Evaluation of a new combined SpO2/PtcCO2 sensor in anaesthetized paediatric patients

The recently introduced TOSCA monitor (Linde Medical Sensors AG, Basel, Switzerland) combines pulse oximetry (SpO2) and transcutaneous PCO2 (PtcCO2) monitoring in a single ear sensor. The aim of the present study was to evaluate accuracy of the TOSCA monitor to estimate SaO2 and PaCO2 in anaesthetized children.

With approval of the hospital ethical committee and after obtaining informed parental consent, the TOSCA sensor was attached to one ear lobe of anaesthetized children in whom arterial access was established for cardiac catheterization or invasive blood pressure monitoring. SpO and PtcCO2 as well as SpO and PECO2 values from the anaesthesia monitoring (AS5; Datex-Ohmeda, Helsinki, Finland) were compared with SaO2 and PaCO2 values from arterial blood gas analysis. Corresponding data were compared using Bland Altman bias analysis.

A total of 111 blood samples were taken from 60 children (median age: 4.41 years; 0.35-16.13 years). SaO2 values ranged from 63 to 100% (median: 98.7%), PaCO2 ranged from 3.8 to 7.3 kPa (median: 4.6 kPa). Mean difference (+/-2 sd) between PaCO2 and PtcCO2 was -0.035 kPa (+/-0.74 kPa), between PaCO2 and PECO2 0.002 kPa (0.73 kPa), respectively (1 kPa = 7.3 mmHg). Bias and precision between SaO2 and SpO was -0.63% (+/-2.77%) and 0.13% (+/-4.52%) between SaO2 and SpO.

In anaesthetized children, the TOSCA ear sensor allows estimation of SaO2 and PaCO2, comparable in accuracy to endtidal capnometry and finger pulse oximetry. This makes the TOSCA monitor a helpful add-on to respiratory monitoring in anaesthetized children, in situations, in which endtidal capnometry is unreliable or difficult to establish.