title: Arterial and end-tidal carbon dioxide difference in pediatric intensive care.
abstract: OBJECTIVE
  Arterial carbon dioxide tension (PaCO2) is considered the gold standard for scrupulous monitoring in pediatric intensive care unit (PICU), but it is invasive, laborious, expensive, and intermittent. The study aims to explore when we can use end-tidal carbon dioxide tension (PETCO2) as a reliable, continuous, and noninvasive monitor of arterial CO2.
  
  
  METHODS
  Concurrent PETCO2, fraction of inspired oxygen, PaCO2, and arterial oxygen tension values of clinically stable children on mechanical ventilation were recorded. Children with extra-pulmonary ventriculoatrial shunts were excluded. The PETCO2 and PaCO2 difference and its variability and reproducibility were studied.
  
  
  RESULTS
  A total of 624 concurrent readings were obtained from 105 children (mean age [SD] 5.53 [5.43] years) requiring invasive bi-level positive airway pressure ventilation in the PICU. All had continuous PETCO2 monitoring and an arterial line for blood gas measurement. The mean (SD) number of concurrent readings obtained from each child, 4-6 h apart was 6.0 (4.05). The PETCO2 values were higher than PaCO2 in 142 observations (22.7%). The PaCO2-PETCO2 difference was individual admission specific (ANOVA, P < 0.001). The PaCO2-PETCO2 difference correlated positively with the alveolar-arterial oxygen tension [P(A-a)O2] difference (ρ = 0.381 P < 0.0001). There was a fixed bias between the PETCO2 and PaCO2 measuring methods, difference +0.66 KPa (95% confidence interval: +0.57 to +0.76).
  
  
  CONCLUSIONS
  The PaCO2-PETCO2 difference was individual specific. It was not affected by the primary disorder leading to the ventilation.
authors.affiliation: Paediatric intensive care unit, Women's and Children's Division, London, UK.
authors.forename: Chulananda Dias
authors.initials: CD
authors.lastname: Goonasekera
authors.affiliation: Paediatric intensive care unit, Women's and Children's Division, London, UK.
authors.forename: Alison
authors.initials: A
authors.lastname: Goodwin
authors.affiliation: Division of Health and Social Care Research, King's College London, London, UK.
authors.forename: Yanzhong
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Anesthetics, King's College Hospital, London, UK.
authors.forename: James
authors.initials: J
authors.lastname: Goodman
authors.affiliation: Paediatric intensive care unit, Women's and Children's Division, London, UK.
authors.forename: Akash
authors.initials: A
authors.lastname: Deep
keywords: Capnography; carbon dioxide partial pressure; critical care; pediatrics