title: Validity of sidestream endtidal carbon dioxide measurement in critically ill, mechanically ventilated children.
abstract: BACKGROUND
  Capnography is used to monitor the endtidal carbon dioxide tension (EtCO2) in exhaled gas. Sidestream capnography has great potential to monitor mechanically ventilated pediatric patients, given the continuous sampling from the endotracheal tube into a gas sensor. However, hemodynamic and respiratory impairments may reduce reliability and validity of sidestream capnography to monitor arterial carbon dioxide tension (PaCO2) in critically ill, mechanically ventilated children.
  
  
  METHODS
  In 47 mechanically ventilated pediatric patients (aged 0-14 years, median age 17.2 months), a total of 341 consecutive measurements of PaCO2, EtCO2, respiratory and hemodynamic parameters were performed, and capnogram shape was determined. Validity was assessed with the Bland-Altman limit of agreement (loa), mixed models were used to adjust for variation between patients, and potential confounders were considered with multivariable analyses.
  
  
  RESULTS
  EtCO2 (mean 4.50 ± 0.96 kPa) underestimated PaCO2 (mean 5.37 ± 0.87) considerably, resulting in a loa of 0.87 kPa [95% confidence interval (95% CI) -1.03;2.77] and 42.2% percentage error. The association improved significantly b = 0.54 [95 %CI = 0.45;0.64, P < 0.001] when corrected for individual differences. The association between EtCO2 and PaCO2 was not influenced by any of the potential confounders.
  
  
  CONCLUSIONS
  Sidestream capnography in mechanically ventilated infants and children seems moderately reliable and valid when corrected for individual differences. Therefore, it could only be used with caution for trend estimation in the individual patient.
authors.affiliation: Department of Intensive Care Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands.
authors.forename: Hylke H A C M
authors.initials: HH
authors.lastname: van der Heijden
authors.affiliation: Department of Pediatrics, Canisius Wilhelmina Hospital, Nijmegen, The Netherlands.
authors.forename: Gerben J
authors.initials: GJ
authors.lastname: Truin
authors.affiliation: Department of Intensive Care Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands.
authors.forename: Joyce
authors.initials: J
authors.lastname: Verhaeg
authors.affiliation: Trimbos Institute, Netherlands Institute of Mental Health and Addiction, Utrecht, The Netherlands.
authors.forename: Peggy
authors.initials: P
authors.lastname: van der Pol
authors.affiliation: Department of Intensive Care Medicine, Radboud University Medical Centre, Nijmegen, The Netherlands.
authors.forename: Joris
authors.initials: J
authors.lastname: Lemson
mesh_terms: D000293:Adolescent; D001784:Blood Gas Analysis; D019296:Capnography / Q000592:standards*; D002245:Carbon Dioxide; D002648:Child; D002675:Child, Preschool; D016638:Critical Illness; D005260:Female; D006439:Hemodynamics; D006801:Humans; D007223:Infant; D008297:Male; D008991:Monitoring, Physiologic / Q000379:methods* / Q000592:standards*; D011446:Prospective Studies; D015203:Reproducibility of Results; D012121:Respiration, Artificial; D012131:Respiratory Insufficiency; D013990:Tidal Volume
chemical_list: D002245:Carbon Dioxide
keywords: capnography; children; reliability; validity