Utilization of a new combined transcutaneous measurement of PCO₂/pulse oximetry oxygen saturation ear sensor in an intensive care unit

Abstract

We report the utilization of a new ear sensor (TOSCA^(R), Linde, Switzerland) that enable both transcutaneous measurement of arterial carbon dioxide tension and pulse oximetry oxygen saturation in an intensive care unit. The subjects were 12 critically ill patients who were admitted to our intensive care unit. The ear sensor was threaded in the right or left ear lobule for serial measurements of transcutaneous carbon dioxide tension (PtcCO₂) and pulse oximetry saturation (SpO₂). Arterial carbon dioxide tension (PaCO₂) and arterial oxygen saturation (SaO₂) were determined by blood gas analysis and were compared with PtcCO₂ and SpO₂, respectively. A significant relationship was found between PtcCO₂ and PaCO₂ (correlation coefficiency: 0.95). However, the difference between PtcCO₂ and PaCO₂ was tended to increase when PaCO₂ was more than 50mmHg. Serious complications associated with utilization of the ear sensor did not occur, and inability of measurement caused by position change of patient was not found. The discrepancy between PtcCO₂ and PaCO₂ increased following norepinephrine administration in a shock case. These results suggested that serial monitoring of PtcCO₂ using the ear sensor (TOSCA^(R)) might be useful during mechanical ventilation in an intensive care unit. However, further evaluation is needed to confirm precise measurements of PtcCO₂ and SpO₂ using the ear sensor (TOSCA^(R)) when patients are in a hypoperfusion state such as hemorrhagic shock.