Pressure Regulating Ear Plug Testing in a Pressure Chamber

Transcription

1 RESEARCH ARTICLE Pressure Regulating Ear Plug Testing in a Pressure Chamber J UMAH MD, S CHLACHTA M, H OELZL M, W ERNER A, S EDLMAIER B. equalization is not performed, a middle ear barotrauma Pressure regulating ear plug testing in a pressure chamber. Aviat Space can develop. A mild manifestation is characterized by otalgia, a sensation of fullness in the ear, and hearing loss. Environ Med 2010; 81: Introduction: Middle ear barotrauma is a condition frequently associated with flying. It is usually caused by Eustachian tube (ET) dysfunction. Complicated cases can be accompanied by nausea, the development of a hemotympanon, or a tympanic membrane Pressure-regulating earplugs (PREP) should improve complaints due to pressure equalization problems. Methods: There were 21 patients with a rupture ( 11,12 ). At a pressure differential of about 60 mmhg history of pressure equalization problems while flying who were examined. ET function was measured with exploratory tests and in a pressure (80 mbar) passengers report ear discomfort and might chamber. In a double-blind study, PREP were examined using continuous impedance measurement in the pressure chamber. Eardrum deflec- higher pressure differentials can cause a more severe mid- show the first signs of a mild middle ear barotrauma; tion and pressure-equalizing maneuvers were also examined. During dle ear barotrauma ( 15 ). pressure exposure the subjective state of patients with and without PREP was compared. Results: Evidence of ET dysfunction was found in twice Pressure-regulating earplugs (PREP) are intended to as many patients with the impedance method in a pressure chamber alleviate such pressure equalization problems while flying. They are commercially available from a number of compared to tympanometry or the Valsalva test. Use of PREP reduced the rate of pressure changes in the external auditory canal. Maximum different manufacturers and can be purchased at drug pressure was reached with a delay of about 7 min. The number of pressure-equalizing maneuvers did not differ significantly. Using PREP the stores, airports, and from some airlines on board the aircraft. The principle of PREP is to seal the external audi- patients reported a significantly better subjective state on the VAS scale of compared to without PREP. Conclusions: tory canal so that pressure equalization at the eardrum Continuous impedance measurements in the pressure chamber identified ET dysfunction more often than the exploratory ET function tests is delayed by an integrated filter. The intended effect of commonly used in routine diagnostics. This novel finding requires further validation. Although use of PREP showed no signs of improving ET the rate of increase in the pressure differential between PREP is thus to lessen eardrum distension by reducing function, it did significantly improve individual subjective state during the external auditory canal and the middle ear, and thus sudden pressure changes. IP: On: Tue, 20 to Nov reduce 2018 complaints 00:31:38 during descent. The functional Keywords: ear barotrauma, eustachian tube, middle Copyright: ear ventilation Aerospace, flying discomfort, impedance measurement. Delivered by Medical unit comprising Association the ET and the middle ear should have Ingenta A IRCREW AND PASSENGERS frequently develop problems related to middle ear pressure equalization during air travel. Depending on the study situation, 20 50% of passengers report ear complaints during the flight or after landing ( 3,19,20 ). The symptoms occur because the Eustachian tube (ET) fails to equalize the pressure in the middle ear, which is referred to as middle ear barotrauma. During the climb and descent phases of a passenger aircraft flight, the cabin pressure changes by up to 200 mmhg (267 mbar) ( 6 ). The cabin pressure decreases during the climb phase, creating relative overpressure in the middle ear. Passive opening of the ET equalizes the pressure difference between the nasopharynx and the middle ear. However, the inverse pressure ratio during descent can cause problems, since the increase in cabin pressure creates relative middle ear underpressure that must be actively equalized by an individual. Under physiological conditions, this is done by swallowing, yawning, or other active pressureequalizing maneuvers. If for whatever reason pressure Masen Dirk Jumah, Miriam Schlachta, Matthias Hoelzl, Andreas Werner, and Benedikt Sedlmaier more time to equalize the pressure difference. It must be emphasized that a direct effect on ET function and middle ear ventilation cannot be assumed. The claim by PREP manufacturers that they improve ET function has rightly been criticized by ENT specialists ( 7 ). To date, PREP have received little attention in the scientific literature. Only one scientific study has examined the effect of PREP on the occurrence of in-flight middle ear barotrauma. Middle ear pressure load during rapid pressure changes was simulated in a pressure chamber From the Department of Otolaryngology, Head & Neck Surgery, Campus Charité Mitte, Charité - University Medicine Berlin, Berlin, Germany, and the Center for Space Medicine Berlin (ZWMB), Department of Physiology, Campus Benjamin Franklin, Berlin, Germany. This manuscript was received for review in November It was accepted for publication in March Address correspondence and reprint requests to: Dr. med. Masen Dirk Jumah, Department of Otolaryngology, Head & Neck Surgery, Charité - University Medicine, Campus Charité Mitte, Charitéplatz 1, Berlin, Germany; masen.jumah@charite.de. Reprint & Copyright by the Aerospace Medical Association, Alexandria, VA. DOI: /ASEM Aviation, Space, and Environmental Medicine x Vol. 81, No. 6 x June 2010

2 ( 12 ). Other study groups used the pressure chamber for testing ET function. Various studies have included impedance measurement in a pressure chamber under experimental conditions in healthy volunteers ( 5,9 ) and patients with inner ( 13 ) and middle ear ( 14 ) pathologies. In order to evaluate the effectiveness of PREP for patients with impaired ET function, the present study investigated the ET function and subjective state with and without PREP in a controlled pressure chamber protocol. METHODS Subjects The study included 21 patients (12 women and 9 men, ages yr) who reported a history of pressure equalization problems in at least one ear while flying. Criteria for exclusion were previous ET surgery, middle ear or eardrum surgery on the affected ear, a ventilation tube in the eardrum at present, a present strong nasal septum deviation, or head and neck malformations. On measurement days just before pressure exposures, patients were reexamined and excluded if otoscopy revealed a middle ear effusion, an irritated eardrum, or if an upper respiratory infection had occurred in the last 2 wk. The study protocol was approved in advance by the Ethics Commission of Charité - University Medicine Berlin and was conducted in agreement with the Declaration of Helsinki (59 th WMA General Assembly, Seoul, Korea, October 2008). All subjects gave their written informed consent before participating. Exploratory ET Function Tests The exploratory ET function tests included automated ET openings equalizing the pressure difference between the middle ear and the actual chamber pressure tympanometry, pure-tone audiometry (PTA) to determine the air-bone gap, and the Valsalva test. Before the were measured for each ear by impedance analysis in tests an otoscopy and endoscopy of the nose and nasopharynx were done. The tympanograms IP: were On: classi- Tue, 20 pressure Nov 2018 exposures 00:31:38 were carried out at least 4 h apart. the preliminary pressure chamber test series. The two fied according to Jerger ( 10 ) into the following Copyright: categories: Aerospace Medical Additionally, Association the patients adapted to the test situation in Delivered by the Ingenta pressure chamber. normal findings (A type), flat tympanogram (B type), or left shift (C type). Additionally, the pressure values of the tympanometric peaks for A and C type tympanograms were reported. In the PTA an air-bone gap. 10 db was assessed as a middle ear hearing impairment. The clinical Valsalva test was termed positive when the examiner observed an eardrum movement in ear-microscopy while the patient performed a Valsalva maneuver. Pressure Chamber Tests A hyperbaric pressure chamber was used to increase pressure during 2 min (compression or descent phase) to 75 mmhg (100 mbar) above ambient pressure. Then the pressure was held constant for 8 min (isopression or cruise phase) and subsequently lowered to ambient pressure over 2 min (decompression or climb phase). The pressure course during descent and climb phase was 37.5 mmhg z min 21 (50 mbar z min 21 ) or approximately 1640 ft z min 21 (500 m z min 21 ). The use of a hyperbaric pressure chamber allowed the patients to interrupt the test during the potentially painful compression phase. Subsequently the pressure can be lowered to ambient pressure without any potentially painful pressure alteration as in a hypobaric chamber setting. The applied method of continuous impedance measurement in a pressure chamber was introduced by Ingelstedt in 1967 ( 8 ). Of critical importance was the identification of the ET opening, which is characterized by an abrupt change in impedance as the pressure difference between the middle ear and the external auditory canal is equalized and the tympanic membrane returns to its initial position. The resulting impedance leap indicates an ET opening. In our study continuous impedance measurements in the pressure chamber were taken while an ear probe was connected with a silicon earplug (same as used for the PREP but without the filter) and fitted airtight in the external auditory canal. A 230-Hz tone was delivered continuously to the eardrum via a miniature speaker in the probe and the sound reflected from the eardrum was simultaneously recorded by a microphone. A pressure channel in the probe could be either left open to enable pressure equalization between the external auditory canal and the pressure chamber or could be connected to the PREP filter to delay pressure increase in the external auditory canal during the PREP test. Equal perception in both ears was ensured by an additional silicon earplug (with or without PREP filter) fitted to the ear that was not being tested. The connection of the PREP filter was not perceptible by the patients. The eardrum impedance and the pressure in the external auditory canal were recorded continuously and evaluated digitally. Preliminary Pressure Chamber ET Function Test PREP Test On a separate day, at least 96 h after the first pressure chamber exposure, measurements to assess the function of PREP were randomly carried out in only the affected ear. If problems in both ears were reported (nine cases), the subjectively more-affected ear was examined. Measurements with a PREP filter ( N 5 21) were repeated in the same ear without PREP filter ( N 5 21) as controls in a random order. A simple double-blind study design was used. Neither the patient nor the examiner in the pressure chamber knew which measurement was being taken with a PREP filter. The PREP measurements were done on the same day with at least 4 h between the pressure chamber exposures. The PREP contains an alloy filter with a milled microslot. According to the manufacturer s data, the filter causes a predetermined delay in the ambient pressure increase (airflow rate of 0.05 cm 3 z min 21 at a constant pressure difference of 75 mmhg). In the pressure chamber the filter-induced reduction of pressure changes was measured by pressure sensors in front Aviation, Space, and Environmental Medicine x Vol. 81, No. 6 x June

3 and behind the filter. The silicon earplugs and the PREP filters were replaced for each measurement. In the descent and the cruise phase the test subjects were asked to perform all subjectively necessary pressureequalizing maneuvers. These were registered and could be classified in the evaluation as successful ET opening or ineffective attempt to equalize pressure. In the climb phase the patient was urged to refrain from active pressure-equalizing maneuvers, since passive ET opening was expected. At the end of each measurement session the patients reported their subjective state during the measuring procedure on a visual analogue scale (VAS) of 0 to 10 (0 5 no pain, 10 5 strong pain). Statistics Data are presented as mean 6 SD. Normal distribution was confirmed by using a one-sided Kolmogorov- Smirnov test based on the squared sum of the differences between the empirical distribution and the normal distribution with the same mean and variance. The t-test for dependent random variables was used to evaluate differences in means between tests. It compares the extent of the deviation between means with a critical value and is, therefore, one-sided, as is the Chi-square test, which has been used for comparison between categorized data. The null hypothesis that measured data with and without PREP is equal was tested with a significance level set at P, RESULTS Despite a history of complaints in all patients only 9 of 21 subjects had a negative Valsalva test. Likewise tympanograms were considered pathological in only nine cases. Findings were normal in 12 of the 21 affected ears and resulted in A type tympanograms with a peak at dapa ( 2 35 to 8 dapa), while the tympanograms in 6 ears had a negative C type pressure peak at dapa ( to dapa) and was extremely flat in 4 (B type). The PTA showed an air-bone gap below 10 db in all patients, which was within the normal range. The results yielded by continuous impedance measurement in the pressure chamber were classified into three different categories. ET function was classified as normal if active and passive pressure equalization was mostly successful, resulting in an impedance leap, and the pressure equalizing maneuvers during the cruise phase resulted in an eardrum impedance comparable to the grade at ambient pressure. ET function was termed blocked if during descent phase a continuous impedance rise to a maximum value was marked, active pressure equalization attempts were ineffective, and impedance level remained elevated until the end of the climb phase and dropped to the initial value. The term no change was used if no changing of the impedance level was measured during the pressure variation and all of the patient s attempts to open the ET were without an effect on the measured impedance. The preliminary pressure chamber ET function test yielded an impaired ET function in 18 patients: a blocked ET was found in 14 patients and no impedance change was detected in 4 patients. In one patient, the measurement had to be discontinued after 30 s because of strong pain. Two patients had normal findings. Table I shows the results of exploratory ET function tests and the preliminary pressure chamber ET function test. TABLE I. RESULTS OF THE EXPLORATORY ET FUNCTION TESTS AND THE PRELIMINARY PRESSURE CHAMBER ET FUNCTION TEST. IP: On: Tue, 20 Nov :31:38 Tympanometry Copyright: Aerospace Medical Association Pressure Chamber Subject Clinical Symptoms Type Delivered dapa by Ingenta Valsalva Test Air-Bone Gap (db) Impedance Test 1 Flight, Fullness C No Change 2 Flight, Diving A No Change 3 Flight, Diving C Blocked 4 Flight B 1 0 Normal 5 Flight, Fullness A Blocked 6 Flight, Ear pressure A No Change 7 Flight, Diving A Blocked 8 Flight, Ear pressure A Blocked 9 Flight B 4 Blocked 10 Flight A Normal 11 Flight, Ear pressure B 0 Blocked 12 Flight A No Change 13 Flight A Blocked 14 Flight A Blocked 15 Flight A Discontinued 16 Flight C Blocked 17 Flight A Blocked 18 Flight C Blocked 19 Flight A Blocked 20 Flight C Blocked 21 Flight B 9 Blocked Patients clinical symptoms: Flight 5 pressure equalization problems during descent phase; Diving 5 pressure equalization problems during diving; Ear Pressure 5 permanent feeling of pressure in the ear; Fullness 5 feeling of fullness in the ear. Tympanometry: A 5 normal, B 5 flat, C 5 negative, and corresponding pressure peaks. Valsalva test: 1 5 positive, 2 5 negative; air-bone gap in db. Pressure chamber impedance measurements of the affected ear under changing pressure: normal, blocked, no change, discontinued. 562 Aviation, Space, and Environmental Medicine x Vol. 81, No. 6 x June 2010

4 The findings of exploratory ET function tests could identify 42.9% of the complaints by a pathologic finding in the tympanometry or by a negative Valsalva test, whereas impedance measurements in the pressure chamber yielded pathological findings in 85.7%. The measurement of PREP function showed a reduced rate of pressure change in the external auditory canal with the PREP filter in all cases. After min, the recorded pressure corresponded to the actual pressure in the pressure chamber. The maximum pressure was reached with a delay of about 7 min. The pressure course with and without the PREP filter is graphically depicted in Fig. 1. Continuous impedance measurements in the pressure chamber with or without the PREP filter in place yielded no significant differences Fig. 2. Results of continuous impedance measurements in the pressure chamber ( N 5 42) with and without PREP filter (normal, blocked, ( P, 0.57). The results of the categorized measurements no change, and discontinued). are shown in Fig. 2. Graphical analysis of the impedance curves showed that the difference between the initial impedance and the maximum impedance deviation was themselves to the rapid pressure changes associated smaller in the measurement with PREP than in the subsequent comparative measurement. For the graphically likely in those cases. The patients included in our study with air travel. Recurrent middle ear barotrauma is most depicted result no quantitative statement could be made had a history of equalization problems during rapid because of the acoustic measuring method applied, where pressure changes and were planning to travel by airplane again. Our results show that twice as many pa- no scaling of the applied sound amplitude was made. The number of pressure-equalizing maneuvers during the compression phase amounted to with continuous impedance measurement in the pressure tients with ET dysfunction could be identified with the and without PREP and did not differ significantly ( P, 0.088). With PREP the percentage of success- tympanometry. This is in agreement with findings sug- chamber compared to using the Valsalva maneuver or ful ET openings of all attempts to equalize pressure gesting that current diagnostic tests of ET function, as yielded % and did not differ significantly ( P, routinely performed by ENT specialists (Valsalva test, 0.263) from the value without PREP with %. tympanometry), cannot reliably detect ET dysfunctions Patients subjective state during measurement with (17). PREP was significantly better with ( ) than The applied continuous impedance measurements in without PREP ( ) ( P, 0.003) as assessed on the pressure chamber seem to be useful in identifying the VAS scale ( Fig. 3 ). With PREP, 13 patients reported patients with recurrent middle ear barotrauma. The fact an improved perception while 8 reported no change. IP: On: Tue, 20 that Nov the 2018 method 00:31:38 has not yet become part of routine ENT Copyright: Aerospace Medical practice Association is due to the high technical and personnel requirements. Ingenta The complexity of the measuring process DISCUSSION Delivered by is Middle ear barotrauma is frequently reported during flight in aircrew and passengers exposed to pressure changes. Although some passengers experience severe barotraumas, a vast majority of them continue to expose considerably reduced by the computer-based recording and evaluation performed in our study for the first time. The study demonstrates that the modified technique for continuous impedance measurements in a pressure Fig. 1. Pressure curves obtained by measurements with (dashed line) and without (solid line) PREP. Fig. 3. Subjective state of patients during pressure chamber tests with and without PREP filter; VAS value 5 value on the visual analogue scale, * 5 significant difference. Aviation, Space, and Environmental Medicine x Vol. 81, No. 6 x June

5 in the ET mucosa and has negative effects on ET function. The pressure course during the descent and climb phases in our study is considerably higher than the standard pressure change rate in a modern aircraft and was chosen to reproduce peak pressure changes during a passenger aircraft s descent. This might overestimate our results compared to an airline flight. In a commercial aircraft the cabin pressure increase during the descent phase is on average 500 ft z min2 1 (152 m z min 2 1 ). The pressure difference of 75 mmhg (100 mbar) in the presented study is considerably less than the overall cabin pressure difference during a passenger aircraft s descent and was chosen to minimize the probability of middle ear barotrauma. The cabin pressurization technology maintains a cabin altitude range from 5000 ft (1520 m) to 8000 ft (2440 m) while aircraft flying altitude range from 30,000 ft (9140 m) to 45,000 ft (13,720 m). Thus the minimal cabin pressure is 564 mmhg (752 mbar) ( 6,18 ) and the maximum overall pressure difference in an aircraft can approach 200 mmhg (267 mbar). The use of PREP was associated with a reduced pressure change rate and a lower maximum eardrum im- chamber could also be feasible in routine clinical practice. pedance deflection. This could indicate the postulated All previous studies that used the continuous im- effect of reduced eardrum distension and lead to a pedance method examined the ET function in a hypobaric weaker stretch stimulus. The result is in agreement with chamber. Exposure to a hypobaric environment could the finding of a significantly improved subjective state have been potentially risky for our patient collective. In while wearing PREP and may be attributed to weaker comparison, a hyperbaric setting allows the subjects to nociceptive stimulation of receptors in the eardrum. One stop the potentially painful compression phase at any patient could only tolerate the measurements while time. In this case the chamber pressure can be lowered wearing PREP and had to discontinue the trial without to normal pressure without a potentially painful pressure them. A decrease in the number of pressure-equalizing increase that would harm the middle and inner ear. maneuvers might be expected in conjunction with re- In a hypobaric chamber the interruption of the investigation duced eardrum distension. However, significantly fewer during the compression phase has to be followed pressure-equalizing maneuvers were not detected with by a further compression until ambient pressure is PREP. It may be that middle ear pressure is regulated reached. not only by the stretch receptors in the pars flaccida of Concurrently, the use of a hyperbaric chamber seems the eardrum but also by pressure sensors in the middle to be the major limit of our study. In contrast to the pressure ear and in the area of the tubal elevation in the nasophar- course in an airplane, the pressure was first inynx (16). creased and then lowered. In the descent phase, relative Support of ET function by PREP has been repeatedly middle ear underpressure can reach a level that causes a discussed. Improving ET function would be expected to blocked ET in patients with ET dysfunction. The subsequent reduce the ineffective attempts to equalize pressure in maximal inward movement of the tympanic favor of successful pressure-equalizing maneuvers with membrane without any further detectable movements opening of the ET. This could not be demonstrated by makes it impossible to measure impedance changes in the results of our study and thus no evidence for an improved the cruise and climb phase. This might overestimate the ET function is given. The impedance measure- impairment of ET function in patients with moderate ET ments in the pressure chamber disclosed no improvement dysfunction. Another inaccuracy is caused by the mild of ET function. Pathological ET function was detected in hyperbaric environment subjects are exposed to in the 18 of the 21 patients even while they were wearing PREP. presented study. This is in contrast to the hypobaric situation In the presented study, measurements with and without to which flight passengers are exposed. This may PREP were done on the same day at least 4 h apart. This affect our conclusion by underestimating the results, because protocol was used to minimize the effect of the high complaints while flying may be aggravated by day-to-day variability on ET function the patient collec- edematous mucosal swelling in conjunction with decreased tive showed in pretests. The applied protocol causes a ambient pressure. Altered tissue thickness and repeated pressure exposure and could possibly affect ET upper body swelling become apparent at moderate altitude function. To minimize possible errors in the results the ( 1 ). Topics currently being discussed include blood order of the tests were randomized using a double-blind flow alterations responsible for the various tissue thickness changes at these altitudes ( 4 ). Further study design. IP: On: Tue, 20 Nov :31:38 Copyright: studies Aerospace are Medical The results Association of the presented study yielded no indication Ingenta of improved ET function while using PREP. needed to clarify whether this phenomenon also Delivered occurs by This concurs with the fact that such an influence cannot be considered plausible, given the assumed mode of action of PREP ( 7,12 ). The only published study on PREP by Klokker et al. examined 27 test subjects in a pressure chamber while simultaneously wearing a PREP in one ear and a placebo in the other. Tympanometry and otoscopy were performed in both ears before and after pressure chamber exposure. The effect of the PREP filters used by Klokker et al. on the pressure in the external ear canal is not clear. Measurements of the filter-induced reduction in the rate of pressure change are not available for assessment ( 2,12 ). As a result, the study performed by Klokker et al. showed that 78% of the test subjects had pain in one or both ears during the pressure increase. In contrast, the patients in the present study reported a significant improvement in their subjective state while using PREP. This discrepancy may be attributed to the fact that Klokker et al. did not distinguish between the ears (verum or placebo) for which pain was reported. Also a different sensation in the two ears could, for example, alter the active equalization behavior. Otoscopic examinations 564 Aviation, Space, and Environmental Medicine x Vol. 81, No. 6 x June 2010

6 demonstrated no prevention of barotrauma in the study performed by Klokker et al.; the ears with active PREP were rated significantly worse. The methods applied, such as otoscopy and tympanometry, yielded values valid only for the time of examination. Continuous measurements during pressure changes were not performed. The results Klokker et al. obtained by otoscopic examinations were significantly poorer after using PREP. It is impossible to judge the value of these results, given the methodological limitations mentioned above. A possible explanation would be that additional overpressure was generated in the external auditory canal when inserting the PREP. Examining the influence of PREP on a reddened eardrum would require a different experimental setup: Klokker et al. would have had to take measurements with PREP in both ears and compare them to those obtained with placebo earplugs. That would exclude the above-mentioned effect caused by different pressure regulation. In conclusion, our data provide evidence that the use of PREP while flying can improve the subjective state in patients with pressure equalization problems. It reduces pressure difference in the external ear canal over time, which causes less discomfort during the descent phase. PREP has no influence on ET function itself. Based on the present results and the results reported by Klokker et al., uncritical pressure exposure with PREP is not advisable in patients with frequent middle ear barotrauma. For these patients pressure chamber testing with and without PREP, ideally with continuous impedance measurement, is recommended. ACKNOWLEDGMENTS The study was performed in the pressure chamber of the Berlin Center for Hyperbaric Oxygen Therapy and Diving Medicine at Vivantes Klinikum in Friedrichshain (HAUX STARMED 2200, 5, year of construction 1996, Haux-Life-Support GmbH, Germany). eustachian tube function in tympanoplasty. Otolaryngol Head Special thanks are due to Dr. med. Grajetzki, IP: M.D., for his technical On: Tue, 20 Nov Neck 2018 Surg 00:31: ; 140 : assistance. Copyright: Aerospace Medical 18. Rosenkvist Association L, Klokker M, Katholm M. Upper respiratory infections The tested pressure-regulating earplugs Sanohra Fly were Delivered provided by Ingenta and barotraumas in commercial pilots: a retrospective survey. by Innosan GmbH in Schwetzingen, Germany. There are no conflicts of interest between the authors and Innosan GmbH. The statistical analysis was done with help of PD Dr. rer. nat. Katinka Wolter, Institute of Computer Science, Freie Universität Berlin. 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