Comparison of the Spo 2 /Fio 2 Ratio and the Pao 2 /Fio 2 Ratio in Patients With Acute Lung Injury or Acute Respiratory Distress Syndrome

Introduction: Diagnostic criteria for acute lung injury (ALI) and Acute RespiratoryDistress syndrome (ARDS) includes acute onset of disease, chest radiographdemonstrating bilateral pulmonary infiltrates, lack of significant left ventriculardysfunction and Pao2/Fio2 (PF) ratio ≤300 for ALI or ≤200 for ARDS. Recent criteriarequire invasive arterial sampling. The pulse oximetric saturation Spo2/Fio2 (SF) ratiomay be a reliable non-invasive alternative to the PF ratio.Methods: In this cross-sectional study, we enrolled 70 patients with ALI or ARDSwho 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 PFwere recorded to determine the relationship between SF and PF ratio. SF values wereexamined as a substitute of PF ratio for diagnosis ARDS and ALI.Results: The relationship between SF and PF ratio was described by the followingregression equation: SF=57+0.61 PF (P<0.001). SF ratios of 181 and 235 correspondedof PF ratio 300 and 200. The SF cutoff of 235 had 57% sensitivity and 100% specificityfor diagnosis of ALI. The SF cutoff of 181 had 71% sensitivity and 82% specificity fordiagnosis of ARDS.Conclusion: SF ratio is a reliable noninvasive surrogate for PF ratio to identify childrenwith ALI or ARDS with the advantage of replacing invasive arterial blood sampling bynon-invasive pulse oximetry.