Endotracheal tube (ETT) intubation is an important airway management procedure to enable appropriate ventilation and gas exchange in the lungs of critically ill patients or patients recovering from a major surgical intervention. Given that patients are not able to breathe and ventilate on their own, one of the most feared and life-threatening occurrences for apatient with an ETT is to have this tube displaced or dislodged so that adequate ventilation is no longer possible. The occurrenceof ETT misplacement is particularly high in newborns and young children due to their shorter trachea. Currently, there is no clinical system that can be utilized to provide accurate and real-time information to care teams about the appropriate position of the ETT and no previous publications of a system that is easily employed in an efficient and inexpensive manner. The current proposal will enable the next logical steps in the development of a novel, easily scalable, new device which will allow care teams to continuously monitor ETT position, limit complications from ETT movement or dislodgement, and substantively improve overall quality of care for any patient with an ETT by allowing this to occur without interruption to the workflow, high cost, and/or need of additional expertise or personnel on-site. Specifically, we propose to develop a near-infrared optical sensor (Opt-ETT) for noninvasive and continuous assessment of ETT position. Opt-ETT uses a side-firing optical fiber embedded in the ETT for tracheaillumination and a sticker with five photodetectors taped on the skin for light detection. Once the tube is precisely placed in the trachea, its position is displayed on the screen of the Opt-ETT in real-time and care teams are immediately notified if the tube moves beyond apreset limit. A proof-of-concept Opt-ETT system will be constructed and characterized on ex vivo porcine tracheal tissues, and the results will be compared and calibrated to that of Monte Carlo simulations in Aim 1. In Aim 2, in vivo studies with piglets will be conducted to test our central hypotheses that Opt-ETT will detect displacement up to ±20 mm with an accuracy of ±0.5 mm and this system is capable of accurately generating an alarm with different chest wall thickness and depth of the trachea. Opt-ETT is mass producible and cost effective, thus can be widely used in neonatal intensive care units and delivery rooms, particularly where a chest X-ray or ultrasonography is not available.