Middle ear barotrauma in scuba divers

Transcription

1 Journal ofwilderness Medicine, 5, (1994) ORIGINAL ARTICLE Middle ear barotrauma in scuba divers MICHAEL J. KORIWCHAK, MD* and JAY A. WERKHAVEN, MD DepartmentofOtolaryngology, Vanderbilt University Medical Center, S-2100 Medical Center North, Nashville, Tennessee , U.S.A. Middle ear barotrauma is the most common health hazard of scuba diving. To investigate the overall incidence of middle ear barotrauma, a prospective incidence study of 51 novice divers and 46 experienced divers was conducted. Otoscopy was performed on the divers before and immediately following a single dive. The overall incidence of mild barotrauma was 40%, and the incidence of severe barotrauma was 27%. No tympanic membrane perforations were found. The most common presenting symptoms were difficulty clearing ears during descent, ear pressure, and ear pain. Barotrauma was not associated with diver age, sex, experience, otolaryngologic history, or medications. Barotrauma was associated with poor underwater visibility, difficulty clearing ears during ascent, and hearing loss after surfacing. Key words: diving; barotrauma; hazard; middle ear Introduction Sport scuba diving has undergone remarkable expansion in the past 15 years. The sport has grown from approximately scuba divers in 1975 [1] to current estimates of million [2]. Each year approximately new scuba divers become certified [3]. This constitutes a large and rapidly growing group with unique health risks and health problems. Ear complaints constitute the most common problem for which divers seek medical attention. In a series of 1001 disorders in 650 scuba divers, ear complaints were the most common (65%) [3]. Furthermore, divers may avoid seeking medical attention in relatively remote dive locations and seek medical attention after returning home. Thus, physicians may expect to see increasing numbers of diving-related ear complaints, regardless of geographic location. Mechanism of middle ear barotrauma (Figure 1) At sea level, the pressures of the external auditory canal and middle ear are equal at 760 mm Hg (1 atm); see Fig. 1. Descent to 2.6 ft below the surface raises the pressure in the external canal to 800 mm, creating a 40-mm gradient across the tympanic membrane. This produces a sensation of pressure in the ear. At this point, the diver must perform the Valsalva maneuver to actively equalize the pressure in the middle ear. Ifthe diver does not equalize and descends to 3.9 ft, the pressure gradient across the tympanic membrane increases to 90 mm Hg. The relative low pressure in the middle ear ruptures blood vessels 'To whom correspondence should be addressed. Additional reprints of this chapter may be obtained from the Reprints Department, Chapman & Hall, One Penn Plaza, New York, NY Chapman & Hall

2 390 Koriwchak and Werkhaven Fig. 1. Mechanism of middle ear barotrauma in scuba divers. At the surface, pressures in the external auditory canal (A) and middle ear (B) are equal at 760 mm Hg. As the diver descends, the pressure in the external ear rises. If the diver does not equalize the middle ear pressure by performing the Valsalva maneuver, the pressure gradient across the tympanic membrane may rise to as high as 90 mm Hg at a depth of 3.9 ft. The tympanic membrane may rupture when the gradient exceeds 100 mm Hg. in the tympanic membrane and middle ear mucosa. These changes in the tympanic membrane are visible with an otoscope. A middle ear effusion of either blood or serous fluid may also result. Because the pressure in the nasopharynx equals the ambient pressure at depth, the pressure gradient across the tympanic membrane is also present across the eustachian tube. A high pressure gradient locks the eustachian tube closed, and active equalization by the diver is impossible unless the pressure gradient is reduced by ascending. If the diver fails to equalize and continues to descend, the pressure gradient across the tympanic membrane rises to 230 mm Hg at 10 ft and 345 mm Hg at 15 ft. The tympanic membrane may rupture at pressures beyond 100 mm Hg [4]. Although equalization during descent is an active process performed by the diver, expanding air in the middle ear during ascent vents passively through the eustachian tube to the nasopharynx. Occasionally, the mucosa of the eustachian tube becomes edematous from forced equalization and/or middle ear barotrauma, and passive equalization is impaired. This causes a sensation of pressure and pain in the ear during ascent. Whereas the pathophysiology of middle ear barotrauma is understood, its epidemiology and frequency are not known. Current information is mostly limited to data from doctor visits by injured divers. As middle ear barotrauma may be asymptomatic, and as many symptomatic divers do not see a doctor, there is a significant selection bias. The purpose of this studywas to survey and examine all divers at thewater's edge, regardless ofsymptoms. Our goal was to identify risk factors in both diving conditions and divers themselves to help predict the occurrence of middle ear barotrauma.

3 Middle ear barotrauma in divers Table 1. Classification of middle ear barotrauma 391 Class o Description Normal tympanic membrane Hemorrhage around malleus Dullness/erythema of tympanic membrane Middle ear hemorrhage Bubbles or air-fluid level visible Complete hemotympanum Tympanic membrane perforation Materials and methods This study is a prospective incidence survey of novice and experienced divers. Divers were examined over a series of trips from Nashville, Tennessee to various locations in Florida. Each trip was arranged through a divemaster or dive instructor. Before entering the water, the divers were approached by one of the authors, and the study was explained. Divers who agreed to participate were interviewed about past otolaryngologic and general medical history, and otoscopy was performed. Those who had dived within the past several days and showed evidence of barotrauma were excluded. At least one of the authors participated in each dive to assess and record diving conditions. Water temperature was recorded from the diving regulator instrument console of one of the authors. Underwater visibility was carefully estimated but not objectively measured. Immediately following the dive, the divers were interviewed about ear symptoms (ear pain or pressure, difficulty clearing ears, hearing loss, tinnitus, dizziness, or drainage). The otologic exam was repeated. Maximum depth and bottom time were recorded from each diver's console or was estimated. Otoscopic findings were graded on a 0-5 scale as outlined in Table 1. This classification is an adaptation of other similar classifications [5,6]. Divers were classified by the degree of barotrauma in the worst ear. Classes 1 and 2 are considered mild barotrauma, and Classes 3,4, and 5 are considered severe barotrauma. Both examiners (the authors) are otolaryngologists. During the first dive trip, each diver was assessed by both examiners together in order to establish consistency between them. The data were recorded on standardized forms and entered into a computer database (Filemaker II, Apple MacIntosh). The chi-square test was used to assess statistical significance.. Results One hundred three divers were examined over 11 dives from September 1990 through August Fifty-seven "beginner" divers were examined on the first open water dive for SCUBA certification. The remaining 46 "experienced" divers had been certified at some point prior to the study dive. Sixty-five males and 38 females were tested. Ages ranged from 12 to 46 years and averaged 26.5 years. Age was inadvertently not recorded in one subject. Forty divers reported some otolaryngologic history. Sixteen divers took medication

4 392 Table 2. Middle ear barotrauma in scuba divers (postdive exam) Koriwchak and Werkhaven Class No. ofdivers % a a a Total either to protect against motion sickness or to improve the ability to equalize the ears. Of the 38 female divers, 16 took oral contraceptives. No significant tympanic membrane abnormalities were noted on the predive otoscopic exams. Table 2 outlines the postdive otoscopic findings for the entire group of 103 divers. Approximately 32% had a normal tympanic membrane after diving (class 0). Forty-one percent had mild barotrauma (Classes 1 or 2) and the remaining 27% had severe barotrauma (Classes 3 or 4). No tympanic membrane perforations (Class 5) were observed. Middle ear barotrauma and diver experience (Table 3) When beginner divers are compared to experienced divers, a trend is observed in which experienced divers tend to sustain mild middle ear barotrauma (MEBT), whereas beginner divers have roughly equal proportions of mild and severe MEBT. However, the difference is not statistically significant (p >.10). Moreover, the proportions of both beginner and experienced divers sustaining MEBT of any kind were similar (66% vs. 70%). MEBT and sex/age (Table 3) The proportion of each sex sustaining MEBT of any kind are very similar (69% vs. 66%). Although males tend to receive mild MEBT and females have a roughly equal likelihood of sustaining either mild or severe MEBT, the difference is not statistically significant (p >.10). When examined with respect to age, MEBT appears somewhat more frequently in those over 25 years of age (72% vs. 66%). However, the difference is not statistically significant. MEBT and otolaryngologic history (Tables 3 and 4) Forty divers reported some otolaryngologic history. Ear problems were most commonly reported. These included a history ofpe tubes in childhood (four cases), otitis media (four cases), and otitis externa (four cases). The remainder consisted of minor problems such as occasional earaches or cerumen. Divers with sinus problems included four with "occasional sinusitis" and four with "sinus headaches." This group included the only diver that had a previous major otolaryngologic procedure (nasal polypectomy). Six divers reported difficulty with clearing the ears or sinuses on previous dives. Thirteen divers had a history of inhalant allergies.

5 Middle ear barotrauma in divers 393 Table 3. Barotrauma and diver characteristics Characteristic Barotrauma Total None Mild Severe (p-value) (Class 0) (Class 1-2) (Class 3-5) Diver experience Beginner 19 (33%) 20 (35%) 18(31%) 57 Experienced 14 (30%) 23 (50%) 09 (20%) 46 Sex Male 20 (31%) 30 (46%) 15 (23%) 65 Female 13 (34%) 13 (34%) 12 (32%) 38 Age <25 17 (38%) 18 (40%) 10 (22%) 45 >25 16 (28%) 24 (42%) 17 (30%) 57 Past Otol. Hx. Yes 14 (30%) 20 (43%) 12 (26%) 46 No 19 (33%) 23 (40%) 15 (26%) 57 Medications (except OCPs) Yes 05 (31%) 04 (25%) 07 (44%) 16 No 28 (32%) 39 (45%) 20 (23%) 87 Oral contraceptives Yes 07 (44%) 05 (31%) 04 (25%) 16 No 06 (28%) 08 (36%) 08 (36%) 22 Neither any of the subgroups nor the entire group reporting an otolaryngologic history had a (statistically) significantly different pattern of MEBT than the parent group. However, the number of divers in each subgroup is quite small. It is noteworthy that all six divers that had previous ear and/or sinus difficulty had some form of MEBT. The diver Table 4. Barotrauma and otolaryngologic history Otol. history Barotrauma None Mild Severe (Class 0) (Class 1-2) (Class 3-5) Total Prevo ear Hx. Prevo sinus Hx. Ear/sinus prob. on a prevo dive Inhalant allergy

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7 Middle ear barotrauma in divers 395 Table 6. Barotrauma and dive conditions Factor Barotrauma Total None Mild Severe (p-value) (Class 0) (Class 1-2) (Class 3-5) Underwater visibility < 15 ft 08 (22%) 13 (37%) 14 (40%) 35 > 15 ft 25 (37%) 30 (44%) 13 (19%) 68 (p < 0.10) Water temperature <70 F 22 (34%) 23 (36%) 19 (30%) 64 > 70 F 11 (28%) 20 (51%) 08 (21 %) 39 Maximum depth <30 ft 14 (28%) 21 (42%) 15 (30%) 50 >30 ft 19 (36%) 22 (42%) 12 (22%) 53 Bottom time <30 min 19 (36%) 17 (32%) 17 (32%) 53 >30min 14 (28%) 26 (52%) 10 (20%) 50 Table 7. Barotrauma and dive symptoms Symptom Barotrauma None Mild Severe (Class 0) (Class 1-2) (Class 3-5) Any symptom No symptoms (p < 0.05) Ear pressure Difficulty clearing (descent) Ear pain Hearing loss Difficulty clearing (ascent) Tinnitus Vertigo Ear drainage Other Eye pain Epistaxis (two cases) "Sinus pain"

8 396 Konwchak and Werkhaven clearing the ears during ascent were less common but were much more strongly predictive of severe MEBT. Tinnitus, vertigo, and ear drainage were rare. Nonotologic symptoms were all related to sinus barotrauma. Dividing the divers into symptomatic and asymptomatic groups allows observations regarding the sensitivity, specificity, and predictive value of symptoms with respect to severe MEBT. Of the 41 divers reporting symptoms, 20 had severe MEBT, giving the presence of symptoms a 49% positive predictive value for severe MEBT. Of the 62 asymptomatic divers, 55 had either no MEBT or mild MEBT. Thus, the absence of symptoms has a predictive value of 89% for the absence of severe MEBT. Similar calculations yield a sensitivity of 74% and a specificity of 72%. Discussion The increasing popularity of sport scuba diving creates a growing group with unique health problems. These problems include various forms of barotrauma, decompression sickness, vertigo, loss of consciousness, polluted water, poisoned air supply, otitis, drowning, and temporomandibular joint syndrome [1-7]. Barotrauma may affect the external, middle, or inner ear, sinuses, lungs, teeth, GI tract, or facial nerve [8]. Physicians are increasingly called upon to advise prospective divers and injured divers of their future risk of barotrauma. Risk may be modified by previous barotrauma or by medical problems such as otitis, sinusitis, allergies, or medications, or previous otolaryngologic procedures. This study attempts to provide some of the data necessary to counsel divers with respect to middle ear barotrauma, the most common hazard of scuba diving. Of the 103 divers examined, approximately one-third had normal tympanic membranes, 40% had mild MEBT (Classes 1 and 2), and 28% had severe MEBT (Classes 3 and 4). Although barotraumatic tympanic membrane perforations (Class 5) are frequently discussed in the literature [1,2,4,7], none were seen in this series. The total incidence of MEBT in this series was, thus, 68%. This is a considerably higher rate than those of prior reviews. In a study assessing the effect of pseudoephedrine use on MEBT in first-time divers, Brown et al. [9] noted a rate of of 46% in the control group. Among naval divers in training, Bayliss found a MEBT rate of only 20% [10]. Neither of these studies examined previously trained divers or attempted to assess the effect of diving conditions on MEBT. A recently published prospective study [11] of 11 divers showed that after 3 days of repetitive diving, otoscopy was abnormal in 82% of subjects. However, this study examined repetitive diving and examined a much smaller group of divers, all of whom were experienced. Middle ear barotrauma was not examined with respect to diver characteristics or diving conditions. In an effort to identify characteristics among divers associated with an increased risk of MEBT, divers were analyzed with respect to dive experience, age, sex, past otolaryngologic history, and medication use including oral contraceptives. No relationship between MEBT and any of these characteristics has ever been suggested, and none was found. It is of some interest, however, that experienced diverswho sustain MEBT may be more likely to have a mild case than beginner divers who experience MEBT. This is a reasonable trend to expect if one assumes that experienced divers have more developed ear clearing skills. No obvious differences in MEBT risk were observed in divers that were taking medication. There were too few divers encountered who were taking any single medication to make further observations. Because of the common use of oral contraceptives among

9 Middle ear barotrauma in divers 397 women, this medication was considered separately. No differences in MEBT occurrence were found in women taking oral contraceptives. Prior reviews note that preexisting otolaryngologic conditions such as deviated septum ornasal polyps may raise the riskofbarotrauma [2]. Our population included divers with a variety of otolaryngologic disorders including childhood PE tubes, otitis medialexterna, inhalant allergy, sinusitis, and nasal polypectomy. The number in any single groupwas too small to draw conclusions regarding the risk of barotrauma. No single group carried a significantly higher risk. A similar study conducted among pilots also found no relationship between otolaryngologic disorders and barotrauma [5]. Risk factors in this area may require more detailed study. In order to identify diving conditions that may carry an increased risk of MEBT, its frequency and severity were examined with respect to four characteristics commonly used to describe diving conditions. These were underwater visibility, water temperature, maximum depth, and bottom time. Interpretation of the findings must be tempered by the fact that only 11 dives, and, therefore, 11 sets of diving conditions, were observed. Because these did not cover many of the possible combinations of these four characteristics, analysis of each parameter independently is limited. The most significant observation regarding MEBT and diving conditions is the relationship between MEBT and underwater visibility. MEBT was both more frequent and more severe when underwater visibility was less than 15 ft. Both experienced and novice divers were similarly affected. A possible explanation relates the diver's need for an underwater visual reference to determine relative position and movement underwater. Orientation and balance are coordinated by three systems: visual, proprioceptive, and vestibular [12]. Orientation is maintained only if at least two systems are functioning. However, underwater conditions compromise all three of these systems. As the diver is floating free underwater, proprioception provides no information about orientation and movement. Because movement and acceleration are damped by the surrounding water, the vestibular system's ability to detect movement may be reduced. This leaves the diver to rely heavily on visual cues to determine orientation and movement underwater. When underwater visibility is poor, a visual reference is often unavailable. The diver may, therefore, unknowingly undergo significant changes in depth and make no effort to clear the ears. Middle ear barotrauma may result. If this is true, diving techniques such as the use of a descent line (which can provide visual and proprioceptive cues) and expert depth (buoyancy) control may reduce the risk of MEBT. Middle ear barotrauma may occur at depths as little as 4 ft and presents with pain, hearing loss [2], dizziness, and nausea [1]. Asymptomatic barotrauma has never been studied. Among asymptomatic divers, we found a significant incidence of mild barotrauma (45%) and a low but measurable incidence of severe barotrauma (11 %). The three most frequent symptoms (difficulty clearing ears during descent, ear pressure during dive, ear pain during dive) place the diver at approximately 50% risk of severe MEBT. The less frequent symptoms carry a higher risk ofsevere MEBT. Difficulty with the passive process ofclearing ears during ascent is a different and more ominous symptom than difficulty with the active process ofearclearing during descent. The former carries an 80% risk ofsevere MEBT, whereas in the latter the risk is only 52%. All six divers with hearing loss had severe MEBT.

10 398 Conclusions Koriwchak and Werkhaven 1. There is a significant incidence of both mild and severe MEBT in sport scuba divers. However, TM perforations are rare. 2. There is no statistically significant relationship between MEBT and diver age, sex, experience, otolaryngologic history, or medication use. 3. MEBT may be more common and more severe when underwater visibility is less than 15 ft. 4. The most common symptoms of MEBT are ear pressure and/or pain during the dive, and difficulty with ear clearing during descent. Difficulty with ear clearing during ascent and hearing loss after the dive are less common symptoms but are much stronger predictors of MEBT. 5. The incidence of asymptomatic MEBT is low but significant. Acknowledgments: The authors are grateful to the following dive shops for their assistance in the project: BIue Water Scuba, Nashville, TN; Scuba South, Nashville, TN; Captain Corky's Dive Shop, Key Largo, FL; Sea Dwellers Dive Shop, Key Largo, FL; Looe Key Reef and Resort Center, Ramrod Key, FL. References 1. Replogle, W.H., Sanders, S.D., Keeton, J.E., and Phillips, D.M. Scuba diving injuries. Ann. Family Practice 1988; 37(6), Becker, G.D. Barotrauma resulting from scuba diving: An otolaryngological perspective. Physician Sports Med 1985; 13(3). 3. Becker, G.D. and Parell, G.J. Medical examination of the sport scuba diver. Otolaryngol Head Neck Surg 1983; 91, Pullen, F.W. Otolaryngological aspects of diving. Insights Otolaryngol1990; 5(4). 5. Ashton, D.H. and Watson, L.A. The use of tympanometry in predicting otic barotrauma. Aviat Space Environ Med 1990; 61, Kizer, Kenneth W. Medical aspects of scuba diving. In: Noble J., ed. Textbook of General Medicine and Primary Care. Boston: Little, Brown and Co. 1987: Becker, G.D. and Parell, G.J. Medical aspects of scuba diving. Instructional Course, American Academy ofotolaryngology-head and Neck Surgery, September, Becker, G.D. Recurrent alternobaric facial paralysis resulting from scuba diving. Laryngoscope 1983; 93, Brown, M., Jones, J., and Krohmer, J. Pseudoephedrine for the prevention ofbarotitis media: A controlled clinical trial in underwater divers. Ann Emerg Med 1992; 21, Bayliss, c.j.a. Aural barotrauma in naval divers. Arch Otolaryngol1968; 88, Green, S.M., Rothrock, S.G., Hummel, C.B., and Green, E.A. Incidence and severity of middle ear barotrauma in recreational scuba diving. J Wilderness Med 1993; 4, Baldwin, R.L. Differential diagnosis of a dizzy patient. Medical Rounds 1990; 3(3),