Jonathan M. Klein, MD
Peer Review Status: Internally Peer Reviewed

The TcPCO2 analyzer operates on a principal similar to that of the TcPO2 analyzer. Because of physiologic differences in O2 and CO2 diffusion through the skin and in electrode design, there are significant differences in the actual arterial pCO2 and TcPCO2 reading. 

The electrode will be applied by the nurse to the anterior chest wall or other acceptable site. The site will be changed every four hours to avoid erythema and burns to the infant's skin. The electrode will be calibrated by the blood gas technician and recalibrated every eight hours. 

With the correlation factor used to calibrate the TcPCO2 analyzer, the TcPCO2 reading will closely approximate PaCO2 value. In certain infants, however, there may be a significant difference between the two values. It is therefore necessary to correlate the TcPCO2 reading with three or four PaCO2 samples. 

The lag time for the TcPCO2 analyzer is 90 seconds; i.e., the analyzer will display the TcPCO2 which was present 90 seconds previously. 

V. The nurse will record the TcPCO2 value and electrode temperature on the nurse's notes at least once an hour and when obtaining an arterial blood gas sample.