Comparison of arterial CO₂ estimation by end-tidal and transcutaneous CO₂ measurements in intubated children and variability with subject related factors

Transcutaneous PCO₂ (P_TCCO₂) and end-tidal PCO₂ (P_ETCO₂) measurement methods serve as alternatives to arterial PCO₂ (PaCO₂), providing continuous non-invasive monitoring. The objective of this study was to evaluate the P_TCCO₂ and P_ETCO₂ methods with actual PaCO₂ levels, and to assess the variability of measurements in relation to subject-related factors, such as skin and subcutaneous adipose tissue thickness and presence of pulmonary diseases. P_TCCO₂, P_ETCO₂ and PaCO₂ were measured at the same time in intubated pediatric subjects. Subjects’ demographic characteristics, clinical features, laboratory parameters, skin and subcutaneous adipose tissue thickness were identified. The study was carried out on 102 subjects with a total of 1118 values for each method. In patients with non-pulmonary disease, the mean difference between P_TCCO₂ and PaCO₂ was − 0.29 mmHg (± 6.05), while it was 0.44 mmHg (± 6.83) bias between P_ETCO₂ and PaCO₂. In those with pulmonary diseases, the mean difference between P_TCCO₂ and PaCO₂ was − 1.27 mmHg (± 8.32), while it was − 4.65 mmHg (± 9.01) between P_ETCO₂ and PaCO₂. Multiple linear regression demonstrated that increased subcutaneous adipose tissue thickness, core body temperature and inotropic index were related with higher P_TCCO₂ values relative to the actual PCO₂ values. Other factors, such as skin tissue thickness, presence of pulmonary disease, measurement location and measurement times were non-significant. The P_TCCO₂ method has higher reliability than the P_ETCO₂ method, and P_TCCO₂ measurements are not influenced by most subject-related factors; however, core body temperature, inotropic index and subcutaneous adipose tissue thickness can lead to significant differences in PCO₂ measurement.