Oxygen saturation is not clinically useful in the exclusion of bacterial pneumonia in febrile infants.

Background: Acute respiratory infection remains a common presentation to Emergency Departments. Oxygen saturations (Sao(2)) may be useful in determining which febrile infants require chest x-rays (CXR) in investigation for bacterial pneumonia (PNA). This study aimed to determine whether Sao(2) is clinically useful in excluding bacterial PNA in febrile infants <24 months.

Methods: A febrile infant registry was instituted at a tertiary care military hospital (55,000 annual patients, 27% children) from December 2002-December 2003. Eligible patients consisted of infants <3 months with temperature ≥38°C or 3-24 months with temperature ≥39°C. Bacterial PNA was defined in this cohort by a CXR revealing a 'lobar infiltrate' by a board-certified radiologist. Descriptive statistics are presented on groups who received CXR versus groups who did not, and on infants who had bacterial PNA versus those who did not. Student t tests were used to compare maximum temperature (Tmax), RR, and Sao(2). Logistic regression for PNA was performed using age, sex, Tmax, RR, HR and Sao(2). A Receiver Operator Characteristic (ROC) curve was created to show Sao(2) cut-off points as related to sensitivity and specificity.

Results: 985 patients (55% boys; median age: 12 months) met entry criteria. 790 underwent CXR and 82 were diagnosed with bacterial PNA. Sao(2) was lower in infants with bacterial PNA (96.6%±2.5% vs 97.7%±1.8%, p<0.001). Sao(2) was also predictive of bacterial PNA by logistic regression (p=0.017) but the ROC curve yielded a poor sensitivity/specificity profile (area under curve (AUC) of 0.6786).

Conclusions: In febrile infants, Sao(2) was not found to be clinically useful for excluding bacterial PNA.