|Ahead of print publication
Middle ear barotrauma and facial baroparesis in underwater diving
Santosh Kumar Swain1, Nibi Shajahan1, Anil Mohapatra2
1 Department of Otorhinolaryngology, IMS and SUM Hospital, Siksha “O” Anusandhan University, Bhubaneswar, Odisha, India
2 Department of Marine Sciences, Zoological Survey of India, Ganjam, Odisha, India
|Date of Submission||03-Apr-2020|
|Date of Decision||25-May-2020|
|Date of Acceptance||24-Aug-2020|
|Date of Web Publication||28-Sep-2020|
Santosh Kumar Swain,
Department of Otorhinolaryngology, IMS and Sum Hospital, Siksha “O” Anusandhan University, K8, Kalinga Nagar, Bhubaneswar - 751 003, Odisha
Source of Support: None, Conflict of Interest: None
Although middle ear barotrauma is considered uncommon, it may involve a great safety risk to the diver. The medical problems associated with diving are seen as a worldwide concern. Trying to cope with such clinical manifestations of middle ear barotrauma such as otalgia, facial palsy ear, fullness, and vertigo, the underwater diving can be very distressing and dangerous. In case of underwater divers, whether experienced or novice, there are several hazards assumed whenever dive is planned. Out of different hazards, there is a spectrum of illness including middle ear barotrauma. This review article focuses on the etiopathology, clinical presentations, facial baroparesis, and current management of the middle ear barotrauma among underwater divers. This article will surely increase awareness among the clinicians and people those are practicing underwater diving and help them to resolve this problem to a great extent.
Keywords: Eustachian dysfunction, facial baroparesis, middle ear barotrauma, scuba diving
| Introduction|| |
Middle ear barotrauma is the most common diving-related medical disorder, affecting more than 40% of the underwater divers at some points of diving. Underwater diving or scuba diving is becoming the popular recreational activity among the present day's youths. However, it has some medical complications, which include a few important neuro-otological hazards. A rapid alteration of pressure in air-filled body parts makes them liable to pathological manifestations during ascent or descent. The middle ear is an enclosed air-filled cavity and the only mechanism of pressure equalization is through the nasopharynx through Eustachian tube. Eustachian tube dysfunction leads to difficult in pressure equalization of the middle ear and outside environment, leading to pathogenesis for middle ear barotrauma. Middle ear barotrauma is usually seen during descent or ascent phases of the diver. Middle ear barotrauma is a common type of diving injury which causes hemorrhage and rupture of the tympanic membrane. Increased pressure in the middle ear can lead to facial nerve paralysis.
Underwater diving is becoming a popular sports or recreational activity; however, research regarding the diving and its audiological consequences is very minimal. As a result, the divers or participants have little or no knowledge regarding the outcome of the underwater diving in deep sea on the auditory system.
| Methods of Literature Search|| |
Research articles regarding middle ear barotrauma in underwater diving were searched through a multiple systemic approaches. First, we conducted an online search of the Scopus, PubMed, and Medline database with the middle ear barotrauma, underwater diving or scuba diving, and hazards of diving. The abstracts of the published articles were identified by this search method and other articles identified manually from citations. This manuscript reviews the details of middle ear barotrauma in underwater diving along with certain important medical problems. This review article presents a baseline from where further prospective trials of the impact of middle ear barotrauma among underwater divers could be designed and help as a spur for further research in the medical issues encountered among divers.
| Epidemiology|| |
There are more than 6 million sports divers of the United States and more than 1.5 licensed divers in Germany., There are several diving-related diseases found among divers. There are more than 80% of cases of adults and more than 85% in childhood with diving involve otolaryngological diseases. The majority of the diving-related diseases are mild, but there are few life-threatening manifestations which can lead to permanent disability or even more fatality to the diver. To minimize the risk of fatality in diving, each diver must undergo a regular medical checkup. The medical assessment includes to find out potential life-threatening physical or psychological condition which can end in a diving-related fatal outcome. There is a study showing, female divers seem to be more prone for middle ear barotrauma than males due to higher prevalence of defective middle ear ventilation among female divers. There has been dramatic increase in the number of recreational scuba divers in the past half-century with more than 9 million of the certified scuba divers in 2015 in the United States and around 100,000 new divers per year. Although scuba diving is considered a safe recreational activity, it sometimes leads to high-risk injury or even death. There are more than 80% of complications among divers are in the head-and-neck region. Out of these complications in head-and-neck region, 65% are at outer, middle, or inner ear. Hence, the clinicians should understand the physiology and physics of the scuba diving as well as diagnosis and management of the diving-related complications.
| Pathophysiology of Middle Ear Barotrauma and Boyle's Law|| |
Diving causes exposure to immersion and elevation of the ambient pressure, which leads to ranges of physiological impact and manifests pathophysiological sequelae over and above the chance of the drowning. Despite all the challenges, recreational diving is also popular. Diving is usually done in three patterns such as breath-holding diving, bounce diving with breathing apparatus, and saturation diving. The breath-hold and bounce pattern of diving are commonly used by occupational recreational diving. The important physiology behind the middle ear barotrauma is gas exchange between the middle ear and external environment through the middle ear mucosa and pressure equalization through the Eustachian tube. Middle ear barotrauma is a pressure-mediated injury to the body or tissue governed by Boyle's law. When the diver descends in the deep sea, the pressure increases, and the volume of the gas compresses. This leads to a relative negative pressure in semi-rigid or rigid walled air-containing cavity or space in the body such as middle ear. Negative pressure can lead to mucosal edema, hemorrhage, and even perforation of the tympanic membrane because of the middle ear space cannot equalize the pressure. If the diver ascends, the volume of gas increases as the outside pressure falls. If an air-containing cavity cannot equalize with the ambient pressure, the expanding gas in the middle ear may result in different head-and-neck pathologies such as middle ear barotrauma and also sinus barotrauma. During diving underwater, there is raised ambient pressure on the descent of 1 atmosphere (101.3 kPa) for each 10 m depth. If there is no Eustachian tube, the pressure difference across the eardrum would be double in the first 10 m of descent, the air pressure in the middle ear cavity being relatively negative. Active opening of the Eustachian tube helps to equalize the transtympanic pressure. If the Eustachian tube will not open during descent, only 0.8 m depth will cause pressure differential of 8 kPa (60 mmHg), which is sufficient to cause mucosal edema and congestion. Further descent of 1.2 m, 12 kPa (90 mmHg) pressure differential is attended. It is then difficult to open the Eustachian tube voluntarily (Eustachian tube locking) and cause intense otalgia and feeling high ear pressure. As the diver moves upward or ascends, the pressure change is just reverse, where the middle ear pressure becomes positive relative to the ambient pressure. The gas which is present in the middle ear starts expanding. The increased pressure in the middle ear is unable to leave through the Eustachian tube due to mucosal edema and hemorrhage in the middle ear, which happened during descent as a result of the Eustachian tube dysfunction. This leads to bulging of the tympanic membrane outward and gives rise to pain and rupture of the tympanic membrane and hearing loss. Sometimes, the increased middle ear pressure also causes inner ear barotrauma, leading to mild sensorineural hearing loss and vertigo.
| Etiopathology|| |
The middle ear cavity is an air-filled space separated from the outside environment by the tympanic membrane. The middle ear pressure is equalized with the outside environment through Eustachian tube, which opens into the nasopharynx. The Eustachian tube function can be impaired by inflammation of the lining mucosa due to allergic rhinitis, common cold, and bronchitis. The etiology for facial nerve paralysis is better explained by its anatomical characteristics. The facial nerve enters the temporal bone through the internal auditory canal from the brain stem. Then, it passes through labyrinthine segment of the facial nerve canal, followed by tympanic segment and mastoid segment. The tympanic segment of the facial nerve is covered by a very thin bony wall in the middle ear cavity. Then, the facial nerve exits the temporal bone through stylomastoid foramen then traverses the parotid gland and gives rises to five terminal branches which innervate the muscles of facial expression. The widely accepted explanation for facial nerve baroparesis is hypoxemia or ischemic neuropraxia seen at the tympanic segment of the facial nerve. The tympanic segment of the facial nerve crosses the middle ear just medial to incus where the facial nerve is separated from the middle ear by a very thin bony layer. Spontaneous dehiscence of the tympanic segment of the fallopian canal is found on computed tomography (CT) scan up to 55% of normal persons, leading to direct exposure of the facial nerve to the middle ear cavity. Middle ear barotrauma is also directly or indirectly associated with inner ear hazards called as inner ear barotrauma. There are two mechanisms for explaining inner ear barotrauma through explosive or impulsive means. When diver descends, the tympanic membrane pressed medially as the pressure in the external auditory canal is raised. This increased pressure is transmitted through stapes and oval window to the inner ear which raise the intralabyrinthine pressure. At the pressure differential of more than 90 mmHg (12 kPa), the Eustachian tube will be closed or locked and prevent a successful Valsalva. Once the diver feels increased pressure, an attempt is made to equalize the pressure, and if unsuccessful, the diver will try forcefully Valsalva maneuver, which finally increases the intracranial pressure. This raised intracranial pressure will be transmitted through perilymphatic duct to cochlea, causing more pressure inside the cochlea which leads to rupture of the round window or annular ligament. Eustachian tube dysfunction disturbs the air pressure in the middle ear and stimulates the perilymph, which is responsible for interfering the balance system. The increased air pressure in the middle ear pushes against the oval window and stimulates the inner ear and leads to vertigo, which is called as alternobaric vertigo.
| Clinical Manifestations|| |
The typical symptoms of the middle ear barotrauma are acute ear pain or otalgia, hearing loss, and bleeding in the middle ear. There may be fullness in the affected ear and tinnitus. Patients usually present with low pitched hissing noise from the affected ear. There may be slight sensorineural hearing loss in middle ear barotrauma due to transient inner barotrauma by high pressure of the middle ear cavity or in internal auditory canal. Patients also complain of facial pain on the affected side of the barotrauma. The patient may present with facial baroparesis, which is seventh cranial nerve paralysis occurs due to transient hypoxemia of the facial nerve due to raised pressure in the middle ear. Facial baroparesis has been classically reported in divers. The facial nerve palsy is a rare clinical entity in middle ear barotrauma. Facial nerve palsy has been reported both in divers and aviators. This is due high pressure inside the middle ear cavity. The overpressure in middle ear cavity will be exerted on the exposed facial nerve (at dehiscence of the facial bony canal) and cause hypoxia and neuropraxia. The neuropraxia of the facial nerve will persist for 3 min to 3 h; however, long-lasting and even permanent facial nerve paralysis has been documented in the medical literature. Although the facial baroparesis is an uncommon complication of middle ear barotrauma, the emergency physicians must think this diagnosis when patient with facial palsy come with diving history. This symptom usually resolves on equalization of the middle ear and ambient atmospheric pressure. Middle ear barotrauma during scuba diving rarely results in sudden onset vertigo and/or hearing loss. Rapid and strong changes of pressure in the middle ear cavity are thought to be the cause of alternobaric vertigo and inner ear barotrauma. Superior semicircular canal dehiscence syndrome (SCDS) is a rare disorder which occurs due to dehiscence of or fracture of the temporal bone overlying the superior semicircular canal. Patient with SCDS, diving can manifest in vertigo and vertical torsional eye movements induced by increased pressure of the middle ear in middle ear barotrauma. Patients of middle ear barotrauma are usually associated with upper respiratory tract infections, adenoid hypertrophy, and allergic rhinitis. All these infections may lead to Eustachian tube dysfunction and further cause middle ear barotrauma. One study with five cases of facial baroparesis in divers was suffering from common cold, and they troubled with equalizing middle ear pressure. Although rare, Eustachian tube can be blocked congenitally, but whether it leads to middle ear barotrauma is not clear.
Patients may present headache and this headache may be due to exacerbation tension or migraine headache due to exposure of the cold or tight face mask or otitic barotrauma or sinus barotrauma. This headache may develop within minutes of ascent. On otoscopic examination, tympanic membrane appears bulged outward due to overpressure in the middle ear. There may be ruptured tympanic membrane if there is excessive pressure in the middle ear cavity and even bleeding from the ear.
| Investigations|| |
High-resolution CT is a useful investigation and helpful to confirm the dehiscence in the temporal bone such as tympanic segment of the fallopian canal. High-resolution CT (HRCT) scan is also helps to confirm the superior semicircular canal dehiscence. Magnetic resonance imaging (MRI) is more useful for visualization of the soft-tissue course of the facial nerve, whereas CT is better for bony canal of the facial nerve and bony structures of the temporal bone. Dehiscence of the fallopian canal of the facial nerve is often seen at the tympanic segment [Figure 1], which on exposure to high pressure in middle ear barotrauma may lead to facial baroparesis. Pure tone audiometry assesses the hearing loss. The patient may present with mixed or sensorineural hearing loss due to inner ear barotrauma. For vestibular assessment, vestibular-evoked myogenic potential (VEMP) is helpful. Tympanometry often shows Type C curve. Eustachian tube function can also be done by sonotubometry. Vestibular function test is done by cold caloric test. Videonystagmography (VNG) or electronystagmography (ENG) can be used for better localization of the exact site of pathology for vertigo. It can be done in the hospital setting for better assessment of the severity of the vestibular symptom such as vertigo. Diagnostic nasal endoscopic examination confirms the pathology of the nasal cavity and nasopharynx. The nasopharyngeal end of the Eustachian tube is better assessed by the endoscopic examination. Sometimes, adenoid hypertrophy obstructs the Eustachian tube opening. Pure tone audiometry will help to assess the hearing level of the patient with middle ear barotrauma. The Eustachian tube dysfunction is better diagnosed by impedance audiometry.
|Figure 1: Dehiscence of the fallopian canal at the tympanic segment of the facial nerve|
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| Treatment|| |
Middle ear barotrauma needs urgent otolaryngological consultation and specialist treatment which include the use of decongestants such as oxymetazoline and pseudoephedrine, nasal and oral antihistamines, analgesics, and antibiotics such as amoxicillin with clavulanic acid. In case middle ear barotrauma with facial nerve paralysis, pressure equalizes in the middle ear and/or oral glucocorticoids are helpful. Facial nerve paralysis in middle ear barotrauma is caused by increased pressure in the middle ear cavity. The transient facial baroparesis is prevented by adequate self-equalization of the middle ear pressure. Although prophylactic medications are not recommended, topical nasal decongestants may be useful for relieving the anticipating symptoms. If facial baroparesis is suspected, the patient is advised to perform swallowing; yawning with a pinched nose and nasal decongestants will relieve the pressure from the middle ear. If these conservative treatment approaches failed, ventilation tube insertion is required. This facial palsy is transient provided that the appropriate treatment such as myringotomy is done early. Simply observation of the tympanic membrane gives rise to both diagnosis and treatment of the facial palsy in diver. Oral steroids are prescribed in case of persistent facial palsy with middle ear barotrauma., Facial nerve decompression has no role because it can worsen the symptoms when Eustachian tube dysfunction is still present. It is not indicated when a diagnosis of isolated facial baroparesis has been made. There are few authors described sporadic case reports of the facial baroparesis due to diving and their outcome [Table 1]. Topical nasal decongestant before ascent thought to be effective. Furthermore, antihistamine use could have been helpful for preventing the middle ear barotrauma and its hazard. Direct medical attention is required in case of a prolonged recovery. If proper care is delayed, 100% oxygen will be continued. This will help in oxygenation of the facial nerve. Endoscopic balloon Eustachian tuboplasty may be considered in certain cases for making the Eustachian tube function. Alternobaric vertigo due to middle ear barotrauma is often benign and self-limiting. It is usually relieved by middle ear pressure equalization by antihistamines, decongestants, and topical nasal steroids. Myringotomy and grommet insertion are helpful in patients with middle ear barotrauma in patients not benefitted by medical treatment. Myringotomy and grommet insertion equalize the middle ear pressure and relieve the symptoms in long run. Preventive measures are required such as awareness, especially among divers for routine health checkup for Eustachian tube dysfunction which will help to resolve this problem.
|Table 1: Middle ear barotrauma with facial palsy in the medical literature|
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| Conclusion|| |
Scuba divining is becoming a popular recreational activity; however, research related to this and its audiological outcome is very minimal. As a result, participants have little or no knowledge of the outcome of scuba diving on the auditory system or middle ear. The beginners of the diving should be educated about to equalize the middle ear pressure during diving as high pressure in the middle often induces the hearing loss, perforation of tympanic membrane, bleeding, and even neuropraxia of the facial nerve. Proper history taking and examination are important to avoid delayed diagnosis and long burden treatment such as facial nerve decompression. Recreational scuba divers must undergo medical examination for Eustachian tube function test and hearing assessment in light of the failure to adequately equalize the middle ear pressure, which may result in certain otological hazards such as facial nerve palsy, rupture of the tympanic membrane, and otalgia. Immediate treatment with myringotomy is helpful for recovery of the hazardous complications such as facial nerve palsy due to middle ear barotrauma.
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