Various embodiments of an tracheal tube having a sensor coupled to a selectively permeable membrane are provided. In some embodiments, the membrane may be permeable to one or more blood gases and/or blood analytes. Certain embodiments of the endotracheal tube may be capable of deploying the sensor during intubation to sense one or more indicators of blood flow characteristics, such as a level of blood gases and/or blood analytes, in the respiratory tract. Embodiments of the present invention may include positioning of the sensor in a variety of suitable positions with respect to the permeable membrane, such as mounting the sensor to the underside of an inflatable permeable membrane.