title: Contralateral Occlusion Test: The effect of external ear canal occlusion on hearing thresholds.
abstract: OBJECTIVE
  Bedside testing with tuning forks may decrease turnaround time and improve decision making for a quick qualitative assessment of hearing loss. The purpose of this study was to quantify the effects of ear canal occlusion on hearing, in order to decide which tuning fork frequency is more appropriate to use for quantifying hearing loss with the Contralateral Occlusion Test.
  
  
  METHODS
  Twenty normal-hearing adults (forty ears) underwent sound field pure tone audiometry with and without ear canal occlusion. Each ear was tested with the standard frequencies. The contralateral ear was suppressed with by masking. Ear occlusion was performed by two examiners.
  
  
  RESULTS
  Participants aged between 21 and 30 years (25.6±3.03 years) showed an increase in hearing thresholds with increasing frequencies from 19.94dB (250Hz) to 39.25dB (2000Hz). The threshold difference between occluded and unoccluded conditions was statistically significant and increased from 10.69dB (250Hz) to 32.12dB (2000Hz). There were no statistically significant differences according to gender or between the examiners.
  
  
  CONCLUSIONS
  The occlusion effect increased the hearing thresholds and became more evident with higher frequencies. The occlusion method as performed demonstrated reproducibility. In the Contralateral Occlusion Test, 256Hz or 512Hz tuning forks should be used for diagnosis of mild hearing loss, and a 2048Hz tuning fork should be used for moderate hearing loss.
authors.affiliation: Department of Otolaryngology of Egas Moniz Hospital, Centro Hospitalar de Lisboa Ocidental (CHLO), NOVA Medical School - Faculdade de Ciências Médicas, Lisbon, Portugal. Electronic address: roque-reis@sapo.pt.
authors.forename: Luis Roque
authors.initials: LR
authors.lastname: Reis
authors.affiliation: Department of Otolaryngology of Egas Moniz Hospital, Centro Hospitalar de Lisboa Ocidental (CHLO), NOVA Medical School - Faculdade de Ciências Médicas, Lisbon, Portugal.
authors.forename: Paulo
authors.initials: P
authors.lastname: Fernandes
authors.affiliation: Department of Otolaryngology of Egas Moniz Hospital, Centro Hospitalar de Lisboa Ocidental (CHLO), NOVA Medical School - Faculdade de Ciências Médicas, Lisbon, Portugal.
authors.forename: Pedro
authors.initials: P
authors.lastname: Escada
mesh_terms: D000328:Adult; D001301:Audiometry, Pure-Tone; D001309:Auditory Threshold; D003430:Cross-Sectional Studies; D004424:Ear Canal; D005260:Female; D034381:Hearing Loss / Q000175:diagnosis* / Q000209:etiology / Q000503:physiopathology*; D006801:Humans; D008297:Male; D055815:Young Adult
keywords: Audiometry; Audiometría; Auditory threshold; Bedside testing; Conductive; Conductivo; Conducto auditivo; Ear canal; Hearing loss; Hearing tests; Hipoacusia; Occlusion; Oclusión; Pruebas auditivas; Pruebas de cabecera; Umbral auditivo