RELIABILITY AND SAFETY OF TRANSCUTANEOUS CARBON DIOXIDE TENSION (tcPCO2): MONITORING AT 42°C SENSOR TEMPERATURE DURING 24 HRS WITHOUT REPLACEMENT

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TcPCO2 monitoring is widely used in the neonatal ICU. Reliability and safety of this indirect method to measure arterial PCO2(PaCO2) have been questioned, particularly when the sensor remains in place for more than 4 hours. Goal of this study was to assess correlation between tcPCO2 and PaCO2 and skin alterations during 24 hours monitoring without replacement.Patients: 51 critically ill newborns who required an arterial catheter for the clinical management. Weights 680-4170 g, Gestational ages 27-41 weeks.Method: An iridium oxide electrode (Transcapnode Hellige) heated at 42°C was chosen because of better stability than conventional glass electrodes. The sensor was calibrated with 5 and 10% CO2 and attached to the trunc or to the thigh. TcPCO2 was recorded continuously. Arterial blood samples were drawn systematically at 30’ and at 24 hours and on clinical indications. PaCO2 was measured with an IL 313 or an AVL 945 gas analyser.Results: After removal of the sensor no visible change of the skin was noted in 44 infants and a discrete erythema in 7. A blister developed in one patient 24 hours later which disappeared without scar. The correlation of tcPCO2(y;Torr) vs. PaCO2(x; Torr) was calculated for 504 paired values: y = 5.4 + 1.4×; r=.89; Sy·x=6.0 Torr. There was no systematic difference between the paired values at 30’ and those at 24 hours. The transcutaneous sensor detected 61% of hypocapnia (PaCO2<30 Torr, n=38) and 88% of hypercapnia PaCO2>50 Torr, n=73).Conclusion: The correlation between tcPCO2(42°C) and PaCO2 is acceptabel for clinical use and not influenced by the duration of fixation of the sensor up to 24 hours.