International Journal of Pediatric Otorhinolaryngology
43 (1998) 105 – 113
Review article
Pathophysiological and therapeutic considerations
of otitis media with effusion from viewpoint of
middle ear ventilation1
Iwao Honjo, Haruo Takahashi *, Masaharu Sudo, Ken Ishijima,
Makito Tanabe
Department of Hearing and Speech Science, Kyoto Uni6ersity Graduate School of Medicine, Sakyo-ku,
Kyoto 606, Japan
Received 22 June 1997; received in revised form 14 November 1997; accepted 16 November 1997
Abstract
Using nitrous oxide, we examined the gas exchange function through the middle ear
mucosa in ears with otitis media with effusion (OME) in children, and found the function to
be impaired in 50% of them. The size of the mastoid was significantly smaller in ears with
negative gas exchange function than those with positive function, and the presence or
absence of the function was even more significantly correlated with the presence or absence
of aeration in the middle ear. Furthermore, the presence or absence of aeration in ears with
OME was found to be significantly correlated with their prognosis (response of OME to
antibiotics treatment) and also with the presence or absence of eardrum mobility examined
by a pneumatic otoscope. Finally, after myringotomy and removal of effusion, the gas
exchange function recovered in most of the ears with impaired function. These results
indicate that the eardrum mobility test may serve as an appropriate indicator for the surgical
treatment for OME. © 1998 Elsevier Science Ireland Ltd. All rights reserved.
* Corresponding author. Tel.: +81 75 7513346; fax: + 81 75 7517225.
1
Presented at the Symposium on ‘Pathogenesis of Otitis Media With Effusion’ in the XVI World
Congress of Otorhinolaryngology Head and Neck Surgery, held on 2 – 7 March 1997, in Sydney,
Australia.
0165-5876/98/$19.00 © 1998 Elsevier Science Ireland Ltd. All rights reserved.
PII S 0 1 6 5 - 5 8 7 6 ( 9 7 ) 0 0 1 7 5 - 4
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Keywords: Eardrum mobility; Gas exchange function; Middle ear ventilation; Otitis media
with effusion (OME); Prognosis
1. Introduction
It is known widely that the pathogenesis of otitis media with effusion (OME) is
closely related to the dysfunction of middle ear (ME) ventilation, and many studies
on the Eustachian tube (ET) function have been reported to date [1,3,4,7,8].
However, several questions still remain unsolved when viewed in terms of the ET
function. For instance, the ME pressure does not progressively decrease even when
the ET fails to open in children [2], and spontaneous resolution of OME cannot be
understood from the viewpoint of the ET pathophysiology, because the ET
function usually remains poor even in the convalescent stage of OME as well as in
the active stage [15].
The answers to these remaining questions regarding the pathophysiology and
treatment of OME have become clearer ever since the gas exchange function
through the ME, namely the mastoid mucosa, has come to be recognized as
important as the ET function in terms of the ME ventilation and pressure
regulation in recent decades [6,10].
This article introduces clinical observations we conducted on the pathophysiology of ventilation in OME which have provided us several clinical indices for the
appropriate diagnosis and treatment of OME mainly from the viewpoint of the gas
exchange function through the ME mucosa [9].
2. Pathophysiology of OME in children
For the ME to function as a sound conduction system, it is important that
atmospheric pressure is constantly maintained by normal ventilation, which is
provided by gas exchange through the ME mucosa as well as by the ET. The gas
exchange is a passive movement of any gas within the body according to the partial
pressure gradient of each gas in the blood, interstitial tissue and any air space
within the body such as the ME cavity. Those passive movements of the gases
always render the ME pressure approximate to the atmospheric pressure through
the summation of all the partial pressures of those gases [6,10]. Therefore, in
normal ears, both positive and negative ME pressures tend to be equalized by this
function even when the ET is unable to open (Fig. 1).
A problem is that there exists only a few reports on the assessment of the ME gas
exchange function, except for those related to the constitution of middle ear gases
[11– 14]. Recently, we developed and established a method for the assessment of the
gas exchange function using nitrous oxide [16]. The presence or absence of the ME
pressure increase by the application of nitrous oxide indicates positive or negative
exchange function of any gas through the ME mucosa (Fig. 2).
I. Honjo et al. / Int. J. Pediatr. Otorhinolaryngol. 43 (1998) 105–113
107
Fig. 1. Chronological changes of applied positive and negative middle ear pressures without deglutition.
Both positive and negative pressures tend to approach to the atmospheric pressure in most cases.
Using this method, we examined the gas exchange function in 84 ears, 44 children
with OME who underwent myringotomy or ventilation tube insertion under general
anesthesia, and then, examined the relationship between the gas exchange function
and the size and aeration (presence or absence of air space) of the mastoid of those
ears [18].
Fig. 2. Typical example of middle ear pressure increase by application of nitrous oxide (N2O) in a
normal ear.
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Fig. 3. Relationship between gas exchange function and size of mastoid in ears with otitis media with
effusion.
The gas exchange function was found to be impaired in 42 ears (50%), and the
size of the mastoid examined on X-ray (Schuller’s view) was significantly larger in
ears with positive gas exchange function than in those without the function (Fig. 3).
More interesting was that the presence or absence of the function was even more
significantly correlated with the presence or absence of an air space in the mastoid
examined on the computed tomography (CT) (Fig. 4).
These results may indicate that an air space (an air-fluid interface) is necessary
for the gas exchange to work, and that a larger mastoid is more advantageous to
preserve the air space in the ME when suffering from OME. This may be one of the
reasons why ears with larger mastoids have lower susceptibility and higher curabil-
Fig. 4. Relationship between gas exchange function and air space (aeration) in the middle ear in ears
with otitis media with effusion.
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Fig. 5. Schematic representation of middle ear pathophysiology in otitis media with effusion. When gas
exchange function is working, middle ear effusion may be excreted despite poor tubal function, while it
may be difficult to be excreted when gas exchange function is impaired because tubal function is
impaired in most of ears with otitis media with effusion.
ity of OME. Furthermore, the presence or absence of an air space in the ME is
considered one of the significant keys for the formation of a pathophysiological
condition in the ME in OME. Since it is well known that the ET ventilatory
function, the other ventilatory function for the ME, is impaired in most of ears
with OME [1,3,4,7,8], the ME ventilation and pressure regulation may be managed only by the gas exchange function in ears with OME. When fluid accumulates in the ME, it may smoothly be excreted from the ME through the ET if
there is an air space left in the ME, because negative ME pressure due to the
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excretion of the fluid can constantly be compensated by the gas exchange (entrance)
through the ME mucosa. On the other hand, if the ME is filled with fluid without
any air space, the fluid may not be excreted completely because the gas exchange
function or ET is not available in the ME; this may cause a dead-locked condition
in the ME characterized by coexistence of the negative pressure and fluid retention
(Fig. 5).
3. Diagnosis
Thus, knowing if an air space exists in the ME is considered important for
understanding of the pathophysiology of the ME in OME, but the question is how
to determine if the space is present or not. To perform CT on every child with
OME is apparently unrealistic, and to our best knowledge there has been no
literature describing another good method to examine it.
For this purpose, we focused on the eardrum mobility test, of which the
diagnostic value for the ME effusions has recently been reevaluated due to its
reasonable cost-effectiveness in comparison with tympanogram [5], and drew a
hypothesis. When there exists an air space in the ME, the eardrum moves according
to the pressure applied from the external ear and is transmitted to the ME through
the eardrum because air easily changes its volume in response to the pressure. In
contrast, OME ears full of fluid in the ME and consequently having no air space
will have no eardrum mobility because fluid almost never changes its volume by
pressure. To test this hypothesis, the eardrum mobility was examined using a
pneumatic otoscope in 56 ears with OME, and the results were correlated with the
presence or absence of an air space in the ME examined by CT [17].
The eardrum mobility was found to be less often impaired in ears with OME
than we expected; 30 of the 56 ears (53.6%) had good mobility of the eardrum.
Incidentally, the tympanogram detected ME effusions by type B or C2 in 21 of the
27 ears examined (77.8%); this indicates that the tympanogram has higher sensitivity in detecting the ME effusion than the eardrum mobility test. CT was performed
in 42 of the 56 ears. Twenty-nine ears showed positive mobility of the eardrum, in
which 25 ears (86.2%) had aeration in the ME, while only three of the 13 ears
(23.1%) without mobility of the eardrum had aeration in the ME, indicating high
correlation of eardrum mobility with aeration of the ME. The presence or absence
of the aeration in the ME in ears with OME can consequently be detected by the
eardrum mobility test by a pneumatic otoscope in most cases.
4. Treatment
Now that we know that ears filled with effusion in the whole ME space are in a
dead-locked condition with inability to expel the effusion from the ME, and that
the condition can be detected by eardrum mobility test by a pneumatic otoscope,
the next question would then be how we should treat OME ears of which the whole
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ME is filled with fluid and the gas exchange function is impaired? Again, to our
best knowledge, there exists no literature examining the relationship between the
condition of ME space (fluid-filled or positive air space) and the prognosis of OME.
What we first attempted was thus to see if antibiotics are effective to release such
a dead-locked condition. We examined the response of 62 ears with OME in
children to antibiotics treatment (30 mg/kg of amoxicillin for 7 days) by tympanogram, and the results correlated with those of the eardrum mobility [17]. Eleven
of 32 ears (34.3%) with movable eardrums showed improvement of OME, while the
improvement was only three of 30 ears (10.0%) with immovable drums. These
results indicate that ears with movable eardrums show a significantly higher
improvement rate than those with immovable eardrums, and that the medical
treatment does not prove effective for OME ears with fluid-filled ME. Furthermore,
it was also suggested that the eardrum mobility test by a pneumatic otoscope has
a significant prognostic value rather than a diagnostic value for OME.
Next we focused on the surgical treatment. Our task was to examine the gas
exchange function after myringotomy and removal of the ME effusions in 21 ears
in which the gas exchange function had not been observed before myringotomy
[18]. In most of the cases (16/21, 76%) the function recovered after myringotomy.
These results suggest that the impairment of the gas exchange function is likely to
be reversible, and that the surgical treatments for OME such as myringotomy and
tympanostomy tube insertion creates an air space in the ME to reactivate the gas
exchange function and the ME ventilation.
5. Discussion
From the results of our several clinical observations on the gas exchange function
of the ME mucosa, several important aspects of the ME pathophysiology of ears
with OME were found.
1. The gas exchange function is impaired in half of ears with OME, and the
impairment is closely related to the absence of aeration in the ME.
2. The absence of aeration in the ME in ears with OME can be detected by the
absence of eardrum mobility using a pneumatic otoscope.
3. Effects of medical treatment such as antibiotics cannot be expected for OME
ears without aeration in the ME.
4. Surgical treatment proves justifiable to those OME ears without aeration in the
ME in terms of reactivation of the gas exchange function, which is the only
ventilation and pressure-regulation function for the ME in ears with OME.
Consequently it is relatively important to take the gas exchange function into
consideration when discussing the pathophysiology of ventilation in the ME in ears
with OME. For instance, we examined the ET function in ears in the convalescent
stage of OME, and found that the most important ET function, the negative ME
pressure equalizing function, has not recovered even at that stage. Assuming that
the ET is the only ventilation system for the ME, a large number of spontaneous
resolutions of OME in children cannot be explained. Now this can be explained by
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the entrance of air through the ME mucosa as the inflammatory factors in the ME
decrease with the age of children. The significance of the mastoid pneumatization
was also clarified in some parts by these studies. A large mastoid should be difficult
to be filled with fluid due to OME, and gas entrance to the ME through the mucosa
may facilitate transtubal excretion of the fluid by constantly equalizing the ME
pressure when fluid production subsides.
The significance of the eardrum mobility test was also clarified. It shows almost
precisely the presence or absence of an air space in the ME, indicating positive or
negative gas exchange function of the ear. This examination thus allows us to
predict the prognosis of OME of whether the spontaneous resolution or effects of
medical treatment can be expected, because an OME ear with impaired gas
exchange function will not be ventilated through any route. Since there has been
almost no easy and consistent method for the determination of surgical treatments
for OME until now, the eardrum mobility test may serve as a good indicator for the
surgical treatment for OME.
References
[1] C.D. Bluestone, J.L. Paradise, Q.C. Berry, Symposium on prophylaxis and treatment of middle ear
effusions: physiology of the Eustachian tube in the pathogenesis and management of middle ear
effusions, Laryngoscope 82 (1972) 1654 – 1670.
[2] A. Bylander, A. Ivarsson, O. Tjernstrom, Eustachian tube function in normal children and adults,
Acta Otolaryngol. (Stockh.) 92 (1981) 481 – 491.
[3] B. Falk, B. Magnuson, Eustachian tube closing failure – occurrence in patients with cleft palate and
middle ear disease, Arch. Otolaryngol. Head Neck Surg. 110 (1984) 10 – 14.
[4] K. Flisberg, S. Ingelstedt, U. Ortegren, Controlled ‘ear aspiration’ of air – a ‘physiological’ test of
the tubal function, Acta Otolaryngol. (Stockh.) Suppl. 182 (1963) 35 – 38.
[5] G.A. Gates, Cost-effectiveness considerations in otitis media treatment, Otolaryngol. Head Neck
Surg. 114 (1996) 525–530.
[6] L. Hergils, B. Magnuson, Regulation of negative middle ear pressure without tubal opening, Arch.
Otolaryngol. Head Neck Surg. 114 (1988) 1442 – 1444.
[7] J. Holmquist, U. Renvall, Eustachian tube function in secretory otitis media, Arch. Otolaryngol.
Head Neck Surg. 99 (1974) 59–61.
[8] I. Honjo, Eustachian Tube and Middle Ear Diseases. Springer-Verlag Tokyo, 1988).
[9] I. Honjo, Pathogenesis and sequelae of OME from the viewpoint of middle ear ventilation.
Proceedings of XVI World Congress of Otorhinolaryngology Head and Neck Surgery, Monduzzi
Editore, Bologna, Italy, vol. 1, 1997, pp. 737 – 740.
[10] T. Iwano, T. Doi, Y. Hosoda, K. Ushiro, T. Yamashita, Transmucosal pressure regulation in the
middle ear cavity, Pract. Otol. Kyoto (in Japanese) 86 (1993) 1265 – 1272.
[11] H. Matsumura, Studies on the composition of air in the tympanic cavity, Arch. Otolaryngol. Head
Neck Surg. 61 (1955) 220–226.
[12] G. Melvill Jones, Pressure change in the middle ear after altering the composition of contained gas,
Acta. Otolaryngol. (Stockh.) 53 (1961) 1 – 11.
[13] E. Ostfeld, Middle ear gas composition, Ann. Otol. Rhinol. Laryngol. 94 (Suppl. 120) (1985) 32 – 33.
[14] J. Sade, M. Luntz, Gaseous pathways in atelectatic ears, Ann. Otol. Rhinol. Laryngol. 98 (1989)
355–358.
[15] H. Takahashi, M. Hayashi, H. Sato, I. Honjo, Primary deficits in Eustachian tube function in
patients with otitis media with effusion, Arch. Otolaryngol. Head Neck Surg. 115 (1989) 581 – 584.
I. Honjo et al. / Int. J. Pediatr. Otorhinolaryngol. 43 (1998) 105–113
113
[16] H. Takahashi, T. Sugimaru, H. Honjo, Y. Naito, A. Fujita, S. Iwahashi, H. Toda, Assessment of
the gas exchange function of the middle ear using nitrous oxide – a preliminary study, Acta
Otolaryngol. (Stockh.) 114 (1994) 643 – 646.
[17] H. Takahashi, I. Honjo, S. Hasebe M. Sudo, M. Tanabe, Eardrum mobility in otitis media with
effusion – diagnostic or prognostic value? Am. J. Otol. (Submitted).
[18] M. Tanabe, H. Takahashi, I. Honjo, et al., Gas exchange function of the middle ear in patients with
otitis media with effusion. Eur. Arch. Otorhinolaryngol. (Berlin) 254 (1997) 453 – 455.
.