Agreement Between Arterial Carbon Dioxide Levels With End-Tidal Carbon Dioxide Levels and Associated Factors in Children Hospitalized With Traumatic Brain Injury

IMPORTANCE: Alterations in the partial pressure of carbon dioxide, arterial (Paco(2)) can affect cerebral perfusion after traumatic brain injury. End-tidal carbon dioxide (EtCO(2)) monitoring is a noninvasive tool used to estimate Paco(2) values. OBJECTIVE: To examine the agreement between Paco(2) and EtCO(2) and associated factors in children with traumatic brain injury. DESIGN, SETTING, AND PARTICIPANTS: A secondary analysis was conducted using data from a prospective cohort study of 137 patients younger than 18 years with traumatic brain injury who were admitted to the pediatric intensive care unit of a level I trauma center between May 1, 2011, and July 31, 2017. Analysis was performed from December 17, 2018, to January 10, 2019. MAIN OUTCOMES AND MEASURES: The closest EtCO(2) value obtained within 30 minutes of a Paco(2) value and the closest systolic blood pressure value obtained within 60 minutes prior to a Paco(2) value during the first 24 hours after admission were recorded. The main outcome of Paco(2)-EtCO(2) agreement was defined as Paco(2) between 0 and 5 mm Hg greater than the paired EtCO(2) value, and it was determined using Bland-Altman analysis, Passing and Bablok regression, and the Pearson correlation coefficient. Multivariable regression models determined which factors were associated with agreement. RESULTS: The analysis included 137 patients (34 girls and 103 boys; mean [SD] age, 10.0 [6.3] years) and 445 paired Paco(2)-EtCO(2) data points. On average, Paco(2) was 2.7 mm Hg (95% limits of agreement, –11.3 to 16.7) higher than EtCO(2). Overall, 187 of all Paco(2)-EtCO(2) pairs (42.0%) agreed. There was larger variation in the Paco(2)-EtCO(2) difference during the first 8 hours compared with 9 to 24 hours after admission to the pediatric intensive care unit. Development of pediatric acute respiratory distress syndrome within 24 hours of admission was associated with a lower likelihood of Paco(2)-EtCO(2) agreement (adjusted odds ratio, 0.20; 95% CI, 0.08-0.51) compared with no development of pediatric acute respiratory distress syndrome. A diagnosis of pediatric acute respiratory distress syndrome 1 to 7 days after admission was associated with a larger first-day Paco(2)-EtCO(2) difference compared with those who never developed pediatric acute respiratory distress syndrome (mean [SD] difference, 4.48 [3.70] vs 0.46 [5.50] mm Hg). CONCLUSIONS AND RELEVANCE: In this study of pediatric traumatic brain injury, Paco(2)-EtCO(2) agreement was low, especially among patients with pediatric acute respiratory distress syndrome. Low Paco(2)-EtCO(2) agreement early in hospitalization may be associated with future development of pediatric acute respiratory distress syndrome. Data on EtCO(2) should not be substituted for data on Paco(2) during the first 24 hours.