for higher-severity disease.
- A repeat chest X-ray at around six weeks is warranted in higher-risk patients to confirm resolution and exclude an underlying tumour.
First-line investigation
Chest X-ray to confirm consolidation, alongside CURB-65 scoring to stratify severity and guide management.
First-line management
Prompt empirical antibiotics chosen according to CURB-65 severity, with supportive oxygen and fluids as needed.
Exam traps
- CURB-65 is calculated at presentation, not after treatment has started, to determine site of care before deterioration occurs.
- A normal chest X-ray very early in the illness does not exclude pneumonia; consolidation can lag behind clinical signs.
- Confusion in an older patient with pneumonia is a CURB-65 criterion and a marker of severity, not simply background cognitive impairment.
- Persistent or non-resolving consolidation, especially in a smoker, should prompt investigation for an underlying lung cancer, not just repeat antibiotics.
Educational content pending clinical review. Not medical advice.