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Volume 17 Supplement 4

Sepsis 2013

  • Poster presentation
  • Open Access

SaO2/FiO2 ratio as risk stratification for patients with sepsis

  • Adriell Ramalho Santana1,
  • Jaqueline Lima de Sousa1,
  • Fábio Ferreira Amorim1,
  • Bárbara Magalhães Menezes1,
  • Fernanda Vilas Bôas Araújo1,
  • Felipe Bozi Soares1,
  • Louise Cristhine de Carvalho Santos1,
  • Mariana Pinheiro Barbosa de Araújo1,
  • Pedro Henrique Gomes Rocha1,
  • Pedro Nery Ferreira Júnior1,
  • Alessandra Vasconcelos da Silva Paiva1,
  • Gabriel Kanhouche2,
  • Alethea Patrícia Pontes Amorim2,
  • José Aires de Araújo Neto3,
  • Edmilson Bastos de Moura3 and
  • Marcelo de Oliveira Maia3
Critical Care201317(Suppl 4):P51

Published: 5 November 2013


Risk StratificationRetrospective CohortCharacteristic CurveRetrospective Cohort StudyPulse Oximetry


The PaO2/FiO2 ratio is a well-known parameter to assess respiratory dysfunction, used in Sequential Organ Failure Assessment (SOFA) [1]. This study aims to determine whether the SaO2/FiO2 ratio can be used in the assessment of respiratory impairment and as a predictor of ICU mortality in patients with sepsis and to evaluate its correlation with PaO2/FiO2.

Materials and methods

A retrospective cohort study conducted in the ICU of Hospital Santa Luzia, Brasilia, DF, Brazil, during 5 months. An arterial blood sample was collected at the time of admission. Patients with sepsis were divided into two groups: survivors group (SG) and nonsurvivors group (NSG). Correlation with SaO2/FiO2 and PaO2/FiO2 was evaluated with the Pearson correlation coefficient. Accuracy of SaO2/FiO2 and PaO2/FiO2 to predict ICU mortality was measured with the area under the receiver operating characteristic curve.


A total of 118 patients with sepsis were enrolled. The mean age was 66 ± 21 years, SAPS3: 50 ± 14, APACHE II: 13 ± 8, PaO2/FiO2: 317 (IQ 233 to 426) and SaO2/FiO2: 362 (IQ 247 to 453). ICU mortality was 17.8% (n = 21). The main sites of infections were respiratory (57%, n = 67), urinary (19%, n = 23) and cutaneous (8.5%, n = 10). Nonsurvivor patients had lower SaO2/FiO2 (258 vs. 366, P = 0.00) and PaO2/FiO2 (285 vs. 354, P = 0.04). PaO2/FiO2 and SaO2/FiO2 had a good correlation (r = 0.645, P = 0.00). The relative risk of death in patients with SaO2/FiO2 <400 was 1.81 (95% CI: 1.47 to 2.24), SaO2/FiO2 <300 was 2.5 (95% CI: 1.54 to 4.05), SaO2/FiO2 <200 was 2.45 (95% CI: 1.27 to 4.71). The sensitivity for ICU mortality of SaO2/FiO2 <300 was 28% and of SaO2/FiO2 <200 was 35%. The specificity for ICU mortality of SaO2/FiO2 <300 was 90% and of SaO2/FiO2 <200 was 86% (95% CI: 93.5 to 100.0%). The area under the ROC curve for SaO2/FiO2 was 0.776 (95% CI: 0.677 to 0.875) and for PaO2/FiO2 was 0.655 (95% CI: 0.507 to 0.804) (Figure 1).
Figure 1
Figure 1

ROC curve for SaO 2 /FiO 2 and PaO 2 /FiO 2 .


A low SaO2/FiO2 was associated with mortality in this group of patients and had a good correlation with PaO2/FiO2. SaO2/FiO2 <300 showed high specificity for mortality. Further analysis is necessary to the validation of less invasive measures such as pulse oximetry saturation (SpO2/FiO2 ratio) in the assessment of patients with sepsis.

Authors’ Affiliations

Escola Superior de Ciências da Saúde, Brasília, Brazil
Liga Acadêmica de Medicina Intensiva de Brasília, Brazil
Hospital Santa Luzia, Brasília, Brazil


  1. Pandharipande P, Shintani A, Hagerman H, St Jacques P, Rice T, Sanders N, Ware L, Bernard G, Ely E: Derivation and validation of Spo2/Fio2 ratio to impute for Pao2/Fio2 ratio in the respiratory component of the Sequential Organ Failure Assessment score. Crit Care Med. 2009, 37: 1317-1321. 10.1097/CCM.0b013e31819cefa9.PubMed CentralView ArticlePubMedGoogle Scholar


© Santana et al.; licensee BioMed Central Ltd. 2013

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