Chest
Volume 148, Issue 6, December 2015, Pages 1477-1483
Journal home page for Chest

Original Research
Critical Care
Clinical Characteristics and Outcomes Are Similar in ARDS Diagnosed by Oxygen Saturation/Fio2 Ratio Compared With Pao2/Fio2 Ratio

https://doi.org/10.1378/chest.15-0169Get rights and content

BACKGROUND

Oxygen saturation as measured by pulse oximetry/Fio2 (SF) ratio is highly correlated with the Pao2/Fio2 (PF) ratio in patients with ARDS. However, it remains uncertain whether SF ratio can be substituted for PF ratio for diagnosis of ARDS and whether SF ratio might identify patients who are systemically different from patients diagnosed by PF ratio.

METHODS

We conducted a secondary analysis of a large observational prospective cohort study. Patients were eligible if they were admitted to the medical ICU and fulfilled the Berlin definition of ARDS with hypoxemia criteria using either the standard PF threshold (PF ratio ≤ 300) or a previously published SF threshold (SF ratio ≤ 315).

RESULTS

Of 362 patients with ARDS, 238 (66%) received a diagnosis by PF ratio and 124 (34%) by SF ratio. In a small group of patients who received diagnoses of ARDS by SF ratio who had arterial blood gas measurements on the same day (n = 10), the PF ratio did not meet ARDS criteria. There were no major differences in clinical characteristics or comorbidities between groups with the exception of APACHE (Acute Physiology and Chronic Health Evaluation) II scores, which were higher in the group diagnosed by PF ratio. However, this difference was no longer apparent when arterial blood gas-dependent variables (pH, Pao2) were removed from the APACHE II score. There were also no differences in clinical outcomes including duration of mechanical ventilation (mean, 7 days in both groups; P = .25), duration of ICU stay (mean, 10 days vs 9 days in PF ratio vs SF ratio; P = .26), or hospital mortality (36% in both groups, P= .9).

CONCLUSIONS

Patients with ARDS diagnosed by SF ratio have very similar clinical characteristics and outcomes compared with patients diagnosed by PF ratio. These findings suggest that SF ratio could be considered as a diagnostic tool for early enrollment into clinical trials.

Section snippets

Study Design

We studied patients who were prospectively enrolled from January 23, 2006, to July 14, 2013, in the Validating Acute Lung Injury Markers for Diagnosis (VALID) study. The VALID study was designed to identify and validate plasma biomarkers for diagnosis and prognosis of ARDS, and all subjects in the study are carefully phenotyped for ARDS. The Vanderbilt University Institutional Review Board approved the study protocol (IRB #051065) with a waiver of informed consent. However, written informed

Characteristics of Patients Who Received a Diagnosis of ARDS by PF Ratio Compared With SF Ratio

A total of 362 patients with ARDS met the inclusion and exclusion criteria and were included in the current study (Fig 1). Of these, 238 patients with ARDS (66%) received a diagnosis by PF ratio, and 124 patients (34%) received a diagnosis by SF ratio. Table 1 includes a comparison of baseline characteristics and risk factors for ARDS between patients who received a diagnosis by PF and SF ratios.

Overall, patients with ARDS diagnosed by PF ratio had similar characteristics to patients who

Discussion

Because of continued uncertainty regarding the usefulness of the SF ratio for diagnosis of ARDS, we sought to investigate whether there are systematic differences between patients who received a diagnosis of ARDS by PF ratio compared with patients with ARDS diagnosed by SF ratio. In a large cohort of 362 carefully phenotyped patients with ARDS in the medical ICU, we found no differences in demographics, comorbidities, or severity of illness between patients with ARDS diagnosed by PF ratio

Acknowledgments

Author contributions: L. B. W. had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis, including and especially any adverse effects. W. C. served as principal author. W. C. and L. B. W. contributed to the study concept design and writing of the manuscript; D. R. J., C. M. S., and J. A. B. contributed to data analysis and interpretation, study design, statistical analysis, and revision of the manuscript; and G.

References (29)

  • VM Ranieri et al.

    Acute respiratory distress syndrome: the Berlin Definition

    JAMA

    (2012)
  • P Merlani et al.

    Quality improvement report: Linking guideline to regular feedback to increase appropriate requests for clinical tests: blood gas analysis in intensive care

    BMJ

    (2001)
  • CS Pilon et al.

    Practice guideline for arterial blood gas measurement in the intensive care unit decreases numbers and increases appropriateness of tests

    Crit Care Med

    (1997)
  • RG Khemani et al.

    Comparison of SpO2 to PaO2 based markers of lung disease severity for children with acute lung injury

    Crit Care Med

    (2012)
  • Cited by (112)

    • An expanded definition of acute respiratory distress syndrome: Challenging the status quo

      2023, Journal of Intensive Medicine
      Citation Excerpt :

      Brown et al.[18] found that the SpO2/FiO2 ratio may be reasonably used to substitute arterial blood gas for determining levels of hypoxemia in ARDS patients. Chen et al.[19] further confirmed that patients inferred to have ARDS based on the SpO2/FiO2 ratio did not have different clinical outcomes compared to those diagnosed based on the PaO2/FiO2 ratio. As the Berlin definition has been developed with reference to resource-rich settings and does not apply to resource-constrained settings, the Kigali modification of the Berlin definition has been proposed for use in the latter.

    • Pulse oximetry for the diagnosis and management of acute respiratory distress syndrome

      2022, The Lancet Respiratory Medicine
      Citation Excerpt :

      In a study that directly compared medical ICU patients diagnosed with ARDS by arterial blood gas analysis versus pulse oximetry in a US tertiary care centre, baseline clinical characteristics and clinical outcomes including mortality were similar.31 Additionally, severe ARDS according to the pulse-oximetric criterion had a stronger association with mortality than severe ARDS diagnosed by arterial blood gas analysis, and diagnostic discordance was rare.31 Because SpO2 is continuously available, the SpO2/FiO2 ratio can be followed longitudinally more easily than the PaO2/FiO2 ratio, increasing available data for prognostication.

    View all citing articles on Scopus

    originally published Online First August 13, 2015

    FUNDING/SUPPORT: This study was funded by the National Institutes of Health [Grants NIH HL103836, HL112656-02, T32 HL087738, and UL1 RR024975], an American Heart Association Clinical Research Award, and an American Heart Association Established Investigator Award.

    View full text