title: The measurement of Eustachian tube function in a hyperbaric chamber using an ear canal microphone.
abstract: OBJECTIVE
  The purpose of this study was to further the understanding of the opening of the Eustachian tube in relation to changes in barometric pressure.
  
  
  METHODS
  An ear canal microphone was used to measure the specific sounds related to tube opening and possible eardrum movements. Five subjects with normal tube function were examined in a hyperbaric chamber (up to 304 kPa). All active and passive equalization events were recorded and correlated with the subjectively perceived pressure regulation in the measured ear.
  
  
  RESULTS
  The signals recorded were clear and reproducible. The acoustic analysis distinguished between the different kinds of equalization. Subjective impressions were confirmed by the recorded frequency of acoustic phenomena (clicks). During compression, the sequence of active equalization manoeuvres was in a more regular and steady pattern than during decompression, when the click sounds varied.
  
  
  CONCLUSIONS
  The study established a simple technical method for analyzing the function of the Eustachian tube and provided new information about barometric pressure regulation of the middle ear.
authors.affiliation: Department of Otorhinolaryngology (ENT), Head and Neck Surgery Military Hospital Lesserstrasse 180 22049 Hamburg, Germany, Phone: +49-(0)176-2197-0320, E-mail: hansgeorgfischer@live.de.
authors.forename: Hans-Georg
authors.initials: HG
authors.lastname: Fischer
authors.affiliation: Naval Institute of Maritime Medicine, Kronshagen, Schleswig-Holstein, Germany.
authors.forename: Andreas
authors.initials: A
authors.lastname: Koch
authors.affiliation: Naval Institute of Maritime Medicine, Kronshagen, Schleswig-Holstein, Germany.
authors.forename: Wataru
authors.initials: W
authors.lastname: Kähler
authors.affiliation: Department of Otorhinolaryngology (ENT), Head and Neck Surgery, Military Hospital, Hamburg, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Pohl
authors.affiliation: Department of Otorhinolaryngology (ENT), Head and Neck Surgery, University of Rostock, Rostock, Germany.
authors.forename: Hans-Wilhelm
authors.initials: HW
authors.lastname: Pau
authors.affiliation: Department of Otorhinolaryngology (ENT), Head and Neck Surgery, University Medical Center Hamburg-Eppendorf, Hamburg, Germany.
authors.forename: Thorsten
authors.initials: T
authors.lastname: Zehlicke
mesh_terms: D000162:Acoustics / Q000295:instrumentation*; D000328:Adult; D003939:Diagnostic Techniques, Otological / Q000295:instrumentation; D005064:Eustachian Tube / Q000502:physiology*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D011312:Pressure; D015203:Reproducibility of Results; D014432:Tympanic Membrane / Q000502:physiology; D014636:Valsalva Maneuver / Q000502:physiology
keywords: ENT; Valsalva manoeuvre; barotrauma; ear; middle ear; physiology