Introduction: Community-acquired pneumonia (CAP) is a common presenting condition in primary care. Assessment of oxygenation status using pulse oximetry is increasingly available, but its precise role in disease severity assessment is unknown.
Aims: To inform the use of pulse oximetry in patients with CAP, including the utility of different oxygenation thresholds, patient subgroups, and interaction with existing severity scores.
Methods: A prospective cohort study of adults with CAP admitted to a UK teaching hospital trust. Oxygen saturations (SpO₂) and the fraction of inspired oxygen were recorded on admission. The value of different SpO₂ thresholds (< 88%, ≤ 90%, ≤ 92%, and < 95%) in predicting 30-day mortality and critical care admission was analysed.
Results: 467 patients had SpO₂ measured on room air. Admission SpO₂ ≤ 90% was observed in 28% of patients and had reasonable specificity (76%) for 30-day mortality or critical care admission, but low sensitivity (46%). Specificity was particularly good for adults <50 years of age (90%) or those with asthma (92.3%).
Conclusion: SpO₂ ≤ 90% has good specificity but low sensitivity for adverse outcomes in CAP. It complements rather than replaces clinical severity scoring.