The Revised Digital Transcutaneous PCO2/SpO2 Ear Sensor Is a Reliable Noninvasive Monitoring Tool in Patients After Cardiac Surgery

ObjectiveThe aim of this study was to validate the revised SenTec V-Sign 2 sensor (SenTec AG, Therwil, Switzerland) for combined noninvasive continuous assessment of pulse rate, pulse oximetry (SpO2), and transcutaneous carbon dioxide tension (PtcCO2) in adults after cardiac surgery.DesignA prospective clinical study.SettingA single-center university hospital.ParticipantsTwenty adult patients aged 36 to 84 years after cardiac surgery.InterventionsSpO2 and PtcCO2 values of three V-Sign 2 sensors (SenTec AG) attached at the earlobe, forehead, and cheek and SpO2 values of the Nellcor Durasensor (Model DS-100A; Nellcor Puritan Bennett Inc, Pleasanton, CA) were compared with simultaneous measurements of blood gases and end-expiratory carbon dioxide.Measurements and Main ResultsMeasurements were performed during periods of hyper-, normo-, and hypocapnia and then at 30-minute intervals up to 5 hours. Bland-Altman analysis and simple regression analysis were used.ResultsThe detection failures for PtcCO2 were 0.3% to 1.3%, for SpO2 10% to 25%, and for pulse rate 5% to 10%. The V-Sign 2 earlobe sensor provided the best results. The mean bias and limits of agreement for PtcCO2ear and PaCO2 were 1.1 and −3.4/+5.5 mmHg. The drift of PtcCO2 was negligible at all locations. The mean bias and limits of agreement of V-Sign SpO2ear and SaO2, as well as V-Sign pulse rate and the electrocardiogram, were −1.7% and −6.8/+3.9% and 1.2 beats/min and −3.3/+5.8 beats/min. End-expiratory carbon dioxide showed a weak correlation with PaCO2 (r2 = 0.47).ConclusionsTranscutaneous capnometry using the revised V-Sign 2 sensor at the earlobe is a reliable monitoring tool during the recovery period of patients after cardiac surgery. This approach has the potential to reduce the number of arterial blood gas samples.