Validity of transcutaneous capnometry in prolonged use in a patient population with acute respiratory failure

Transcutaneous capnometry is a widespread method for monitoring carbon dioxide in respiratory care. Studies on its use in emergency medicine, the sensors long-term stability its practicability in this setting are lacking. This study aimed to clarify whether transcutaneous capnometry is a valid and feasible method for monitoring critically ill patients.

100 patients with acute respiratory failure were monitored simultaneously with arterial blood gas analysis (paCO2) and transcutaneous capnometry (tcpCO2), using Radiometer TCM5, at baseline (T1) and after a maximum of 12 h (T2) an analyzed regarding clinically acceptable concordance and interruptions.

Ninety-three patients (176 paired samples of paCO2 and tcpCO2) were included in the analysis. We found a good correlation between pCO2 and tcpCO2 (r = 0.9706) at T1, which weakened at T2 (r = 0.7760). However, the difference in the concordance of the measured values at T1 and T2 was not significantly different (p = 0.0545). Significantly frequent deviations between T1 and T2 occurred in patients with circulatory impairment (p = 0.0039). 22.9% of all values were outside the clinically acceptable range, but with paCO2 underestimated by tcpCO2 in only 5 cases (2.8%). In all clinically relevant deviations, we found an underlying technical error which would have been found by a trained examiner.

Transcutaneous capnometry is a feasible method for monitoring CO₂ trends. However, its successful application requires thorough knowledge of the analysis technique and potential sources of error. The validity of the method is limited in patients with significant circulatory dysregulation. Additionally, long-term use in clinical practice is often restricted by suboptimal patient conditions.