title: A three-microphone acoustic reflection technique using transmitted acoustic waves in the airway.
abstract: The acoustic reflection technique noninvasively measures airway cross-sectional area vs. distance functions and uses a wave tube with a constant cross-sectional area to separate incidental and reflected waves introduced into the mouth or nostril. The accuracy of estimated cross-sectional areas gets worse in the deeper distances due to the nature of marching algorithms, i.e., errors of the estimated areas in the closer distances accumulate to those in the further distances. Here we present a new technique of acoustic reflection from measuring transmitted acoustic waves in the airway with three microphones and without employing a wave tube. Using miniaturized microphones mounted on a catheter, we estimated reflection coefficients among the microphones and separated incidental and reflected waves. A model study showed that the estimated cross-sectional area vs. distance function was coincident with the conventional two-microphone method, and it did not change with altered cross-sectional areas at the microphone position, although the estimated cross-sectional areas are relative values to that at the microphone position. The pharyngeal cross-sectional areas including retropalatal and retroglossal regions and the closing site during sleep was visualized in patients with obstructive sleep apnea. The method can be applicable to larger or smaller bronchi to evaluate the airspace and function in these localized airways.
authors.affiliation: Division of Respiratory Disease.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Fujimoto
authors.forename: Jyongsu
authors.initials: J
authors.lastname: Huang
authors.forename: Toshiharu
authors.initials: T
authors.lastname: Fukunaga
authors.forename: Ryo
authors.initials: R
authors.lastname: Kato
authors.forename: Mari
authors.initials: M
authors.lastname: Higashino
authors.forename: Shohei
authors.initials: S
authors.lastname: Shinomiya
authors.forename: Shoko
authors.initials: S
authors.lastname: Kitadate
authors.forename: Yutaka
authors.initials: Y
authors.lastname: Takahara
authors.forename: Atsuyo
authors.initials: A
authors.lastname: Yamaya
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Saito
authors.forename: Makoto
authors.initials: M
authors.lastname: Kobayashi
authors.forename: Koji
authors.initials: K
authors.lastname: Kojima
authors.forename: Taku
authors.initials: T
authors.lastname: Oikawa
authors.forename: Ken
authors.initials: K
authors.lastname: Nakagawa
authors.forename: Katsuma
authors.initials: K
authors.lastname: Tsuchihara
authors.forename: Masaharu
authors.initials: M
authors.lastname: Iguchi
authors.forename: Masakatsu
authors.initials: M
authors.lastname: Takahashi
authors.forename: Shiro
authors.initials: S
authors.lastname: Mizuno
authors.forename: Kazuhiro
authors.initials: K
authors.lastname: Osanai
authors.forename: Hirohisa
authors.initials: H
authors.lastname: Toga
mesh_terms: D000162:Acoustics / Q000295:instrumentation*; D000465:Algorithms; D016022:Case-Control Studies; D004867:Equipment Design; D006801:Humans; D008168:Lung / Q000473:pathology* / Q000503:physiopathology; D008904:Miniaturization; D008953:Models, Anatomic; D008954:Models, Biological; D009038:Motion; D010614:Pharynx / Q000473:pathology* / Q000503:physiopathology; D011237:Predictive Value of Tests; D011312:Pressure; D012815:Signal Processing, Computer-Assisted; D020181:Sleep Apnea, Obstructive / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D013016:Sound; D013997:Time Factors; D014159:Transducers
keywords: acoustic transmission; algorithm; intra-airway microphone; pharyngeal cross-sectional area; reflection coefficient; sleep apnea