Review articles 47 The effects of barotrauma on the ear N Roocroft, E Hogg, R Williams

Abstract

Ear barotrauma represents a spectrum of pathology ranging from a mild, self-limiting condition, to significant morbidity with occupational implications. This article describes the anatomy of a normal functioning ear and how this function is disrupted in patients with ear barotrauma. It will discuss the clinical features of the condition, as well as how to investigate and manage a patient presenting with ear barotrauma, including the occupational considerations that should be made.

Roocroft N, Hogg E, Williams R. J R Nav Med Serv 2019;105(1):47–52

Introduction The whole structure can be divided into the outer, middle Barotrauma is an injury caused by a change of pressure in and inner ear. The outer ear comprises the pinna and external an enclosed gas-filled space. Ear (or otic) barotrauma refers auditory canal, which ends at the tympanic membrane (TM). to the consequences of changes in pressure in the ear which Sound travels down the external auditory canal to the TM most commonly occur secondary to alterations in a person’s where it is then transmitted through the malleus, incus and altitude or depth in water. Over the past century, developments stapes, the three small bones which occupy the enclosed, air- in technology have allowed humans to travel to both higher filled middle ear. altitudes and greater depths. The pressures found in these environments can cause barotrauma injuries due to effects The middle and inner ear are separated by two membranes; on hollow, air-containing structures. Royal Navy (RN) the round and oval windows. The oval window transmits personnel are at risk of these injuries due not only to their vibrations from the stapes bone in the air-filled middle ear, service roles but also to the recreational activities which to the fluid-filled inner ear. Propagation of waves through the many pursue. This review will outline the clinical features of perilymph fluid in the inner ear is transduced to nerve impulses ear barotrauma; discuss how to assess and diagnose a patient in the cochlea, along the auditory pathway which ends in the with the condition; and detail management and occupation auditory cortex, registering as sound. considerations that should be made. It will mainly focus on the condition in divers, but will also briefly consider aviation- Pressure in the middle ear must equal pressure in the outer related barotrauma. ear (atmospheric pressure) for the TM to vibrate optimally to allow maximal transmission of sound energy into the inner ear. The Eustachian tube connects the middle ear to the Normal ear anatomy and pathophysiology nasopharynx, and functions to equalise pressure on both sides In order to understand the sequelae of barotrauma, it is of the TM. One-third of the Eustachian tube is surrounded important to understand the anatomy of the normal functioning by bone, and the remainder by cartilage. Its diameter varies ear (Figure 1). between individuals. If the pressure in the outer ear changes,

Tympanic Outer membrane ear canal

Inner ear

Middle Eustachian ear tube Round and oval windows

Figure 1: Diagram illustrating the anatomy of a normal ear. Image downloaded from https://www.dreamstime.com. 48 Journal of the Royal Naval Medical Service 2019; 105(1) the Eustachian tube should function to allow pressure in the the pressure reduces, air expands and must escape, normally middle ear to equalise pressure in the outer ear. If this does via the Eustachian tube to the nasopharynx. Dysfunction not happen the TM can distort, and injury from barotrauma in the Eustachian tube, or narrowing as a result of an upper can occur. respiratory tract infection, may obstruct the flow of air . This leads to distension and increased pressure in the middle ear The most common example of this pressure change occurs cavity, and can result in the same pressure effects as seen in during air travel. On ascent there is an expansion of gas in the middle ear barotrauma during descent. middle ear, which results in the TM being pushed laterally, before the Eustachian tube is forced open and excess air is Inner ear barotrauma released. The reverse occurs in descent, resulting in a negative Damage to either the round or oval window is classified as pressure in the middle ear compared to the surrounding inner ear barotrauma. This can be caused on descent if the environment and a relative vacuum in the middle ear cavity. diver does not successfully equilibrate middle ear pressure Passage of air from the nasopharynx into the middle ear cavity despite repeated Valsalva manoeuvres. At a certain depth, is required to offset this; unlike the situation during ascent, the Eustachian tube, which is usually collapsed, may become this is an active process through the actions of the levator ‘locked’ due to the increased pressure differential between palati muscles and can be achieved by yawning, swallowing itself and the middle ear. When this locking occurs, the power 1 or performing the Valsalva manoeuvre. of the levator palati muscles is insufficient to counter the pressure differential and open the Eustachian tube, which can The same process occurs in diving, except that only 10 metres only be reopened on ascent, where the pressure difference is of depth is required to double atmospheric pressure. The suitably reduced.1 The Valsalva manoeuvre increases pressure significant pressure change so close to the surface means that in the cerebrospinal fluid which is in equilibrium with ear barotrauma injuries are found predominantly in divers, the inner ear fluid. If a diver continues to attempt Valsalva on whom the remainder of the review will focus. In diving, unsuccessfully, inner ear pressure increases, which in turn can barotrauma can affect the outer ear, middle ear, or inner ear result in the gradient between the inner ear perilymph and the and can occur as a result of pressure changes during both middle ear becoming large enough to rupture the round or oval descent and ascent. window, causing perilymph to leak from the inner ear through a perilymphatic fistula.2 Outer ear barotrauma Leakage of fluid into the middle ear affects both the Outer ear barotrauma may occur if air becomes trapped in the and balance components of the inner ear, potentially resulting external auditory canal during descending during a dive. This in incapacitation during a dive, through acute vertiginous may be due to several factors: a hood having a tight fit; earwax; symptoms; however, signs can also present more subtly hours bony growths in the ear canal (exostoses), or ear-plugs. The to days after the dive has taken place.3 change in pressure on the trapped air causes damage to the tissues of the external auditory canal. Clinical history

Middle ear barotrauma A full clinical history is required, comprising analysis of pre- dive, dive, and post-dive symptoms. Barotrauma can occur Middle ear barotrauma is the most common form of in any dive, but patients will often report difficulty near the barotrauma. When a pressure differential develops across the surface, where the change in pressure is the greatest. Before TM on descent, the patient may experience the sensation of the dive, it is important to assess the presence of risk factors fullness in the ear, with a desire to equalise the pressure. The for Eustachian tube dysfunction. These include concurrent relative vacuum in the middle ear causes the TM to become upper respiratory tract infection, rhinosinusitis, and adenoid displaced inwards, so-called “middle ear squeeze”, resulting hypertrophy. In addition, the use of equipment which may in pain (otalgia) in the affected ear. If the relative difference have blocked the external auditory canal, such as ear-plugs or in pressure continues to increase, an effusion may develop as a tight-fitting hood, should also be determined. tissue fluid is drawn into the middle ear. Pressure changes may also cause damage to the middle ear vasculature resulting in Patients will almost invariably report a history of having had a haemotympanum (blood within the middle ear cleft) or in difficulty equalising their ears during the dive; this can be due 1 damage to the TM itself, with potential perforation or rupture. to the failure of a conscious effort, or to lack of opportunity to If cold water enters the middle ear following TM rupture, a equalise, such as a rushed ascent in an emergency. caloric effect can occur which leads to transient unilateral vestibular dysfunction, experienced by the subject as acute Symptoms after the dive will depend on the injury sustained. vertiginous symptoms.2 Deformity of the TM, reduced Outer ear barotrauma causes a sensation of blockage in the membrane mobility and otitis media with effusion may result ear, otalgia, and discomfort resulting from damage to the in a conductive . external auditory canal. Middle ear barotrauma may present with similar symptoms, but due to the damage to the tissues in Barotrauma can also occur in the middle ear on ascent, albeit the middle ear, there may also be hearing loss, due to blood or less commonly. As a diver ascends through the water and fluid in the middle ear, or TM perforation. Review articles 49

Patients with inner ear barotrauma predominantly report In mild middle ear barotrauma, there is distortion of the impaired hearing (which may not be noticed until after a dive), TM (Teed scale grade 1). Moderate middle ear barotrauma imbalance, or both. These may be accompanied by nausea and is characterised by a haemorrhagic TM, with possible vomiting,2 in addition to symptoms of middle ear trauma, haemotympanum or fluid in the middle ear (Teed scale grades which often occurs prior to inner ear trauma. 2-4). The TM may also be distorted. In severe middle ear barotrauma there is perforation of the TM (Teed scale grade 5). Clinical examination Outer ear barotrauma presents with signs indicating disruption It may be difficult to see a perforation, and wax should be to the tissues in the external auditory canal, including removed, if possible, to aid diagnosis by providing full ecchymosis, oedema of the skin and occasionally blood.. visualisation of the membrane. Other signs of perforation are blood in the external auditory canal, or whistling from the ear The severity of middle ear barotrauma can be determined by when the patient performs the Valsalva manoeuvre. the appearance of the TM on otoscopy. Middle ear barotrauma can be mild, moderate or severe, based on this appearance, Middle ear barotrauma resulting in either serous fluid or blood which is classified using the Teed scale.4 The greater the Teed in the middle ear, or TM perforation, causes a conductive 6 score, the greater the severity of injury and the longer the hearing loss, whereas inner ear barotrauma presents with 2 likely recovery period. The appearance of the TM during each sensorineural hearing loss. Rinne and Weber tests help to 7 of these stages is shown in Figure 2.5 differentiate between the two.

Grade 0 Grade 1

Grade 2 Grade 3

Grade 4 Grade 5

Figure 2: Images showing the appearance of the TM during grades 0-5 of the Teed scale for classifying middle ear barotraumas (from Edmonds et al.).5 50 Journal of the Royal Naval Medical Service 2019; 105(1)

Inner ear barotrauma can result in imbalance. The unable to equalise on demand, and a continued failure to Unterberger test, in which a patient walks on the spot with equalise their ears necessitates a referral for ENT assessment their eyes closed and their arms out in front of them, can be of Eustachian tube function. used to help assess for vestibular pathology. If the patient rotates to one side, the test is positive, and in the context of Factors which affect normal Eustachian tube function, such as ear barotrauma suggests an inner ear problem.8 Other tests, upper respiratory tract infections and rhinosinusitis, predispose such as inspection for , and analysis of a patient’s to injury as they reduce the ability to equalise successfully gait, can support this. underwater. Avoidance of diving is recommended when these conditions are present. Investigations Divers should not wear ear-plugs when diving, and should Pure tone should be tested, as it provides a have removed significant ear wax, as they both predispose subjective assessment of hearing, and can be used to assess to outer ear barotrauma. Education of divers to recognise if there is a conductive, sensorineural or mixed hearing symptoms and how to manage them is part of service dive impairment. This should be compared to pre-dive audiometry training and should be borne in mind for recreational diving; to identify whether there has been pre-existing impairment, or for instance, if descending and feeling the squeeze associated whether the hearing loss is new in onset. Most diving when with middle ear barotrauma, divers should ascend to a level deployed occurs whilst a ship is alongside, or close to shore, where the ears can be equalised. Similarly, learning to equalise allowing for early referral within 24 hours. If referral is not properly, never forcefully equalising, descending feet down, immediately available in the maritime setting, it should be and equalising on the surface before descending all reduce the made at the next port of call. risk; divers should also be prepared to abort any dive if they have significant difficulty equalising. Tympanometry, which tests middle ear function and the compliance of the TM, can be utilised to further investigate The use of oral or nasal decongestants and antihistamines whether the barotrauma is middle or inner ear in nature. Inner prior to flying may reduce obstruction caused through upper ear barotrauma may result in a normal test, whereas in middle respiratory tract infections or allergic oedema.1 However, ear barotrauma, the test shows reduced pressure, or a flat these should not to be used when diving, due to the risk of the tympanogram. A flat tympanogram with a normal middle ear medication effect waning mid-dive and leading to a relative volume suggests an effusion, whereas a flat result with a high reduction in Eustachian tube function. If these medications are volume may represent TM perforation. needed to equalise, then the individual should not dive.

Differential diagnosis Similarly, ventilation tubes can be inserted through the TM Inner ear decompression illness (DCI) is the main differential if a subject has persistent barotrauma-related problems when diagnosis for inner ear barotrauma, potentially presenting with flying, but this is contraindicated in diving due to the risk of similar symptoms and signs. The dive profile is important exposing the middle ear to water. to help differentiate the two, with DCI less likely if adive is shallow. Whilst DCI usually presents after a latent period Treatment - pre-shore or pre-hospital post-dive, barotrauma usually presents during the dive itself, Patients with uncomplicated outer ear barotrauma rarely after failed equalisation attempts. Generally, DCI presents present to clinicians. Middle ear barotrauma is common and with milder inner ear symptoms than barotrauma, and often may be managed in primary healthcare; however, it also often presents with other cranial nerve symptoms and signs; if goes unreported in patients. Inner ear barotrauma is rare, but suspected, a full neurological examination is warranted. In may be associated with significant morbidity. An emergency cases where there is doubt, the case should be discussed with referral to an ENT specialist should be made if it is suspected. the Duty Diving Medical Officer at the Institute of Naval Medicine (+44 (2392)768020). Most outer and middle ear barotrauma injuries, including those with perforations, heal with time if further injury is avoided, Rarely, acute otitis media may be mistaken for middle ear and can therefore be managed in primary care with watchful barotrauma, as it presents with similar symptoms and signs; waiting. Many middle ear injuries will settle within weeks a timeline of when symptoms commenced can help to of presentation, but if TM perforation persists beyond six differentiate between the two. weeks then a routine secondary care referral should be made. In occupational divers, early referral is advocated to limit the Clinical management impact of such injuries on the patient’s function. Pain can be managed by simple analgesics and dry, warm compresses over Prevention the ear. Individuals must be able to equalise their ears during a diving medical, in order to prove their fitness to dive. This Infection prevention is important. In cases of TM perforation, can be demonstrated during otoscopy by auto-inflation when water should be prevented from entering the external ear canal performing the Valsalva manoeuvre. Some people may be as it increases the risk of infection. Ear protection is needed Review articles 51 when showering, and swimming is prohibited until the TM is or both), should be referred to an ENT specialist as soon as healed. This is best achieved using ear-plugs of cotton wool possible. generously coated in petroleum jelly. Surgical tympanotomy, for exploration of a fistula and to Whilst there is no routine need for antibiotics, if the ear canal patch the round or oval window, may be offered if significant or TM show signs of infection, this should be treated with non- pathology is present, such as if there are severe vestibular ototoxic antibiotic drops (e.g. ciprofloxacin drops).6 If the TM symptoms or hearing loss, deterioration of symptoms, or is perforated, then oral antibiotics are recommended due to lack of improvement over 10 days.9 However, the benefits the risks of infection associated with the surrounding water of the procedure are currently uncertain and conservative at the time of the barotrauma.1 Due to the risk of ototoxicity, management is the recommended first line therapy for inner ear-drop preparations containing aminoglycoside antibiotics ear barotrauma. should be used with caution if there is a perforation. Patients can return to the water once the TM has healed and they have Sensorineural loss may be permanent despite early demonstrated that they can equalise. intervention. Dizziness usually resolves even when managed conservatively, but this can take many weeks or months as, Treatment – hospital whilst there is often a rapid initial improvement, there is also further progression over a period of time owing to the Whilst most TM perforations will heal within a few weeks, plasticity of the brain adapting to the injury. Given the relative if not healed within this time patients should be referred to risk versus the uncertain benefit of surgical management, it is an ENT specialist for consideration of surgical repair of the imperative that all options are explained to the patient prior perforation via a myringoplasty. to consent being sought for surgical treatment. Inner ear barotrauma is rare but can be catastrophic for a Occupational considerations military career. All suspected cases of inner ear barotrauma (patients presenting with sensorineural , dizziness, Assessment and recovery of fitness to dive is an important part of the management of divers suffering a barotrauma injury. For

History: Chronology; pre, during, post-dive Symptoms; pain, fullness, hearing loss, imbalance/

Examination: External ear; damage to ear canal? TM; Teedscore? Perforation? Rinne and Weber;conductive or sensorineural loss? Vestibular signs; Unterberger positive? Nystagmus? Gait? Cranial nerves; if DCS differential.

Investigations: ; conductive versus sensorineural (if available) Tympanometry; middle versus inner ear

Outer Ear Middle Ear: Inner Ear: Pre-shore: Pre-shore: Hospital: - Analgesia - Analgesia - Refer all - Warm compress - Warm compress - Future diving - Advice - Advice contraindicated - Antibiotics (if TM rupture) Hospital: - ENT referral if TM perforation not healed 3/12

Figure 3: Flowchart summarising the diagnosis and management of ear barotrauma. 52 Journal of the Royal Naval Medical Service 2019; 105(1) all barotrauma injuries short of a perforation, diving must not Examiner prior to return to flying. This decision will depend be resumed until the diver can completely equalise pressure, on the degree of the original barotrauma and resolution of any due to the risk of further barotrauma injury. Any patient with underlying problems.2 For other military personnel, flying a TM perforation can return to diving once the rupture has should be avoided if possible until healing of the injury, completely healed or been surgically corrected, and the diver or surgical repair, is complete; this will potentially affect can equalise pressure.10 immediate deployability.

With regards to inner ear barotrauma, due to the risk of The diagnosis and subsequent management of barotrauma additional damage from further diving, and the importance injuries is summarised in Figure 3. of protecting the remaining good ear,11 the patient should be made permanently medically unfit to dive.10 For patients Conclusion with hearing loss, a functional hearing check, in addition to Ear barotrauma is the most common injury sustained from audiometry results, should be used to determine whether the diving. Whilst the majority of cases are mild and self-limiting, patient is able to complete both routine and hearing-critical it has the potential to cause significant morbidity through inner duties. Aircrew, communications technicians and submarine ear manifestations, which can have occupational implications. sensor warfare specialists require a higher standard of hearing Advice given prior to diving can minimise the risk of this on audiogram than other trades in the RN.12 occurring. A thorough history and examination can aid diagnosis, enabling appropriate treatment in primary care, and Whilst the majority of aircrew in the RN operate rotary-wing accurate referral to secondary care when merited. aircraft, and so do not experience the same degree of pressure change as fast jet crews, all aviators suffering barotrauma Conflicts of interest injuries should be assessed by a Military Aircrew Medical The authors have no conflicts of interest.

References

1. Caldera S. . In: Ernsting’s Aviation and Space Medicine. CRC Press; 2016. p. 527-9. 2. Bove AA. Diving medicine. Am J Respir Crit Care Med 2014;189:1479-86. 3. Duplessis C, Hoffer M. in an active Navy diver: a review of inner ear barotrauma, tinnitus and its treatment.Undersea Hyperbaric Med 2006;33:223-30. 4. Teed, RW. Factors producing obstruction of the auditory tube in submarine personnel. US Navy Medical Bulletin. 1944. 42(2):293-303. 5. Edmonds C, Lowry C, Pennefather J. Diving and Subaquatic Medicine. Hodder Arnold; 1994. 6. Eagles K, Fralich, L, Stevenson JH. Ear trauma. Clin Sports Med 2013;32:303-16. 7. Henderson A, Wadell A, Pearson C. A review of the diagnosis and management of sudden hearing loss in the military population. J R Nav Med Serv 2016;102(2):110-6. 8. Unterberger’s stepping test - General Practice Notebook. [Internet] Cited 2017 Apr 14. Available from: http://www.gpnotebook.co.uk/ simplepage.cfm?ID=-194314209. 9. Eliott EJ, Smart DR. The assessment and management of inner ear barotrauma in divers and recommendations for returning to diving. Diving Hyperb Med 2014; 44(4):208-22. 10. Ministry of Defence. Handbook of Naval Medical Standards. BR 1750a 2013; Chapter 12. 11. Paris – v – Stepney Borough Council [1950] UKHL 3 (AC367) House of Lords. 12. Ministry of Defence. Handbook of Naval Medical Standards. BR1750a 2013; Chapter 07.

Authors

Surgeon Lieutenant NT Roocroft Royal Navy Medical Officer, HMS ARGYLL, BFPO 210 [email protected]

Dr E Hogg Aintree University Hospitals NHS Foundation Trust, Liverpool, UK

Surgeon Commander R Williams Royal Navy Consultant in ENT Surgery, DMG SW, University Hospitals Plymouth NHS Trust, Plymouth