Official websites use. Share sensitive information only on official, secure websites. Carbon dioxide CO 2 monitoring in human subjects is of crucial importance in medical practice. Yet, such monitors are not only expensive, but also bulky and continuously drifting, requiring frequent recalibrations by trained medical staff. Aiming at finding alternatives, the full panel of CO 2 measurement techniques is thoroughly reviewed. The physicochemical working principle of each sensing technique is given, as well as some typical merit criteria, advantages, and drawbacks.
An overview of the main CO 2 monitoring methods and sites routinely used in clinical practice is also provided, revealing their constraints and specificities. The reviewed CO 2 sensing techniques are then evaluated in view of the latter clinical constraints and transcutaneous sensing coupled to a dye-based fluorescence CO 2 sensing seems to offer the best potential for the development of a future non-invasive clinical CO 2 monitor.
In medical practice, the accurate monitoring of vital signs is of crucial importance to provide appropriate and effective care to the patients. In particular, the measurement of blood gases—namely di-oxygen O 2 and CO 2 —gives respiratory as well as circulatory clues on the state of a patient [ 1 ].
Yet, the continuous monitoring of the arterial partial pressure in O 2 —paO 2 —and CO 2 —paCO 2 —implies frequent arterial blood sampling, a process which is both painful and risky [ 2 ], requiring trained staff and expensive blood gas analyzers. Furthermore, the blood samples must be promptly analyzed upon collection, adding logistic constraints on the whole healthcare system [ 3 ].
Thus, the development of non-invasive paO 2 and paCO 2 monitoring techniques has been an active research field for decades [ 4 , 5 , 6 ], but while pulse oximetry proved to be a reliable proxy for paO 2 [ 7 , 8 ], no satisfactory equivalent exists for paCO 2.
