Development and Validation of a CO2 Sensor for Extra Corporeal Life Support Applications

Measurement of carbon dioxide (CO2) in medical applications is a well-established method for monitoring patient’s pulmonary function in a noninvasive way widely used in emergency, intensive care, and during anaesthesia. Even in extra corporeal life support (ECLS) applications, such as Extra corporeal Carbon Dioxide Removal (ECCO2R), Extra corporeal Membrane Oxygenation (ECMO), and cardiopulmonary by-pass (CPB), measurement of the CO2 concentration in the membrane oxygenator exhaust gas is proven to be useful to evaluate the treatment progress as well as the performance of the membrane oxygenator. This thesis presents the development of a new optical sensor specifically designed for the measurement of CO2 concentration in the oxygenator exhaust gas. The project’s goal is to develop a sensor with Technology Readiness Level of 9, meaning that the developed sensor shall also be proven and validated in the operational environment. Initially, to allow a better comprehension of the application for which the developed sensor is intended, an overview of the ECLS application scenario is given, describing the key components of an ECLS device, as well as the most used ECLS procedures. Further, considerations about the importance of CO2 concentration measurement in the membrane oxygenator exhaust gas are reported. Then, the measurement principle for carbon dioxide concentration is described, as well as state-of-the-art technologies used in this field. Moreover, design requirements that the developed sensor should meet are analyzed and disclosed. Sensor architecture is described, focusing on the method implemented to prevent condensation of the water vapour in the membrane oxygenator’s exhaust gas. Effects of temperature on the sensor optical elements performance are addressed through theoretical and experimental analysis, and methods to avoid signal–temperature dependency are described. Finally, the results of the test performed on the developed sensor both in-vitro and in-vivo conditions are reported and discussed.