Eustachian Tube Function in Flight Attendants

Abstract

Eustachian tube (ET) function is of utmost importance in people who are under constant barometric pressure changes in their daily lives. Proper functioning is essential in avoiding pressure related injuries. We aimed to investigate how well the ET functions in flying personnel and how it compares to the non-flying population.Prospective study. Acibadem University Atakent Hospital. 115 participants were included in the study. Each underwent a thorough otorhinolarynglogic examination then undertook a tympanogram followed by eustachian tube function (EtFT) test. A statistically significant difference in ear volume was observed in flight personnel. EtFT results showed the ability to equalize pressure after Valsalva manouvre was also significantly higher in flight personnel. Flight attendants that are subject to pressure changes throughout their careers do seem to be more capable of equalizing pressure through manoeuvres such as the Valsalva. This may be due to the fact that continuous pressure changes creates a more pliable tympanic membrane.

Introduction

The Eustachian tube (ET) plays an important role in middle ear function especially in flight attendants. It protects the middle ear from sinonasal diseases and assists in the the equalization of air pressure across the tympanic membrane, which is created by the absorption of gas through the mucous membrane in the middle ear and by the variation in ambient atmospheric pressure. The absorption of gases creates a negative pressure in the middle ear, whereas atmospheric pressure change can produce both negative and positive pressure changes. Whatever the case the eustachian tube functions to equalize pressure differences so as to facilitate normal middle ear function and protect it from harm. Eustachian tube dysfunction is a common condition seen by Otolaryngologists. ET dysfunction can result in continuous negative middle ear pressure which may lead to hearing loss and cholesteatoma formation [1]. Hearing loss due to ET dysfunction is almost always conductive in nature and is due to the inability of the tympanic membrane to vibrate properly due to the lack of pressure equilibrium in the middle ear.

Otitic barotrauma is defined as an acute or chronic traumatic inflammation of the middle ear caused by a pressure difference remaining between the air in the middle ear and the surrounding environment. The pressure difference occurs because of failure of the eustachian tube to equilibrate middle ear and atmospheric pressures. The reduction of air pressure at high altitude is the major aetiological factor in air travel barotrauma. The condition is a common problem, presenting with ear fullness, otalgia and deafness. Severe cases may result in tympanic membrane perforation and even round window membrane rupture [2].

Failure of pressure equilibration during flight may be caused by poor function of the eustachian tube due to any condition that narrows the lumen of the tube through oedema, increases the amount or viscosity of the mucus coating the tubal membrane, or impairs the ability of the tube to open. Commonest among these are the effects of upper respiratory tract infections and allergic or vasomotor rhinitis. Congenital and traumatic malformations of the nasal skeleton, as well as gross malocclusion of the teeth and jaws, may also impair eustachian tube function [2].

Each episode of barotrauma causes mucous membrane oedema and tubal system deterioration, further compromising the middle ear so that one attack of barotrauma predisposes to another [3].

A well functioning ET is very important in flight attendants who will be exposed to rapid pressure changes in their business life. In this study, we compared the difference of Eustachian tube functions of flight attendants with people, who are not exposed to atmospheric pressure differences during their daily life. Our aim is to determine whether exposure to repetitive rapid pressure changes has a positive or negative effect on Eustachian tube functions.

Patients and Methods

Our study included 115 participants. 73 of whom were healthy aircrew members and 42 of whom were healthy individuals who had never experienced pressure changes in the form of flying or diving (i.e. have never been on a flight or diving excursion). All individuals underwent a full otorhinolaryngologic examination to rule out any acute or chronic ear problems. The exam consisted of endoscopic evaluation of the external auditory canal and tympanic membrane, nasal endoscopy of the nose and nasopharynx and and orofarengeal examination to rule out any palatal abnormalities.

A tympanogram and a subsequent eustachian tube function test (EtFT) was then performed for all participants. For the tympanogram, data regarding the external ear canal volume, compliance (external ear pressure = middle ear pressure), tympanogram peak pressure and gradient were collected. Only type A tympanograms were included in the study. The EtFT was performed using the Toynbee and Valsalva manoeuvres. Three parameters P1,P2,P3 were evaluated where P = tympanogram peak pressure value. P1 after a simple tympanogram, P2 after the Toynbee manoeuvre and P3 after the Valsalva manoeuvre. A healthy response was accepted when the P2 value was lower than the P1 value and the P3 value was higher than the P2 value. All data was collected and noted.

Inclusion Criteria for our Study was as Follows

1. No evidence of acute or chronic ear problems (e.g. acute serous otitis media, chronic otitis media)

2. No evidence of septal deviation, turbinate hypertrophy, chronic rhinosinusitis.

3. No history of allergic rhinitis, non-allergic rhinitis

4. No history of previous surgery for ear problems, septal deviation, turbinate hypertrophy or chronic rhinosinusitis.

Exclusion Criteria Included

1. Acute of chronic ear infections

2. Presence of septal deviation, turbinate hypertrophy, acute of chronic rhinosinusitis.

3. History of surgery for ear problems, septal deviation, turbinate hypertrophy or chronic rhinosinusitis

4. A history of flying or diving-for the control group only

5. Anything other than a Type A tympanogram.

Statistical Analysis

In this study, statistical analysis was performed with NCSS (Number Cruncher Statistical System) 2007 Statistical Software, Utah, USA.) package program. In the evaluation of the data, descriptive statistical methods (mean, standard deviation, median, interquartile range, frequency and percentage distributions) as well as Shapiro–Wilk normality test were used for distribution of variables. Wilcoxon test was used for comparison of non-normally distributed variables. Chi-square and Mc Nemar's test were used for the comparison of qualitative data, and Pearson correlation test was used to determine the relationships between variables. The results were evaluated at p < 0.05 level of significance.

Results

73 air flight attendants group and 42 individuals for the control group were included in our study. Thirty (41%) of the flight attendants were male and 43 (59%) were female. The median age was 35, 53 (± 6, 73). In the control group 11 (26%) were men and 31 (74%) women. Median age was 33, 26 (± 8, 94). No statistical significance was found between the right and left ears in all groups. Totally 230 ears were included in our study.

Tympanometric Ear Volume (Tymp Ev) values were higher in the flight attendants group (1, 27 ± 0, 29) compared to the control group (1, 11 ± 0, 27). In addition, these parameters were higher in males than females in both groups. In tympanometric examinations there was no significant difference in compliance, pressure and gradient values in both groups and both genders. (Table 1).

Table 1.

Tympanometry and ETF test results of both groups

		Control group n:84	Flight atendant n:146	p‡
Tymp. Ear Volume	avg ± SD	1, 11 ± 0, 27	1, 27 ± 0, 29	0,0001*
	Med (IQR)	1,11 (0, 9–1, 33)	1, 24 (1, 07–1, 48)
Tymp. comp	avg ±	0, 79 ± 0, 61	0, 76 ±0, 49	0,729
	Median (IQR)	0, 61 (0,43–0, 9)	0, 62 (0, 46–0, 92)
Tymp. pres	avg ±	− 16, 29 ± 0, 49	− 8,43 ± 22,72	0,366
	Median (IQR)	− 13 (− 19,75–5)	− 12 (− 19, 25–4)
Tymp. grad	avg ± SD	0,6 ± 0,58	0,56 ± 0, 42	0,669
	Median (IQR)	0, 45 (0, 28–0, 66)	0, 44 (0, 3–0, 71)
ETF ear volume	avg ± SD	1,25 ± 0, 35	1, 37 ± 0, 35	0,015*
	Median (IQR)	1, 19 (1–1,49)	1, 31 (1,08–1, 69)
ETF pressure 1	avg ± SD	− 16,54 ± 22, 34	− 8,48 ± 23, 9	0,032*
	Median (IQR)	− 16 (− 22,75–9)	− 14 (− 20–2)
ETF pressure 2	avg ± SD	− 30, 68 ± 23	− 26,49 ± 14, 82	0,378
	Median (IQR)	− 28 (− 34–22)	− 27 (− 32–22)
ETF pressure 3	avg ± SD	− 24,92 ± 28, 74	− 4,3 ± 48, 99	0,003*
	Median (IQR)	− 24, 5 (− 34–15, 25)	− 22 (− 27–1)

In the comparison of the flight attendants and control group in the Eustachian Tube Function Test (EFT), the ear volume value measured before the maneuvers was found to be statistically significant in flight attendants compared to the control group, similar to the tympanometric examinations.

In the eustachian tube function test, no statistically significant difference was found in the pressure values measured after the Toynbee maneuver (P2). On the other hand, the pressure values measured during Valsalva maneuver (P3) were found to be statistically significantly higher than the control group. This may be due to repeated experience with the manoeuvre for aviation personnel.

In the Eustachian Tube Function Test, the flight attendants group (39, 73%) achieved statistically more successful opening rates with Valsalva maneuver than control group (21, 43%). However, we did not reach statistical opening rates between two groups with toynbee maneuver. (Table 1).

No significant difference for any value was found between flight attendants and the control group in individuals that smoked regularly. On the other hand, Tympanometric ear volume values, ETF test ear volume value and opening rates with Valsalva maneuver of flight attendants were significantly higher in the non-smoking group than the control group. (Table 2 and Fig. 1).

Table 2.

Responses of the control group and flight atendant group to the maneuvers

		Control group		Flight atendant		p
		n:84		n:146
Toynbee	Yes	47	55,95%	83	56,85%	0,895
	No	37	44,05%	63	43,15%
Valsalva	Yes	18	21,43%	58	39,73%	0,005*
	No	66	78,57%	88	60,27%

Fig. 1.

Positive responses of the control group and flight attendant group to the maneuvers

Discussion

The importance of the Eustachian Tube for middle ear health is evident. People with Eustachian Tube dysfunction may experience many problems with atmospheric pressure changes. In the general population otic barotrauma may develop in 9% of air passengers [4]. The tympanic Membrane is highly innervated [5]. The subepidermal connective tissue and lamina propria of the human tympanic membrane contain mechanoreceptors that seem to play an important role in sensing pressure [6].

In 1991, Shupak et al. investigated 42 diver candidates. As a result of their study they showed that the tympanometry measurements reflects the compliance of the middle ear at a given moment. The normal results do not mean that the divers will be able to equalize the ears smoothly in the pressure chamber and that the Eustachian function measurement in the laboratory is inadequate to predict Hyperbaric Oxygen related barotrauma [7].

These atmospheric pressure changes have been proven to cause problems such as barotrauma in the healthy middle ear in the short term [4]. So what happens in the long run? In 1993, Rinaldi et al. showed that there are neural connections between the tympanic plexus, brain stem and eustachian tube and this system works together with mechanoreceptors [8]. Unilateral electrical stimulation of the monkey's tympanic nerve has been shown to evoke bilateral electromyographic responses from eustachian tube muscles [9]. Can people who are exposed to pressure changes for a long time, such as flight attendants, improve their pressure equalization capabilities? or can continuous pressure exposure lead to a decrease in this capability?. At present, exposure to frequent pressure changes is not a predisposing factor for otic barotrauma developed during hyperbaric oxygen therapy or serous otitis media [10].

In this regard, Ivarson et al. evaluated the effects of barotrauma on the middle ear volume in addition to the acute effects of long-term recurrent minor traumas. For this purpose, they compared experienced divers with normal healthy population. They found that the middle ear volume change was greater in experienced divers and attributed this to increased eardrum elasticity due to multiple pressure equalization maneuvers. However, this study did not evaluate maneuvers and eustachian tube functions [11]. In our study, middle ear volumes of flight attendants were found to be significantly higher in support of this study.

For this purpose, we excluded subjects with eustachian tube dysfunction and middle ear disease. Eustachian tube functions were evaluated with Valsalva and Toynbee maneuvers. We compared the eustachian tube functions of healthy individuals who were not exposed to pressure changes in their lives and flight attendants who had been exposed to pressure changes for a long time. We found that middle ear volume was better in males in all groups. This was in support of the reliability of our study. We also found that men were able to perform Valsalva maneuver better in all groups.

In the flight attendants who were exposed to pressure changes for a long time, we found the middle ear volume higher than the control group as Ivarson and colleagues described [11]. In addition, in this occupational group, we found that the ability to equalize pressure in the middle ear using the valsalva maneuver was statistically significant. We suggest that subjects in this group may have this ability due to the effect of the tympanic plexus-brain stem-eustachian reflex arch.

The effect of smoking on mucociliary clearance and eustachian tube functions has been determined. In 1997, Steiger did not find a significant difference in the immittance measurements of the smokers and nonsmokers for the 20–35 age range, but found that the non-smoker group performed the valsalva maneuver statistically more successfully in the same groups [12]. In our study, no significant difference was found in the eustachian tube functions of non-flight attendants in smokers compared to non-smoking persons, whereas in non-smoker group, flight attendants performed statistically more successful valsalva maneuvers than non-flight attendants.

Alshawi investigated the efficacy of Valsalva and Toynbee maneuvers in groups with Type A and Type C tympanograms. According to their studies, both maneuvers were effective in the type A tympanogram group. In the group with type C tympanogram, they found that Valsalva maneuver had efficacy in eustachian tube functions, whereas Toynbee maneuver had no effect [13]. Hıdır et al. found no significant difference between the two maneuvers in their study in which they compared middle ear pressure equalization techniques in otoscopically healthy flight attendants [14]. In our study, we found that valsalva maneuver is more effective in healthy flight attendants than the healthy non-flying group. However, we did not find a significant difference in Toynbee maneuver.

Conclusion

• Flight attendants have improved ability to equalize middle ear pressure using the Valsalva maneuver. This may be due to continuous use of the maneuver during their work life

• This improved ability decreases with smoking.

• Multiple barometric mechanisms may play a role in adaptation to middle ear equalizing maneuvers due to constant pressure exposure.

Compliance with Ethical Standards

Ethical Approval

This research was approved by IRB ATADEK, Istanbul, Turkey. 2020–02/56.