(P. Lewin, J.E. McGowan)

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Abstract: Endotracheal intubation is a common procedure in critically ill neonates, as it is the most secure method of providing ventilatory support. The ideal location for the tip of the endotracheal tube is midway between the vocal cords and the carina; if the tip of the tube is at or above the vocal cords or, conversely, distal to the carina in the right mainstem bronchus, then the patient’s respiratory status will be suboptimal. While this is an issue in all intubated patients, the level of concern is much higher in the neonatal population, where the difference between optimal positioning of the endotracheal tube and respiratory compromise due to improper placement may be only a few millimeters. The current standard for identifying the location of the tip of the endotracheal tube is to obtain a chest radiograph (1). In most neonatal intensive care units, this means requesting the film, waiting for a technician to come to the NICU, take the film, and process it, and then, finally interpreting the image. This process may result in delays in correcting suboptimal tube position as well as exposure to ionizing radiation. The latter concern has been highlighted in an article published earlier this year in the New York Times (2). There is currently no commercially available device that can identify the position of an endotracheal tube (ETT) in the trachea without the use of X-ray imaging. To address these concerns we proposed to develop an ultrasound-based method for detecting the position of the endotracheal tube with in the airway in neonates.

Our project team proposes to alter the acoustic impedance of the endotracheal tube by embedding microbubbles within the wall of the ETT. Endovascular microbubbles have been used to enhance imaging within tissues with good success (4). The size of the microbubbles affects the amount of reflection that occurs and can also increase the subharmonic reflections that can be detected by ultrasound imaging and enhance the images obtained. Microbubbles vibrate in an ultrasound field and these vibrations are most vigorous at a specific resonance frequency that is determined by the bubble size and composition, and the medium in which the bubbles exist. We believe that embedding microbubbles in ETTs will enhance the visibility of the ETT in the ultrasound field, thereby improving our ability to localize the tip of the ETT.