Chest
Volume 152, Issue 6, December 2017, Pages 1151-1158
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Original Research: Critical Care
Oxygenation Saturation Index Predicts Clinical Outcomes in ARDS

https://doi.org/10.1016/j.chest.2017.08.002Get rights and content

Background

Traditional measures of ARDS severity such as Pao2/Fio2 may not reliably predict clinical outcomes. The oxygenation index (OI [Fio2 × mean airway pressure × 100)/Pao2]) may more accurately reflect ARDS severity but requires arterial blood gas measurement. We hypothesized that the oxygenation saturation index (OSI [Fio2 × mean airway pressure × 100)/oxygen saturation by pulse oximetry (Spo2)]) is a reliable noninvasive surrogate for the OI that is associated with hospital mortality and ventilator-free days (VFDs) in patients with ARDS.

Methods

Critically ill patients enrolled in a prospective cohort study were eligible if they developed ARDS (Berlin criteria) during the first 4 ICU days and had mean airway pressure, Spo2/Fio2, and Pao2/Fio2 values recorded on the first day of ARDS (N = 329). The highest mean airway pressure and lowest Spo2/Fio2 and Pao2/Fio2 values were used to calculate OI and OSI. The association between OI or OSI and hospital mortality or VFD was analyzed by using logistic regression and linear regression, respectively. The area under the receiver-operating characteristic curve (AUC) for mortality was compared among OI, OSI, Spo2/Fio2, Pao2/Fio2, and Acute Physiology and Chronic Health Evaluation II scores.

Results

OI and OSI were strongly correlated (rho = 0.862; P < .001). OSI was independently associated with hospital mortality (OR per 5-point increase in OSI, 1.228 [95% CI, 1.056-1.429]; P = .008). OI and OSI were each associated with a reduction in VFD (OI, P = .023; OSI, P = .005). The AUC for mortality prediction was greatest for Acute Physiology and Chronic Health Evaluation II scores (AUC, 0.695; P < .005) and OSI (AUC, 0.602; P = .007). The AUC for OSI was substantially better in patients aged < 40 years (AUC, 0.779; P < .001).

Conclusions

In patients with ARDS, the OSI was correlated with the OI. The OSI on the day of ARDS diagnosis was significantly associated with increased mortality and fewer VFDs. The findings suggest that OSI is a reliable surrogate for OI that can noninvasively provide prognostic information and assessment of ARDS severity.

Section snippets

Study Design

This trial was a nested retrospective cohort study of patients prospectively enrolled in the Validating Acute Lung Injury Markers for Diagnosis (VALID) study. Patients who were eligible for enrollment in VALID were ≥ 18 years old and admitted to the Vanderbilt University Medical Center medical, surgical, cardiovascular, or trauma ICU for at least 2 days. Full inclusion and exclusion criteria have been previously described elsewhere.24 Written informed consent was obtained at the time of

Patient Characteristics

A total of 329 patients met inclusion criteria for this study. Demographic characteristics and clinical data are described in Table 1. Predicted body weights were not available in the VALID study. Average tidal volume/kilogram (based on actual weight on day of diagnosis as we did not have height available for all patients to calculate ideal body weight) was 5.7 ± 1.9 cc/kg. The highest PEEP value on the day of ARDS diagnosis was 10 ± 4 cm H2O.

OI and OSI Are Strongly Correlated With Each Other

In this cohort of patients, OI and OSI were strongly

Discussion

In 329 adults with ARDS who were mechanically ventilated, the OSI was highly correlated with the OI. Both the OSI and the OI were independently associated with fewer VFDs, whereas the traditional metric for characterizing ARDS severity, Pao2/Fio2, was not. Among the ARDS severity measures analyzed, only OSI was significantly associated with mortality in this cohort. Furthermore, both OSI and OI were superior to the Pao2/Fio2 in prognostic performance. Based on analysis of receiver-operating

Conclusions

Measurement of the OSI on the day of ARDS diagnosis performed as well as the OI in predicting clinical outcomes, was simple to calculate and continuously available, and offered more prognostic information than traditional measures of ARDS severity such as Pao2/Fio2, while avoiding invasive arterial blood gas monitoring.

Acknowledgments

Author contributions: L. B. W. is the guarantor of this study and 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. K. D. served as principal author; K. D. and L. B. W. contributed to the study concept design and writing of the manuscript; and J. B. M., C. M. S., J. A. B., and C. W. contributed to data analysis and interpretation, study design, statistical

References (30)

  • C. Guerin et al.

    Prone positioning in severe acute respiratory distress syndrome

    N Engl J Med

    (2013)
  • C. Brun-Buisson et al.

    Epidemiology and outcome of acute lung injury in European intensive care units. Results from the ALIVE study

    Intensive Care Med

    (2004)
  • L.B. Ware

    Prognostic determinants of acute respiratory distress syndrome in adults: impact on clinical trial design

    Crit Care Med

    (2005)
  • K.N. Kangelaris et al.

    Is there still a role for the lung injury score in the era of the Berlin definition ARDS?

    Ann Intensive Care

    (2014)
  • E. Seeley et al.

    Predictors of mortality in acute lung injury during the era of lung protective ventilation

    Thorax

    (2008)
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    FUNDING/SUPPORT: This study was funded by the National Institutes of Health [grant HL103836], Courtney’s Race for the ARDS Cure, the Courtney Charneco Family, and the Vanderbilt Office of Medical Student Research.

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