Conway A, et al. - In this review, researchers tested transcutaneous carbon dioxide (TcCO₂) measurements (a non-invasive alternative to arterial blood sampling) for accuracy and precision. For 7,021 paired measurements taken from 2,817 participants in 73 studies, the reported mean bias was −0.1 mm Hg and the population limits of agreement were −15 to 15 mm Hg. As reported in the studies, 18 mm Hg and 103 mm Hg were the lowest and the highest PaCO₂, respectively. Sensor location and temperature were identified as the major sources of inconsistency. Based on the context in which the technology was used, substantial differences between TcCO₂ and PaCO₂ were reported in the studies. Based on the findings, they recommended to preferentially apply TcCO₂ sensors to the earlobe. They also suggested that, when monitoring at other sites, users set the temperature of the sensor higher than 42°C.