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

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. 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. 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. 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.