Comparison of arterial CO 2 estimation by end-tidal and transcutaneous CO 2 measurements in intubated children and variability with subject related factors.

Transcutaneous PCO2 (PTC CO2 ) and end-tidal PCO2 (PET CO2 ) measurement methods serve as alternatives to arterial PCO2 (PaCO2 ), providing continuous non-invasive monitoring. The objective of this study was to evaluate the PTC CO2 and PET CO2 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. PTC CO2 , PET CO2 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 PTC CO2 and PaCO2 was - 0.29 mmHg (± 6.05), while it was 0.44 mmHg (± 6.83) bias between PET CO2 and PaCO2 . In those with pulmonary diseases, the mean difference between PTC CO2 and PaCO2 was - 1.27 mmHg (± 8.32), while it was - 4.65 mmHg (± 9.01) between PET CO2 and PaCO2 . Multiple linear regression demonstrated that increased subcutaneous adipose tissue thickness, core body temperature and inotropic index were related with higher PTC CO2 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 PTC CO2 method has higher reliability than the PET CO2 method, and PTC CO2 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.