A comparative study of SpO2/FiO2 and PaO2/FiO2 ratios as markers of acute lung injury/acute respiratory distress syndrome

Dr Atul Kaushik; Dr Ratan Kumar Choudhary; Dr Praveen Kumar; Dr Shailja Sharma

Volume : IX, Issue : IX, September - 2019

A comparative study of SpO2/FiO2 and PaO2/FiO2 ratios as markers of acute lung injury/acute respiratory distress syndrome

Dr Atul Kaushik, Dr Ratan Kumar Choudhary, Dr Praveen Kumar, Dr Shailja Sharma

Abstract :

Acute respiratory distress syndrome is the clinical manifestation of severe acute lung injury, which is characterized by acute onset of diffuse, bilateral pulmonary infiltrates secondary to noncardiogenic pulmonary edema, refractory hypoxia and decreased lung compliance. One of the diagnostic criteria for acute lung injury (ALI) is the PaO2/FiO2 (P/F) ratio measured by blood gas analysis, which involves an invasive procedure (arterial blood draw). In order to reduce invasive procedures on critically ill patients, an alternative non–invasive marker SpO2/FiO2 (S/F) ratio for ALI is needed which requires pulse oximetry. Objective: To evaluate sensitivity and specificity S/F ratio and P/F ratio, in order to find an alternative non–invasive marker of ALI. Methods: We conducted a cross–sectional study at the pediatric intensive care unit (PICU) RAMA MEDICAL COLLEGE AND HOSPITAL HAPUR GHAZIABAD from June 2018 to June 2019. Subjects (children aged 1 month– 18 years) underwent blood gas analysis when their pulse oximetry showed saturation of 80–97% within 24 hours of ventilator use. We measured PaO2, SpO2, and FiO2 and calculated S/F and P/F ratios. Data were analyzed by Spearman’s correlation and linear regression tests. Results: Out of 69 PICU patients, 39 children fulfilled the criteria for ALI. The S/F ratio and P/F ratio had a weak correlation (r=0.2; P=0.18). The linear regression equation was S/F ratio = 129.67 +0.11 (P/F), with S/F ratio values of 162.67 and 151.67 correlating to P/F ratio values of 300 and 200, respectively. Conclusion: The S/F ratio has a weak correlation with P/F ratio for ALI in children.