Middle-Ear Muscle Contractions Should Not Be Included in Damage-Risk Criteria

Details

• Personal Author:
  Ahroon W ; Deiters K ; Flamme G ; Greene NT ; Jones H ; McGregor K ; Murphy W ; Smith M ; Tasko S
• Description:
  Middle-ear muscle contractions (MEMCs) involve activation of the stapedius and/or tensor tympani muscles. MEMCs can be elicited by acoustic and non-acoustic stimuli, and can sometimes be engaged voluntarily. Responses typically increase the middle-ear impedance for low frequencies ( 95 % confidence of > 95% prevalence) within the population, and are of sufficient strength and duration to serve as a protective mechanism. These assumptions were addressed by determining (1) the prevalence of acoustic reflexes using clinical protocols, (2) the likelihood of observing an MEMC for short-duration acoustic and non-acoustic stimuli among people with clinically-measured acoustic reflexes, and (3) attempts to condition or train an anticipatory MEMC in laboratory environments. Studies varied in size from 26 to 15,106 participants. The largest study examined the prevalence of clinically-measured acoustic reflexes drawn from the U.S. National Health and Nutrition Examination Survey. The laboratory studies included 220 healthy adults with excellent hearing (n=194) or slight/mild hearing impairment (n=26). Reflexive MEMCs to short-duration acoustic and non-acoustic stimuli were assessed in all laboratory studies. Additionally, the presence of conditioned MEMCs was investigated using five different training tasks administered to subgroups chosen at random. No participant group exhibited pervasive MEMCs, which obviated the need for assessment of whether the observed responses had sufficient strength or duration. Results indicated the likelihood of observing an MEMC for short-duration acoustic stimuli was much lower than for non-acoustic stimuli and that voluntary eye closure produced the greatest likelihood of an MEMC. Conditioned MEMC responses were well below the 0.95 criterion necessary to consider the responses pervasive. Interestingly, participant attention greatly influenced the likelihood of observing an early, conditioned MEMC. Although clinical acoustic reflexes are often observed in a normal hearing population, clinical observations do not generalize to the stimuli and contexts relevant to DRC. Collectively, these studies indicate MEMCs should not be included as a protective factor in DRC for impulsive noises. [Description provided by NIOSH]
• Subjects:
  Hearing Loss Hearing Loss, Noise-Induced Noise Noise, Occupational Occupational Health Safety
• Keywords:
  Acoustics Hearing Impairment Hearing Loss Impulse Noise Muscle Contraction Noise Exposure Noise Frequencies Physiological Effects
• ISSN:
  0742-3152
• Publisher:
  Association for Research in Otolaryngology
• Document Type:
  Text
• Genre:
  Abstract or Summary
• Place as Subject:
  Alabama ; Colorado ; Maryland ; Michigan ; Ohio ; OSHA Region 3 ; OSHA Region 4 ; OSHA Region 5 ; OSHA Region 8
• CIO:
  National Institute for Occupational Safety and Health (NIOSH)
• Division:
  DFSE - Division of Field Studies and Engineering
• Topic:
  Workplace Safety & Health
• Location:
  North America
• Volume:
  42
• NIOSHTIC Number:
  nn:20060895
• Citation:
  Abstr Midwinter Res Meet Assoc Res Otolaryngol 2019 Feb; 42:176
• Federal Fiscal Year:
  2019
• Peer Reviewed:
  False
• Source Full Name:
  Abstracts of the 42nd Midwinter Research Meeting of the Association for Research in Otolaryngology, February 9-13, 2019, Baltimore, Maryland
• Collection(s):
  National Institute for Occupational Safety and Health
• Main Document Checksum:
  urn:sha-512:4877abb2ddebbebd4b399095141f2b329e42512d15d6fe187a6a858fefe8d7e8e913a2054708c9d13f4c4203de8b2ff7d7fa4dc5907e1c6a97f8352ee0302377
• Download URL:
  https://stacks.cdc.gov/view/cdc/224666/cdc_224666_DS1.pdf
• File Type:
  [PDF - 406.27 KB ]