Objective: The aim of this study was to validate the V-Sign digital sensor (SenTec AG, Therweil, Switzerland) for combined noninvasive assessment of pulse oxymetric oxygen saturation (SpO2) and transcutaneous carbon dioxide tension (PtcCO2) in adults after cardiac surgery. Methods: In twenty one patients, aged 51-86years, simultaneous measurements of blood gases with the V-Sign Sensor and with two Nellcor Durasensors (model DS-100A), one at the opposite earlobe and one with a finger clip, were compared first during hyper-, normo- and hypocapnia and at different pulse rates using a pacemaker, and then at 2-h intervals up to 8h. Agreement was assessed by Bland-Altman analysis. Results: PtcCO2 data of three patients were excluded because of calibration failure of the device. Median (range) PtcCO2 for the remaining patients was 5.49 (3.3-7.6) kPa and arterial carbon dioxide tension (PaCO2) was 5.43 (3.61-7.41) kPa. Corresponding mean bias was +0.05kPa and limits of agreement (LOA) were −1.2/+1.3kPa. During normo- and hypoventilation, mean bias was good at +0.02 and +0.04kPa respectively, but limits of agreement were poor at −0.67/+0.69 and −0.81/+0.88kPa. In 10 patients, an initial overshoot of PtcCO2 was observed. Mean bias of SpO2 and pulse rate was close to zero (−1.5% and +0.001bpm respectively), but limits of agreement were unacceptably high (−21.4/+18.4% and −22.3/+22.3bpm). Conclusions: In the present state of development the SenTeC Digital monitor V-Sign device has serious limitations. Additional efforts are necessary to eliminate calibration failures and the initial overshoot of PtcCO2 as well as to improve detection of SpO2 and pulse rat
