Otology & Neurotology 35:850Y856 Ó 2014, Otology & Neurotology, Inc.
Altered Eustachian Tube Function in SCUBA Divers With Alternobaric Vertigo *†Naoharu Kitajima, *‡Akemi Sugita-Kitajima, and *Seiji Kitajima *Kitajima ENT Clinic, 1-15-15 Tagara Nerima-ku, Tokyo, Japan; ÞDepartment of Otolaryngology, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo, Japan; and þDepartment of Otolaryngology, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, Japan
Objectives: The number of people participating in sport selfcontained underwater breathing apparatus (SCUBA) diving has increased tremendously, bringing with it a rise in diving accidents. Alternobaric vertigo (AV) is a common problem in SCUBA divers. We investigated the relationship between Eustachian tube function and incidence of AV in sport SCUBA divers. We also followed the progress of these divers after Eustachian tube function improved. Method: Forty-four patients who experienced a SCUBA diving accident affecting the middle ear (11 men and 33 women; mean T SD: 37.5 T 11.5 yr) and 20 healthy volunteer divers who did not experience an accident (6 men and 14 women; mean T SD: 33.5 T 13.9 yr) were compared. We divided the divers with an accident into two groups (those with AV vs. those without) and then compared the two groups. All patients regularly underwent Eustachian tube function tests (sonotubometry and impedance test).
Results: In sonotubometry and impedance testing, the mean duration ( p G 0.001), amplitude ( p G 0.002), and maximum air content ( p G 0.05) of divers who experienced a diving accident were significantly different from those of healthy volunteers. However, these parameters in divers with AV did not differ significantly from those in divers without AV. In 7 of 15 divers, vestibular symptoms disappeared immediately after ascent. In the remaining eight divers, however, vertigo/dizziness persisted and even was observed at their first clinic visit. Conclusion: To prevent AV or barotraumas in SCUBA divers, we recommend a thorough Eustachian tube function evaluation. Any dysfunction should be treated before engaging in SCUBA diving. Key Words: Alternobaric vertigoVEustachian tube dysfunctionVInner ear barotraumaVPersistent alternobaric vertigoVSCUBA diving.
In recent years, more and more people have been participating in sport self-contained underwater breathing apparatus (SCUBA) diving. Alternobaric vertigo (AV) is a common problem in SCUBA divers and is also sometimes present in Air Force pilots (1). AV was first described by Lundgren in 1965 (2). It is a type of vertigo that occurs as a result of alternating (alterno) pressure (baric) changes; it occurs in the absence of cochlear or hearing apparatus changes (3). During ascent from a dive, AV commonly occurs because middle-ear pressure of each ear changes asymmetrically, pushing the eardrum outward and pressing the footplate of the stapes into the vestibule of the inner ear (3,4). A diver who experiences AV typically has problems equilibrating middle-ear pressure as barometric pressure changes. It has also been reported that they have a history of otitis media or Eustachian tube
dysfunction (5). The vertigo associated with AV is usually transitory but can last for several minutes and is often associated with nausea and vomiting (2). Bluestone et al. (6) reported an unusual case of AV occurring spontaneously at ground level. This type of AV occurs as a result of repeated insufflation of positive pressure during swallowing, demonstrating that the duration of AV is not necessarily transient. In the present study, we investigated the relationship between Eustachian tube function and the incidence of AV in sport SCUBA divers. Sonotubometry is based on the principle that sound applied to the nasopharyngeal ostium is conducted through the Eustachian tube to the middle ear during swallowing. Bluestone et al. (6) noted that positive pressure during swallowing affected persistent AV. Therefore, we reasoned that sonotubometry would be a useful tool for evaluating AV, especially persistent AV. Impedance testing mainly evaluates changes in air content within the middle ear during the Valsalva maneuver and swallowing. Thus, we concluded that impedance testing would be an ideal method for examining ‘‘ear clearing’’
Otol Neurotol 35:850Y856, 2014.
Address correspondence and reprint requests to Naoharu Kitajima, M.D., Ph.D., Kitajima ENT Clinic, 1-15-15 Tagara Nerima-ku, Tokyo 179-0073, Japan; E-mail: [email protected] The authors report no conflicts of interest.
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ALTERNOBARIC VERTIGO IN DIVERS
FIG. 1. Examples of sonotubometry curves measured from a normal subject. Swallowing-induced external auditory sound pressure changes that synchronize with pharyngeal noise. Amplitude is the maximum sound pressure level change value, and duration is the length of time it takes for the Eustachian tube to open and close. Durations less than 116.9 milliseconds or amplitudes less than 5 dB were consistent with a diagnosis of tubal stenosis, whereas durations more than 788.1 milliseconds were consistent with a diagnosis of patulous Eustachian tube.
in divers. This is why all divers were subjected to sonotubometry and impedance testing. Here, we describe the evaluation of AV using sonotubometry and impedance testing, which, to our knowledge, is a type of evaluation that has not been previously used and reported.
MATERIALS AND METHODS Forty-four patients who experienced a SCUBA diving accident affecting the middle ear (11 men and 33 women; mean T SD: 37.5 T 11.5 yr) and 20 healthy volunteers who did not experience a diving accident (6 men and 14 women; mean T SD: 33.5 T 13.9 yr) participated. This study was conducted in accordance with the Declaration of Helsinki. All procedures were carried out with the consent of the participants. We considered AV as a type of middle-ear disease. We excluded patients with concomitant sensorineural hearing loss, especially those with perilymph fistula or inner ear decompression sickness (IEDCS). Patients were divided into two groups: divers with AV or divers without AV. In a previous study, we classified patients with SCUBA divingYrelated accidents into two groups (a unilateral group and a bilateral group) according to whether one ear or both ears were affected (7). In the present study, we examined the unilateral group. Generally, if a diver experienced a transient sensation of vertigo during or immediately after diving without hearing loss and tinnitus, and if this acute vertigo did not last longer than a few seconds to several minutes, the vertigo was labeled as AV (2,4,8). In the present study, patients experiencing short-lasting AV, as just described, were diagnosed with transient AV. However, patients experiencing persistent sensations of vertigo/ dizziness without hearing loss or tinnitus, even a day after diving, were diagnosed with persistent AV regardless of whether they exhibited nystagmus. To exclude perilymph fistula and IEDCS, we performed a fistula test and checked for decompression sickness symptoms, such as ‘‘bends’’ (joint/bone pain), ‘‘chokes’’ (breathing problems), and other neurologic manifestations. During the patients’ first visit to our clinic, we denoted the side affected by AV as the side having Eustachian tube dysfunction. If Eustachian tube function was normal, we denoted the affected side as the ear that the diver had difficulty in
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clearing during dives. During this visit, all patients also underwent nystagmic examinations and audiometric measurements, including hearing testing (pure tone audiometry [PTA]), tympanometry, and Eustachian tube function testing. In addition to assessing vestibular function in AV, if possible, we performed caloric testing and head impulse testing (9). A JK-05 Eustachian tube function analyzer (RION, Japan) was used to perform sonotubometry and impedance testing. Examples of sonotubometry curves measured from a normal subject are shown in Figure 1. The equipment used in the present study comprised a sound generator (frequency: 7 kHz, band-noise), which was placed in the patient’s nostril, and a measurement microphone, which was placed in the patient’s ipsilateral external ear canal. We measured sound pressure changes caused by the opening and closing of the Eustachian tube that occurs during swallowing movements. Amplitude was defined as the maximum sound pressure level change value, and duration was defined as the length of time it took for the Eustachian tube to open and close. Durations less than 116.9 milliseconds or amplitudes less than 5 dB were consistent with a diagnosis of tubal stenosis, whereas durations greater than 788.1 milliseconds were consistent with a diagnosis of patulous Eustachian tube (7). If the duration was more than 1,000 milliseconds, we set the duration to 1,000 milliseconds. If the amplitude did not rise above baseline levels and if the duration could not be measured, we diagnosed the patient with tubal stenosis and set the duration to 0 millisecond (7). Examples of impedance test curves measured from a normal subject are shown in Figure 2. Impedance tests were performed by simultaneously recording tympanic membrane impedance and nasopharyngeal pressure. The passive opening capacity of the Eustachian tube during the Valsalva maneuver can be determined from the curve pattern of impedance changes recorded from the external ear canal (10). Open pressures less than 200 daPa were consistent with a diagnosis of patulous Eustachian tube, whereas open pressures more than 650 daPa were consistent with a diagnosis of tubal stenosis. We defined the maximum value of equivalent volume as maximum air content in the
FIG. 2. Examples of impedance test curves measured from a normal subject. Impedance tests were performed by simultaneously recording tympanic membrane impedance and nasopharyngeal pressure. The passive opening capacity of the Eustachian tube that occurs as the subject performs a Valsalva maneuver can be determined by examining the curve and pattern of changes in the impedance recorded from the external ear canal. Open pressures less than 200 daPa were consistent with a diagnosis of patulous Eustachian tube, whereas open pressures greater than 650 daPa were consistent with a diagnosis of tubal stenosis. If we could not accurately determine the open pressure because of a technical error, we diagnosed the patient with either tubal stenosis or patulous Eustachian tube based on the shape of the compliance curve. We designated the maximum value of equivalent volume as maximum air content in the middle ear. Otology & Neurotology, Vol. 35, No. 5, 2014
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N. KITAJIMA ET AL.
middle ear. If we could not accurately determine the open pressure because of technical error, we diagnosed the patient with either tubal stenosis or patulous Eustachian tube from the shape of his or her compliance curve. Classification of Eustachian tube function based on compliance curves are shown in Figure 3. In each curve, the arrow at the lower left represents the start of the Valsalva maneuver and the arrow at the lower right represents swallowing after the Valsalva maneuver. When the Eustachian tube did not open or close for more than 10 seconds, we designated the compliance curve as type A or a, respectively. If the Eustachian tube opened or closed immediately, we designated the curve as type C or c, respectively. If Eustachian tube opening or closing was delayed, we designated the curve as type B or b, respectively. Compliance curves showing normal patterns were designated as type D (Cc), whereas those showing abnormal patterns were designated as ‘‘other types’’ (A; Ba, Bb, Bc; and Ca, Cb; see Fig. 3). If the Eustachian tube slightly opened (maximum air content G0.1 ml), we designated the curve as type A for convenience and set maximum air content to 0.1 ml. If the duration and amplitude improved in sonotubometry testing and/or the maximum air content improved and/or the patterns of the compliance curves changed from type A to type D in impedance testing, we concluded that these changes represented an improvement in Eustachian tube function. We prescribed divers with a Eustachian tube dysfunction anti-allergic agents (loratadine and montelukast) and nasal steroid spray (fluticasone propionate). We suspected that divers with persistent vertigo/dizziness and strong nystagmus might have suffered barotrauma, resulting in inner ear dysfunction. Thus, for these divers we prescribed adenosine triphosphate disodium to improve the circulatory disturbance in the inner ear, mecobalamin to improve peripheral neuropathy, and betahistine mesilate to improve vertigo/dizziness.
First, we compared Eustachian tube function in healthy volunteers with that in patients who experienced a SCUBA divingY related accident. Second, we compared patients with AV with those without AV. The patients with AV underwent Eustachian tube function testing a second time after their vertigo/dizziness and nystagmus improved. Calculations were performed with Stat Mate 3 software (Atoms, Japan). The Mann-Whitney U test was used for statistical analysis; p G0.05 was considered significant.
RESULTS Divers Without Diving Complications (Healthy Volunteers) On the basis of the criteria mentioned above, 9 of 20 healthy volunteers (45.0%) were diagnosed with Eustachian tube dysfunction (Table 1). All of the healthy volunteers with Eustachian tube dysfunction had tubal stenosis. With sonotubometry, the mean T SD duration was 366.8 T 176.6 milliseconds, and the mean T SD amplitude was 14.3 T 6.5 dB for the affected ears. With the impedance test, the mean T SD open pressure was 383.7 T 184.4 daPa, and the mean T SD maximum air content was 0.5 T 0.2. Seven of 20 healthy volunteers (35.0%) were judged to have irregular compliance curves. Divers With Diving Complications Almost all divers with otological symptoms (97.7%) were diagnosed with Eustachian tube dysfunction (Table 1), and all divers with Eustachian tube dysfunction had tubal stenosis. In sonotubometry, the mean T SD duration was
FIG. 3. Classification of Eustachian tube function based on compliance curves. In each graph, the arrow at the lower left represents the start of the Valsalva maneuver, and the arrow at the lower right represents swallowing after the Valsalva maneuver. The type D curve has a normal pattern, whereas the other types of curves (A; Ba, Bb, Bc; and Ca, Cb) have abnormal patterns. When the pattern of the compliance curves improved from type A to type D, we concluded that it reflects an improvement in Eustachian tube function. Otology & Neurotology, Vol. 35, No. 5, 2014
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ALTERNOBARIC VERTIGO IN DIVERS TABLE 1.
853
Results of subjects with or without diving complications Impedance test
Age N Divers without otological symptoms (healthy volunteers) Divers with otological symptoms With AV Without AV
(yr)
20 33.5 T 13.9
Sex
Eustachian tube (M/F) dysfunction
(normal/irregular) 13:7
43/44
229.8 T 219.4c
9.1 T 7.9b 463.9 T 154.7
0.4 T 0.2a
4:40
14/15 29/29
242.7 T 200.3 228.3 T 230.0
9.9 T 7.6 9.1 T 8.1
0.3 T 0.3 0.4 T 0.2
2:13 2:27
15 35.2 T 8.6 29 38.8 T 12.7
(daPa)
Compliance curves
(ml)
44 37.5 T 11.5 11:33
(dB)
Maximum air content
0.5 T 0.2a
9/20
(ms)
Open pressure
366.8 T 176.6c 14.3 T 6.5b 383.7 T 184.4
6:14
3:12 8:21
Sonotubometry Duration Amplitude
443.7 T 181.7 491.0 T 154.1
a
p G 0.05. p G 0.002. p G 0.001. AV indicates alternobaric vertigo.
b c
229.8 T 219.4 milliseconds, and the mean T SD amplitude was 9.1 T 7.9 dB for the affected ears. For the impedance test, the mean T SD open pressure was 463.9 T 154.7 daPa, and the mean T SD maximum air content was 0.4 T 0.2. Thirty-six of 40 (90.0%) divers were judged to have irregular compliance curves. Fifteen of the divers with otological symptoms (34.1%) experienced AV. There were significant differences between the mean duration ( p G 0.001), amplitude ( p G 0.002), and maximum air content ( p G 0.05) of divers with otological symptoms and those of healthy volunteers. However, there were no significant differences in these parameters between divers with AV and those without AV.
signs or DCS symptoms. The mean T SD duration of vertigo/dizziness symptoms after treatment was 11.1 T 5.4 days, but nystagmus continued for 25.0 T 20.6 days. Eustachian tube function of the affected side in divers with AV is shown in Table 3. Within the observational period, the Eustachian tube dysfunction of 14 divers improved. Their vestibular symptoms also improved and stabilized. After treatment, only one diver (no. 12) experienced AV; the remaining divers (9/10; 90.0%) did not experience AV. No other complications, such as progressive sensorineural deafness or DCS symptoms, occurred while the divers were being followed clinically.
Divers With AV The clinical findings of divers with AV are summarized in Table 2. For 7 of the 15 divers, it was the first time they had experienced AV. The remaining eight divers had experienced AV previously. Eleven of 13 divers (84.6%) had allergic rhinitis; none of these divers received allergy treatment. Except for one diver (no. 8; see Table 2) who suffered from otitis media with effusions, divers with AV (93.3%) did not present with cochlear symptoms. In addition, their tympanometry results were normal (Jerger A type). In nearly all of the divers with AV (11/15; 73.3%), AV symptoms appeared after ascent. In 7 of the 15 divers, vestibular symptoms had disappeared immediately (within less than 10 min) after ascent. The remaining eight divers, however, experienced continuous vertigo/dizziness symptoms up to the time of their first visit to our clinic. At the first clinic visit, we observed nystagmus in eight divers. However, in most of the divers (5/8; 62.5%) the nystagmus was trivial. Of the three divers with definitive nystagmus, one diver (no. 15) exhibited gaze nystagmus toward the unaffected side (Grade I), whereas two divers (nos. 13, 14) exhibited positional nystagmus toward the unaffected side. Of the six divers who underwent head impulse testing or caloric testing, all of them exhibited normal results. None of the divers had positive fistula
Generally, AV is thought to be elicited by a degree of inadequate pressure equilibration of the middle ear (2). The symptoms of AV are transient and do not cause permanent damage to the vestibulocochlear apparatus (11). In divers, AV mostly occurs on ascent from a dive or at the surface just after ascent (5). In the present study, 11 of 15 divers (73.3%) experienced symptoms of AV after ascent, and nine of these divers (81.8%) displayed type a or b (including type A) compliance curves when subjected to impedance testing (Tables 2, 3). The one diver (no. 12) who experienced AV after treatment had a type Ca compliance curve (Table 3). These findings indicate that divers with type a or b compliance curves are prone to AV as they ascend from a dive, probably because the expanding air in the middle ear is not released from the Eustachian tube. Roydhouse (3,4) proposed that the increased middle-ear pressure that occurs during dives pushes the eardrum outward and depresses the footplate of the stapes into the vestibule of the inner ear, resulting in AV. This hypothesis is compatible with our results. Interestingly, in the present study, 8 of 15 divers manifested persistent vertigo/dizziness. Swallowing when the nose is obstructed could result in abnormal negative or positive pressure in the middle ear; this is termed the Toynbee phenomenon (12). Past studies showed that positive middle-ear pressure results in an objective
DISCUSSION
Otology & Neurotology, Vol. 35, No. 5, 2014
Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
First attack
First attack
Yes
First attack
First attack
Yes
Yes
Yes
97
97
97
3
2
97
6
97
97
2
4
1
4
5
6
7
8
9
10
11
12
13
14
15
Yes
Yes
First attack
First attack
First attack
97
3
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
NT
Yes
No
NT
Yes
Yes
Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Normal
Normal
Normal
Normal
Normal
Normal
Normal
Conductive
Normal
Normal
Normal
Normal
Normal
Normal
A
A
A
A
A
A
A
C1
A
A
A
A
A
A
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
Yes
A
97
Normal
2
Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Normal
After ascent G10 min
Yes
Yes
7
1
After ascent Persistent dizziness After ascent Persistent dizziness During Persistent diving dizziness After ascent Persistent dizziness After ascent Persistent dizziness During Persistent descent vertigo After ascent Persistent vertigo After ascent Persistent vertigo
During G10 min safety stop After ascent G10 min
During G10 min diving After ascent G10 min
After ascent G10 min
After ascent G10 min
Duration
Beginning
Vertigo
Yes
Yes
Yes
Very fine
Very fine
No
No
No
Very fine
Very fine
Very fine
No
No
No
No
Normal
NT
NT
NT
Normal
NT
Normal
Normal
NT
NT
NT
Normal
NT
NT
NT
Head impulse Nystagmus test
Clinical findings of divers with AV
Period of time from onset Eustachian to first Allergic tube Pure tone No. visit (d) Recurrence rhinitis dysfunction audiometry Tympanometry Tinnitus
TABLE 2.
NT
NT
NT
NT
NT
NT
NT
NT
NT
CP negative NT
NT
NT
NT
NT
Caloric test
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
9
14
7
15
7
22
7
8
9
52
42
15
7
32
47
15
Improvement DCS Fistula symptoms Vertigo/ Nystagmus sign (e.g., bends) dizziness (d) (d)
854 N. KITAJIMA ET AL.
Otology & Neurotology, Vol. 35, No. 5, 2014
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ALTERNOBARIC VERTIGO IN DIVERS TABLE 3.
Eustachian tube function of affected side in divers with AV
At first clinic visit Sonotubometry
No.
Duration (ms)
Amplitude (dB)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
245 340 175 490 0 0 690 0 310 160 315 0 420 210 285
10 14 9 20 0 0 20 0 20 9 11 0 20 11 5
Upon improvement of vertigo
Impedance test Open pressure (daPa) 371 177 545 304 † 401 682 † 626
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Sonotubometry
Impedance test
Maximum air content (ml)
Compliance curve
Duration (ms)
Amplitude (dB)
Open pressure (daPa)
0.5 0.1a 0.4 0.4 0.2 0.2 0.1a 0.1a 1.0 0.1a 0.5 0.1a 0.3 0.1a 0.6
Bb A Ca Ba D Bc A A D A Cb A Cb A Ca
350 605 180 320 165 175 630 420 320 † 295 410 355 230 †
15 21 6 15 8 5 16 27 17 † 20 7 15 12 †
184 520 † † 918 † 631 579 562 639 664 354 485 † 625
Maximum air content (ml)
Compliance curve
Outcome of AV
0.7 0.5 0.5 0.4 0.5 0.4 0.5 0.5 1.2 0.3 0.5 0.4 0.4 0.6 0.2
D Cb D D D Bc D D D Ca D Ca Ca D D
No recurrence No recurrence N/A No recurrence No recurrence No recurrence No recurrence No recurrence N/A No recurrence N/A Recurrence N/A No recurrence No recurrence
†Parameters were technically difficult to measure. a Maximum equivalent volume in A type was set to 0.1 ml for convenience. AV indicates alternobaric vertigo; N/A, not available.
vestibular response (13). Bluestone et al. (14) proposed that any type of nasal obstruction could create the Toynbee phenomenon during swallowing. This notion is consistent with a report of a 15-year-old female patient who experienced persistent AV at ground level. They hypothesized that the persistent vertigo in this patient was a result of chronic nasal obstruction and Toynbee phenomenon, which caused repeated insufflation of positive pressure into her affected ear during swallowing (6). Allergic rhinitis is representative of chronic nasal obstruction, and allergic rhinitis patients have a higher risk of Eustachian tube dysfunction (15). In the present study, the majority of divers with AV had allergic rhinitis (Table 2). Their vestibular symptoms improved with treatment of their allergic rhinitis, which also improved Eustachian tube function (Table 3). These results indicate that nasal allergy is an important risk factor for AV, especially persistent AV. In the present study, Eustachian tube function in divers with a SCUBA divingYrelated accident was significantly impaired compared to that in healthy volunteers (Table 1). Tjernstrom (16) used a pressure chamber to compare the Eustachian tube function of 12 divers who had experienced AV with that of six divers who had not. The divers with a history of AV had higher opening pressures. Moreover, half of the divers with a history of AV experienced vertigo and nystagmus in the chamber (16). Surprisingly, in our study, we did not observe a significant difference in Eustachian tube function of divers with AV and divers without AV (Table 1). These results suggest that Eustachian tube dysfunction can contribute to SCUBA divingYrelated accidents and that divers with Eustachian tube dysfunction are prone to developing AV. AV onset may be caused not only by Eustachian tube dysfunction but also by other factors, such as excessive speed on ascending/descending, inexperience, underdeveloped
diving skills, health condition, and so on. For instance, because of discomfort associated with plugged ears, divers who have difficulty clearing their ears may become impatient, performing the Valsalva maneuver to the point of putting excessive positive pressure on the mesotympanum, which could severely injure the affected ear. Further investigation is needed to clarify additional factors contributing to the onset of AV. According to Parell and Becker (17), the differential diagnoses of vestibulocochlear symptoms in SCUBA divers include barotrauma like perilymph fistula, IEDCS, nitrogen narcosis, high-pressure nervous syndrome (HPNS), contaminated air, AV, unequal caloric simulation or response, hyperventilation, and sensory deprivation. Generally, all of these symptoms except perilymph fistula, IEDCS, and HPNS are transient. IEDCS occurs after diving that exceeds the no-decompression limits. HPNS is associated with deep diving (over 130 m) while breathing a helium-oxygen mixture. IEDCS and HPNS are usually complicated by neurologic findings. In the present study, all of the divers dove to moderate depths (not more than 30 m) and did not breathe a heliumoxygen mixture. They followed the instructions of a dive computer and decompressed appropriately. They did not experience any neurologic manifestations, only vestibular symptoms. Therefore, we ruled out IEDCS and HPNS as potential diagnoses. AV can be mistaken for not only IEDCS and HPNS but also for inner ear barotrauma. Molvaer and Albrektson (8) reported that the odds for AV in divers experiencing middle-ear barotrauma are 2.63 times than that for divers who never experienced barotrauma. This suggests that AV is closely connected with barotrauma. Parell and Becker (17) proposed four categories of inner ear barotrauma: (1) hemorrhage within the inner ear; (2) Otology & Neurotology, Vol. 35, No. 5, 2014
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856
N. KITAJIMA ET AL. divers should undergo thorough evaluation of their vestibular system and for Eustachian tube dysfunction. Accurate assessment is necessary if they are to receive proper treatment. Various other factors, however, make it is difficult to evaluate divers correctly. To address this problem, even if a diver’s symptoms improve, he or she should forego diving if vertigo occurs at the surface as the diver performs the Valsalva maneuver (18). We believe that persistent AV might be an intermediate condition between AV and inner ear barotraumas. It could progress into serious barotrauma such as perilymph fistula.
REFERENCES
FIG. 4. SCUBA divingYassociated diseases that present with vestibular symptoms. Acute vertigo lasting no longer than a few seconds to several minutes was defined as transient alternobaric vertigo (AV). Persistent vertigo/dizziness occurring after diving was defined as persistent AV.
rupture of Reissner’s membrane, resulting in the mixing of endolymph and perilymph; (3) round or oval window fistula; and (4) mixed injuries consisting of one, two, or three of these entities. In the present study, for all of the divers with persistent AV, AV was not associated with cochlear and fistula symptoms. Therefore, there was little possibility of perilymph fistula in these cases. Suzuki et al. (13) proposed the following series of events leading to AV. The transmission of pressure from the middle ear to the inner ear occurs when changes in middle-ear pressure cause the oval windows to vibrate, which affects endolymphatic flow. This leads to alterations in the activity of primary vestibular neurons, ultimately resulting in the pressure-induced vestibular response that causes AV. These divers might have had slight barotrauma without cochlear symptoms. However, previous findings led us to hypothesize that persistent AV might reflect an intermediate condition between AV and inner ear barotrauma. Figure 4 lists diseases, in addition to persistent AV, that manifest as vestibular symptoms after SCUBA diving. To prevent these types of pressure-related injuries in SCUBA divers, further investigations are needed to accurately diagnose persistent AV. CONCLUSION In summary, our study provides evidence supporting specific evaluation of divers who experience AV. These
1. Ildiz F, Onder T, Dunder A. Alternobaric vertigo. Turk J Med Res 1993;11:151Y4. 2. Lundgren CEG. Alternobaric vertigoVa diving hazard. Br J Med 1965;2:511Y2. 3. Roydhouse N. Underwater Ear and Nose Care. 3rd ed. Auckland: Best Publishing Company, 1993. 4. Roydhouse N. 1001 disorders of the ear, nose and sinuses in scuba divers. Can J Appl Sport Sci 1985;10:99Y103. 5. Uzen C, Yagiz R, Tas A, et al. Alternobaric vertigo in sports SCUBA divers and risk factors. J Laryngol Otol 2003;117:854Y60. 6. Bluestone CD, Swarts JD, Furman JM, et al. Persistent alternobaric vertigo at ground level. Laryngoscope 2012;122:868Y72. 7. Kitajima N, Kitajima-Sugita A, Kitajima S. A study of the Eustachian tube function in patients with a scuba diving accident. Nippon Jibiinkoka Gakkai Kaiho (Tokyo) 2012;115:1029Y36. 8. Molvaer OI, Albrektson G. Alternobaric vertigo in professional divers. Undersea Biomed Res 1988;15:271Y81. 9. Halmagyi GM, Curthoys IS. A clinical sign of canal paresis. Arch Neurol 1988;45:737Y9. 10. Kumazawa T, Iwano T, Ushiro K, et al. Eustachian tube function tests and their diagnostic potential in normal and diseased ears. Acta Otolaryngol Suppl (Stockh) 1993;500:10Y3. 11. Baird B. Alternobaric Vertigo. Palm Beach Marine Institute, Inc. Available at: http://www.nyscuba.org/Articles/Alternobaric% 20Vertigo.htm. Accessed February 9, 2003. 12. Toynbee J. On the muscles which open the Eustachian tube. Proc R Soc Lond 1853;6:286Y8. 13. Suzuki M, Kitano H, Yazawa Y, et al. Involvement of round and oval windows in the vestibular response to pressure changes in the middle ear of guinea pigs. Acta Otolaryngol 1998;118:712Y6. 14. Bluestone CD, Paradise JL, Berry QC. Physiology of the Eustachian tube in the pathogenesis and management of middle ear effusions. Laryngoscope 1972;82:1654Y70. 15. Lazo-Sa´enz JG, Galva´n-Aguilera AA, Martı´nez-Ordaz VA, VelascoRodrı´guez VM, Nieves-Renterı´a A, Rinco´n-Castan˜eda C. Eustachian tube dysfunction in allergic rhinitis. Otolaryngol Head Neck Surg 2005;132:626Y9. 16. Tjernstrom O. Function of the Eustachian tubes in divers with a history of alternobaric vertigo. Undersea Biomed Res 1974;1:343Y51. 17. Parell GJ, Becker GD. Conservative management of inner ear barotrauma resulting from scuba diving. Otolaryngol Head Neck Surg 1985;93:393Y7. 18. Neblett LM. Otolaryngology and sport SCUBA diving update and guidelines. Ann Otol Rhinol Laryngol Suppl 1985;115:1Y12.
Otology & Neurotology, Vol. 35, No. 5, 2014
Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
Altered Eustachian Tube Function in SCUBA Divers With Alternobaric Vertigo *†Naoharu Kitajima, *‡Akemi Sugita-Kitajima, and *Seiji Kitajima *Kitajima ENT Clinic, 1-15-15 Tagara Nerima-ku, Tokyo, Japan; ÞDepartment of Otolaryngology, Tokyo Medical University, 6-7-1 Nishishinjuku, Shinjuku-ku, Tokyo, Japan; and þDepartment of Otolaryngology, St. Marianna University School of Medicine, 2-16-1 Sugao, Miyamae-ku, Kawasaki, Kanagawa, Japan
Objectives: The number of people participating in sport selfcontained underwater breathing apparatus (SCUBA) diving has increased tremendously, bringing with it a rise in diving accidents. Alternobaric vertigo (AV) is a common problem in SCUBA divers. We investigated the relationship between Eustachian tube function and incidence of AV in sport SCUBA divers. We also followed the progress of these divers after Eustachian tube function improved. Method: Forty-four patients who experienced a SCUBA diving accident affecting the middle ear (11 men and 33 women; mean T SD: 37.5 T 11.5 yr) and 20 healthy volunteer divers who did not experience an accident (6 men and 14 women; mean T SD: 33.5 T 13.9 yr) were compared. We divided the divers with an accident into two groups (those with AV vs. those without) and then compared the two groups. All patients regularly underwent Eustachian tube function tests (sonotubometry and impedance test).
Results: In sonotubometry and impedance testing, the mean duration ( p G 0.001), amplitude ( p G 0.002), and maximum air content ( p G 0.05) of divers who experienced a diving accident were significantly different from those of healthy volunteers. However, these parameters in divers with AV did not differ significantly from those in divers without AV. In 7 of 15 divers, vestibular symptoms disappeared immediately after ascent. In the remaining eight divers, however, vertigo/dizziness persisted and even was observed at their first clinic visit. Conclusion: To prevent AV or barotraumas in SCUBA divers, we recommend a thorough Eustachian tube function evaluation. Any dysfunction should be treated before engaging in SCUBA diving. Key Words: Alternobaric vertigoVEustachian tube dysfunctionVInner ear barotraumaVPersistent alternobaric vertigoVSCUBA diving.
In recent years, more and more people have been participating in sport self-contained underwater breathing apparatus (SCUBA) diving. Alternobaric vertigo (AV) is a common problem in SCUBA divers and is also sometimes present in Air Force pilots (1). AV was first described by Lundgren in 1965 (2). It is a type of vertigo that occurs as a result of alternating (alterno) pressure (baric) changes; it occurs in the absence of cochlear or hearing apparatus changes (3). During ascent from a dive, AV commonly occurs because middle-ear pressure of each ear changes asymmetrically, pushing the eardrum outward and pressing the footplate of the stapes into the vestibule of the inner ear (3,4). A diver who experiences AV typically has problems equilibrating middle-ear pressure as barometric pressure changes. It has also been reported that they have a history of otitis media or Eustachian tube
dysfunction (5). The vertigo associated with AV is usually transitory but can last for several minutes and is often associated with nausea and vomiting (2). Bluestone et al. (6) reported an unusual case of AV occurring spontaneously at ground level. This type of AV occurs as a result of repeated insufflation of positive pressure during swallowing, demonstrating that the duration of AV is not necessarily transient. In the present study, we investigated the relationship between Eustachian tube function and the incidence of AV in sport SCUBA divers. Sonotubometry is based on the principle that sound applied to the nasopharyngeal ostium is conducted through the Eustachian tube to the middle ear during swallowing. Bluestone et al. (6) noted that positive pressure during swallowing affected persistent AV. Therefore, we reasoned that sonotubometry would be a useful tool for evaluating AV, especially persistent AV. Impedance testing mainly evaluates changes in air content within the middle ear during the Valsalva maneuver and swallowing. Thus, we concluded that impedance testing would be an ideal method for examining ‘‘ear clearing’’
Otol Neurotol 35:850Y856, 2014.
Address correspondence and reprint requests to Naoharu Kitajima, M.D., Ph.D., Kitajima ENT Clinic, 1-15-15 Tagara Nerima-ku, Tokyo 179-0073, Japan; E-mail: [email protected] The authors report no conflicts of interest.
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ALTERNOBARIC VERTIGO IN DIVERS
FIG. 1. Examples of sonotubometry curves measured from a normal subject. Swallowing-induced external auditory sound pressure changes that synchronize with pharyngeal noise. Amplitude is the maximum sound pressure level change value, and duration is the length of time it takes for the Eustachian tube to open and close. Durations less than 116.9 milliseconds or amplitudes less than 5 dB were consistent with a diagnosis of tubal stenosis, whereas durations more than 788.1 milliseconds were consistent with a diagnosis of patulous Eustachian tube.
in divers. This is why all divers were subjected to sonotubometry and impedance testing. Here, we describe the evaluation of AV using sonotubometry and impedance testing, which, to our knowledge, is a type of evaluation that has not been previously used and reported.
MATERIALS AND METHODS Forty-four patients who experienced a SCUBA diving accident affecting the middle ear (11 men and 33 women; mean T SD: 37.5 T 11.5 yr) and 20 healthy volunteers who did not experience a diving accident (6 men and 14 women; mean T SD: 33.5 T 13.9 yr) participated. This study was conducted in accordance with the Declaration of Helsinki. All procedures were carried out with the consent of the participants. We considered AV as a type of middle-ear disease. We excluded patients with concomitant sensorineural hearing loss, especially those with perilymph fistula or inner ear decompression sickness (IEDCS). Patients were divided into two groups: divers with AV or divers without AV. In a previous study, we classified patients with SCUBA divingYrelated accidents into two groups (a unilateral group and a bilateral group) according to whether one ear or both ears were affected (7). In the present study, we examined the unilateral group. Generally, if a diver experienced a transient sensation of vertigo during or immediately after diving without hearing loss and tinnitus, and if this acute vertigo did not last longer than a few seconds to several minutes, the vertigo was labeled as AV (2,4,8). In the present study, patients experiencing short-lasting AV, as just described, were diagnosed with transient AV. However, patients experiencing persistent sensations of vertigo/ dizziness without hearing loss or tinnitus, even a day after diving, were diagnosed with persistent AV regardless of whether they exhibited nystagmus. To exclude perilymph fistula and IEDCS, we performed a fistula test and checked for decompression sickness symptoms, such as ‘‘bends’’ (joint/bone pain), ‘‘chokes’’ (breathing problems), and other neurologic manifestations. During the patients’ first visit to our clinic, we denoted the side affected by AV as the side having Eustachian tube dysfunction. If Eustachian tube function was normal, we denoted the affected side as the ear that the diver had difficulty in
851
clearing during dives. During this visit, all patients also underwent nystagmic examinations and audiometric measurements, including hearing testing (pure tone audiometry [PTA]), tympanometry, and Eustachian tube function testing. In addition to assessing vestibular function in AV, if possible, we performed caloric testing and head impulse testing (9). A JK-05 Eustachian tube function analyzer (RION, Japan) was used to perform sonotubometry and impedance testing. Examples of sonotubometry curves measured from a normal subject are shown in Figure 1. The equipment used in the present study comprised a sound generator (frequency: 7 kHz, band-noise), which was placed in the patient’s nostril, and a measurement microphone, which was placed in the patient’s ipsilateral external ear canal. We measured sound pressure changes caused by the opening and closing of the Eustachian tube that occurs during swallowing movements. Amplitude was defined as the maximum sound pressure level change value, and duration was defined as the length of time it took for the Eustachian tube to open and close. Durations less than 116.9 milliseconds or amplitudes less than 5 dB were consistent with a diagnosis of tubal stenosis, whereas durations greater than 788.1 milliseconds were consistent with a diagnosis of patulous Eustachian tube (7). If the duration was more than 1,000 milliseconds, we set the duration to 1,000 milliseconds. If the amplitude did not rise above baseline levels and if the duration could not be measured, we diagnosed the patient with tubal stenosis and set the duration to 0 millisecond (7). Examples of impedance test curves measured from a normal subject are shown in Figure 2. Impedance tests were performed by simultaneously recording tympanic membrane impedance and nasopharyngeal pressure. The passive opening capacity of the Eustachian tube during the Valsalva maneuver can be determined from the curve pattern of impedance changes recorded from the external ear canal (10). Open pressures less than 200 daPa were consistent with a diagnosis of patulous Eustachian tube, whereas open pressures more than 650 daPa were consistent with a diagnosis of tubal stenosis. We defined the maximum value of equivalent volume as maximum air content in the
FIG. 2. Examples of impedance test curves measured from a normal subject. Impedance tests were performed by simultaneously recording tympanic membrane impedance and nasopharyngeal pressure. The passive opening capacity of the Eustachian tube that occurs as the subject performs a Valsalva maneuver can be determined by examining the curve and pattern of changes in the impedance recorded from the external ear canal. Open pressures less than 200 daPa were consistent with a diagnosis of patulous Eustachian tube, whereas open pressures greater than 650 daPa were consistent with a diagnosis of tubal stenosis. If we could not accurately determine the open pressure because of a technical error, we diagnosed the patient with either tubal stenosis or patulous Eustachian tube based on the shape of the compliance curve. We designated the maximum value of equivalent volume as maximum air content in the middle ear. Otology & Neurotology, Vol. 35, No. 5, 2014
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N. KITAJIMA ET AL.
middle ear. If we could not accurately determine the open pressure because of technical error, we diagnosed the patient with either tubal stenosis or patulous Eustachian tube from the shape of his or her compliance curve. Classification of Eustachian tube function based on compliance curves are shown in Figure 3. In each curve, the arrow at the lower left represents the start of the Valsalva maneuver and the arrow at the lower right represents swallowing after the Valsalva maneuver. When the Eustachian tube did not open or close for more than 10 seconds, we designated the compliance curve as type A or a, respectively. If the Eustachian tube opened or closed immediately, we designated the curve as type C or c, respectively. If Eustachian tube opening or closing was delayed, we designated the curve as type B or b, respectively. Compliance curves showing normal patterns were designated as type D (Cc), whereas those showing abnormal patterns were designated as ‘‘other types’’ (A; Ba, Bb, Bc; and Ca, Cb; see Fig. 3). If the Eustachian tube slightly opened (maximum air content G0.1 ml), we designated the curve as type A for convenience and set maximum air content to 0.1 ml. If the duration and amplitude improved in sonotubometry testing and/or the maximum air content improved and/or the patterns of the compliance curves changed from type A to type D in impedance testing, we concluded that these changes represented an improvement in Eustachian tube function. We prescribed divers with a Eustachian tube dysfunction anti-allergic agents (loratadine and montelukast) and nasal steroid spray (fluticasone propionate). We suspected that divers with persistent vertigo/dizziness and strong nystagmus might have suffered barotrauma, resulting in inner ear dysfunction. Thus, for these divers we prescribed adenosine triphosphate disodium to improve the circulatory disturbance in the inner ear, mecobalamin to improve peripheral neuropathy, and betahistine mesilate to improve vertigo/dizziness.
First, we compared Eustachian tube function in healthy volunteers with that in patients who experienced a SCUBA divingY related accident. Second, we compared patients with AV with those without AV. The patients with AV underwent Eustachian tube function testing a second time after their vertigo/dizziness and nystagmus improved. Calculations were performed with Stat Mate 3 software (Atoms, Japan). The Mann-Whitney U test was used for statistical analysis; p G0.05 was considered significant.
RESULTS Divers Without Diving Complications (Healthy Volunteers) On the basis of the criteria mentioned above, 9 of 20 healthy volunteers (45.0%) were diagnosed with Eustachian tube dysfunction (Table 1). All of the healthy volunteers with Eustachian tube dysfunction had tubal stenosis. With sonotubometry, the mean T SD duration was 366.8 T 176.6 milliseconds, and the mean T SD amplitude was 14.3 T 6.5 dB for the affected ears. With the impedance test, the mean T SD open pressure was 383.7 T 184.4 daPa, and the mean T SD maximum air content was 0.5 T 0.2. Seven of 20 healthy volunteers (35.0%) were judged to have irregular compliance curves. Divers With Diving Complications Almost all divers with otological symptoms (97.7%) were diagnosed with Eustachian tube dysfunction (Table 1), and all divers with Eustachian tube dysfunction had tubal stenosis. In sonotubometry, the mean T SD duration was
FIG. 3. Classification of Eustachian tube function based on compliance curves. In each graph, the arrow at the lower left represents the start of the Valsalva maneuver, and the arrow at the lower right represents swallowing after the Valsalva maneuver. The type D curve has a normal pattern, whereas the other types of curves (A; Ba, Bb, Bc; and Ca, Cb) have abnormal patterns. When the pattern of the compliance curves improved from type A to type D, we concluded that it reflects an improvement in Eustachian tube function. Otology & Neurotology, Vol. 35, No. 5, 2014
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ALTERNOBARIC VERTIGO IN DIVERS TABLE 1.
853
Results of subjects with or without diving complications Impedance test
Age N Divers without otological symptoms (healthy volunteers) Divers with otological symptoms With AV Without AV
(yr)
20 33.5 T 13.9
Sex
Eustachian tube (M/F) dysfunction
(normal/irregular) 13:7
43/44
229.8 T 219.4c
9.1 T 7.9b 463.9 T 154.7
0.4 T 0.2a
4:40
14/15 29/29
242.7 T 200.3 228.3 T 230.0
9.9 T 7.6 9.1 T 8.1
0.3 T 0.3 0.4 T 0.2
2:13 2:27
15 35.2 T 8.6 29 38.8 T 12.7
(daPa)
Compliance curves
(ml)
44 37.5 T 11.5 11:33
(dB)
Maximum air content
0.5 T 0.2a
9/20
(ms)
Open pressure
366.8 T 176.6c 14.3 T 6.5b 383.7 T 184.4
6:14
3:12 8:21
Sonotubometry Duration Amplitude
443.7 T 181.7 491.0 T 154.1
a
p G 0.05. p G 0.002. p G 0.001. AV indicates alternobaric vertigo.
b c
229.8 T 219.4 milliseconds, and the mean T SD amplitude was 9.1 T 7.9 dB for the affected ears. For the impedance test, the mean T SD open pressure was 463.9 T 154.7 daPa, and the mean T SD maximum air content was 0.4 T 0.2. Thirty-six of 40 (90.0%) divers were judged to have irregular compliance curves. Fifteen of the divers with otological symptoms (34.1%) experienced AV. There were significant differences between the mean duration ( p G 0.001), amplitude ( p G 0.002), and maximum air content ( p G 0.05) of divers with otological symptoms and those of healthy volunteers. However, there were no significant differences in these parameters between divers with AV and those without AV.
signs or DCS symptoms. The mean T SD duration of vertigo/dizziness symptoms after treatment was 11.1 T 5.4 days, but nystagmus continued for 25.0 T 20.6 days. Eustachian tube function of the affected side in divers with AV is shown in Table 3. Within the observational period, the Eustachian tube dysfunction of 14 divers improved. Their vestibular symptoms also improved and stabilized. After treatment, only one diver (no. 12) experienced AV; the remaining divers (9/10; 90.0%) did not experience AV. No other complications, such as progressive sensorineural deafness or DCS symptoms, occurred while the divers were being followed clinically.
Divers With AV The clinical findings of divers with AV are summarized in Table 2. For 7 of the 15 divers, it was the first time they had experienced AV. The remaining eight divers had experienced AV previously. Eleven of 13 divers (84.6%) had allergic rhinitis; none of these divers received allergy treatment. Except for one diver (no. 8; see Table 2) who suffered from otitis media with effusions, divers with AV (93.3%) did not present with cochlear symptoms. In addition, their tympanometry results were normal (Jerger A type). In nearly all of the divers with AV (11/15; 73.3%), AV symptoms appeared after ascent. In 7 of the 15 divers, vestibular symptoms had disappeared immediately (within less than 10 min) after ascent. The remaining eight divers, however, experienced continuous vertigo/dizziness symptoms up to the time of their first visit to our clinic. At the first clinic visit, we observed nystagmus in eight divers. However, in most of the divers (5/8; 62.5%) the nystagmus was trivial. Of the three divers with definitive nystagmus, one diver (no. 15) exhibited gaze nystagmus toward the unaffected side (Grade I), whereas two divers (nos. 13, 14) exhibited positional nystagmus toward the unaffected side. Of the six divers who underwent head impulse testing or caloric testing, all of them exhibited normal results. None of the divers had positive fistula
Generally, AV is thought to be elicited by a degree of inadequate pressure equilibration of the middle ear (2). The symptoms of AV are transient and do not cause permanent damage to the vestibulocochlear apparatus (11). In divers, AV mostly occurs on ascent from a dive or at the surface just after ascent (5). In the present study, 11 of 15 divers (73.3%) experienced symptoms of AV after ascent, and nine of these divers (81.8%) displayed type a or b (including type A) compliance curves when subjected to impedance testing (Tables 2, 3). The one diver (no. 12) who experienced AV after treatment had a type Ca compliance curve (Table 3). These findings indicate that divers with type a or b compliance curves are prone to AV as they ascend from a dive, probably because the expanding air in the middle ear is not released from the Eustachian tube. Roydhouse (3,4) proposed that the increased middle-ear pressure that occurs during dives pushes the eardrum outward and depresses the footplate of the stapes into the vestibule of the inner ear, resulting in AV. This hypothesis is compatible with our results. Interestingly, in the present study, 8 of 15 divers manifested persistent vertigo/dizziness. Swallowing when the nose is obstructed could result in abnormal negative or positive pressure in the middle ear; this is termed the Toynbee phenomenon (12). Past studies showed that positive middle-ear pressure results in an objective
DISCUSSION
Otology & Neurotology, Vol. 35, No. 5, 2014
Copyright © 2014 Otology & Neurotology, Inc. Unauthorized reproduction of this article is prohibited.
First attack
First attack
Yes
First attack
First attack
Yes
Yes
Yes
97
97
97
3
2
97
6
97
97
2
4
1
4
5
6
7
8
9
10
11
12
13
14
15
Yes
Yes
First attack
First attack
First attack
97
3
Yes
Yes
Yes
Yes
Yes
No
Yes
Yes
NT
Yes
No
NT
Yes
Yes
Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Normal
Normal
Normal
Normal
Normal
Normal
Normal
Conductive
Normal
Normal
Normal
Normal
Normal
Normal
A
A
A
A
A
A
A
C1
A
A
A
A
A
A
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
Yes
A
97
Normal
2
Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Tubal stenosis Normal
After ascent G10 min
Yes
Yes
7
1
After ascent Persistent dizziness After ascent Persistent dizziness During Persistent diving dizziness After ascent Persistent dizziness After ascent Persistent dizziness During Persistent descent vertigo After ascent Persistent vertigo After ascent Persistent vertigo
During G10 min safety stop After ascent G10 min
During G10 min diving After ascent G10 min
After ascent G10 min
After ascent G10 min
Duration
Beginning
Vertigo
Yes
Yes
Yes
Very fine
Very fine
No
No
No
Very fine
Very fine
Very fine
No
No
No
No
Normal
NT
NT
NT
Normal
NT
Normal
Normal
NT
NT
NT
Normal
NT
NT
NT
Head impulse Nystagmus test
Clinical findings of divers with AV
Period of time from onset Eustachian to first Allergic tube Pure tone No. visit (d) Recurrence rhinitis dysfunction audiometry Tympanometry Tinnitus
TABLE 2.
NT
NT
NT
NT
NT
NT
NT
NT
NT
CP negative NT
NT
NT
NT
NT
Caloric test
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
No
9
14
7
15
7
22
7
8
9
52
42
15
7
32
47
15
Improvement DCS Fistula symptoms Vertigo/ Nystagmus sign (e.g., bends) dizziness (d) (d)
854 N. KITAJIMA ET AL.
Otology & Neurotology, Vol. 35, No. 5, 2014
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ALTERNOBARIC VERTIGO IN DIVERS TABLE 3.
Eustachian tube function of affected side in divers with AV
At first clinic visit Sonotubometry
No.
Duration (ms)
Amplitude (dB)
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
245 340 175 490 0 0 690 0 310 160 315 0 420 210 285
10 14 9 20 0 0 20 0 20 9 11 0 20 11 5
Upon improvement of vertigo
Impedance test Open pressure (daPa) 371 177 545 304 † 401 682 † 626
855
Sonotubometry
Impedance test
Maximum air content (ml)
Compliance curve
Duration (ms)
Amplitude (dB)
Open pressure (daPa)
0.5 0.1a 0.4 0.4 0.2 0.2 0.1a 0.1a 1.0 0.1a 0.5 0.1a 0.3 0.1a 0.6
Bb A Ca Ba D Bc A A D A Cb A Cb A Ca
350 605 180 320 165 175 630 420 320 † 295 410 355 230 †
15 21 6 15 8 5 16 27 17 † 20 7 15 12 †
184 520 † † 918 † 631 579 562 639 664 354 485 † 625
Maximum air content (ml)
Compliance curve
Outcome of AV
0.7 0.5 0.5 0.4 0.5 0.4 0.5 0.5 1.2 0.3 0.5 0.4 0.4 0.6 0.2
D Cb D D D Bc D D D Ca D Ca Ca D D
No recurrence No recurrence N/A No recurrence No recurrence No recurrence No recurrence No recurrence N/A No recurrence N/A Recurrence N/A No recurrence No recurrence
†Parameters were technically difficult to measure. a Maximum equivalent volume in A type was set to 0.1 ml for convenience. AV indicates alternobaric vertigo; N/A, not available.
vestibular response (13). Bluestone et al. (14) proposed that any type of nasal obstruction could create the Toynbee phenomenon during swallowing. This notion is consistent with a report of a 15-year-old female patient who experienced persistent AV at ground level. They hypothesized that the persistent vertigo in this patient was a result of chronic nasal obstruction and Toynbee phenomenon, which caused repeated insufflation of positive pressure into her affected ear during swallowing (6). Allergic rhinitis is representative of chronic nasal obstruction, and allergic rhinitis patients have a higher risk of Eustachian tube dysfunction (15). In the present study, the majority of divers with AV had allergic rhinitis (Table 2). Their vestibular symptoms improved with treatment of their allergic rhinitis, which also improved Eustachian tube function (Table 3). These results indicate that nasal allergy is an important risk factor for AV, especially persistent AV. In the present study, Eustachian tube function in divers with a SCUBA divingYrelated accident was significantly impaired compared to that in healthy volunteers (Table 1). Tjernstrom (16) used a pressure chamber to compare the Eustachian tube function of 12 divers who had experienced AV with that of six divers who had not. The divers with a history of AV had higher opening pressures. Moreover, half of the divers with a history of AV experienced vertigo and nystagmus in the chamber (16). Surprisingly, in our study, we did not observe a significant difference in Eustachian tube function of divers with AV and divers without AV (Table 1). These results suggest that Eustachian tube dysfunction can contribute to SCUBA divingYrelated accidents and that divers with Eustachian tube dysfunction are prone to developing AV. AV onset may be caused not only by Eustachian tube dysfunction but also by other factors, such as excessive speed on ascending/descending, inexperience, underdeveloped
diving skills, health condition, and so on. For instance, because of discomfort associated with plugged ears, divers who have difficulty clearing their ears may become impatient, performing the Valsalva maneuver to the point of putting excessive positive pressure on the mesotympanum, which could severely injure the affected ear. Further investigation is needed to clarify additional factors contributing to the onset of AV. According to Parell and Becker (17), the differential diagnoses of vestibulocochlear symptoms in SCUBA divers include barotrauma like perilymph fistula, IEDCS, nitrogen narcosis, high-pressure nervous syndrome (HPNS), contaminated air, AV, unequal caloric simulation or response, hyperventilation, and sensory deprivation. Generally, all of these symptoms except perilymph fistula, IEDCS, and HPNS are transient. IEDCS occurs after diving that exceeds the no-decompression limits. HPNS is associated with deep diving (over 130 m) while breathing a helium-oxygen mixture. IEDCS and HPNS are usually complicated by neurologic findings. In the present study, all of the divers dove to moderate depths (not more than 30 m) and did not breathe a heliumoxygen mixture. They followed the instructions of a dive computer and decompressed appropriately. They did not experience any neurologic manifestations, only vestibular symptoms. Therefore, we ruled out IEDCS and HPNS as potential diagnoses. AV can be mistaken for not only IEDCS and HPNS but also for inner ear barotrauma. Molvaer and Albrektson (8) reported that the odds for AV in divers experiencing middle-ear barotrauma are 2.63 times than that for divers who never experienced barotrauma. This suggests that AV is closely connected with barotrauma. Parell and Becker (17) proposed four categories of inner ear barotrauma: (1) hemorrhage within the inner ear; (2) Otology & Neurotology, Vol. 35, No. 5, 2014
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N. KITAJIMA ET AL. divers should undergo thorough evaluation of their vestibular system and for Eustachian tube dysfunction. Accurate assessment is necessary if they are to receive proper treatment. Various other factors, however, make it is difficult to evaluate divers correctly. To address this problem, even if a diver’s symptoms improve, he or she should forego diving if vertigo occurs at the surface as the diver performs the Valsalva maneuver (18). We believe that persistent AV might be an intermediate condition between AV and inner ear barotraumas. It could progress into serious barotrauma such as perilymph fistula.
REFERENCES
FIG. 4. SCUBA divingYassociated diseases that present with vestibular symptoms. Acute vertigo lasting no longer than a few seconds to several minutes was defined as transient alternobaric vertigo (AV). Persistent vertigo/dizziness occurring after diving was defined as persistent AV.
rupture of Reissner’s membrane, resulting in the mixing of endolymph and perilymph; (3) round or oval window fistula; and (4) mixed injuries consisting of one, two, or three of these entities. In the present study, for all of the divers with persistent AV, AV was not associated with cochlear and fistula symptoms. Therefore, there was little possibility of perilymph fistula in these cases. Suzuki et al. (13) proposed the following series of events leading to AV. The transmission of pressure from the middle ear to the inner ear occurs when changes in middle-ear pressure cause the oval windows to vibrate, which affects endolymphatic flow. This leads to alterations in the activity of primary vestibular neurons, ultimately resulting in the pressure-induced vestibular response that causes AV. These divers might have had slight barotrauma without cochlear symptoms. However, previous findings led us to hypothesize that persistent AV might reflect an intermediate condition between AV and inner ear barotrauma. Figure 4 lists diseases, in addition to persistent AV, that manifest as vestibular symptoms after SCUBA diving. To prevent these types of pressure-related injuries in SCUBA divers, further investigations are needed to accurately diagnose persistent AV. CONCLUSION In summary, our study provides evidence supporting specific evaluation of divers who experience AV. These
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Otology & Neurotology, Vol. 35, No. 5, 2014
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