Respiratory

Community-Acquired Pneumonia

An acute infection of the lung parenchyma acquired outside hospital that fills alveoli with inflammatory exudate and impairs gas exchange. Confirm the syndrome, assess severity and sepsis risk, and start appropriate antibiotics promptly.

Definition

Community-acquired pneumonia is an acute infection of the lung parenchyma acquired outside hospital or within 48 hours of admission, in which alveoli fill with inflammatory exudate and gas exchange is impaired.

First principles

Pneumonia fills alveoli rather than primarily narrowing airways

Pathogens reaching the distal airspaces trigger inflammation, oedema and neutrophil-rich exudate that replace air in the alveoli. The affected lung therefore becomes poorly ventilated while perfusion continues, producing ventilation-perfusion mismatch and hypoxaemia. This explains focal crackles or bronchial breathing and distinguishes pneumonia from a purely obstructive airway exacerbation.

You’ve reached the end of the preview

The rest of this extended textbook page is part of full access. Create a free account to read the sample topics in full and try sample questions, then upgrade to unlock every high-yield and extended page, plus the complete question bank.

This page is exam revision material, not medical advice, and must not be used for patient care. Always check drug doses against the BNF and current guidance. Full disclaimer.