Page 107 - 2020 JSOM Winter

HMS Formidable sustained temporary hearing loss as a result cytoprotective activity), and hyperbaric oxygen therapy. Of
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of cannon fire; in 1801, permanent deafness from cannon fire these, the most widely studied and promising is considered to
was documented in an officer at the Battle of Copenhagen. be glucocorticoids, administered orally, by intratympanic ste-
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In 1831, John Fosbroke comprehensively described AAT and roid injection (ITSI) into the middle ear cavity, intravenously,
NIHL, stating: “deafness [can be] caused by sudden explo- or through combinations of these. 8,24 Timely administration of
sion of cannon and by continued noise as in blacksmith’s steroids is essential; in 2001, Harada et al. identified that
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deafness.” In 1890, Haberman undertook a postmortem patients receiving steroid treatment within 14 days of acoustic
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examination of a blacksmith and was the first to document injury had better outcomes than did those who presented later.
the histopathological effects of noise, identifying damaged
hair cells in the organ of Corti and atrophy of both the co- Our Aim
chlear nerve and ganglion. Evidence for the causative effect of
military noise exposure on hearing was strengthened by the The goal of this study was to highlight the availability of new,
publication of six independent reports describing AAT follow- accurate hearing assessments in the far-forward setting. This
ing the Spanish-American War of 1898. As many as a third allows for efficient triaging and therefore treatment of specific
of veterans of the American Civil war (1861–1865) received casualties with new hearing-rescue treatments. The DAT has
compensation for hearing loss. After the First World War, been used by UK Forces extensively in Role 1 over the past
up to a fifth of the French army received pension payments 18 months to assess many hundreds of acoustic casualties.
for hearing loss, coinciding with an increased prevalence of This has allowed successful identification of AAT, allowing
hearing loss resulting from the introduction of more power- for prompt CASEVAC and treatment offsite; additionally, it
ful weapons and explosives. Prior to the Second World War, has identified SP without AAT, allowing for reassurance and
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Cordia Bunch, the pioneer of clinical audiometry, published prompt return to duty. The DAT has been found to be easy to
his report “Traumatic Deafness.” Having amassed consid- use, durable, and reliable in the far-forward setting. Specific
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erable evidence from the previous century of gunfire-induced data, where security considerations allow, will be presented
deafness, he conclusively demonstrated that excess noise re- for peer review in a separate paper and are not currently avail-
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sulted in loss of perception in the higher frequencies. During able in the public domain.
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the Second World War, the British recognized the operational
“handicap” of the soldiers with AAT (such as missing a “snap Development of the Downrange Acoustic Toolbox
of a twig” during a night operation ), and preventive measures
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began to be introduced. Nevertheless, it would take another To mitigate military frontline AAT, the UK Defence hearWELL
30 years until this was enshrined in policy under the British Research Collaboration conceived the DAT. This project was,
Army Hearing Conservation Program (AHCP) in 1974. At in part, supported by the US DoD, which provided access to
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this time, the US DoD also developed the Hearing Evaluation a ruggedized boothless audiometer: the Wireless Automated
and Reporting System (HEARS), which allowed military audi- Hearing-Test System (WAHTS).
ologists to track hearing conservation compliance. 12
The DAT consists of:
Current preventive measures are described by the British and 1. A boothless audiometer headset, currently the WAHTS 33
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US Army hearing programs. These include effective identifi- a. Weight: 685g (1.5lb)
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cation of noise hazards; criteria for wearing hearing protection b. Dimensions: (Figure 1) 23.5cm × 23.5cm × 10.8cm
devices (HPDs); passive and active hearing protection, (e.g., (9.25" × 9.25" × 4.25");
noise-attenuating helmets and Tactical Communication and 2. Mobile phone–compatible endoscopic imaging hardware
Protection System devices); annual hearing education; and pe- and software (endoscope-i [Endscope-i]):
riodic audiometry. Although these preventive measures have a. Weight: 200g (0.44lb) for light source, adapter, and
conferred benefit in protecting against hearing loss, there is endoscope
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strong anecdotal evidence that soldiers may omit the use of b. Dimensions: (Figure 2) endoscope 10cm (3.9") long,
HPDs because of a perceived negative impact on auditory situ- light source 13cm (5.1") long. Phone: model dependent;
ational awareness. A detailed understanding of poor compli- 3. A tympanometer; and
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ance with HPDs was highlighted as an area of need in a recent 4. Immediately “holding” pharmacologic treatment options:
review of the related literature. 21 oral steroids, proton pump inhibitors (PPIs), and topical
steroid drops.
Rationale for Acute Acoustic Testing
These items are presented in a toolbox weighing 3600g (8lb)
Although prevention remains the mainstay, not all instances and measuring 38.1cm × 31.1cm × 17.8cm (15" × 12.25" ×
of acute military noise exposure are avoidable. AAT is now 7"). The DAT is likely to be predominantly used by the Role
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a treatable condition, and doctrine must shift to include ac- 1 medic; however, the WAHTS and endoscope-i are able to be
curate diagnosis of acute hearing injury and the delivery of transported independent of the box as far forward as needed,
evidence-based treatment in an optimum time frame. reducing the combined weight to just 865g (1.9lb).

Conservative treatment, such as immediate postexposure The utility, validity, and accuracy of both remote otoscopy
placement in a quiet environment, can mitigate some NIHL ; (tele-otology) and boothless audiometry have been explored,
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however, this is likely to be insufficient or impractical in a and the results are extremely promising. A study released by
military setting. Other interventions have been mooted: glu- Magro et al. in 2019 found a sensitivity of 100% in identify-
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cocorticoids, 24,25 magnesium, N-acetyl cysteine (NAC), 27,28 ing hearing loss in 120 schoolchildren using the WAHTS head-
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antioxidant vitamins, 29,30 Ebselen (a synthetic organosele- phones in a noisy environment (i.e., school). Furthermore, the
nium drug molecule with anti-inflammatory, antioxidant, and study by Meinke et al. found the WAHTS performance to
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The Downrange Acoustic Toolbox | 105