title: Assessment of PaO₂/FiO₂ for stratification of patients with moderate and severe acute respiratory distress syndrome.
abstract: OBJECTIVE
  A recent update of the definition of acute respiratory distress syndrome (ARDS) proposed an empirical classification based on ratio of arterial partial pressure of oxygen to fraction of inspired oxygen (PaO₂/FiO₂) at ARDS onset. Since the proposal did not mandate PaO₂/FiO₂ calculation under standardised ventilator settings (SVS), we hypothesised that a stratification based on baseline PaO₂/FiOv would not provide accurate assessment of lung injury severity.
  
  
  METHODS
  A prospective, multicentre, observational study.
  
  
  METHODS
  A network of teaching hospitals.
  
  
  METHODS
  478 patients with eligible criteria for moderate (100<PaO₂/FiO₂≤200) and severe (PaO₂/FiO₂≤100) ARDS and followed until hospital discharge.
  
  
  METHODS
  We examined physiological and ventilator parameters in association with the PaO₂/FiO₂ at ARDS onset, after 24 h of usual care and at 24 h under a SVS. At 24 h, patients were reclassified as severe, moderate, mild (200<PaO₂/FiO₂≤300) ARDS and non-ARDS (PaO₂/FiO₂>300).
  
  
  METHODS
  Group severity and hospital mortality.
  
  
  RESULTS
  At ARDS onset, 173 patients had a PaO₂/FiO₂≤100 but only 38.7% met criteria for severe ARDS at 24 h under SVS. When assessed under SVS, 61.3% of patients with severe ARDS were reclassified as moderate, mild and non-ARDS, while lung severity and hospital mortality changed markedly with every PaO₂/FiO₂ category (p<0.000001). Our model of risk stratification outperformed the stratification using baseline PaO₂/FiO₂ and non-standardised PaO₂/FiO₂ at 24 h, when analysed by the predictive receiver operating characteristic (ROC) curve: area under the ROC curve for stratification at baseline was 0.583 (95% CI 0.525 to 0.636), 0.605 (95% CI 0.552 to 0.658) at 24 h without SVS and 0.693 (95% CI 0.645 to 0.742) at 24 h under SVS (p<0.000001).
  
  
  CONCLUSIONS
  Our findings support the need for patient assessment under SVS at 24 h after ARDS onset to assess disease severity, and have implications for the diagnosis and management of ARDS patients.
  
  
  BACKGROUND
  NCT00435110 and NCT00736892.
authors.affiliation: CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Madrid, Spain Multidisciplinary Organ Dysfunction Evaluation Research Network, Research Unit, Hospital Universitario Dr Negrín, Las Palmas, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Villar
authors.affiliation: CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Madrid, Spain Intensive Care Unit, Hospital Universitario Río Hortega, Valladolid, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Blanco
authors.affiliation: Intensive Care Unit, Hospital General de Ciudad Real, Ciudad Real, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: del Campo
authors.affiliation: Intensive Care Unit, Hospital Clínico Universitario de Valladolid, Valladolid, Spain.
authors.forename: David
authors.initials: D
authors.lastname: Andaluz-Ojeda
authors.affiliation: Intensive Care Unit, Hospital Universitario General de León, León, Spain.
authors.forename: Francisco J
authors.initials: FJ
authors.lastname: Díaz-Domínguez
authors.affiliation: Intensive Care Unit, Hospital Universitario Río Hortega, Valladolid, Spain.
authors.forename: Arturo
authors.initials: A
authors.lastname: Muriel
authors.affiliation: Intensive Care Unit, Complejo Hospitalario Universitario de Albacete, Albacete, Spain.
authors.forename: Virgilio
authors.initials: V
authors.lastname: Córcoles
authors.affiliation: CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Madrid, Spain Department of Surgical Sciences, Anesthesiology & Critical Care, Hedenstierna Laboratory, Uppsala University Hospital, Uppsala, Sweden.
authors.forename: Fernando
authors.initials: F
authors.lastname: Suárez-Sipmann
authors.affiliation: Intensive Care Unit, Hospital Virgen de la Concha, Zamora, Spain.
authors.forename: Concepción
authors.initials: C
authors.lastname: Tarancón
authors.affiliation: Intensive Care Unit, Hospital Virgen de la Luz, Cuenca, Spain.
authors.forename: Elena
authors.initials: E
authors.lastname: González-Higueras
authors.affiliation: Intensive Care Unit, Hospital Universitario La Paz, Madrid, Spain.
authors.forename: Julia
authors.initials: J
authors.lastname: López
authors.affiliation: CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Madrid, Spain Critical Care Center, Corporació Sanitaria Parc Taulí, Sabadell, Spain.
authors.forename: Lluis
authors.initials: L
authors.lastname: Blanch
authors.affiliation: CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Madrid, Spain Research Unit, Hospital Universitario NS de Candelaria, Tenerife, Spain.
authors.forename: Lina
authors.initials: L
authors.lastname: Pérez-Méndez
authors.affiliation: CIBER de Enfermedades Respiratorias, Instituto de Salud Carlos III, Madrid, Spain Multidisciplinary Organ Dysfunction Evaluation Research Network, Research Unit, Hospital Universitario Dr Negrín, Las Palmas, Spain.
authors.forename: Rosa Lidia
authors.initials: RL
authors.lastname: Fernández
authors.affiliation: Department of Respiratory Care, Massachusetts General Hospital, Boston, Massachusetts, USA Department of Anesthesiology, Harvard University, Boston, Massachusetts, USA.
authors.forename: Robert M
authors.initials: RM
authors.lastname: Kacmarek
mesh_terms: D000328:Adult; D000368:Aged; D019540:Area Under Curve; D001784:Blood Gas Analysis; D005260:Female; D017052:Hospital Mortality; D006784:Hospitals, Teaching; D006801:Humans; D001239:Inhalation; D008168:Lung / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D008991:Monitoring, Physiologic / Q000379:methods*; D010100:Oxygen / Q000502:physiology*; D010313:Partial Pressure; D011175:Positive-Pressure Respiration; D011446:Prospective Studies; D012372:ROC Curve; D012121:Respiration, Artificial / Q000379:methods; D012128:Respiratory Distress Syndrome / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology; D045169:Severe Acute Respiratory Syndrome / Q000175:diagnosis* / Q000401:mortality / Q000503:physiopathology; D012720:Severity of Illness Index; D013990:Tidal Volume
chemical_list: D010100:Oxygen
keywords: RESPIRATORY MEDICINE (see Thoracic Medicine)
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