Download Otitic barotrauma

DAvMed 44
Otorhinolaryngology — 47/717
KCL 2011
Otorhinolaryngology
OTITIC BAROTRAUMA
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One of the most common ENT problems in aviation medicine.
= Any damage to the ear that results from changes in pressure.
In order to maintain maximum tympanic membrane compliance (⇔maximize hearing), the air
pressure on either side of the tympanic membrane should be equal.
The function of the Eustachian tube is to maintain this equality of air pressure.
In the normal state, absorption of gases from the middle ear results in a tendency towards
negative pressure.
The Eustachian tube
 Remains closed in the rested state.
 Opened involuntarily by actions such as swallowing and yawning.
 During ascent,
o Gas expansion in the middle ear
o Pushes initially the tympanic membrane laterally.
o Then the Eustachian tube opens passively, letting the gas escape.
 During descent:
o Relative negative pressure in the middle ear
o In order to adjust the pressure, the Eustachian tube must be actively opened by
swallowing, yawning or a Valsalva manoeuvre.
o If this fail, the increased pressure around the tube itself prevents further opening.
o Further increasing the pressure gradient causes:
 Punctate haemorrhages on the tympanic membrane
 Serous exudate or haemorrhage into the middle ear
 Rupture of the tympanic membrane.
©Jean-Michel Ferrieux-2011
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DAvMed 44
Otorhinolaryngology — 47/717
KCL 2011
Factors contributing to barotrauma
 = Anything that impedes the ability of the tympanic membrane or Eustachian tube to attempt
to normalize pressure changes.
o Any condition that causes narrowing of the Eustachian tube lumen
o Upper Respiratory Tract Infection (URTI)
o Allergy
o Rhinitis
o Abnormalities of the palate
o Anatomical obstruction of the Eustachian tube orifices (ADP…)
o Scarring or tympanosclerosis will limit the movement of the tympanic membrane
 The main predictors remain previous history of nasal or otologic disease and abnormal
otoscopy.
Inner-ear barotrauma
 The inner ear fluids are in close proximity to the middle ear cavity.
 During descent:
o The round window membrane bulges laterally in towards the tympanic cavity.
o Further rise in pressure may result in rupture of this membrane or even rupture of the
oval window ➪perilymph fistula.
 ➪Sensorineural hearing loss and vertigo.
Alternobaric barotrauma
 Transient vestibular auditory dysfunction believed to occur as a result of elevated and
asymmetric middle-ear pressure.
Reversed ear: barotrauma of the external auditory meatus
 An obstruction at the external auditory meatal entrance will prevent an increase in pressure
within the external canal.
o ➪the pressures on each side of the tympanic membrane cannot equilibrate.
 Reversed ear is more common in the diving population than in aircrew.
Delayed otitic barotrauma
 Clinical entity consisting in ear discomfort and hearing loss some hours after flight.
 Usually occurs after long flights when breathing high oxygen concentrations.
o Nitrogen is washed out of the tympanic cavity.
o With the subsequent reabsorption of oxygen through the mucous membrane results in
significant relative negative pressure in the middle ear.
o Usually occurs during sleep, as there is reduced rate of swallowing.
Management of otitic barotrauma
 The main symptom is pain.
o Pain relief with analgesics.
 Treatment that attempts to ventilate the middle ear cleft.
o Topical decongestants
 Tympanic perforations have a high rate of infection.
o Prophylactic antibiotics
 The majority of cases of acute otitic barotrauma will settle with such conservative measures.
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The main cause of chronic otitic barotrauma is:
o The original predisposing factor is still persistent
o The oedema and bleeding caused by the original event have not recovered sufficiently.
©Jean-Michel Ferrieux-2011
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DAvMed 44
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Otorhinolaryngology — 47/717
KCL 2011
o ➪Important to give sufficient time to recover from the barotrauma before considering
return to flying.
o The tympanic membrane should look normal and Eustachian tube function shoulb be
assessed by auto-inflating during otoscopy.
Other causes may be treated:
o Surgery for nasal septal deviation
o Short-term ventilation tubes into the tympanic membrane.
o Longer-term ventilation tubes
o Perilymph fistula should be investigated by direct surgical visualisation and closed by a
tissue graft. Full otological assessment after surgery, prior to return to flying duties.
o Alternobaric vertigo is usually related to an underlying URTI.
o Delayed otitic barotrauma is usually mild and is relieved by gentle auto-inflation of air
in the middle ear.
SINUS BAROTRAUMA
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Mucus secreted by glands within the respiratory mucosa is cleared from the sinuses by ciliary
activity towards the sinus ostia. This drainage is required for normal function, as is adequate sinus
ventilation.
The air in the sinuses is subject to ambient pressure changes, but there is no voluntary control of
the sinus ostium.
Usually, air passively vents from the sinus cavity through the sinus ostium.
o Obstruction of the sinus ostia by mucoal oedema, polyp, neoplasm, etc. may occur.
During descent:
o The continued negative pressure within the sinus causes engorgement of the sinus mucosa
➪rupture of the mucosal vessels, haematoma or occasionally frank haemorrhage.
o The frontal sinuses are the most commonly affected.
Predisposing factors to sinus barotrauma
 URTI
 History of chronic inflammatory nasal disease (rhinitis, polyps)
 (Mucociliary disorders).
Management of sinus barotrauma
 The main presentation feature is pain within the affected sinus ± epistaxis.
 Most cases can be managed conservatively with topical nasal decongestion ± prophylactic
antibiotics to prevent infection.
 Return to flying duties once the symptomes have resolved and normal
looking nasal cavity.
Weber
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Chronic or recurrent sinus barotrauma rarely settles spontaneously and
does not respond well to conservative management.
o Sinus drainage, occasionally CT assisted.
o Ensure that there is no ongoing predisposing factor and test
the ability of the sinus to withstand pressure changes before
return to further flying duties.
RINNE
©Jean-Michel Ferrieux-2011
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DAvMed 44
Otorhinolaryngology — 47/717
KCL 2011
HEARING LOSS
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Two main types of hearing loss:
o Conductive hearing loss
 Arises from any failure of transmission of sound waves through the external and
middle ear.
o Sensorineural hearing loss
 Implies a defect in the central pathways of hearing.
Sensorineural hearing loss
 Sensorineural hearing depends on the integrated action of:
o hair cells,
o stria vascularis cochlear neurones,
o and the central neural network.
 Various systemic disorders and local insults can impair sensorineural hearing.
Preby(a)cusis
 Bilateral symmetrical deterioration of hearing thresholds with ageing of the cellular
elements of the cochlea.
 Typically loss in the higher frequencies.
Noise-induced hearing loss
 Caused by noise exposure
o May follow brief high-intensity exposure —acoustic trauma—
o or high-intensity exposure to noise over long periods of time.
 Typically dip @ 4kHz.
 Noise exposure is common in aviation.
Ototoxic drugs
 Many agents are associated with cochlear toxicity:
o Antibiotics —aminoglycoside—
o Loop diuretics
o Anti-inflammatory medications
o Cancer chemotherapeutic drugs
o Haemolytic agents.
Viral infections
 Mumps (oreillons)
 HZV
 Weil's disease
 EBV
 CMV…
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Other causes of sensorineural hearing loss include:
o Trauma
o Perilymph fistula
o Acoustic neuromas
o Ménière's disease.
Management and prognosis are dependent on the underlying cause
Hearing loss in the aerospace environment needs close assessment, due to the necessity for verbal
communications within a noisy environment.
o Helmets with earmuffs, together with built-in transducers
o Active noise reduction
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DAvMed 44
Otorhinolaryngology — 47/717
KCL 2011
Conductive hearing loss
 Often amenable to treatment.
 Treatments vary from simple to increasingly complicated, depending on the cause.
o Obstruction of the external ear canal: usually by wax or foreign body.
o Perforation of the ear drum
o Discontinuity of the ossicular chain:
 by chronic infective processes,
 chronic inflammatory processes
 and trauma.
o Fixation of the ossicular chain:
 infection
 inflammatory processes
 otosclerosis
o Eustachian tube abnormalities.
Management of conductive hearing loss
 Depends on the underlying condition.
o External ear canal obstruction is usually easy to clear with syringing, o
occasionally using an operating microscope.
o Chronic otitis externa may require long-term medical (or surgical) management.
o Most perforations of the tympanic membrane will resolve spontaneously.
 Persistent defects are usually repaired (myringoplasty) to prevent
recurrent episodes of otitis media.
 Aircrew should not fly after such an operation until the tympanic
membrane healing is assessed and the Eustachian tubes function is
returned to normal.
o Discontinuity or fixation of the ossicular chain require tympanotomy for
diagnosis and surgical correction.
 In aircrew, a stapedotomy fine fenestra technique with vein graph is
preferred.
o Persistent secretory otitis media can be managed by myringotomy and
aspiration of the effusion = insertion of a ventilation tube.
o Chronic middle-ear disease spreading into the mastoid segment may require
mastoidectomy.
 Following such surgery, careful consideration must be givcen to the
ability to perform flying duties.
VERTIGO
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Illusion of movement when the individual believes, falsely, that he/she or the environment is
moving.
Balance is obtained by use of sensory information from the eyes, proprioceptive receptors and
vestibular labyrinth.
Vertigo occurs when information from the vestibular sources conflicts with information from the
other sensory systems.
Vertigo is always a symptom of vestibular defect.
Causes of vertigo:
o Central
o Peripheral
o External influences such as:
 Drugs
 Anaemia
 Hypoglycaemia
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KCL 2011
Hypotension
Viral infection
Syphilis
Middle-ear disease.
Benign paroxysmal positional vertigo
 Most common cause of vertigo.
 Provided by movements of the head,
and last a few seconds.
 Diagnosis with Hallpike manoeuvre.
 Due to detachment of calcium carbonate
crystals from the otoconia within the
posterior semicircular canal.
 Particle-repositioning
manoeuvres
(Epley) have shown remarkable
effectiveness.
 Has a good outcome and most patients
will be fit to fly.
Sudden vestibular failure
 Sudden hypofunction of one labyrinth.
 Causes severe vertigo, usually lasting
over 24 hours.
 The common causes are:
o Head injury
o Viral infection ( ➪labyrinthitis)
o Arterial occlusion
o Diabetic neuropathy
 Sudden vestibular failure usually improves as a result of central compensation.
 Usually recovers with a good restoration of balance.
Ménière's disease
 Unknown aetiology
 Consists of a triad of symptoms:
o Vertigo
o Hearing loss (lower frequencies)
o Tinnitus.
o + symptoms of fullness within the affected ear.
 Remissions and unpredictable exacerbations.
 Usually severe vertigo, lasting for several hours.
 With resolution, the hearing loss recovers between attacks.
o Over time, however, the hearing deteriorates, with a pattern of loss of the lower
frequencies.
 Conservative treatment includes the use of bendrofluazide and betahistine.
 It may possible for some patients with well-controlled symptoms, to return to flying duties
with OML restriction. A full assessment of vestibular function is necessary before returning to
flying duties.
©Jean-Michel Ferrieux-2011
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