Incidence and severity of middle ear barotrauma in recreational scuba diving

Transcription

1 Journal of Wilderness Medicine 4, (1993) ORIGINAL ARTICLE Incidence and severity of middle ear barotrauma in recreational scuba diving STEVEN M. GREEN, MD 1 *, STEVEN G. ROTHROCK, MD 2, CHRISTOPHER B. HUMMEL, MD3, and?l.izabeth A. GREEN, RN4 /Department ofemergency Medicine, Riverside GeneralHospital, 9851 Magnolia A venue, Riverside, CA, 92503, USA 2Department ofemergency Medi~ine, Orlando Regional Medical Center, Orlando, FL, USA 3Department ofemergency Medicine, Loma Linda University Medical Center, Loma Linda, CA, USA 4Intensive Care Unit, Eisenhower Medical Center, Rancho Mirage, CA, USA This prospective observational study was designed to assess the incidence and severity of middle ear barotrauma associated with repetitive recreational scuba diving. Eleven healthy adult experienced scuba divers were observed performing repetitive daily scuba diving over a 15 day period. Otoscopy and tympanometry were performed on days 0,3, 7, 11 and 15. Participants averaged 41 dives during the study period. Mild otalgia occurred at some point in 23% of ears and subsequently resolved in all but one despite continued diving. Eight-two per cent of ears demonstrated otoscopic evidence of middle ear barotrauma by day 3, and all exhibited barotrauma by day 11. Tympanic membrane perforation, hemotympanum, or evidence of inner ear barotrauma did not occur. Tympanometry revealed a significant decrease in middle ear pressures but no evidence of middle ear effusions. Gross measurements of otologic acuity and conduction remained normal. No complications or sequelae were noted at three month follow-up. Otoscopic evidence of middle ear barotrauma and tympanometric evidence of eustachian tube dysfunction developed rapidly in a group of experienced scuba divers performing repetitive recreational diving. Symptoms were minimal and infrequent. No serious otologic dysfunction was noted despite continued repetitive diving, and it is possible that middle ear barotrauma at the degrees observed represents a more benign disorder than has been previously assumed. Key words: barotrauma, middle ear, tympanometry, scuba diving Introduction Recreational scuba diving is extremely popular worldwide. In the US alone there are currently more than five million certified divers [1]. Although pressure-induced traumatic injury to the middle ear is the most common medical complication of scuba diving [2-8], the actual incidence and severity of such middle ear barotrauma (MEBT) in experienced divers is unknown. Scuba divers experience changes in ambient pressure while ascending and descending, which necessitates the frequent equalization, or 'clearing', of their ears every few feet. These equalizations, accomplished by a gentle Valsalva maneuver or by swallowing, transiently open the eustachian tube and allow the middle ear cavity pressure to *To whom correspondence should be addressed Chapman & Hall

2 Incidence of middle ear barotrauma in scuba diving 271 equilibrate with ambient pressure. The tympanic membrane is forced to bulge or retract between each equalization as the abient pressure shifts. These repetitive pressure changes stress the fragile mucosal surfaces of the middle ear and localized edema, congestion and hemorrhage can result. MEBT, also referred to as 'middle ear squeeze' or 'barotitis media', can be associated with otalgia or a mild conductive hearing deficit. Occasionally hemotympanum, pronounced serious effusion, or tympanic membrane rupture can occur [2-4,9-17]. MEBT is typically self-limited and not associated with permanent hearing deficits, except in cases with associated injury to the inner ear [2,3,14,15,18-20]. The appearance of loud tinnitus, persistent vertigo, or sensorineural hearing loss suggests barotrauma to the inner ear and necessitates prompt evaluation by an otologist [9,15,20]. The recent development of dive computers and the availability of live-aboard dive boats have allowed multiple daily dives during periods extending days or weeks. It is likely that this pattern of intensive repetitive diving might precipitate MEBT more frequently or exaggerate its severity; however, there is little original research to guide physicians in counseling their diving patients. We were unable to locate any prospective series describing otologic observations in experienced scuba divers. Two limited reports in novice divers noted symptoms in 20-48% and otoscopic abnormalities in 37% [21,22]. Therefore, we performed a prospective observational study to define the incidence and severity of acute MEBT in a group of experienced, repetitive recreational divers. Methods Eleven healthy adult scuba divers performed repetitive scuba diving from a live-aboard dive vessel over a 15 day period in tropical ocean waters. All used commercially available dive computers for dive planning. Subjects were aware that data were being collected, but no attempts were made to alter their diving behavior. Otoscopy and tyrnpanometry were performed on days 0, 3, 7, 11, and 15. Otoscopic examinations were performed by a single evaluator for all subjects except himself, a second evaluator performed otoscopy on the first evaluator. Tympanic membrane appearance was graded according to the Teed criteria as modified by Edmonds [2,14] (Fig. 1). GRADE 0: Normal appearing tympanic membrane. GRADE 3: Gross hemorrhage throughout the tympanic,membrane. GRADE 1: Erythema of malleus, GRADE 4: Free blood in middle ear. GRADE 2: Erythema of malleus plus mild hemorrhage into the tympanic membrane. GRADE 5: Perforation of the tympanic membrane. Fig. 1. The Teed classification of otoscopic barotrauma.

3 272 Green, Rothrock, Hummel and Green Tympanometry was performed by placing a hand-held sensor into the external auditory canal. A soft rubber tip was used to create an airtight seal, and a painless range of pressure (both above and below ambient) was generated by the instrument (AE105 Tympanometer, American Electromedics Corporation, Hudson, NH, USA). Tympanic membrane compliance was calculated at each pressure and a printed tracing obtained of middle ear compliance in milliliters plotted from -400 to +200 decapascals (dapa) relative to ambient pressure. Tympanograms were classified according to the criteria of Paradise et al. [23] (Fig. 2). A normal tracing (Paradise category NL or TR-s) was defined as a peak compliance 0.2 ml or greater between -100 and 50 dapa, a low compliance tracing (Paradise EFF or TR-g) as a peak compliance less than 0.2 ml at any pressure, a high pressure tracing (Paradise HP) as a peak compliance 0.2 ml or greater at more than 50 dapa, and a low pressure tracing (Paradise HN-s or HN-g) as a peak compliance 0.2 ml or greater at less than -100 dapa. Tympanograms classified as low compliance, high pressure, or low pressure were considered abnormal. Peak compliance and the pressure at peak compliance were determined for each tracing. All otoscopic and tympanometric evaluations were performed at least 90 min after the day's last dive, with subjects in the upright position. At each evaluation period, subjects were questioned regarding otologic symptoms, including pain, hearing impairment or a plugged sensation in either ear. Auditory acuity was grossly tested at frequencies of 128, 256, 512, and 1024 Hz with tuning forks, and was judged as present or absent. Weber and Rinne tests were used to evaluate auditory conduction ~ttwptftsure(dapa) NORMAL LOW COMPLIANCE Complianoe 1m' Compliance 1m' o~~=:;:::::~~~--.j Ral&ltivepressu", (clapaj HIGH PRESSURE R...tivep~IJU.. (d.pa) LOW PRESSURE Fig. 2. Classification of tympanometric tracings.

4 Incidence ofmiddle ear barotrauma in scuba diving 273 Statistical methods consisted of Cochran's test for related observations, Friedman twoway analysis of variance, Wilcoxon signed ranks test, analysis of variance with one-way repeated measures, y! and the paired-samples t-test. A significance level of 5% was chosen and all calculations were two-tailed. The study was approved by the institutional review board of the sponsoring hospital. Results Characteristics of the 11 study subjects are shown (Table 1). None reported pre-existing acute or chronic middle ear dysfunction, sinusitis, upper respiratory infection, otitis media or otitis externa. None had been diving in the three weeks prior to the study period. Overall, the group was comprised of scuba divers with considerable experience; the median number of previous dives was 211. Seven subjects (64%) had commercial involvement in activities related to scuba: certified dive instructor (3), professional underwater photographer (2), marine archaeologist (1) and underwater photography equipment manufacturer (1). One subject was 72 years old and had logged 3800 dives upon study initiation, the first of which was in 1936 using a homemade dive helmet. Medication use by study subjects was infrequent and sporadic, with the following being taken at any time during the study period: transdermal scopolamine (5 subjects), aspirin (5), oral decongestants (3), inhaled decongestants (2), external ear antibiotic drops (2), oral antibiotics (1) and non-steroidal anti-inflammatories (1). Subjects averaged 2.7 dives per day during the study period with typical dive profiles (Table 2). Otalgia was noted in 23% of ears at some point during the study period. This discomfort, when present, was mild and never resulted in missed dives. Despite Table 1. Characteristics of study subjects (n=l1) Characteristic Study subjects Range Age mean years (median) 43 (41) Prior dives mean number (median) 876 (211) Sex female 3 (27%) male 8 (73%) Table 2. Dive profiles of study subjects (n=l1)* Characteristic Study subjects Range Mean dives per subject per day Mean dive depth per subject Mean dive duration per subject (number ± so) (meters ± so) (minutes ± so) 2.7± ± ± *Values expressed are means, standard deviations (SD) and ranges of the individual subject means

5 274 Green, Rothrock, Hummel and Green Table 3. Serial otologic assessments* Characteristic Significance Mild otalgia 0% 5% 18% 18% 5% p < Moderate or severe otalgia 0% 0% 0% 0% 0% p=ns Other otologic symptoms 0% 0% 0% 0% 0% p=ns Abnormal otoscopy 0% 82% 91% 100% 100% p < Abnormal tympanometry 5% 9% 18% 14% 14% p=ns Day *Based on ears, n = 22. All statistical calculations are Cochran's test for related observations. NS = not significant. continued diving, otalgia had resolved by study completion in all cases except one (Table 3). No subjects reported hearing impairment or a plugged sensation in their ears at any time. Serial acuity, Weber and Rinne evaluations were consistently normal. No symptoms suggestive of inner ear barotrauma occurred at any time. Otoscopic evidence of MEBT occurred in all study subjects; 82% of ears had abnormal findings by day 3 and all were abnormal by day 11 (Fig. 3). A Teed grade 2 appearance was the most prevalent upon study completion. No ears demonstrated Teed grade 4 or 5 findings at any time. Most ears were asymptomatic in spite of otoscopic abnormalities, although painful ears exhibited more advanced pathologic findings than did painless ears (X 2, p < 0.001). Thirty-two per cent of ears demonstrated abnormal tympanometry at some point during the study period; however these patterns usually normalized despite continued diving (Table 4). Low compliance tracings suggestive of middle ear effusion were not encountered. Abnormal tympanometry was not associated with the degree of otoscopic abnormality (Table 5). A trend toward increased tympanic membrane peak compliance over time was noted Table 4. Serial tympanometry* Pattern Normal 95% 91% 82% 86% 86% Low compliance 0% 0% 0% 0% 0% High pressure 0% 0% 9% 5% 0% Low pressure 5% 9% 9% 9% 14% *Based on ears, n = 22. Comparison of normal versus abnormal was not statistically significant (Cochran's test for related observations, p > 0.25) Day

6 Incidence ofmiddle ear barotrauma in scuba diving % Ears 6O"k 40% o Teed 0 o Teed 1 Teed 2 Teed 3 20% O%.L.L...&ILo Day of Evaluation Fig. 3. Otoscopic findings: the distribution of Teed classifications seen on sequential otoscopic evaluations was significantly different overall (Friedman two-way analysis of variance, P = 0.001). Subsequent comparison of individual evaluation days (Wilcoxon signed ranks test) revealed that days 0 and 3 were significantly different than all other evaluation days and days 7, 11 and 15 were statistically similar to all other evaluation days. No ears demonstrated Teed grade 4 or 5 findings at any time. (Fig. 4), although this difference was not statistically significant. Pressures at peak compliance, however, were significantly decreased at day 3 and remained approximately 25 dapa below baseline throughout the study period, indicating a persistent low pressure condition in the middle ear (Fig. 5). No subjective complications or sequelae were noted in any study subjects at three month follow-up. Table 5. Correlation of otoscopy with tympanometry* Teed Pattern Normal Low compliance High pressure Low pressure *Based on 110 separate measurements (22 ears at 5 periods each). Comparison of normal versus abnormal tyrnpanometry was not statistically significant (X 2, p = 0.381).

7 Green, Rothrock, Hummel and Green :=- E-CI) U 0.8 C.! Q. E ~ as CI) a C as CI) :IE 0.2 o o Day of Evaluation Fig. 4. Mean peak tympanic membrane compliance ± SE. These means were not statistically different (analysis of variance with one-way repeated measures, F = 2.302, P = 0.098). Discussion Our observations suggest that MEBT occurs rapidly and consistently in repetitive recreational scuba divers. Our participants experienced minimal or no symptoms despite the presence of pronounced otoscopic abnormalities. We were unable to locate any prospective series describing otologic observations in experienced scuba divers, and found only two such reports [21,22] in novice divers. Other literature regarding MEBT consists of reviews [1,3,5,9-12,16-18,24-33], case reports [2,15,19,20,34], textbooks [2,4,6,8] or situations not analogous to recreational scuba diving (i.e. pressure chambers, submarine escape chambers) [14,34-37]. Bayliss [21] described his experience at the Royal Australian Navy Diving School with 526 trainees, most with no diving experience. One hundred and six of these student divers (20%) developed aural symptoms and otoscopy revealed MEBT in the majority of these ears (33%, 36%, 29%, 1%, 0% and 1% for Teed grades 0 to 5, respectively). Asymptomatic divers were not examined, so the overall incidence of otoscopic abnormalities was not determined. Paaske et al. [22] evaluated 21 students in a beginning scuba course. Forty-eight per cent of divers developed aural symptoms and 37% of ears overall exhibited MEBT (0%, 35%, 1%, 1%, 0% and 0% for Teed grades 0 to 5, respectively). All otoscopic abnormalities had resolved one week after diving.

8 Incidence ofmiddle ear barotrauma in scuba diving Q. III ~ CD () c.! 'a 9990 E 0 0.II: III 9980 CD Q.-III CD..~ 9970 ~Q. c 9960 III CD ::E o 3 7 Day of Evaluation Fig. 5. Mean middle ear pressure at peak tympanic membrane compliance ± SE. These means were statistically different (analysis of variance with one-way repeated measures, F = 3.712, p = 0.023). Subsequent comparison of individual evaluation days (paired samples t test) revealed that day 0 was statistically different than all other evaluation days and days 3, 7, 11 and 15 were not. The reports of Bayliss and Paaske et al. demonstrate that novice divers undergoing a small number of dives frequently experience MEBT and otologic symptoms. Our experienced divers also developed MEBT; however, the frequency of symptoms was far less than the reported for beginners. We presume that experienced divers are better able to maintain effective eustachian tube patency. Available literature uniformly recommends that persons with MEBT immediately discontinue diving until full otoscopic recovery [2-6,9-11,14,16-19,21,27-29,32,33]. Unfortunately, justification for this maxim appears anecdotal, as we were unable to locate any controlled trials on treatment options for MEBT. Our subjects continued repetitive diving for many days after the diagnosis of MEBT was established, and despite tbis continued diving, their otoscopic findings worsened only slightly and their symptoms were minimal and infrequent. Tympanic membrane perforation, hemotympanum or evidence of inner ear barotrauma did not occur. Thus, MEBT at the levels observed appears more subjectively benign than has been previously assumed. Recommendations that asymptomatic experienced divers with Teed grades 1 to

9 278 Green, Rothrock, Hummel and Green 3 MEBT immediately discontinue diving may be unnecessarily restrictive. The presence of hemotympanum (Teed 4) or tympanic membrane perforation (Teed 5), however, represent clear contraindications to continued diving. Abstinence also seems prudent for divers with substantial otalgia. Divers manifesting evidence of inner ear barotrauma (e.g. vertigo, tinnitus, sensorineural hearing loss) should avoid further diving and promptly seek the attentions of an otologist [1,9,15,20]. People who continue diving in the presence of Teed 1 to 3 MEBT should take special precautions to clear their ears more frequently than usual. Decongestants may be a useful adjunct [1,2,4,6,9,32]. There is no literature evidence to suggest that his continued diving places one at higher risk for inner ear barotrauma. Our tympanometric evaluations verified that, despite abnormal otoscopy, our study subjects maintained normal aeration of their middle ear cavities. Low compliance tracings are virtually diagnostic of middle ear effusion [23,38-43] and these patterns did not occur in our study subjects. The few abnormalities seen in our group consisted of high or low pressure tracings, suggesting difficulty in equalizing middle ear pressures. Frequently, the abnormal tympanometric tracings reverted to normal at the next evaluation point, suggesting that this eustachian dysfunction often improved spontaneously despite continued diving. We found that tympanometry did not correlate with otoscopic abnormalities at the levels observed (Teed grades 1 to 3), suggesting that relatively normal middle ear pressure physiology was maintained despite MEBT. Tymopanometry would have confirmed Teed grades 4 and 5 MEBT if they had occurred in our group. Hemorrhagic fluid or clots in the middle ear (Teed grade 4) would impair tympanic membrane mobility and produce a low compliance tracing [23,38-43]1' Tympanic membrane rupture (Teed grade 5) allows complete transmittal of pressure changes through the perforation, resulting in a characteristic flat-line tympanometric tracing [23]. Further studies of MEBT might benefit from audiometric and vestibular testing. Although our gross assessments of hearing acuity were consistently normal, it is possible that mild hearing loss imperceptible to our participants may have occurred. Similarly, a small degree of vestibular dysfunction might have resulted, although no labyrinthine symptoms or sequelae were noted. Little is known about prophylactic or therapeutic interventions for MEBT. Decongestants are frequently recommended for both indications [1,2,4;6,9,32], and the usefulness of salicylates, antibiotics, and oral steroids has been conjectured [3,4,6,44]. Our data might provide the basis for future controlled trials of these modalities. Conclusion A prospective observational study was performed to assess the incidence and severity of MEBT associated with repetitive recreational scuba diving. We found that otoscopic evidence of middle ear barotrauma and tympanometric evidence of eustachian tube dysfunction developed rapidly despite minimal and infrequent symptoms. No serious otologic dysfunction was noted despite continued repetitive diving and it is possible that middle ear barotrauma at the degrees observed represents a more benign disorder than has been previously assumed.

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