Journal of Intensive Care Medicine http://jic.sagepub.com/
SpO2/FiO2 Ratio on Hospital Admission Is an Indicator of Early Acute Respiratory Distress Syndrome Development Among Patients at Risk Emir Festic, Vikas Bansal, Daryl J. Kor, Ognjen Gajic and US Critical Illness and Injury Trials Group: Lung Injury Prevention Study Investigators (USCIITG-LIPS) J Intensive Care Med published online 20 December 2013 DOI: 10.1177/0885066613516411 The online version of this article can be found at: http://jic.sagepub.com/content/early/2013/12/19/0885066613516411
Published by: http://www.sagepublications.com
Additional services and information for Journal of Intensive Care Medicine can be found at: Email Alerts: http://jic.sagepub.com/cgi/alerts Subscriptions: http://jic.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav
>> OnlineFirst Version of Record - Dec 20, 2013 What is This?
Downloaded from jic.sagepub.com at Scientific library of Moscow State University on January 13, 2014
Article
SpO2/FiO2 Ratio on Hospital Admission Is an Indicator of Early Acute Respiratory Distress Syndrome Development Among Patients at Risk
Journal of Intensive Care Medicine 201X, Vol XX(X) 1-8 ª The Author(s) 2013 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/0885066613516411 jic.sagepub.com
Emir Festic, MD1, Vikas Bansal, MBBS, MPH2, Daryl J. Kor, MD3, and Ognjen Gajic, MD, MSc4; US Critical Illness and Injury Trials Group: Lung Injury Prevention Study Investigators (USCIITG–LIPS)
Abstract Purpose: Oxygen saturation to fraction of inspired oxygen ratio (SpO2/FiO2) has been validated as a surrogate marker for partial pressure of oxygen to fraction of inspired oxygen ratio among mechanically ventilated patients with acute respiratory distress syndrome (ARDS). The validity of SpO2/FiO2 measurements in predicting ARDS has not been studied. Recently, a Lung Injury Prediction Score (LIPS) has been developed to help identify patients at risk of developing ARDS. Methods: This was a secondary analysis of the LIPS-1 cohort. A multivariate logistic regression included all established variables for LIPS, Acute Physiology and Chronic Health Evaluation 2, age, and comorbid conditions that could affect SpO2/FiO2. The primary outcome was development of ARDS in the hospital. The secondary outcomes included hospital mortality, hospital day of ARDS development, and hospital day of death. Results: Of the 5584 patients, we evaluated all 4646 with recorded SpO2/FiO2 values. Median SpO2/FiO2 in those who did and did not develop ARDS was 254 (100, 438) and 452 (329, 467), respectively. There was a significant association between SpO2/FiO2 and ARDS (P .001). The SpO2/FiO2 was found to be an independent predictor of ARDS in a ‘‘dosedependent’’ manner; for SpO2/FiO2 < 100—odds ratios (OR) 2.49 (1.69-3.64, P < .001), for SpO2/FiO2 100 < 200—OR 1.75 (1.16-2.58, P ¼ .007), and for SpO2/FiO2 200 < 300—OR 1.62 (1.06-2.42, P ¼ .025). The discriminatory characteristics of the multivariable model and SpO2/FiO2 as a single variable demonstrated area under the curve (AUC) of 0.81 and AUC of 0.74, respectively. Conclusions: The SpO2/FiO2, measured within the first 6 hours after hospital admission, is an independent indicator of ARDS development among patients at risk. Keywords ARDS, oxygenation, prediction, admission
Introduction Acute respiratory distress syndrome (ARDS) is a lifethreatening clinical syndrome with associated mortality as high as 40%.1,2 Survivors frequently face prolonged exercise limitation, psychological sequelae, and decreased quality of life, which all lead to increased use of health care services, representing a major health burden.3 Therapeutic trials have been mostly disappointing, and the current therapeutic strategy is largely supportive. Recently, there has been a shift in the interventional approach emphasizing prevention among patients at high risk of ARDS development. Among attempts to identify patients at risk, the most successful thus far has been the Lung Injury Prediction Score (LIPS).4 This score, ascertained within the initial 6 hours after hospital admission, has been validated in a large, multicenter cohort of patients at risk. The score combines various predisposing conditions and risk modifiers as well as markers of hypoxemia (oxygen saturation) and oxygen
requirement (fractional inspired oxygen concentration). The LIPS is limited by complexity and the effort needed to collect necessary variables, prompting the development and testing of simpler alternatives, including oxygen saturation to fraction of inspired oxygen ratio (SpO2/FiO2).
1
Pulmonary and Critical Care Medicine, Mayo Clinic, Jacksonville, FL, USA Critical Care Research, Mayo Clinic, Jacksonville, FL, USA 3 Anesthesiology and Critical Care, Mayo Clinic, Rochester, MN, USA 4 Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, MN, USA 2
Received July 3, 2013, and in revised form September 5, 2013. Accepted for publication September 6, 2013. Corresponding Author: Emir Festic, Pulmonary and Critical Care Medicine, Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL 32224, USA. Email: [email protected]
Downloaded from jic.sagepub.com at Scientific library of Moscow State University on January 13, 2014
2
Journal of Intensive Care Medicine XX(X)
Although the ARDS criteria require the measurement of partial pressure of arterial oxygen to fraction of inspired oxygen ratio (PaO2/FiO2),5,6 majority of the patients at risk but without fully established ARDS do not have arterial blood gasses performed. A surrogate, noninvasive measure of oxygenation, SpO2/FiO2 has been used by Rice et al among patients with ARDS to substitute for PaO2/FiO2.7 These authors further detailed specific threshold levels for SpO2/FiO2 that could be used in patients with ARDS as a substitute whenever PaO2/ FiO2 was unavailable. Khemani et al have also demonstrated close agreement between PaO2/FiO2 and SpO2/FiO2, acknowledging that SpO2/FiO2 was an efficient, noninvasive indicator of PaO2/FiO2 among children with acute lung injury (ALI) or ARDS.8,9 However, the value of SpO2/FiO2 as an early predictor of subsequent ARDS development has not been studied. Given the paradigm shift in the approach to ARDS investigations (toward prevention and early treatment), a noninvasive surrogate marker of impaired oxygenation that can be determined early in the course of patient presentation is clearly desirable. We hypothesized that SpO2/FiO2 would be a reliable early independent predictor of ARDS development.
Methods This is a secondary analysis of the previously published LIPS-1 study,4 a prospective cohort investigation conducted under the auspices of the US Critical Illness and Injury Trials Group (USCIITG). This initial investigation aimed to evaluate the predictive accuracy of LIPS, with the main outcome being development of ARDS in the hospital among patients at risk. The principal study was conducted among 5584 patients from 22 hospitals, of whom 377 (6.8%) developed ARDS, 95% of whom required invasive mechanical ventilation.4 The study protocol was approved by the institutional review board at each participating location. This secondary study was approved by the USCIITG/LIPS ancillary study committee.
Study Population The details of the study population have been previously described.4 Briefly, consecutive adult patients admitted to academic and community acute care hospitals were eligible for the study if they presented with at least 1 major risk factor for ARDS: sepsis, shock, pancreatitis, pneumonia, aspiration, high-risk trauma, or major high-risk surgery. Exclusion criteria were ALI or ARDS at the time of admission or within first 6 hours of hospital admission, transfer from an outside hospital, death in the emergency department (ED), comfort or hospice care, or hospital readmission during the study period.4 In addition, for the purpose of this secondary study, we excluded patients who did not have variables necessary for SpO2/FiO2 calculation recorded within first 6 hours of the hospital admission.
Predictor Variables Demographic and clinical information was obtained at the time of hospital admission or preoperatively at the time of surgery but within 6 hours of admission. The main predictor variable of this secondary study was SpO2/FiO2, which included oxygen saturation obtained by pulse oximetry and the fraction of inspired oxygen concentration, variables previously validated within the LIPS database.4 These variables were ascertained within the first 6 hours of admission to 22 participating hospitals. The principal investigator at each site was responsible for accurate data abstraction from the medical records into the Research Electronic Data Capture (REDCap), where oxygen saturation and inspired oxygen concentration obtained at the same time were abstracted together, on the same line, within the vital signs section, per standardized operating protocol. If these variables were obtained more than once within first 6 hours, then the protocol required the worst values to be recorded. We evaluated the SpO2/FiO2 as a continuous as well as a categorical variable by creating the following arbitrarily chosen SpO2/FiO2 cutoffs:
SpO2/FiO2 Ratio on Hospital Admission Is an Indicator of Early Acute Respiratory Distress Syndrome Development Among Patients at Risk Emir Festic, Vikas Bansal, Daryl J. Kor, Ognjen Gajic and US Critical Illness and Injury Trials Group: Lung Injury Prevention Study Investigators (USCIITG-LIPS) J Intensive Care Med published online 20 December 2013 DOI: 10.1177/0885066613516411 The online version of this article can be found at: http://jic.sagepub.com/content/early/2013/12/19/0885066613516411
Published by: http://www.sagepublications.com
Additional services and information for Journal of Intensive Care Medicine can be found at: Email Alerts: http://jic.sagepub.com/cgi/alerts Subscriptions: http://jic.sagepub.com/subscriptions Reprints: http://www.sagepub.com/journalsReprints.nav Permissions: http://www.sagepub.com/journalsPermissions.nav
>> OnlineFirst Version of Record - Dec 20, 2013 What is This?
Downloaded from jic.sagepub.com at Scientific library of Moscow State University on January 13, 2014
Article
SpO2/FiO2 Ratio on Hospital Admission Is an Indicator of Early Acute Respiratory Distress Syndrome Development Among Patients at Risk
Journal of Intensive Care Medicine 201X, Vol XX(X) 1-8 ª The Author(s) 2013 Reprints and permission: sagepub.com/journalsPermissions.nav DOI: 10.1177/0885066613516411 jic.sagepub.com
Emir Festic, MD1, Vikas Bansal, MBBS, MPH2, Daryl J. Kor, MD3, and Ognjen Gajic, MD, MSc4; US Critical Illness and Injury Trials Group: Lung Injury Prevention Study Investigators (USCIITG–LIPS)
Abstract Purpose: Oxygen saturation to fraction of inspired oxygen ratio (SpO2/FiO2) has been validated as a surrogate marker for partial pressure of oxygen to fraction of inspired oxygen ratio among mechanically ventilated patients with acute respiratory distress syndrome (ARDS). The validity of SpO2/FiO2 measurements in predicting ARDS has not been studied. Recently, a Lung Injury Prediction Score (LIPS) has been developed to help identify patients at risk of developing ARDS. Methods: This was a secondary analysis of the LIPS-1 cohort. A multivariate logistic regression included all established variables for LIPS, Acute Physiology and Chronic Health Evaluation 2, age, and comorbid conditions that could affect SpO2/FiO2. The primary outcome was development of ARDS in the hospital. The secondary outcomes included hospital mortality, hospital day of ARDS development, and hospital day of death. Results: Of the 5584 patients, we evaluated all 4646 with recorded SpO2/FiO2 values. Median SpO2/FiO2 in those who did and did not develop ARDS was 254 (100, 438) and 452 (329, 467), respectively. There was a significant association between SpO2/FiO2 and ARDS (P .001). The SpO2/FiO2 was found to be an independent predictor of ARDS in a ‘‘dosedependent’’ manner; for SpO2/FiO2 < 100—odds ratios (OR) 2.49 (1.69-3.64, P < .001), for SpO2/FiO2 100 < 200—OR 1.75 (1.16-2.58, P ¼ .007), and for SpO2/FiO2 200 < 300—OR 1.62 (1.06-2.42, P ¼ .025). The discriminatory characteristics of the multivariable model and SpO2/FiO2 as a single variable demonstrated area under the curve (AUC) of 0.81 and AUC of 0.74, respectively. Conclusions: The SpO2/FiO2, measured within the first 6 hours after hospital admission, is an independent indicator of ARDS development among patients at risk. Keywords ARDS, oxygenation, prediction, admission
Introduction Acute respiratory distress syndrome (ARDS) is a lifethreatening clinical syndrome with associated mortality as high as 40%.1,2 Survivors frequently face prolonged exercise limitation, psychological sequelae, and decreased quality of life, which all lead to increased use of health care services, representing a major health burden.3 Therapeutic trials have been mostly disappointing, and the current therapeutic strategy is largely supportive. Recently, there has been a shift in the interventional approach emphasizing prevention among patients at high risk of ARDS development. Among attempts to identify patients at risk, the most successful thus far has been the Lung Injury Prediction Score (LIPS).4 This score, ascertained within the initial 6 hours after hospital admission, has been validated in a large, multicenter cohort of patients at risk. The score combines various predisposing conditions and risk modifiers as well as markers of hypoxemia (oxygen saturation) and oxygen
requirement (fractional inspired oxygen concentration). The LIPS is limited by complexity and the effort needed to collect necessary variables, prompting the development and testing of simpler alternatives, including oxygen saturation to fraction of inspired oxygen ratio (SpO2/FiO2).
1
Pulmonary and Critical Care Medicine, Mayo Clinic, Jacksonville, FL, USA Critical Care Research, Mayo Clinic, Jacksonville, FL, USA 3 Anesthesiology and Critical Care, Mayo Clinic, Rochester, MN, USA 4 Pulmonary and Critical Care Medicine, Mayo Clinic, Rochester, MN, USA 2
Received July 3, 2013, and in revised form September 5, 2013. Accepted for publication September 6, 2013. Corresponding Author: Emir Festic, Pulmonary and Critical Care Medicine, Mayo Clinic, 4500 San Pablo Road, Jacksonville, FL 32224, USA. Email: [email protected]
Downloaded from jic.sagepub.com at Scientific library of Moscow State University on January 13, 2014
2
Journal of Intensive Care Medicine XX(X)
Although the ARDS criteria require the measurement of partial pressure of arterial oxygen to fraction of inspired oxygen ratio (PaO2/FiO2),5,6 majority of the patients at risk but without fully established ARDS do not have arterial blood gasses performed. A surrogate, noninvasive measure of oxygenation, SpO2/FiO2 has been used by Rice et al among patients with ARDS to substitute for PaO2/FiO2.7 These authors further detailed specific threshold levels for SpO2/FiO2 that could be used in patients with ARDS as a substitute whenever PaO2/ FiO2 was unavailable. Khemani et al have also demonstrated close agreement between PaO2/FiO2 and SpO2/FiO2, acknowledging that SpO2/FiO2 was an efficient, noninvasive indicator of PaO2/FiO2 among children with acute lung injury (ALI) or ARDS.8,9 However, the value of SpO2/FiO2 as an early predictor of subsequent ARDS development has not been studied. Given the paradigm shift in the approach to ARDS investigations (toward prevention and early treatment), a noninvasive surrogate marker of impaired oxygenation that can be determined early in the course of patient presentation is clearly desirable. We hypothesized that SpO2/FiO2 would be a reliable early independent predictor of ARDS development.
Methods This is a secondary analysis of the previously published LIPS-1 study,4 a prospective cohort investigation conducted under the auspices of the US Critical Illness and Injury Trials Group (USCIITG). This initial investigation aimed to evaluate the predictive accuracy of LIPS, with the main outcome being development of ARDS in the hospital among patients at risk. The principal study was conducted among 5584 patients from 22 hospitals, of whom 377 (6.8%) developed ARDS, 95% of whom required invasive mechanical ventilation.4 The study protocol was approved by the institutional review board at each participating location. This secondary study was approved by the USCIITG/LIPS ancillary study committee.
Study Population The details of the study population have been previously described.4 Briefly, consecutive adult patients admitted to academic and community acute care hospitals were eligible for the study if they presented with at least 1 major risk factor for ARDS: sepsis, shock, pancreatitis, pneumonia, aspiration, high-risk trauma, or major high-risk surgery. Exclusion criteria were ALI or ARDS at the time of admission or within first 6 hours of hospital admission, transfer from an outside hospital, death in the emergency department (ED), comfort or hospice care, or hospital readmission during the study period.4 In addition, for the purpose of this secondary study, we excluded patients who did not have variables necessary for SpO2/FiO2 calculation recorded within first 6 hours of the hospital admission.
Predictor Variables Demographic and clinical information was obtained at the time of hospital admission or preoperatively at the time of surgery but within 6 hours of admission. The main predictor variable of this secondary study was SpO2/FiO2, which included oxygen saturation obtained by pulse oximetry and the fraction of inspired oxygen concentration, variables previously validated within the LIPS database.4 These variables were ascertained within the first 6 hours of admission to 22 participating hospitals. The principal investigator at each site was responsible for accurate data abstraction from the medical records into the Research Electronic Data Capture (REDCap), where oxygen saturation and inspired oxygen concentration obtained at the same time were abstracted together, on the same line, within the vital signs section, per standardized operating protocol. If these variables were obtained more than once within first 6 hours, then the protocol required the worst values to be recorded. We evaluated the SpO2/FiO2 as a continuous as well as a categorical variable by creating the following arbitrarily chosen SpO2/FiO2 cutoffs:
