• G Ortiz, A Bastidas, M Garay-Fernández, A Lara, M Benavides, E Rocha, A Buitrago, G Díaz, J Ordóñez, and L F Reyes.
• Pulmonary Medicine, Universidad El Bosque, Intensive Care Unit, Hospital Santa Clara Bogotá, Colombia.
• Med Intensiva. 2021 Jun 21.

ObjectiveTo establish the correlation and validity between PaO2/FiO2 obtained on arterial gases versus noninvasive methods (linear, nonlinear, logarithmic imputation of PaO2/FiO2 and SpO2/FiO2) in patients under mechanical ventilation living at high altitude.DesignAmbispective descriptive multicenter cohort study.SettingTwo intensive care units (ICU) from Colombia at 2600m a.s.l.Patients Or ParticipantsConsecutive critically ill patients older than 18 years with at least 24h of mechanical ventilation were included from June 2016 to June 2019.InterventionsNone.VariablesVariables analyzed were demographic, physiological messures, laboratory findings, oxygenation index and clinical condition. Nonlinear, linear and logarithmic imputation formulas were used to calculate PaO2 from SpO2, and at the same time the SpO2/FiO2 by severe hypoxemia diagnosis. The intraclass correlation coefficient, area under the ROC curve, sensitivity, specificity, positive predictive value, negative predictive value, positive and negative likelihood ratio were calculated.ResultsThe correlation between PaO2/FiO2 obtained from arterial gases, PaO2/FiO2 derived from one of the proposed methods (linear, non-linear, and logarithmic formula), and SpO2/FiO2 measured by the intraclass correlation coefficient was high (greater than 0.77, p<0.001). The different imputation methods and SpO2/FiO2 have a similar diagnostic performance in patients with severe hypoxemia (PaO2/FiO2 <150). PaO2/FiO2 linear imputation AUC ROC 0,84 (IC 0.81-0.87, p<0.001), PaO2/FiO2 logarithmic imputation AUC ROC 0.84 (IC 0.80-0.87, p<0.001), PaO2/FiO2 non-linear imputation AUC ROC 0.82 (IC 0.79-0.85, p<0.001), SpO2/FiO2 oximetry AUC ROC 0.84 (IC 0.81-0.87, p<0.001).ConclusionsAt high altitude, the SaO2/FiO2 ratio and the imputed PaO2/FiO2 ratio have similar diagnostic performance in patients with severe hypoxemia ventilated by various pathological conditions.Copyright © 2021 Elsevier España, S.L.U. y SEMICYUC. All rights reserved.

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