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  • Open Access

Determination of SpO2/FiO2 thresholds to impute for PaO2/FiO2 ratios in the Sequential Organ Failure Assessment score

  • 1,
  • 1,
  • 1,
  • 1,
  • 1 and
  • 1
Critical Care200812 (Suppl 2) :P499

https://doi.org/10.1186/cc6720

  • Published:

Keywords

  • Respiratory Distress Syndrome
  • Linear Regression Model
  • Distress Syndrome
  • Organ Dysfunction
  • Acute Respiratory Distress Syndrome

Introduction

The Sequential Organ Failure Assessment (SOFA) score is a well-validated and effective method by which to measure organ dysfunction in critically ill patients and is a good indicator of prognosis. However, repeated arterial blood gas data are often lacking for calculating the respiratory component of the SOFA score on a daily basis. The aim of this study was to derive SpO2/FiO2 (S/F) ratio correlations with the PaO2/FiO2 (P/F) ratio in assessing the respiratory parameters of the SOFA score, incorporating the level of positive end-expiratory pressure (PEEP).

Methods

Matched measurements of SpO2 (limited to values ≤ 98%) and PaO2 from patients admitted with acute respiratory distress syndrome were used to determine the relationship between S/F and P/F, using three separate linear regression models, for patients on <8 cmH2O PEEP, 8–12 cmH2O PEEP and >12 cmH2O PEEP. S/F threshold values correlating with P/F ratios of 100, 200, 300 and 400 were determined, using the equation derived from the model.

Results

The linear regression coefficients of determination (R2) for the three models (PEEP < 8 cmH2O, n = 1,107; PEEP 8–12 cmH2O, n = 1,404 and PEEP >12 cmH2O, n = 405) were 0.58, 0.61 and 0.59, respectively. S/F threshold values correlating with P/F ratios of 100, 200, 300 and 400, according to PEEP, are presented in Table 1.
Table 1

(abstract P499)

Variable

SF ratio

SF ratio

SF ratio

PF ratio

PEEP < 8 cmH2O

PEEP 8 - 12 cmH2O

PEEP > 12 cmH2O

100

115

130

129

200

240

259

234

300

370

387

332

400

502

515

425

Conclusion

S/F ratios categorized by the level of PEEP can be used to impute for P/F ratios in the calculation of the respiratory component of the SOFA score.

Authors’ Affiliations

(1)
Vanderbilt University, Nashville, TN, USA

Copyright

© BioMed Central Ltd 2008

This article is published under license to BioMed Central Ltd.

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