IEEE transactions on bio-medical engineering
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IEEE Trans Biomed Eng · Dec 1993
An acoustical guidance and position monitoring system for endotracheal tubes.
A prototype instrument to guide the placement and continuously monitor the position of an endotracheal tube (ETT) was developed. An incident audible sound pulse is introduced into the proximal ETT and detected as it travels down the ETT via a miniature microphone located in the wall. This pulse is then emitted from the tube tip into the airways and the reflected signal from the airways is detected by the microphone. ⋯ The amplitude and polarity of an additional reflection that occurs at the ETT tip is used to estimate the cross-sectional area of the airway in which the ETT is placed. This combined information allows discrimination between tracheal and bronchial intubation and can be used to insure an adequate fit between the ETT and trachea. The instrument has proven extremely reliable in multiple intubations in eight canines and offers the potential to noninvasively and inexpensively monitor ETT position in a continuous manner.