Pediatric airway and esophageal profiles with acoustic reflectometry

Acoustic reflectometry is a technique by which the dimensions of a cavity can be estimated in the form of an area-distance profile. We conducted a pilot study to obtain the acoustic reflectometry (AR) images associated with breathing tube (endotracheal tube, ETT) placement (inner diameter 4.5-6 mm) and positioning in 21 (n = 21) children, aged 2-12 yr. Characteristic AR profiles, as previously noted in adults, were obtained for tracheal and esophageal intubations in children. Both types of profiles showed constant area throughout the ETT length, followed distally by either a rapid area increase (tracheal) or an area decrease to a near zero value (esophageal). Relative to a tracheal profile, a bronchial intubation exhibits a decrease in area distal to the carina position. With deeper ETT insertion, abutment of the ETT against the bronchial wall can occur, with a possible profound area decrease. The occurrence of ETT abutment in children and neonates, and its possible AR detection and treatment, is discussed.