Is continuous transcutaneous monitoring of PCO2 (TcPCO2) over 8 h reliable in adults?

Monitoring of non-invasive ventilation (NIV) in a non-intensive care unit (non-ICU) setting requires a method of evaluating nocturnal PaCO2, such as transcutaneous CO2 monitoring (TcPCO2). However, changing the probe site after 4h and recalibrating las recommended) is time-consuming and impractical. Continuous (8-h) TcPCO2 monitoring at a lower electrode temperature (43 degreesC) in this setting has never been formally studied. Patients under intermittent NIV were studied (n=28, aged 69 +/-9 years, PaO2: 71 +/- 13mmHg, PaCO2: 49 +/- 9mmHg). After calibration and stabilization of TcPCO2 (Radiometer (R) Tina TCM3 capnograph), arterial blood gases (ABG) were measured and compared with transcutaneous readings. In 10 patients who underwent continuous 8-h TcPCO2 recording, ABGs were also measured after 4 and 8 h. The correlation between TcPCO2 and PaCO2 was highly significant (r(2) = 0(.)91. P <0(.)0001). Mean (TcPCO2-PaCO2) gradient (bias) was: -2(.)8 +/-3(.)8 mmHg; limits of agreement were: (-10(.)4 +/-4(.)8 mmHg). TcPCO2-PaCO2 gradient was lowest (i.e. within-bias +/-2 mmHg) between 40 and 54 mmHg, increasing below and above these values. Over 8 h, no significant drift of the TcPCO2 signal occurred (ANOVA). No discomfort or skin lesion was noted. In conclusion, with an electrode temperature of 43 degreesC, 8-h continuous monitoring of TcPCO2 was well tolerated, without any local side-effects or significant drift of TcPCO2 signal. when compared to previous reports. lowering the electrode temperature did not decrease performance for CO2 monitoring.