We had got enough data, therefore we stopped the study and published the data.

Arterial carbon dioxide partial pressure (PaCO2) is an essential indicator of ventilation and respiratory function. It is routinely tested invasively by arterial blood gas analysis (ABGA) but recently developed miniaturized carbon dioxide tension sensors promise non-invasive and continuous transcutaneous PCO2 (PtcCO2) monitoring. We, the researchers at University Hospital, Basel, Switzerland, determined the accuracy of two PtcCO2 monitors (TOSCA 500 with Sensor 92, Linde Medical Sensors AG, Basel; and Sentec Digital Monitor with V-Sign Sensor, Sentec AG, Therwil) for measurement of single values and trends in PaCO2 in critically ill patients, using ABGA as a reference.

Measurement of SO2 is used in nearly every patient receiving anesthesia or sedation, whereas monitoring of pCO2 is important in patients during and shortly after major surgery and in critically ill patients. But measurement of pCO2 requires arterial blood sampling and laboratory testing. Non-invasive monitors for continuous assessment of arterial pCO2 have been developed but their accuracy and feasibility were insufficient to make them useful in the clinical setting. Recently, a new digital system for continuous and non-invasive monitoring of arterial pCO2 and SO2 has been introduced (SenTec Digital Monitor System, SenTec AG, Therwil, Switzerland). This present study has been designed to evaluate the accuracy of the SenTec V-SignTM monitoring system for measuring pCO2 in comparison with repeated arterial blood gas testing in the operation room and in the intensive care unit.

Inclusion Criteria:

• Patients older than 18 years with clinical indication of repeated arterial blood gas analyses

Exclusion Criteria:

• No informed consent

patients undergoing surgery in general anesthesia and with clinical indication for repeated arterial blood gas sampling