Characterizing the active opening of the eustachian tube in a hypobaric/hyperbaric pressure chamber

Concordance Analysis of the Pressure Chamber and Tubomanometer According to Estève for the Determination of Eustachian Tube Opening Pressure

INTRODUCTION

For the diagnosis of Eustachian tube dysfunction (ETD), clinical procedures such as tympanometry, micro-otoscopy, and maneuvers according to Toynbee and Valsalva only allow an indirect assessment for the moment. With a prevalence of up to 5%, the selection of patients with ETD and its subtypes is clinically relevant. Dynamic methods of Eustachian tube function assessment include a hypo/hyperbaric pressure chamber and Estève's tubomanometer (TMM). One method of assessing ETD is the evaluation of Eustachian tube opening pressure (ETOP).

MATERIAL AND METHODS

We performed a concordance analysis between pressure chamber and TMM to determine ETOP. For this purpose, we analyzed the measurements of both methods from 28 healthy subjects using Bland-Altman plots, regression according to Passing-Bablok and Lin's concordance correlations coefficient. The maximum tolerated clinical deviation of measured values was set at 10%.

RESULTS

A maximum of 53 measurements of ETOP between pressure chamber and TMM were compared. Mean ETOP for TMM was 28.7 hPa, passive opening was 32 hPa, Toynbee maneuver was 28.4 hPa, and Valsalva maneuver was 54.6 hPa. Concordance analysis revealed following results: passive opening versus TMM: Bland-Altman mean difference 3.3 hPa, limits of agreement ±31.8 hPa; Passing-Bablok regression y = 0.67 x + 9.36; Lin's rccc = 0.18. Toynbee versus TMM: Bland-Altman mean difference 0.7 hPa, limits of agreement ±35.8 hPa; Passing-Bablok regression y = 0.47x + 14.03; Lin's rccc = 0.14. Valsalva versus TMM: Bland-Altman mean difference 24.2 hPa, limits of agreement ±117.5 hPa; Passing-Bablok regression y = 0.17x + 25.12; Lin's rccc = 0.18.

CONCLUSION

Estève's tubomanometer and pressure chamber measurements of ETOP are not concordant. The two methods cannot be interchanged without reservation.

Intraindividual variability of the Eustachian tube function: a longitudinal study in a pressure chamber

INTRODUCTION

The Eustachian tube (ET) is essential for fast and direct pressure equalisation between middle ear and ambient pressure. It is not yet known to what extent Eustachian tube function in healthy adults changes in a weekly periodicity due to internal and external factors. This question is particularly interesting with regard to scuba divers among whom there is a need to evaluate intraindividual ET function variability.

METHODS

Continuous impedance measurement in a pressure chamber was performed three times at one-week intervals between measurements. Twenty healthy participants (40 ears) were enrolled. Using a monoplace hyperbaric chamber, individual subjects were exposed to a standardised pressure profile consisting of a 20 kPa decompression over 1 min, a 40 kPa compression over 2 min, and a 20 kPa decompression over 1 min. Measurements of Eustachian tube opening pressure (ETOP), opening duration (ETOD), and opening frequency (ETOF) were made. Intraindividual variability was assessed.

RESULTS

Mean ETOD during compression (actively induced pressure equalisation) on the right side was 273.8 (SD 158.8) ms, 259.4 (157.7) ms, and 249.2 (154.1) ms (Chi-square 7.30, P = 0.026) across weeks 1-3. Mean ETOD for both sides was 265.6 (153.3) ms, 256.1 (154.6) ms, and 245.7 (147.8) ms (Chi-square 10.00, P = 0.007) across weeks 1-3. There were no other significant differences in ETOD, ETOP and ETOF across the three weekly measurements.

CONCLUSIONS

This longitudinal study suggests low week-to-week intraindividual variability of Eustachian tube function.

A Systematic Review of Eustachian Tube Procedures for Baro-challenge Eustachian Tube Dysfunction

OBJECTIVE

To examine the effectiveness of Eustachian tube procedures for the treatment of baro-challenge Eustachian tube dysfunction.

METHODS

Following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, databases, including PubMed (National Library of Medicine, National Institutes of Health), Scopus (Elsevier), and CINAHL (EBSCO), were searched for articles examining the effectiveness of Eustachian tube procedures for baro-challenge Eustachian tube dysfunction. Outcome measures included symptom resolution, ability to return to work, equalization problems (EP) scores, Eustachian Tube Dysfunction Questionnaire (ETDQ-7) scores, and pressure chamber testing parameters. Pooled meta-analysis was performed for dichotomous measures and ETDQ-7 scores.

RESULTS

Eleven articles with 81 patients were included. Seventy-two patients from 10 articles underwent balloon Eustachian tube dilation; nine patients in 1 study underwent laser Eustachian tuboplasty (LET). All 81 patients were preoperatively symptomatic with barometric pressure change, and 26/30 (86.7%) were unable to work due to symptoms. On meta-analysis, after balloon dilation Eustachian tuboplasty (BDET), 82.5% (n = 30 [95% confidence interval: 42%-100%]) had improvement in ability to valsalva, 79.1% (n = 16 [57.9%-94.1%]) in ability to return to work, and 84.3% (n = 69 [69.8%-94.7%]) in any symptom. Of 25 patients with individual ETDQ-7 scores, 79.1% [51.4, 96.9] had improvements after BDET. For four case series with 36 patients, ETDQ-7 scores decreased by 1.2 [0.7, 1.7] (p < 0.00001). Of 20 patients with preoperative ETDQ-7 scores >2.0, there was a mean decrease of 2.1 [1.3, 2.8] (p < 0.00001).

CONCLUSION

From the available evidence, Eustachian tube procedures appear to be effective at improving symptoms of baro-challenge Eustachian tube dysfunction. However, higher quality evidence is needed to support making definite recommendations for the use of balloon Eustachian tube dilation or LET for these patients. Laryngoscope, 132:2473-2483, 2022.

Influence of 30 and 60 Min of Hypobaric Hypoxia in Simulated Altitude of 15,000 ft on Human Proteome Profile

The human body reacts to hypobaric hypoxia, e.g., during a stay at high altitude, with several mechanisms of adaption. Even short-time exposition to hypobaric hypoxia leads to complex adaptions. Proteomics facilitates the possibility to detect changes in metabolism due to changes in proteins. The present study aims to identify time-dependent changes in protein expression due to hypobaric hypoxia for 30 and 60 min at a simulated altitude of 15,000 ft. N = 80 male subjects were randomized and assigned into four different groups: 40 subjects to ground control for 30 (GC30) and 60 min (GC60) and 40 subjects to 15,000 ft for 30 (HH30) and 60 min (HH60). Subjects in HH30 and HH60 were exposed to hypobaric hypoxia in a pressure chamber (total pressure: 572 hPa) equivalent to 15,000 ft for 30 vs. 60 min, respectively. Drawn blood was centrifuged and plasma frozen (−80 °C) until proteomic analysis. After separation of high abundant proteins, protein expression was analyzed by 2-DIGE and MALDI-TOF. To visualize the connected signaling cascade, a bio-informatical network analysis was performed. The present study was approved by the ethical committee of the University of Cologne, Germany. The study registry number is NCT03823677. In comparing HH30 to GC30, a total of seven protein spots had a doubled expression, and 22 spots had decreased gene expression. In a comparison of HH60 to GC60, a total of 27 protein spots were significantly higher expressed. HH60, as compared to GC30, revealed that a total of 37 spots had doubled expression. Vice versa, 12 spots were detected, which were higher expressed in GC30 vs. HH60. In comparison to GC, HH60 had distinct differences in the number of differential protein spots (noticeably more proteins due to longer exposure to hypoxia). There are indicators that changes in proteins are dependent on the length of hypobaric hypoxia. Some proteins associated with hemostasis were differentially expressed in the 60 min comparison.

Prospective study on the Eustachian tube function during Frenzel maneuver in a hypobaric/hyperbaric pressure chamber

Introduction

The Frenzel maneuver describes a technique for middle ear equalizing which is frequently used by apnea divers. It offers advantages compared to the most commonly used techniques such as the Valsalva or Toynbee maneuver. Until now, there is insufficient literature about the pressure dynamics and Eustachian tube (ET) function during the Frenzel maneuver. The aim of the present study was to characterize the ET function during the Frenzel maneuver.

Materials and methods

By means of an established standardized profile of compression and decompression in a hypo/hyperbaric pressure chamber, we examined different parameters such as the ET opening pressure (ETOP), ET opening duration (ETOD), and ET opening frequency (ETOF) in 11 experienced apnea divers and compared them to the parameters during the Valsalva and Toynbee maneuver.

Results

Standard values for ETOP, ETOD, and ETOF could be established for the Frenzel maneuver under standardized conditions in a hypo/hyperbaric pressure chamber. Compared to the Frenzel maneuver, ETOP was higher and ETOD longer (both p < 0.001) during the Valsalva maneuver whereas ETOP was lower and ETOD shorter (both p < 0.001) during the Toynbee maneuver. No difference regarding ETOF was observed between the Frenzel, Valsalva, and Toynbee maneuver.

Discussion

The Frenzel maneuver was shown to be at least as effective as the Valsalva maneuver concerning ET opening. We believe that knowledge of the Frenzel technique might facilitate the pressure equalization during diving and recommend implementation of an appropriate equalization training in apnea and scuba diving education.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00405-021-06888-1.

Middle ear barotrauma in diving

INTRODUCTION

Middle ear barotrauma (MEBt) is the most common medical complication in diving, posing a serious risk to dive safety. Given this prevalence and the continuing growth of the diving industry, a comprehensive overview of the condition is warranted.

METHODS

This was a survey study. An anonymous, electronic questionnaire was distributed to 7,060 recipients: professional divers of the Finnish Border Guard, the Finnish Rescue Services, and the Finnish Heritage agency; and recreational divers registered as members of the Finnish Divers' Association reachable by e-mail (roughly two-thirds of all members and recreational divers in Finland). Primary outcomes were self-reported prevalence, clinical characteristics, and health effects of MEBt while diving. Secondary outcomes were adjusted odds ratios (OR) for frequency of MEBt with respect to possible risk factors.

RESULTS

A total of 1,881 respondents participated in the study (response rate 27%). In total, 81% of the respondents had experienced MEBt while diving. Of those affected, 38% had used medications and 1% had undergone otorhinolaryngology-related surgical procedures due to MEBt. Factors most associated with MEBt were poor subjective success in Valsalva ('occasionally' versus 'always' successful: OR 11.56; 95% CI 7.24-18.47) and Toynbee ('occasionally' versus 'always' successful: OR 3.51; 95% CI 1.95-6.30) manoeuvres.

CONCLUSIONS

MEBt is common in both recreational and professional divers, having affected 81% of the respondents. The main possible risk factors include poor success in pressure equalisation manoeuvres.

Middle Ear Barotraumas in Commercial Aircrew

BACKGROUND: Middle ear (ME) barotraumas are the most common condition in aviation medicine, sometimes seriously compromising flight safety. Considering this and the ever-increasing amount of commercial aviation, a detailed overview is warranted.METHODS: In this survey study, an anonymous, electronic questionnaire was distributed to commercial aircrew of the three major commercial airlines operating in Finland (N 3799), covering 93% of the target population (i.e., all commercial aircrew operating in Finland, N 4083). Primary outcomes were self-reported prevalence, clinical characteristics, and health and occupational effects of ME barotraumas in flight. Secondary outcomes were adjusted odds ratios (OR) for frequency of ME barotraumas with respect to possible risk factors.RESULTS: Response rate was 47% (N 1789/3799), with 85% (N 1516) having experienced ME barotraumas in flight. Of those affected, 60% had used medications, 5% had undergone surgical procedures, and 48% had been on sick leave due to ME barotraumas (40% during the last year). Factors associated with ME barotraumas included a high number of upper respiratory tract infections [3 URTIs/yr vs. 0 URTIs/yr: OR, 9.02; 95% confidence interval (CI) 3.9920.39] and poor subjective performance in Valsalva (occasionally vs. always successful: OR, 7.84; 95% CI 3.9715.51) and Toynbee (occasionally vs. always successful: OR, 9.06; 95% CI 2.6730.78) maneuvers.CONCLUSION: ME barotraumas were reported by 85% of commercial aircrew. They lead to an increased need for medications, otorhinolaryngology-related surgical procedures, and sickness absence from flight duty. Possible risk factors include a high number of URTIs and poor performance in pressure equalization maneuvers.Lindfors OH, Ketola KS, Klockars TK, Leino TK, Sinkkonen ST. Middle ear barotraumas in commercial aircrew. Aerosp Med Hum Perform. 2021; 92(3):182189.

[Is Flying or Diving risky after cochlear implantation? Examination in a pressure chamber]

OBJECTIVE

 Complications after cochlear implantation are relatively rare but patients are asked to follow certain behavioral rules. Until now there is no evidence if pressure changes that occur during flying and diving are safe for patients after cochlear implantation. For example, no recommendation exists for SCUBA- diving activities.

MATERIALS AND METHODS

 In a hypo-/hyperbaric pressure chamber patients after cochlear implantation were exposed to a standardized profile of decompression and compression simulating a flight in a common airplane and a dive. Pre and after the exposure in the pressure chamber, ENT examination and a control of impedances of the cochlear implant were performed. Additionally, patients filled in a questionnaire about complaints they had experienced in the pressure chamber or after.

RESULTS

 A total of 11 subjects (17 ears with CI) were examined in the pressure chamber. 2/3 of the subjects stated that they had slight complaints during the examination. Only in one patient the measurement needed to be stopped due to pain. Seven patients showed a vascular injection of the malleus in ear microscopy. In none of the patients there was a subjective change in hearing after the examination. Objective measurements of the impedance did not show relevant changes.

CONCLUSION

 The exposure of cochlear implanted patients to overpressure and underpressure in a pressure chamber did not result in any significant deviation of the impedances, so that no further adjustment was necessary. Since there are no certified in vivo studies on pressure changes while diving and flying with a cochlear implant, further studies are required in order to be able to adequately advise CI patients about diving and flying.

Subjective and Objective Effectiveness of Eustachian Tube Balloon Dilatation for Patients With Eustachian Tube Dysfunction-Evaluation in a Pressure Chamber

INTRODUCTION

The Eustachian tube plays a crucial role in pressure equalization between the middle ear and ambient pressure for fast and large pressure differences. In patients with chronic Eustachian tube dysfunction, Eustachian tube balloon dilatation is increasingly used as surgical therapy. Subjectively, many patients report an improvement of the symptoms postoperatively. Hence, there is a need to objectively measure this effect.

METHODS

The objectivity of Eustachian tube balloon dilatation was evaluated using a precise method of measuring Eustachian tube function. In a hypo/hyperbaric pressure chamber, 23 ears in 13 patients were exposed to a standardized profile of compression and decompression before Eustachian tube balloon dilatation and 4 weeks afterwards. Standardized parameters of Eustachian tube function were determined and statistically compared before and 4 weeks after intervention. In addition, an Eustachian Tube Dysfunction Questionnaire-7 (ETDQ7) questionnaire was completed beforehand and 4 weeks postoperatively to determine subjective surgical success.

RESULTS

The results from the ETDQ7 questionnaire showed a significant improvement in symptoms after Eustachian tube balloon dilatation (p = 0.0002). Objective measurements results showed a significant reduction of the Eustachian tube opening pressure during pressure decrease 4 weeks after intervention (p = 0.0012).

CONCLUSION

Eustachian tube balloon dilatation significantly reduced Eustachian tube opening pressure, in addition to subjective improvement of symptoms determined by ETDQ7.

Measuring dynamic Eustachian tube function using tympanometry in a pressure chamber: the effect of nasal betahistine application

OBJECTIVE

To assess the effect of topical betahistine on Eustachian tube function in subjectively abnormal subjects in a hyperbaric chamber.

METHOD

Active and passive Eustachian tube function was examined using tympanometry in a pressure chamber.

RESULTS

Active Eustachian tube function was tested against the negative middle ear pressure induced by increasing the chamber pressure to +3 kPa. One voluntary swallow decreased middle-ear pressure by a mean of 1.36 kPa. Passive Eustachian tube function was tested by measuring spontaneous Eustachian tube openings as the chamber pressure dropped from +10 kPa to ambient. Four distinct patterns of Eustachian tube behaviour were seen, three of which indicated Eustachian tube dysfunction. Betahistine had no positive effect on Eustachian tube opening, although previous animal studies had suggested a beneficial effect.

CONCLUSION

Topical betahistine had no effect on Eustachian tube function. Combining a hyperbaric chamber with tympanometry proved ideal for evaluating Eustachian tube function.

Evaluation of the Parameter "Mean Impedance" for Representing Eustachian tube Functions During Pressure Increase and Decrease in Pressure Chamber Measurements

HYPOTHESIS

The hypothesis of the study is that the mean impedance (MI) during compression and decompression provides additional information of the Eustachian tube (ET) function.

BACKGROUND

The continuous impedance measurement in a pressure chamber can provide valuable information about the opening function of the ET.

METHODS

Around 55 ear-healthy volunteers were examined in a pressure chamber. These were subjected to a decompression phase and a compression phase. The pressure change was constantly 20 kPa/min. Using evaluation software, the MI could be determined for both ears in each case for the phases of compression and decompression.

RESULTS

In 49 participants, we could interpret the data successfully. On average, an output value (without pressure changes) of the impedance of 0.58 ±0.11 Pa on the right side and 0.43 ± 0.1 Pa on the left side were measured. During decompression, 0.098 ± 0.05 Pa (right) and 0.087 ± 0.043 Pa (left) could be determined. For compression, values of 0.086 ± 0.044 Pa on the right and 0.079 ± 0.045 Pa on the left were detected. The retest reliability was higher with an intraclass correlation coefficient for the decompression MI of 0.833 than the 0.772 compression MI.

CONCLUSIONS

It is possible to measure MI in healthy subjects during compression and decompression. This value represents a good average in terms of the pressure tolerance of the middle ear. In future, studies will be required to determine whether MI will be a useful parameter in differentiating normal and abnormal ET function.

Influence of repetitive diving in freshwater on pressure equalization and Eustachian tube function in recreational scuba divers

INTRODUCTION

We investigated the effect of repetitive pressure exposure during freshwater dives on Eustachian tube function and the middle ear, assessed by the Eustachian tube function test (ETFT).

METHODS

This prospective observational cohort study included 23 divers over three consecutive days of diving in freshwater lakes in Nordhausen, Germany. Participants underwent otoscopy and ETFT before the first dive, between each dive and after the last dive. ETFT included regular tympanometry (R-tymp), tympanometry after Valsalva (V-tymp) and after swallowing (S-tymp). The peak pressure difference between the R-tymp and the V-tymp (R-V_dP) defined effectiveness of pressure equalization after Valsalva manoeuvres. We evaluated the change in compliance and peak pressure and correlated the results to the otoscopic findings and diving experience.

RESULTS

Twenty-three divers performed 144 dives. Middle ear barotrauma was assessed using the Edmonds modification of the TEED scoring system. In the ETFT, the R-tymp peak pressure displayed a negative shift from day one to three (P = 0.001) and differed significantly between the experience groups (P = 0.01). R-V_dP did not change significantly on any of the three days of diving (all P > 0.05). Participants without MEBt showed significantly lower R-tymp values than did those with barotrauma (P = 0.019).

CONCLUSION

Repetitive pressure exposure during three consecutive days of freshwater diving led to a negative shift of the peak pressure in the middle ear. Less experienced divers showed significantly higher middle ear peak pressure and higher pressure differences after equalization manoeuvres. Higher middle ear peak pressure was also associated with a higher prevalence of barotrauma.

Assessment of the Importance of Tympanic Membrane Mechanoreceptors on Eustachian Tube Function Based on Pressure Chamber Measurements

INTRODUCTION

Previously, it was demonstrated how the Eustachian tube (ET) opening function can be influenced by middle ear pressure and movement of the tympanic membrane via neural control. Mechanoreceptors on the tympanic membrane may be part of the afferent arc and could influence the middle ear pressure by activating the musculus veli palatini as part of a reflex.

METHODS

In a hypo and hyperbaric pressure chamber, 17 participants (34 ears) were twice exposed to a standardized pressure profile of pressure decrease and increase. The ET function reflecting parameters-ET opening pressure (ETOP), ET opening duration (ETOD), and ET opening frequency (ETOF)-were determined before and after local anesthesia of the right tympanic membrane.

RESULTS

After pressure exposure by pressure increase (active induced equalization) and pressure decrease (passive equalization) there was no significant difference between the mean value of ETOP, ETOD, and ETOF before and after local anesthesia of the right tympanic membrane on the right (anesthetized) or left side (not anesthetized).

CONCLUSION

These results may lead to the hypothesis that tympanic membrane mechanoreceptors may play a minor role in regulating the ET function in humans.

Influence of repetitive diving in saltwater on pressure equalization and Eustachian tube function in recreational scuba divers

INTRODUCTION

We investigated in a prospective, observational trial the feasibility of using the Eustachian tube function test (ETFT) to measure the effect of repetitive pressure exposure during open seawater dives on Eustachian tube function.

METHODS

The study included 28 adult divers during six consecutive days of diving in the Red Sea. Participants underwent otoscopy and ETFT before the first dive, between each dive and after the last dive. ETFT included regular tympanometry (R-tymp), tympanometry after Valsalva (V-tymp) and after swallowing (S-tymp). The R-tymp was obtained as 'baseline' peak pressure. After a Valsalva, the peak pressure should shift (positively), revealing a positive shift of the tympanic membrane. This pressure shift is defined here as R-VdP. The changes in compliance and peak pressure were recorded and correlated with otoscopic findings and diving experience. Middle ear barotrauma was scored using the Edmonds modified TEED scale.

RESULTS

The 28 participants performed 437 dives. Positive shift of pressure in the middle ear was evident with significant changes from day one to day three (P < 0.0001). Divers with barotrauma showed significantly lower values of R-tymp peak pressure and significantly higher negative R-VdP, compared to divers with normal otoscopic findings (P < 0.05). Diving experience significantly correlated with R-tymp peak pressure and prevalence of middle ear barotrauma.

CONCLUSION

Significant changes in middle ear pressure and pressure equalization from repeated pressure exposure in saltwater were seen using ETFT. Repetitive, multi-day diving led to significantly decreased compliance and increased R-tymp peak pressure (overpressure) in the middle ear. Most profound changes were observed in less and intermediate experienced divers.

Prevalence of Barotrauma in Recreational Scuba Divers After Repetitive Saltwater Dives

INTRODUCTION

The aim was to investigate the prevalence of middle ear barotrauma (MEB) and to establish risk factors of MEB after repeated saltwater dives.

METHODS

In this prospective observational cohort study 28 divers were examined over 6 consecutive days of diving in the Red Sea, Egypt. Participants underwent an otoscopic examination before the first dive, between each dive and after the last dive. In addition, they performed Valsalva maneuver (VM) and were questioned about dive-related complaints. Otoscopic findings were classified according to TEED classification for MEB (0 = normal otoscopy to 4 = perforation) separately for each ear. First examination was conducted before the first dive. Final examination, including a questionnaire, was conducted at least 12 h after the last dive.

RESULTS

In total, 436 dives were performed and 1161 otoscopic findings were analyzed. All participants showed a normal eardrum and a positive VM during initial exam. MEB prevalence (TEED >0) was 36.5% at final examination. Prevalence increased significantly with number of dives per day (p < 0.001) as with number of diving days (p = 0.032). Neither depth nor duration of dives significantly influenced MEB prevalence (all p > 0.05). More experienced divers (>200 dives lifetime) showed significantly less barotrauma (p < 0.0001). Despite the high prevalence of MEB, 81.7% (316 of 387) of all dives were reported asymptomatic.

CONCLUSIONS

After 6 days of repetitive diving, MEB prevalence was high (36.5%). It was the most often cause of otalgia in divers. Cumulative pressure exposure during repetitive dives resulted in significant increase of MEB. Diving experience significantly reduced the MEB prevalence. Interestingly, the severity of MEB did not correlate with subjective complaints.

Thirty Minutes of Hypobaric Hypoxia Provokes Alterations of Immune Response, Haemostasis, and Metabolism Proteins in Human Serum

Hypobaric hypoxia (HH) during airline travel induces several (patho-) physiological reactions in the human body. Whereas severe hypoxia is investigated thoroughly, very little is known about effects of moderate or short-term hypoxia, e.g. during airline flights. The aim of the present study was to analyse changes in serum protein expression and activation of signalling cascades in human volunteers staying for 30 min in a simulated altitude equivalent to airline travel. After approval of the local ethics committee, 10 participants were exposed to moderate hypoxia (simulation of 2400 m or 8000 ft for 30 min) in a hypobaric pressure chamber. Before and after hypobaric hypoxia, serum was drawn, centrifuged, and analysed by two-dimensional gel electrophoresis (2-DIGE) and matrix-assisted laser desorption/ionization followed by time-of-flight mass spectrometry (MALDI-TOF). Biological functions of regulated proteins were identified using functional network analysis (GeneMania®, STRING®, and Perseus® software). In participants, oxygen saturation decreased from 98.1 ± 1.3% to 89.2 ± 1.8% during HH. Expression of 14 spots (i.e., 10 proteins: ALB, PGK1, APOE, GAPDH, C1QA, C1QB, CAT, CA1, F2, and CLU) was significantly altered. Bioinformatic analysis revealed an association of the altered proteins with the signalling cascades "regulation of haemostasis" (four proteins), "metabolism" (five proteins), and "leukocyte mediated immune response" (five proteins). Even though hypobaric hypoxia was short and moderate (comparable to an airliner flight), analysis of protein expression in human subjects revealed an association to immune response, protein metabolism, and haemostasis.

Reliability of Eustachian tube function measurements in a hypobaric and hyperbaric pressure chamber

OBJECTIVES

Measurement of the Eustachian tube (ET) function is a challenge. The demand for a precise and meaningful diagnostic tool increases-especially because more and more operative therapies are being offered without objective evidence. The measurement of the ET function by continuous impedance recording in a pressure chamber is an established method, although the reliability of the measurements is still unclear.

METHODS

Twenty-five participants (50 ears) were exposed to phases of compression and decompression in a hypo- and hyperbaric pressure chamber. The ET function reflecting parameters-ET opening pressure (ETOP), ET opening duration (ETOD) and ET opening frequency (ETOF)-were determined under exactly the same preconditions three times in a row. The intraclass correlation coefficient (ICC) and Bland and Altman plot were used to assess test-retest reliability.

RESULTS

ICCs revealed a high correlation for ETOP and ETOF in phases of decompression (passive equalisation) as well as ETOD and ETOP in phases of compression (active induced equalisation). Very high correlation could be shown for ETOD in decompression and ETOF in compression phases. The Bland and Altman graphs could show that measurements provide results within a 95 % confidence interval in compression and decompression phases.

CONCLUSIONS

We conclude that measurements in a pressure chamber are a very valuable tool in terms of estimating the ET opening and closing function. Measurements show some variance comparing participants, but provide reliable results within a 95 % confidence interval in retest. This study is the basis for enabling efficacy measurements of ET treatment modalities.

[The pressure-equalizing function of the Eustachian tube : Evaluation in a hypo-/hyperbaric pressure chamber]

BACKGROUND

The Eustachian tube connects the tympanic cavity (cavum tympani) and the nasopharynx, and enables pressure equalization between the middle ear and ambient pressure. Functional pressure compensation is very important for flying and diving in particular, due to non-physiologically large pressure differences.

OBJECTIVE

Evaluation of the pressure-equalizing function of the Eustachian tube is still a clinical challenge. This review article evaluates the existing data.

METHODS

Based on a selective literature search, different methods for evaluation of tube function are presented and evaluated, with special reference to evaluation of the pressure-equalizing function in a hypo-/hyperbaric pressure chamber.

RESULTS

The pressure chamber enables the dynamics of active and passive pressure compensation to be provoked and also permits accurate measurement of pressures in the millibar range.

CONCLUSION

A pressure chamber seems to be suitable to evaluate Eustachian tube function and therapeutic approaches to tube dysfunction. Further studies are needed to assess the value of the pressure chamber in combination with other functional tests.