title: PaO2/FIO2 Ratio Derived From the SpO2/FIO2 Ratio to Improve Mortality Prediction Using the Pediatric Index of Mortality-3 Score in Transported Intensive Care Admissions.
abstract: OBJECTIVE
  To derive a relationship between the SpO2/FIO2 ratio and PaO2/FIO2 ratio across the entire range of SpO2 values (0-100%) and to evaluate whether mortality prediction using the Pediatric Index of Mortality-3 can be improved by the use of PaO2/FIO2 values derived from SpO2/FIO2.
  
  
  METHODS
  Retrospective analysis of prospectively collected data.
  
  
  METHODS
  A regional PICU transport service.
  
  
  METHODS
  Children transported to a PICU.
  
  
  METHODS
  None.
  
  
  RESULTS
  The relationship between SpO2/FIO2 and PaO2/FIO2 across the entire range of SpO2 values was first studied using several mathematical models in a derivation cohort (n = 1,235) and then validated in a separate cohort (n = 306). The best SpO2/FIO2-PaO2/FIO2 relationship was chosen according to the ability to detect respiratory failure (PaO2/FIO2 ≤ 200). The discrimination of the original Pediatric Index of Mortality-3 score and a derived Pediatric Index of Mortality-3 score (where SpO2/FIO2-derived PaO2/FIO2 values were used in place of missing PaO2/FIO2 values) were compared in a different cohort (n = 1,205). The best SpO2/FIO2-PaO2/FIO2 relationship in 1,703 SpO2/FIO2-to-PaO2/FIO2 data pairs was a linear regression equation of ln[PF] regressed on ln[SF]. This equation identified children with a PaO2/FIO2 less than or equal to 200 with a specificity of 73% and sensitivity of 61% in children with SpO2 less than 97% (92% and 33%, respectively, when SpO2 ≥ 97%) in the validation cohort. PaO2/FIO2 derived from SpO2/FIO2 (derived PaO2/FIO2) was better at predicting PICU mortality (area under receiver operating characteristic curve, 0.64; 95% CI, 0.55-0.73) compared with the original PaO2/FIO2 (area under receiver operating characteristic curve, 0.54; 95% CI, 0.49-0.59; p = 0.02). However, there was no difference in the original and derived Pediatric Index of Mortality-3 scores and their discriminatory ability for mortality.
  
  
  CONCLUSIONS
  SpO2-based metrics perform no worse than arterial blood gas-based metrics in mortality prediction models. Future Pediatric Index of Mortality score versions may be improved by the inclusion of risk factors based on oxygen saturation values, especially in settings where PaO2 values are missing in a significant proportion of cases.
authors.affiliation: 1Respiratory Critical Care and Anaesthesia Unit, UCL Great Ormond Street Institute of Child Health, London, United Kingdom. 2Children's Acute Transport Service, Great Ormond Street Hospital, London, United Kingdom. 3UCL Clinical Operational Research Unit, London, United Kingdom.
authors.forename: Samiran
authors.initials: S
authors.lastname: Ray
authors.forename: Libby
authors.initials: L
authors.lastname: Rogers
authors.forename: Christina
authors.initials: C
authors.lastname: Pagel
authors.forename: Sainath
authors.initials: S
authors.lastname: Raman
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Peters
authors.forename: Padmanabhan
authors.initials: P
authors.lastname: Ramnarayan
mesh_terms: D000293:Adolescent; D002648:Child; D002675:Child, Preschool; D003422:Critical Care / Q000379:methods*; D016638:Critical Illness; D003661:Decision Support Techniques; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D015278:Intensive Care Units, Pediatric; D016014:Linear Models; D008297:Male; D010092:Oximetry / Q000379:methods*; D012131:Respiratory Insufficiency / Q000097:blood / Q000175:diagnosis* / Q000401:mortality*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index; D014187:Transportation of Patients