To evaluate the precision of a non-invasive digital ear-clip sensor providing continuous transcutaneous (Tc) monitoring of carbon dioxide tension (PaCO2) and oxygen saturation (SaO2%) using arterial blood gases (ABG) as the gold-standard technique.
Population: patients referred to the Pulmonary Function Testing Laboratory of our Institution. Instrumentation: Spirometry was performed on the admission day. The ear-clip V-signTM (SenTec) was placed and after stabilization, the lecture was performed. While the patient wore the ear-clip, ABG were performed, the blood was analyzed in two different blood gas analyzers and the mean value was taken as the gold-standard measurement. Statistical evaluation: Student’s t test for paired data was used to compare the mean values obtained from the Tc and the ABG measurement. A Pearson correlation coefficient (r) was obtained. Bland-Altman plot was used to detect bias in the readings. This evaluation was performed for the whole group and for sub-groups stratified according to lung obstruction severity and PaCO2 value (normal≤ 45 mmHg; elevated PaCO2 (>45 mmHg).
130 patients were included (10 were excluded for calibration problems of the sensor in two consecutive days). Data are given as mean±SD.The subgroup analysis did not show relevant differences. The Bland Altman plot did not show marked dispersion at any values of PaC02.
1) The differences found in the measurements of PaCO2 and SaO2 with both methods, although statistically significant, were not clinically relevant. 2) Appropriate calibration and stabilization period of the Tc sensor is needed before a measurement is considered reliable.
Tc measurement is a reliable method to determine carbon dioxide tension and oxygen saturation. In many cases, this technique can substitute ABG analysis.
ABGTc*Mean DifferenceIC (95%)r*CO2 mmHg42.16±7.240.93±8.41.22±4.1-1.9;-0.50,875SaO2%93.46±4.494.35±4.40.88±3.10.3;1.40,747*
Christian Domingo, None.