title: Acoustic method to quantitatively assess the position and patency of infant endotracheal tubes: preliminary results in rabbits.
abstract: In this preliminary laboratory study, an acoustical method was evaluated to quantitatively assess the position and patency of an infant-size endotracheal tube (ETT) by in vivo and in vitro measurements. The method consists of emitting an audible sound pulse into the ETT and the airways, and deriving position and patency information from the timing and characteristics of the returning echoes. The method's capacity to measure ETT changes of position in the tracheae of five anesthetized New Zealand white rabbits (weight, 4.3-4.9 kg; age, 1.5-3 years) was found to be accurate to 0.7 +/- 3.6 mm (mean +/- 95% CI) over a distance of 5 cm. The method was also shown to reliably differentiate between tracheal, bronchial, and esophageal intubations by means of an acoustically inferred diameter of the passageway just beyond the ETT tip. To assess the accuracy of estimating lumen obstruction, in vitro acoustical measurements were performed in different size ETTs (2.5, 3.0, 3.5, and 4.0 mm inner diameter), with obstructions ranging from 5-100% reduction in cross-sectional area. The system identified the sizes of these obstructions to within +/-7%. This technology has the potential for continuous, computer-based monitoring of breathing-tube function through instantaneous detection of ETT malposition or obstruction before it leads to a serious medical condition.
authors.affiliation: School of Electrical and Computer Engineering and Hillenbrand Biomedical Engineering Center, Purdue University, West Lafayette, Indiana 47907-1285, USA.
authors.forename: J P
authors.initials: JP
authors.lastname: Mansfield
authors.forename: D C
authors.initials: DC
authors.lastname: Shannon
authors.forename: G R
authors.initials: GR
authors.lastname: Wodicka
mesh_terms: D000162:Acoustics / Q000295:instrumentation; D000818:Animals; D004867:Equipment Design; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007234:Infant, Premature; D007442:Intubation, Intratracheal / Q000295:instrumentation* / Q000706:statistics & numerical data; D008991:Monitoring, Physiologic / Q000295:instrumentation / Q000706:statistics & numerical data; D011817:Rabbits