Validation of transcutaneous CO₂ measurement in awake children undergoing sleep studies

Despite the reliance on transcutaneous CO₂ measurement (PtcCO₂) for continuous alveolar ventilation monitoring in pediatric sleep studies, the agreement between PtcCO₂ and arterial CO₂ pressure in hemodynamically stable children has not been assessed. To address this gap, we conducted a retrospective study to compare PtcCO₂ and arterialized capillary CO₂ pressure (PcapCO₂) values obtained upon awakening and to identify factors influencing any differences. We retrospectively analysed 335 pediatric records where each patient underwent both earlobe arterialized capillary blood gas measurement and PtcCO₂ recording (Sentec ResMed or Radiometer TCM4) prior to sleep on the day of polysomnography while breathing room air. Statistical analysis included Bland-Altman analysis, student's t-test, chi-square test, and univariate and multivariate regression models to determine predictors of the PtcCO₂ - PcapCO₂ difference (ΔCO₂). The median age of the participants was 12.2 years (IQR 8.8-15.3), with 60 % being male. Paired measurements showed a strong positive correlation (r = 0.703; p < 0.0001) between PtcCO₂ and PcapCO₂. Bland-Altman analysis indicated a ΔCO₂ mean bias of -0.59 mmHg, with limits of agreement from -5.56 to +4.38 mmHg. No significant differences in ΔCO₂ were found across devices (p = 0.41). In the multivariate regression analysis, mean pH emerged as the sole independent predictor of ΔCO₂, with each 0.01-unit pH increase associated with an approximately 0.31 mmHg larger ΔCO₂ (β = 0.31; 95 % CI = 0.18, 0.43). These findings suggest that PtcCO₂ measurements provide a reliable estimation of PcapCO₂ in this population, although temporary differences may arise due to hyperventilation during blood sampling.