Arterial and end-tidal carbon dioxide difference in pediatric intensive care

BACKGROUND AND AIM: Arterial carbon dioxide tension (PaCO(2)) 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 (P(ET)CO(2)) as a reliable, continuous, and noninvasive monitor of arterial CO(2) MATERIALS AND METHODS: Concurrent P(ET)CO(2), fraction of inspired oxygen, PaCO(2), and arterial oxygen tension values of clinically stable children on mechanical ventilation were recorded. Children with extra-pulmonary ventriculoatrial shunts were excluded. The P(ET)CO(2) and PaCO(2) 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 P(ET)CO(2) 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 P(ET)CO(2) values were higher than PaCO(2) in 142 observations (22.7%). The PaCO(2)–P(ET)CO(2) difference was individual admission specific (ANOVA, P < 0.001). The PaCO(2)–P(ET)CO(2) difference correlated positively with the alveolar-arterial oxygen tension [P(A-a)O(2)] difference (ρ = 0.381 P < 0.0001). There was a fixed bias between the P(ET)CO(2) and PaCO(2) measuring methods, difference +0.66 KPa (95% confidence interval: +0.57 to +0.76). CONCLUSIONS: The PaCO(2)–P(ET)CO(2) difference was individual specific. It was not affected by the primary disorder leading to the ventilation.