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ORGAN SYSTEMS Otolaryngeal system (ENT)

Otic barotrauma (OBT)

Tissue injury to the ear secondary to inadequate pressure equalization between gas-filled body spaces and the external environment.

Tissue injury to the ear secondary to inadequate pressure equalization between gas-filled body spaces and the external environment.


Aetiology

External auditory canal (EAC) BT (rare):

Less common as the canal typically communicates with the external environment.
  • Cerumen impaction or tight drysuit/wetsuit hood that inhibits external communication and results in an airspace vacuum on descent
  • Exostoses: Can lead to cerumen impaction which may increase the risk

Middle ear BT (MEBT): M/C

Vacuum created in the middle ear-space causes an increase in blood flow through the subcutaneous vessels in the EAC, TM, ET, and middle ear space. This results in the vessels engorging with blood. As the pressure in the EAC rises and the vacuum in the middle ear space is further increased, blood vessels eventually extrude serum into the interstices and cause inflammation of the middle ear. This is otherwise known as a serous effusion or serous otitis. The effusion may contain small amounts of blood, converting it to a serosanguinous effusion, or trapped air bubbles. As pressure continues to increase without equalization of the middle ear space, blood vessels will eventually rupture, causing bleeding into or behind the TM. It will be appreciated as non-transparent frank blood. If allowed to continue, the increase in ambient pressure will eventually result in perforation of the TM and its associated complications.
  • Rapid diving: Asymmetric entrance of water into middle ear, resulting in caloric stimulation and vestibular symptoms
  • Reverse block: Decompression injury from decreased pressurization due to inability of increasing pressure within middle ear (due to expanding gas volume) to be released via the ET. This reverse blockage may also occur due to middle ear effusion and tubal ET edema caused on descent, which impairs the ability to ventilate the middle ear on ascent.
    • Decompressing hyperbaric chamber at end of patient treatment
    • Ending a SCUBA dive by beginning the swim to the surface
  • Alternobaric vertigo: Discrepancy in equalization between ears due to asymmetric stimulation of vestibular system
    • Commonly occurs on ascent and results in transient vertigo that resolves with middle ear equalization.

Inner Ear BT (IEBT):

Occurs when pressure changes are transmitted to the inner ear from middle ear space or cerebral spinal fluid (CSF), resulting in inner ear hemorrhage, labyrinthine membrane tear, or perilymphatic fistula (PLF).
  • Explosive or implosive force: Sudden increase in CSF pressures (inner ear perilymph is connected to the CSF):
    • Valsalva against a locked ET: Transmitted through perilymph to labyrinthine windows, causing rupture of round/oval windows into the middle ear space (explosive)

Clinical faetures

Middle Ear BT (MEBT):

Initially, the negative pressure gradient across the TM causes a sensation of fullness or dullness, which progresses to discomfort. This will advance to severe pain if the ambient pressure increase does not cease, or the pressure in the middle ear space is not equalized.
  • Varying degrees of hearing loss secondary to serous/serosanguinous effusion within the middle ear space, or due to hemotympanum
  • TM rupture: Increasing pain with abrupt improvement, associated with varying degrees of hearing loss

Inner Ear BT (IEBT)/perilymphatic fistula (PLF):

  • Hearing loss
  • Tinnitus
  • Hyperacusis
  • Vertigo, nausea, and vomiting

Diagnosis

Direct otoscopic examination:

Directly and easily visualizes the EAC and TM, however, visualization of the TM may be obstructed due to impacted cerumen or exostoses. Cerumen should be disimpacted to facilitate visualization of the TM (and to facilitate middle ear equalization).
  • Varying degrees of erythema or bleeding into tissues
  • Middle ear space effusions
  • TM perforation (if present)
  • IEBT (additional features): Gait instability, nystagmus, and audiometric hearing loss

Modified Teed Classification 

In 1944, Dr. Teed evaluated U.S. Navy diver trainees with otoscopic visualization following hyperbaric exposures in submarine escape training. TM pressure-related pathology became apparent during the course of those exercises and examinations, from which he developed the Teed classification. The original Teed classification was modified to include another TM grade totaling 6 possible Teed results: 
  • Grade 0: Symptoms with no ontological signs of trauma
  • Grade 1: diffuse redness and retraction of the TM
  • Grade 2:  Grade 1 plus slight hemorrhage within the tympanic membrane
  • Grade 3: Grade 1 plus gross hemorrhage within the TM
  • Grade 4: Dark and slightly bulging TM due to free blood in the middle ear (a fluid level may also be present)
  • Grade 5: Free hemorrhage into the middle ear, TM perforation with blood visible in the external auditory canal.

O’Neill Grading System for ETD and MEBT:

This system employs the use of a video otoscope to take a baseline photo of the TM before any hyperbaric exposure. The photo maintains a permanent record of what the initial physician visualized during the baseline exam that may be referenced with any episode of ETD or MEBT, and assists in reducing interpersonal grading variation. This baseline may be useful in the realm of clinical hyperbaric medicine, although baseline images would likely not be available for unforeseen MEBT due to diving, air travel, or trauma.
  • Grade 0: Symptoms with no otologic signs of trauma
  • Grade 1: Any increased redness of the TM when compared to baseline, serous or slightly serosanguinous fluid and/or trapped air behind the TM
  • Grade 2: Frank bleeding in any location and/or perforation of the TM

Management

MEBT:

Treatment of MEBT varies along a spectrum, from trigger management and enhanced equalization education to medical and/or surgical interventions. Most commonly, MEBT is managed by the hyperbaric team, emergency physician, or general practitioner. It is often treated conservatively and resolved without medical interventions.
  • Conservative management: Prevent further pressurization (to allow ET and middle ear space to clear)
    • Reinforced equalization techniques (allows for equalization): Swallowing
    • Oral decongestants (for underlying ETD)
    • Avoid exposure to hyperbaric environment
  • Emergency needle myringotomy and/or urgent placement of tympanostomy ventilation tubes: If conservative management ineffective.

Inner Ear BT (IEBT)/perilymphatic fistula (PLF):

Any patient suspected of IEBT should be assessed and managed by an otolaryngologist. While a small TM perforation may be managed by the team, a large TM perforation, a perforation that is not resolving, or a perforation associated with IEBT symptoms should be referred to otolaryngology as these cases may require advanced surgical correction.
  • Conservative therapy:
    • Bed rest
    • Avoiding maneuvers that increase pressure transmission: Coughing, straining with bowel movement, further changes in ambient pressure, Valsalva, loud noises, etc
  • Surgical exploration and/or repair: If significant symptomatology exists, or if deterioration occurs despite conservative therapy

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