title: Correlation of oxygen saturation as measured by pulse oximetry/fraction of inspired oxygen ratio with Pao2/fraction of inspired oxygen ratio in a heterogeneous sample of critically ill children.
abstract: OBJECTIVE
  Oxygen saturation as measured by pulse oximetry (Spo2)/fraction of inspired oxygen (Fio2) (SF) ratio has demonstrated to be an adequate marker for lung disease severity in children under mechanical ventilation. We sought to validate the utility of SF ratio in a population of critically ill children under mechanical ventilation, noninvasive ventilation support, and breathing spontaneously.
  
  
  METHODS
  A retrospective database study was conducted in a pediatric intensive care unit of a university hospital. Children with Spo2 less than or equal to 97% and an indwelling arterial catheter were included. Simultaneous blood gas and pulse oximetry were collected in a database. Derivation and validation data sets were generated, and a linear mixed modeling was used to derive predictive equations. Model performance and fit were evaluated using the validation data set.
  
  
  RESULTS
  Three thousand two hundred forty-eight blood gas and Spo2 values from 298 patients were included. 1/SF ratio had a strong linear association with 1/Pao2/Fio2 (PF) ratio in both derivation and validation data sets, given by the equation 1/SF = 0.00164 + 0.521/PF (derivation). Oxygen saturation as measured by pulse oximetry/Fio2 values for PF criteria of 100, 200, and 300 were 146 (95% confidence interval [CI], 142-150), 236 (95% CI, 228-244), and 296 (95% CI, 285-308). Areas under receiver operating characteristic curves for diagnosis of PF ratio less than 100, 200, and 300 with the SF ratio were 0.978, 0.952, and 0.951, respectively, in the validation data set.
  
  
  CONCLUSIONS
  Oxygen saturation as measured by pulse oximetry/Fio2 ratio is an adequate noninvasive surrogate marker for PF ratio. Oxygen saturation as measured by pulse oximetry/Fio2 ratio may be an ideal noninvasive marker for patients with acute hypoxemic respiratory failure.
authors: Pediatric Intensive Care Unit, Hospital Universitario Central de Asturias, University of Oviedo, Oviedo, Spain. carloslobete@hotmail.com
authors: Carlos
authors: C
authors: Lobete
authors: Alberto
authors: A
authors: Medina
authors: Corsino
authors: C
authors: Rey
authors: Juan
authors: J
authors: Mayordomo-Colunga
authors: Andrés
authors: A
authors: Concha
authors: Sergio
authors: S
authors: Menéndez
mesh_terms: D019540:Area Under Curve; D002408:Catheters, Indwelling; D002675:Child, Preschool; D016638:Critical Illness; D005260:Female; D006801:Humans; D007223:Infant; D015278:Intensive Care Units, Pediatric; D016014:Linear Models; D008297:Male; D010092:Oximetry; D010100:Oxygen / Q000097:blood*; D011237:Predictive Value of Tests; D012372:ROC Curve; D012121:Respiration, Artificial; D012128:Respiratory Distress Syndrome / Q000097:blood / Q000628:therapy*; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D012720:Severity of Illness Index
chemical_list: D010100:Oxygen
keywords: Clinical markers; Critical care; Hypoxemia; Mechanical ventilation; Non invasive positive-pressure ventilation; Pediatrics; Respiratory insufficiency