title: Is there a difference between active opening of the Eustachian tube in a hypobaric surrounding compared to a hyperbaric surrounding?
abstract: BACKGROUND
  The Eustachian tube (ET) is the key to pressure equalization between the middle ear and ambient pressure. To date, little is known about differences of the opening mechanisms under hyper- or hypobaric conditions. Aim of this study was to compare standard ET opening parameters during standardized hypo- and hyperbaric exposures.
  
  
  METHODS
  Thirty healthy participants were exposed to a standardized profile of decompression and compression (SPDC) in a hypo-/hyperbaric pressure chamber. Impedance, expressed as tympanic membrane compliance, was recorded at intervals during the excursions from 1 atmosphere absolute (atm abs) to 0.8 and 1.2 atm abs respectively. Parameters for tubal opening were obtained during SPDC: ET opening pressure (ETOP), ET opening duration (ETOD) and ET opening frequency (ETOF), hypobaric (Phase 1) and hyperbaric (Phase 2) data were compared.
  
  
  RESULTS
  Mean value for Valsalva maneuver ETOP was 40.10 ± 19.02 mbar in Phase 2 vs. 42.82 ± 21.75 mbar in Phase 1. For ETOD it was 2.80 ± 2.09 seconds in Phase 2 vs. 2.51 ± 1.90 seconds in Phase 1. For swallowing, mean value for ETOP was 33.47 ± 14.50 mbar in Phase 2 vs. 28.44 ± 14.04 in Phase 1. ETOD was 0.82 ± 0.60 seconds in Phase 2 vs. 0.76 ± 0.55 seconds in Phase 1. There was no statistical significance for ETOP, ETOD and ETOF between the two phases.
  
  
  CONCLUSIONS
  No statistical significant difference was evident for active pressure equalization (Valsalva and swallowing) between a hyperbaric setting (dive) and a hypobaric setting (flight) in healthy subjects.
authors.forename: Stefanie
authors.initials: S
authors.lastname: Mikolajczak
authors.forename: Moritz Friedo
authors.initials: MF
authors.lastname: Meyer
authors.forename: Moritz
authors.initials: M
authors.lastname: Felsch
authors.forename: Masen Dirk
authors.initials: MD
authors.lastname: Jumah
authors.forename: Karl-Bernd
authors.initials: KB
authors.lastname: Hüttenbrink
authors.forename: Maria
authors.initials: M
authors.lastname: Grosheva
authors.forename: Jan-Christoffer
authors.initials: JC
authors.lastname: Luers
authors.forename: Dirk
authors.initials: D
authors.lastname: Beutner
mesh_terms: D000328:Adult; D000399:Air Pressure; D001273:Atmosphere Exposure Chambers; D003664:Decompression; D003679:Deglutition / Q000502:physiology; D004432:Ear, Middle / Q000502:physiology; D005064:Eustachian Tube / Q000502:physiology*; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D014432:Tympanic Membrane / Q000502:physiology; D014636:Valsalva Maneuver / Q000502:physiology