Abstract
Transcutaneous oxygen electrodes are widely used in neonatal intensive care and are gaining acceptance in paediatric and adult intensive care. Transcutaneous CO2 electrodes are less well established.
We measured transcutaneous arterial CO2 (TcCO2, PaCO2) in 57 critically ill children aged 10 days to 14.3 years. Two electrodes (Roche 632) were used in an overlapping design to provide 16 - 24 studies at 4 electrode temperatures, 45, 44,43, and 42° centigrade. Mean calibration time with 5 and 10% CO2 was 43 range 38-58 minutes. Mean arterialisation time was 10.5 range 3 - 30 minutes.
Electrodes were left for 4 hours with duplicate hourly samples from indwelling arterial lines. TcCO2/PaCO2 correlation was independent of electrode temperature and child age, over the electrode temperature range 44 - 42°C. At one hour TcCO2 = PaCO2 × 1.41 + 1.00. Recalibration demonstrated baseline drift of more than 5 torr during 22% of studies. For prediction of PaCO2 95% confidence limits around the regression mean rose from ± 7.8 torr at one hour to ± 11.7 torr at four hours. For a drift of less than 5 torr respectively, values were 6.5 and 8.4 torr.
Arterial CO2 can be estimated from surface electrodes. Improved electrode stability and speed of calibration should made this a valuable monitoring technique.
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Cheriyan, G., Chiu, R., Helms, P. et al. ESTIMATION OF ARTERIAL CO2 FROM SURFACE ELECTRODES. Pediatr Res 19, 1100 (1985). https://doi.org/10.1203/00006450-198510000-00189
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DOI: https://doi.org/10.1203/00006450-198510000-00189