Middle ear barotrauma

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Middle ear barotrauma
Other namesEar squeeze, reverse squeeze
Symptoms Hearing loss, local pain
Complications inner ear barotrauma, deafness, vertigo, nausea
CausesPressure difference between the external environment and the gas filled space of the middle ear

Middle ear barotrauma (MEBT), also known to underwater divers as ear squeeze and reverse ear squeeze, is an injury caused by a difference in pressure between the external ear canal and the middle ear. It is common in underwater divers and usually occurs when the diver does not equalise sufficiently during descent or, less commonly, on ascent. Failure to equalise may be due to inexperience or eustachian tube dysfunction, which can have many possible causes. [1] Unequalised ambient pressure increase during descent causes a pressure imbalance between the middle ear air space and the external auditory canal over the eardrum, referred to by divers as ear squeeze, causing inward stretching, serous effusion and haemorrhage, and eventual rupture. During ascent internal over-pressure is normally passively released through the eustachian tube, but if this does not happen the volume expansion of middle ear gas will cause outward bulging, stretching and eventual rupture of the eardrum known to divers as reverse ear squeeze . This damage causes local pain and hearing loss. Tympanic rupture during a dive can allow water into the middle ear, which can cause severe vertigo from caloric stimulation. This may cause nausea and vomiting underwater, which has a high risk of aspiration of vomit or water, with possibly fatal consequences. [1]

Contents

Middle ear barotrauma can also be caused by shock waves and blows to the external ear, particularly in water, and large or fast changes in altitude.

Classification

Deformation stress trauma caused by externally applied (environmental) pressure differences on the middle ear.

Signs and symptoms

Localised pain in one or both ears while the eardrums are stretched, which may be partly relieved if the eardrum ruptures, followed by longer term dull pain in the injured ears,and possible hearing loss. [1]

Complications

Causes

Any cause of sufficiently large and rapid environmental pressure change can potentially cause barotrauma. Several commonly recognised examples are listed below.

Depth changes while diving

When diving, the pressure differences which cause the barotrauma are changes in hydrostatic pressure: There are two components to the surrounding pressure acting on the diver: the atmospheric pressure and the water pressure. A descent of 10 metres (33 feet) in water increases the ambient pressure by an amount approximately equal to the pressure of the atmosphere at sea level. So, a descent from the surface to 10 metres (33 feet) underwater results in a doubling of the pressure on the diver. This pressure change will reduce the volume of a flexible gas-filled space by half. Boyle's law describes the relationship between the volume of the gas space and the pressure in the gas. [3] [4]

Barotraumas of descent are caused by preventing the free change of volume of the gas in a closed space in contact with the diver, resulting in a pressure difference between the tissues and the gas space, and the unbalanced force due to this pressure difference causes deformation of the tissues resulting in cell rupture. [5]

Barotraumas of ascent are also caused when the free change of volume of the gas in a closed space in contact with the diver is prevented. In this case the pressure difference causes a resultant tension in the surrounding tissues which exceeds their tensile strength. [5]

Use of a hyperbaric chamber

Patients undergoing hyperbaric oxygen therapy must equalize their ears to avoid barotrauma. High risk of otic barotrauma is associated with unconscious patients. [6]

Rapid decompression or pressurisation of an artificial environment

Explosive decompression of a hyperbaric environment can produce severe barotrauma, followed by severe decompression bubble formation and other related injury. Rapid uncontrolled decompression from caissons, airlocks, pressurised aircraft, spacecraft, and pressure suits can have similar effects of decompression barotrauma.

Collapse of a pressure resistant structure such as a submarine, submersible, or atmospheric diving suit can cause rapid compression barotrauma.

Rapid change of altitude

A rapid change of altitude can cause barotrauma when internal air spaces cannot be equalised.

Self inflicted barotrauma

Excessively strenuous efforts to equalise the ears using the Valsalva manoeuvre can overpressurise the middle ear, and can cause middle ear barotrauma. [7] This is more likely to happen when one tube opens and the other remains blocked. When a Valsalva maneuver is performed during descent with the intention of opening the Eustachian tubes, but they do not open, intrathoracic pressure, central venous pressure, spinal fluid pressure, and inner ear pressure are raised further above ambient pressure, which increases the pressure difference between perilymph of the inner ear and the gas space of the middle ear. This can cause the round or oval window to rupture outwards, allowing leakage of perilymph into the middle ear. [8]

Blast-induced barotrauma

An explosive blast and explosive decompression create a pressure wave that can induce barotrauma. The difference in pressure between internal organs and the outer surface of the body causes injuries to internal organs that contain gas, such as the lungs, gastrointestinal tract, and ear. [9]

Impact over the external auditory canal

Blows to the outer ear which seal the canal and compress the trapped gas or water can burst an eardrum or cause lesser barotrauma to the middle ear. This is a recognised hazard in several contact sports. [10] [11]

Mechanism

The middle ear is an air-filled space between the external and inner ears. it is separated from the outer ear canal by the eardrum, and connected to the nose and throat cavity by the Eustachian tube. Pressure in the middle ear should match the ambient pressure for normal functioning of hearing. Under-pressure equalisation is normally through periodic opening of the Eustachian tubes during swallowing and yawning, and over-pressure usually vents passively through the collapsed soft part of the tube, as the inner end of the tube is normally closed. [12]

Middle ear barotrauma occurs when a pressure difference develops over the eardrum, causing bulging towards the low pressure side, stretching the tissues which in a severe case can rupture, which immediately equalises the pressure and removes the stretching forces, but leaves local trauma. Stretching of the eardrum to a lesser extent can also cause damage, including engorged blood vessels which exude serum into the surrounding tissues and cause inflammation. increased pressure difference will cause blood vessels to rupture, which may bleed into or inside of the membrane. [2] In divers this usually occurs during descent, when the ambient pressure rises due to increasing hydrostatic pressure. Pressure on the outer side of the eardrum normally closely follows ambient pressure, and in the inner ear pressure equalises through the Eustachian tube, which must be open for gas to flow through. If the diver does not equalise sufficiently a pressure difference may develop that is large enough to damage the eardrum as described. During ascent, the convere occurs, with the internal pressure higher than external. This is usually passively released by the Eustachian tube, but in some cases it does not function correctly causing the eardrum to bulge and possibly rupture outward. [1]

The pressure difference required to rupture the eardrum is thought to be approximately 100 kPA (1 bar or 10 msw). [2]

Diagnosis

Diagnosis is by symptoms, otoscope examination and history. [1]

Differential diagnosis

Differential diagnosis should consider alternative conditions which could produce the same symptoms. Depending on the actual symptoms presented, such conditions could include: otitis media, otitis externa, cerumen impaction, inner ear decompression sickness, caloric stimulation, benign paroxysmal positional vertigo (BPPV), vestibular neuronitis, Ménière's disease, acoustic neuroma, and possibly others. [2]

If there is sensorineural hearing loss or vertigo after exposure to a large change in ambient pressure or a change of breathing gas, the possibility of concurrent barotrauma and inner ear decompression sickness (IEDCS) should be considered, because the symptoms can be very similar, and IEDCS is treated with recompression and hyperbaric oxygen. [2]

Prevention

Among people playing underwater and swimming contact sports, such as water polo, underwater hockey or underwater rugby, a cap with perforated ear cups is often used, such as a water polo cap.

The a risk of stretched or burst eardrums, can be reduced by any of a variety of methods to let air into or out of the middle ears via the Eustachian tubes. Sometimes swallowing will open the Eustachian tubes and equalise the ears. [13] Most of the methods are less likely than the Valsalva maneuver to cause collateral damage to the inner ear.

The Eustachian tubes will close completely with a pressure difference of about 3msw (10fsw) above the middle ear pressure, at which point none of the equalising maneuvers will work, and the pressure difference must be decreased to make it possible again, This implies ascending during a dive, venting some of the pressure from a hyperbaric chamber, and ascending to a higher altitude in an aircraft, which is not always practicable. [2]

Treatment and management

If inner ear barotrauma and decompression sickness can be excluded, treatment may include any combination of short term use of nasal decongestants, intranasal steroid sprays and antibiotics for secondary infections. Surgical repair of persistent perforation of the eardrum may be necessary. [1]

Treatment is in proportion to the injury, and may include education to reduce risk of repeat injury. It is often treated conservatively and usually resolves without medical intervention. Some cases are due to simple ambient pressure change and Eustachian tube dysfunction at the time, while others may be partly the consequence of a less obvious underlying condition. [2]

Antibiotics are not usually needed unless infection develops or the ear was exposed to contaminated water. [2]

MEBT may occur during pressurization for hyperbaric treatment for other conditions. If this happens, pressurization should be stopped and if necessary, reversed sufficiently to allow the Eustachian tubes to be opened more easily, and the middle ear to be cleared. Physician-prescribed oral decongestants may help. Compression should normally be aborted if equalization remains unsuccessful. In urgent clinical hyperbaric treatment, an emergency needle myringotomy or placement of tympanostomy ventilation tubes may be required. These will passively equalise the middle ear, and are effective with an unconscious person. [2]

Outcomes

Mild symptoms may resolve within 1 to 2 weeks. [13] All symptoms should be resolved before diving or flying recommences, including healing of any perforations of the eardrum, and equalisation must be possible, [1] with no abnormal sounds, and hearing is normal. [13]

Modified Teed classification for middle ear barotrauma [1]
Barotrauma gradeOtoscope findingsTypical time to return to diving
0Normal tympanic membrane7 to 10 days for complete resolution
1Tympanic membrane erythematous/inflamede7 to 10 days for complete resolution
3Gross haemorrhage of the tympanic membraneSix weeks needed for blood reabsorption
4Extensive free blood in middle ear with bubbles
visible behind tympanic membrane (haemotympanum)		Six weeks needed for blood reabsorption
5Perforation of the tympanic membraneThree months to heal perforation
No grade 2 is defined in this modification

Epidemiology

Middle ear barotrauma is the single most common diving disorder for which treatment is sought, at nearly 50% of all reported diving injuries. Many more milder cases may go unreported.

A history of head and neck cancers, with associated radiation treatment, has been associated with a relatively higher incidence of MEBT, possibly due to radiation damage of the soft tissues of the Eustachian tubes or pharynx. [2]

See also

Related Research Articles

<span class="mw-page-title-main">Decompression sickness</span> Disorder caused by dissolved gases forming bubbles in tissues

Decompression sickness is a medical condition caused by dissolved gases emerging from solution as bubbles inside the body tissues during decompression. DCS most commonly occurs during or soon after a decompression ascent from underwater diving, but can also result from other causes of depressurisation, such as emerging from a caisson, decompression from saturation, flying in an unpressurised aircraft at high altitude, and extravehicular activity from spacecraft. DCS and arterial gas embolism are collectively referred to as decompression illness.

<span class="mw-page-title-main">Eardrum</span> Membrane separating the external ear from the middle ear

In the anatomy of humans and various other tetrapods, the eardrum, also called the tympanic membrane or myringa, is a thin, cone-shaped membrane that separates the external ear from the middle ear. Its function is to transmit sound from the air to the ossicles inside the middle ear, and then to the oval window in the fluid-filled cochlea. Hence, it ultimately converts and amplifies vibration in the air to vibration in cochlear fluid. The malleus bone bridges the gap between the eardrum and the other ossicles.

<span class="mw-page-title-main">Eustachian tube</span> Tube connecting middle ear to throat

The Eustachian tube, also called the auditory tube or pharyngotympanic tube, is a tube that links the nasopharynx to the middle ear, of which it is also a part. In adult humans, the Eustachian tube is approximately 35 mm (1.4 in) long and 3 mm (0.12 in) in diameter. It is named after the sixteenth-century Italian anatomist Bartolomeo Eustachi.

<span class="mw-page-title-main">Valsalva maneuver</span> Technique for equalising pressure in the middle ears

The Valsalva maneuver is performed by a forceful attempt of exhalation against a closed airway, usually done by closing one's mouth and pinching one's nose shut while expelling air, as if blowing up a balloon. Variations of the maneuver can be used either in medical examination as a test of cardiac function and autonomic nervous control of the heart, or to clear the ears and sinuses when ambient pressure changes, as in scuba diving, hyperbaric oxygen therapy, or air travel.

<span class="mw-page-title-main">Air embolism</span> Vascular blockage by air bubbles

An air embolism, also known as a gas embolism, is a blood vessel blockage caused by one or more bubbles of air or other gas in the circulatory system. Air can be introduced into the circulation during surgical procedures, lung over-expansion injury, decompression, and a few other causes. In flora, air embolisms may also occur in the xylem of vascular plants, especially when suffering from water stress.

<span class="mw-page-title-main">Barotrauma</span> Injury caused by pressure

Barotrauma is physical damage to body tissues caused by a difference in pressure between a gas space inside, or in contact with, the body and the surrounding gas or liquid. The initial damage is usually due to over-stretching the tissues in tension or shear, either directly by an expansion of the gas in the closed space or by pressure difference hydrostatically transmitted through the tissue. Tissue rupture may be complicated by the introduction of gas into the local tissue or circulation through the initial trauma site, which can cause blockage of circulation at distant sites or interfere with the normal function of an organ by its presence. The term is usually applied when the gas volume involved already exists prior to decompression. Barotrama can occur during both compression and decompression events.

Decompression Illness (DCI) comprises two different conditions caused by rapid decompression of the body. These conditions present similar symptoms and require the same initial first aid. Scuba divers are trained to ascend slowly from depth to avoid DCI. Although the incidence is relatively rare, the consequences can be serious and potentially fatal, especially if untreated.

Dysbarism refers to medical conditions resulting from changes in ambient pressure. Various activities are associated with pressure changes. Underwater diving is the most frequently cited example, but pressure changes also affect people who work in other pressurized environments, and people who move between different altitudes.

<span class="mw-page-title-main">Diving medicine</span> Diagnosis, treatment and prevention of disorders caused by underwater diving

Diving medicine, also called undersea and hyperbaric medicine (UHB), is the diagnosis, treatment and prevention of conditions caused by humans entering the undersea environment. It includes the effects on the body of pressure on gases, the diagnosis and treatment of conditions caused by marine hazards and how relationships of a diver's fitness to dive affect a diver's safety. Diving medical practitioners are also expected to be competent in the examination of divers and potential divers to determine fitness to dive.

Diving disorders, or diving related medical conditions, are conditions associated with underwater diving, and include both conditions unique to underwater diving, and those that also occur during other activities. This second group further divides into conditions caused by exposure to ambient pressures significantly different from surface atmospheric pressure, and a range of conditions caused by general environment and equipment associated with diving activities.

<span class="mw-page-title-main">Underwater diving</span> Descending below the surface of the water to interact with the environment

Underwater diving, as a human activity, is the practice of descending below the water's surface to interact with the environment. It is also often referred to as diving, an ambiguous term with several possible meanings, depending on context. Immersion in water and exposure to high ambient pressure have physiological effects that limit the depths and duration possible in ambient pressure diving. Humans are not physiologically and anatomically well-adapted to the environmental conditions of diving, and various equipment has been developed to extend the depth and duration of human dives, and allow different types of work to be done.

In aviation and underwater diving, alternobaric vertigo is dizziness resulting from unequal pressures being exerted between the ears due to one Eustachian tube being less patent than the other.

<span class="mw-page-title-main">Ear clearing</span> Equalising of pressure in the middle ears

Ear clearing or clearing the ears or equalization is any of various maneuvers to equalize the pressure in the middle ear with the outside pressure, by letting air enter along the Eustachian tubes, as this does not always happen automatically when the pressure in the middle ear is lower than the outside pressure. This need can arise in scuba diving, freediving/spearfishing, skydiving, fast descent in an aircraft, fast descent in a mine cage, and being put into pressure in a caisson or similar internally pressurised enclosure, or sometimes even simply travelling at fast speeds in an automobile.

The Frenzel Maneuver is named after Hermann Frenzel. The maneuver was developed in 1938 and originally was taught to dive bomber pilots during World War II. The maneuver is used to equalize pressure in the middle ear. Today, the maneuver is also performed by scuba divers, free divers and by passengers on aircraft as they descend.

In physiology, isobaric counterdiffusion (ICD) is the diffusion of different gases into and out of tissues while under a constant ambient pressure, after a change of gas composition, and the physiological effects of this phenomenon. The term inert gas counterdiffusion is sometimes used as a synonym, but can also be applied to situations where the ambient pressure changes. It has relevance in mixed gas diving and anesthesiology.

<span class="mw-page-title-main">Ascending and descending (diving)</span> Procedures for safe ascent and descent in underwater diving

In underwater diving, ascending and descending is done using strict protocols to avoid problems caused by the changes in ambient pressure and the hazards of obstacles near the surface such as collision with vessels. Diver certification and accreditation organisations place importance on these protocols early in their diver training programmes. Ascent and descent are historically the times when divers are injured most often when failing to follow appropriate procedure.

Hypobaric decompression or altitude decompression is the reduction in ambient pressure below the normal range of sea level atmospheric pressure. Altitude decompression is the natural consequence of unprotected elevation to altitude, while hypobaric decompression is due to intentional or unintentional release of pressurization of a pressure suit or pressurized compartment, vehicle or habitat, and may be controlled or uncontrolled, or the reduction of pressure in a hypobaric chamber.

<span class="mw-page-title-main">Physiology of decompression</span> The physiological basis for decompression theory and practice

The physiology of decompression is the aspect of physiology which is affected by exposure to large changes in ambient pressure, and involves a complex interaction of gas solubility, partial pressures and concentration gradients, diffusion, bulk transport and bubble mechanics in living tissues. Gas is breathed at ambient pressure, and some of this gas dissolves into the blood and other fluids. Inert gas continues to be taken up until the gas dissolved in the tissues is in a state of equilibrium with the gas in the lungs,, or the ambient pressure is reduced until the inert gases dissolved in the tissues are at a higher concentration than the equilibrium state, and start diffusing out again.

Human physiology of underwater diving is the physiological influences of the underwater environment on the human diver, and adaptations to operating underwater, both during breath-hold dives and while breathing at ambient pressure from a suitable breathing gas supply. It, therefore, includes the range of physiological effects generally limited to human ambient pressure divers either freediving or using underwater breathing apparatus. Several factors influence the diver, including immersion, exposure to the water, the limitations of breath-hold endurance, variations in ambient pressure, the effects of breathing gases at raised ambient pressure, effects caused by the use of breathing apparatus, and sensory impairment. All of these may affect diver performance and safety.

Inner ear decompression sickness, (IEDCS) or audiovestibular decompression sickness is a medical condition of the inner ear caused by the formation of gas bubbles in the tissues or blood vessels of the inner ear. Generally referred to as a form of decompression sickness, it can also occur at constant pressure due to inert gas counterdiffusion effects.

References

  1. 1 2 3 4 5 6 7 8 Nofz, Lyndon; Porrett, Jemma; Yii, Nathan; De Alwis, Nadine. "Diving related otological injuries". www1.racgp.org.au. Reprinted from AJGP vol 49, no 8, August 2020 The Royal Australian College of General Practitioners 2020
  2. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ONeill, Owen J.; Brett, Kaighley; Frank, Anthony J. (1 May 2022). "Middle Ear Barotrauma". www.ncbi.nlm.nih.gov. StatPearls Publishing LLC. Retrieved 1 August 2022.
  3. ↑ US Navy Diving Manual, 6th revision. United States: US Naval Sea Systems Command. 2006.
  4. ↑ "Mechanism of Injury for Pulmonary Over-Inflation Syndrome". DAN Medical Frequently Asked Questions. Diver's Alert Network. Retrieved 17 January 2017.
  5. 1 2 Brubakk, A. O.; Neuman, T. S. (2003). Bennett and Elliott's physiology and medicine of diving, 5th Rev ed. United States: Saunders Ltd. p. 800. ISBN   978-0-7020-2571-6.
  6. ↑ Lehm, Jan P.; Bennett, Michael H. (2003). "Predictors of middle ear barotrauma associated with hyperbaric oxygen therapy". South Pacific Underwater Medicine Society Journal. 33: 127–133. Archived from the original on 22 July 2009.{{cite journal}}: CS1 maint: unfit URL (link)
  7. ↑ "Valsalva Maneuver". www.mercy.com. Retrieved 2 August 2022.
  8. ↑ Bove, Alfred A.; Neuman, Tom S. (2016). "78 - Diving Medicine". Murray and Nadel's Textbook of Respiratory Medicine. Vol. 2 (6th ed.). ScienceDirect - Elsevier. pp. 1385–1395. doi:10.1016/B978-1-4557-3383-5.00078-6.
  9. ↑ Torkki, Markus; Koljonen, Virve; Sillanpää1, Kirsi; Tukiainen, Erkki; Pyörälä, Sari; Kemppainen, Esko; Kalske, Juha; Arajärvi, Eero; Keränen, Ulla; Hirvensalo, Eero (August 2006). "Triage in a Bomb Disaster with 166 Casualties". European Journal of Trauma. 32 (4): 374–80. doi:10.1007/s00068-006-6039-8. S2CID   32968659.{{cite journal}}: CS1 maint: numeric names: authors list (link)
  10. ↑ Landsberg PG (December 1976). "South African Underwater Diving Accidents, 1969–1976" (PDF). SA Medical Journal. 50 (55): 2156. PMID   1013870 . Retrieved 29 March 2013.
  11. ↑ Hutson, Michael; Speed, Cathy, eds. (2011). "Section 4: Special considerations – Water polo". Sports Injuries (illustrated ed.). Oxford, UK: Oxford University Press. p. 466. ISBN   9780199533909.
  12. ↑ Vernick, David M. Deschler, Daniel G. (ed.). "Ear barotrauma". www.uptodate.com. Retrieved 3 August 2022.
  13. 1 2 3 Kay, E. (2000). "Prevention of middle ear barotrauma". Doc's Diving Medicine. staff.washington.edu. Archived from the original on 16 January 2017. Retrieved 13 January 2017.

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