In-line acoustic system to position and monitor infant-sized endotracheal tubes

Ensuring that the distal end of an endotracheal tube is properly located within the trachea, and that the tube is not obstructed by mucous deposition, is a major clinical concern. This concern is heightened in infant care, where the relatively small geometries predicate higher risks. A novel acoustic system was developed to allow for the continuous monitoring of endotracheal tube position and patency. A miniature sound source and two sensing microphones are placed in-line between the ventilator hose and the proximal end of the endotracheal tube. Reflections of an acoustic pulse from the endotracheal tube lumen and the airways are digitally analyzed to estimate the location and degree of obstruction, as well as the position of the distal end of the tube in the airway. The system was evaluated in a rabbit model. During advancement and retraction of the distal end of the tube within the trachea, changes in position were estimated acoustically to within -0.4/spl plusmn/2.0 mm (mean /spl plusmn/95% CI). Through reflection analysis, the system reliably differentiated tracheal from improper bronchial or esophageal placement in all cases. In addition, the system acoustically estimated the area of intralumenal obstruction to within 5.4/spl plusmn/8.6%.