Abstract: Embodiments of the present disclosure relate to a double-lumen endotracheal tube having an access sheath or optical system positioned between the two lumens. Embodiments of the the present disclosure are directed toward systems, devices, and methods that provide continuous visual input to a clinician during initial lung separation with the use of a double-lumen endotracheal tube device and throughout a treatment procedure to facilitate the ongoing maintenance of a proper position of the double-lumen endotracheal tube.