A microoptical sidestream cuvette based on fast passive gas exchange for capnography

•A new system concept for sidestream capnography sensors is shown.•The optimized connection of sidestream system to breathing tube allows for a passive gas flow without valves and pumps.•The cuvette can be freely designed for optimized optical and fluidic properties without influence of the breathing behavior. In the case of clinical ventilation, sensors are needed that analyze the carbon dioxide concentration during the exhalation cycle. For devices capable to individually control and adjust parameters for each patient, the analysis of the breathing conditions including carbon dioxide concentration is of critical importance. We present a miniaturized system that is optimized for a fast passive gas exchange with low dead volumes in the side stream. The presented system which is also suitable for neonates shows high dynamics and no influence on the breathing behavior due to small systems sizes. Cost reduction is achieved through a fully passive gas flow that does not require active elements such as valves and pumps. The cuvette has been designed for optimized optical and fluidic properties for surveillance in a wide range of breathing conditions.