Comparison of the Spo2/Fio2 Ratio and the Pao2/Fio2 Ratio in Patients With Acute Lung Injury or Acute Respiratory Distress Syndrome

INTRODUCTION Diagnostic criteria for acute lung injury (ALI) and Acute Respiratory Distress syndrome (ARDS) includes acute onset of disease, chest radiograph demonstrating bilateral pulmonary infiltrates, lack of significant left ventricular dysfunction and Pao2/Fio2 (PF) ratio ≤300 for ALI or ≤200 for ARDS. Recent criteria require invasive arterial sampling. The pulse oximetric saturation Spo2/Fio2 (SF) ratio may be a reliable non-invasive alternative to the PF ratio. METHODS In this cross-sectional study, we enrolled 70 patients with ALI or ARDS who were admitted in Tabriz children's hospital pediatrics intensive care unit (PICU). Spo2, Fio2, Pao2, charted within 5 minutes of each other and calculated SF and PF were recorded to determine the relationship between SF and PF ratio. SF values were examined as a substitute of PF ratio for diagnosis ARDS and ALI. RESULTS The relationship between SF and PF ratio was described by the following regression equation: SF=57+0.61 PF (P<0.001). SF ratios of 181 and 235 corresponded of PF ratio 300 and 200. The SF cutoff of 235 had 57% sensitivity and 100% specificity for diagnosis of ALI. The SF cutoff of 181 had 71% sensitivity and 82% specificity for diagnosis of ARDS. CONCLUSION SF ratio is a reliable noninvasive surrogate for PF ratio to identify children with ALI or ARDS with the advantage of replacing invasive arterial blood sampling by non-invasive pulse oximetry.