Acta Oto-Laryngologica

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Middle Ear Ventilation Mechanism Toshio Yamashita, Norio Maeda, Koichi Tomoda & Tadami Kumazawa To cite this article: Toshio Yamashita, Norio Maeda, Koichi Tomoda & Tadami Kumazawa (1990) Middle Ear Ventilation Mechanism, Acta Oto-Laryngologica, 110:sup471, 33-38, DOI: 10.3109/00016489009124806 To link to this article: http://dx.doi.org/10.3109/00016489009124806

Published online: 08 Jul 2009.

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Date: 19 April 2016, At: 16:04

Acta Otolaryngol (Stockh) 1990; Suppl. 471: 33-38

'Middle Ear Ventilation Mechanism TOSHIO YAMASHITA, NOR10 MAEDA, KOICHI TOMODA and TADAMI KUMAZAWA From the Department of Otolaryngology, Kansai Medical University, Moriguchi, Osaka 570, Japan

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Yamashita T, Maeda N, Tomoda K, Kumazawa T. Middle ear ventilation mechanism. Acta Otolaryngol (Stockh) 1990; Suppl. 471: 33-38. The ventilation mechanism of the middle ear is very important as regards the pathogenesis of middle ear disease, but its mode of function is still obscure. Therefore, we tried to measure the ventilation and clearance of the middle ear using radio-isotope imaging techniques and '33Xe in order to gain a clearer picture of the ventilation mechanism. In normal Eustachian tube cases, approximately 10% of the initially insufflated gas immediately entered into the middle ear cavity and mastoid air cells. The gas introduced into the middle ear diminished at a rate of 8 % of volume per hour in the normal resting state. Two hours after the first procedure, air was insufflated, and gas volume in the middle ear cavity immediately diminished by 30%. In stenotic tube cases, it proved difficult to insufflate the gas into the middle ear, however, its diminishing rate with the passage of time was slightly faster than in normal tube cases. From this data, it was evident that air could easily and quickly enter into even the periphery of the mastoid air cells by insufflation via the Eustachian tube, despite the fact that the middle ear and mastoid air cells form a closed cavity. In the resting state, moreover, the air in the middle ear was thought to be absorbed mainly into the middle ear mucosa at a regular rate. It was confirmed that the insufflation procedure as a therapy for tuba1 stenosis and OME is very useful for the ventilation of the middle ear. Toshio Yamashita, Department of Otolaryngology, Kansai Medical University, 1 Fumizono-cho Moriguchi, Osaka 570, Japan.

INTRODUCTION The ventilation mechanism of the middle ear is important as regards the pathogenesis and therapy of middle ear disease, especially otitis media with effusion. Almost all studies on gas transport in the middle ear in the past have been done by indirect methods-for example, by observing pressure changes in the middle ear by the insuflation of various gases (1, 2). One reason for the weakness in this research field might be that gases cannot be observed directly. However, radio-isotope techniques have made it possible to observe their images. In the present study, the ventilation mechanisms of the middle ear were illustrated in clear pictures, and numerical values were obtained using radioactive 133 xenon gas. METHODS AND SUBJECTS Model experiment As a preparatory experiment, the influx of 133 Xenon (Xe) gas into the middle ear and Eustachian tube was examined by using two different 'models'. Two 5-ml disposable syringes were cut at the 1 ml level. One was sealed at one end with a rigidgolyethylene plate (model A) and the other with a thin rubber membrane (model B). A thin trumpetshaped rubber tube was connected to each syringe, and 1 ml of Xe gas was insufflated into both models. The Xe gas in the syringes was then measured with a scintiscanner (Fig. 1). 3-898419

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A

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B

Fig. 1. Model experiments: A: model A; B: model B. In model A , the open end of the syringe was sealed with a rigid polyethylene plate ( t t ). 1 % of the initial gas entered the syringe. In model B, the open end of the syringe was sealed with a thin rubber membrane ( t f f ). 13% of the initial gas entered into the syringe.

Normal subjects Twelve volunteers were selected as normal subjects, based on audiometry, tympanometry and tubotympano-aerodynamicography (3) results. A small bore polyethylene tube was inserted to the pharyngeal orifice of the Eustachian tube, through an inserted insufflation catheter. I ml of Xe gas was then insufflated into the middle ear through a syringe connected to the polyethlene tube, and the excess gas in the nose, throat and lungs was carefully removed over a 5-min period. Five minutes after inflation, Xe gas in the middle ear of the subject was represented as an image by scintiscanner, and compared with a simple X-ray image. Its numerical value was counted with the passage of time during 2 h at rest. The insufflation procedure using ambient air was repeated one or more times in several of the subjects after 2 h. Pathological subjects Seven cases with occluded Eustachian tubes and 4 cases with patent Eustachian tubes were selected as pathological subjects, based on diagnosis by audiometry, tympanometry and tubotyrnpano-aerodynamicography. The same experimental procedure as described above was performed in these 11 pathological subjects and Xe gas values were measured with the passage of time. RESULTS Model experiment In model A , in which the opened end of the syringe was sealed with a rigid hard plate, the numerical values of the original 1 ml Xe gas (source) and inner syringe Xe gas were 469 and 6 K counts, respectively. That is, only 1 % of the original Xe gas could enter into the syringe. By contrast, in model B , where the open end of the syringe was sealed with a flexible thin rubber membrane, the numerical values of the original 1 ml Xe gas (source) and inner syringe Xe gas were 193 and 24 K counts, respectively. That is, 13% of the original Xe gas entered into the syringe. Normal subjects The isotope image of the Xe gas and the simple X-ray image of the middle ear were compared for shape, and we found that, in all cases, the shape of the radio-isotope image

-

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Middle ear ventilation

Fig. 2 . Comparison of '33Xegas image with simple X-ray in 3 typical cases.

coincided with the configuration of the mastoid air cell represented by the simple X-ray image (Fig. 2). The actual count values and the dynamic movement of Xe gas in all 12 normal subjects are shown in Table I. The initial counts of 1 ml of radioactive xenon gas (source) were compared with counts 5 min after inflation. For example, in case 1 , 97 of I 1 1 1 K counts inflated into the middle ear resulted in 9 % value, the average in 12 cases being 1 1 %. This means that I 1 % of the initial amount of the gas entered the middle ear. Regarding changes with the passage of time, for example, in case 1 , 97 counts at 5 min diminished to 95,93,90 and 83 in the subsequent 2 h, and after insufflation procedure to 57 counts. The diminishing rates during the following 2 h after inflation were 97, 95, 92 and 88%. The diminishing rates (percent) of average changes in the passage of time at rest are illustrated in Fig. 3. The diminishing rate was almost linear and these data suggests that approximately 8% of Xe gas dispersed per hour into the resting state. After 2 h, if insufflation procedure was done once, as is shown in cases 8 and 9, the value diminished slightly, but if it was done several times as is shown in cases 1 and 12, it diminished dramatically. Pathological subjects

In subjects with occluded tubes, in case 1 for example, 37 of 703 initial value counts (source) entered into the middle ear, i.e. 5%. The average in 7 cases was 6% (Table 11). The averages with the passage of time were 91, 84, 72 and 59% and approximately 30% percent of the Xe gas dispersed in 1 h (Fig. 3). On the other hand, in subjects with patent tubes, an average of 13% of the gas entered into the middle ear. The averages with the passage of time were 90, 72, 63 and 55% percent (Table 11) and approximately 40% of the Xe gas dispersed in 1 h (Fig. 3 ) . DISCUSSION Radioactive gas, 133 Xenon (Xe) is widely used in pulmonary function diagnosis. In 1974, Kirchner (4) first used this gas to study the ventilation of the middle ear and sinuses. He

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100-

90mrmal (n=12)

80 -

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min

5

15

30

ti-

1

1

50

%

'r'

. T

60 -

J

t'-

\mraI

70 -

40

zi.7

Fig. 3. Changes in Xenon gas in the middle ear cavity with the passage of time.

120

60

lnsuf f latim

injected a bolus of Xe gas, using a syringe, into the mouth of the subject, who was then instructed to pinch his nose and execute several Valsalva maneuvres. As a result, it was shown by images that the gas could enter into all the sinuses and ears. Two years later, using an improved method, Kirchner, et al. reported on changes with the passage of time Table I . Findings in 12 normal subjects Case

Source

5 min

15 min

30 min

60 min

120 min

Insufflation

1

1111 (100%)

97 (9%) (100%)

95 (97 %)

93 (96%)

90 (93 %)

83 (86%)

57, several times (58%)

2

610 (100%)

59 (10%) (100%)

58 (98%)

56 (95 %)

54 (91%)

52 (88%)

3

1812 (100%)

128 (7 %) (100%)

125 (97%)

122 (95 %)

117 (9170)

111 (86%)

4

1586 (100%)

64 (4%) (100 %)

62 (96%)

61 (95%)

60 (93%)

59 (92 %)

5

1624 (100%)

416 (26%) (100%)

412 (99 %)

403 (96 %)

304 (94%)

382 (92 %)

6

739 (100%)

15 (2%) (100%)

14 (93 %)

13 (86 %)

13 (86 %)

12 (80%)

7

606 (100%)

55 (9%) (100%)

54 (98 %)

54 (98%)

52 (94 %)

50 (90%)

8

1266 (100%)

115 (9%) (100%)

115 (100%)

115 (100%)

114 (99 %)

110 (96%)

99, one time (86 %)

9

980 (100%)

238 (24%) (100%)

23 1 (97%)

227 (95%)

22 1 (93 %)

208 (87 %)

199, one time (84 %)

10

1562 (100%)

17 (1%) (100%)

16 (94%)

15 (93%)

14 (82 %)

14 (82 %)

11

924 (100%)

84 (9%) (100%)

80 (95 %)

80 (95 %)

79 (94 %)

75 (89 %)

12

877 (100%)

123 (14%) (100%)

119 (96 %)

113 (91 %)

112 (91 %)

109 (88 %)

Average

100%

11% 100%

97 %

95 %

92 %

88 %

83, several times (67 %)

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Middle ear ventilation

of Xe gas in the middle ear (5). Unfortunately his report was a preliminary one concerned mainly with the technique. There have been no further similar reports. In the physiological situation, a slow continuous absorption of middle ear gas into the surrounding tissue causes negative pressure in middle ear. When this negative pressure reaches a certain level, the Eustachian tube opens and a pressure equilibrium is re-established. If dysfunction of the Eustachian tube occurs due to disorders of the tuba1 muscle or mucous membrane, an occluded or patent situation occurs in the Eustachian tube. Severe and continuous dysfunction of the tube can lead to otitis media with effusion, in combination with infection or allergy of the nasopharynx, Eustachian tube and middle ear. The insufflation procedure is thought to be an effective therapeutical method for dysfunction of the Eustachian tube. However, there is some doubt as to whether sufficient air can enter into middle ear cavity in this procedure. Although insufflated Xe gas scarcely entered into the syringe in the case of model A, which had a rigid wall, sufficient gas could enter in model B which had a flexible wall. This result theoretically testified to the facts that insufflated air may enter into the middle ear cavity due to the flexibility of the tympanic membrane. It was clear from the comparison of both images of Xe gas and the simple X-ray, that air could easily and quickly enter into even the periphery of the mastoid

Table 11. Findings in patients with occluded and patent tube Case

Source

5 min

15 rnin

30 rnin

60 rnin

120 rnin

(100%)

37 (5%) (100%)

33 (89%)

32 (83 %)

27 (72 %)

23 (62 %)

2

838 (100%)

23 (3%) (100%)

20 (87 %)

18 (78 %)

I5 (65 %)

10 43 %)

3

964

29 (3%) (100%)

25 (86 %)

22 (75 %)

16 (55 %)

12 (41 %)

101 (15%) (100%) 45 (5%) (100%)

95 (94 %) 40 (88 %)

93 (92 %) 34 (75 %)

89 (88 %) 23 (51 %)

83 (82 %) 13 (28 %)

(100%)

75 (6%) (100%)

74 (98 %)

72 (96 %)

69 (92 %)

63 (84 %)

1206 (100%)

70 (6%) (100%)

65 (93 9%)

62 (88 %)

59 (84 %)

53 (76 %)

100%

6% 100%

91 %

84 %

72 %

59 %

886 (100%)

(100%)

176 (98 9%)

175 (97 %)

I70 (95%)

160 (89 %)

(100%)

84 (9%) (100%)

78 (93 %)

72 (86 %)

65 (77 %)

55 (65 %)

3

1492 (100%)

204 (14%) (100%)

154 (75 %)

77 (38 %)

33 (16%)

19 (9 %)

4

1108 (100%)

73 (7%) (100%)

68 (93 %)

50 (68 %)

46 (63 %)

43 (58 %)

100%

I3 % 100%

90 %

72 %

63 %

55 %

Occluded (OME) 1 703

(100%)

4

672 (100%)

5

835 (100%)

6

7

I301

Average Putent 1

2

870

Average

178 (20 %)

37

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T . Yamashita et al.

air ceil by insufflation procedure via a tube, even though the middle ear and mastoid air cells constitute a closed cavity and are under normal pressure conditions (Fig. 2). In our experiment, the inflation volumes of the initial gas in the middle ear in normal, occluded and patent tubes were 1 1 %, 6 % and 13% respectively. These data suggest that in occluded tubes, the gas had difficulty in entering into the middle ear via the tube. How does the mechanism of gas exchange (ventilation) in the middle ear cavity work? The ventilation route of the middle ear is theoretically thought to function in three ways; first by production and absorption through the surrounding tissue, second by active ventilation via the Eustachian tube and third, is diffusion through the tympanic membrane. Regarding the third route, Elner (6) reported, from experiments using cadaver tympanic membranes, that the normal tympanic membrane did not seem to be able to contribute to the ventilation of the middle ear. The gas absorption from the middle ear to the surrounding tissues is 0.7-1.1 ml during 24 h (7) and the total amount of gas passing through the Eustachian tube in 24 h is about 1-2 ml (8). These data clearly showed that the absorption of middle ear gas into the surrounding tissues causes negative pressure in the middle ear followed by active ventilation via the Eustachian tube. In our experiment, the insufflated middle ear gas diminished linearly at rest during 2 h. This suggests that the gas was absorbed mainly into the surrounding tissue and not exchanged via the Eustachian tube. Our data on gas dynamics of the middle ear, compiled from direct radio-isotope images, supports data gathered by Elner and others using indirect measuring of pressure changes in the middle ear. In addition, our data that approximately 8 % , 30% and 40% of the gas volume dispersed in 1 h in normal, occluded, and patent tubes respectively, lead to the hypothesis that the rate of absorption by pathologic middle ear mucosa might be greater than that of normal cases. When the insufflation procedure was done once, the gas volume diminished slightly, but when it was done several times, the gas diminished dramatically. This suggests that repeated insufflation is more useful than a single insufflation for ventilation of the middle ear as therapy for tuba1 obstruction and otitis media with effusion. ACKNOWLEDGEMENT This work was supported by a Grant-in-Aid for General Scientific Research from the Ministry of Education of Japan (no. 613040-52).

REFERENCES WJ, Phillips DC, Bluestone CD. Gas absorption in middle ear. Ann Otol Rhinol Laryngol 1980; Suppl 68: 71-75. Jones GM. Pressure changes in the middle ear after altering the composition of contained gas. Acta Otolaryngol (Stockh) 1961; 53: 1-11. Kumazawa T, Honjo I, Honda K. Aerodynamic evaluation of Eustachian tube function. Arch Oto-Rhino-Laryngol 1974; 208: 147-56. Kirchner FR. Radioscanning studies of ear and sinuses. Laryngoscope 1974; 84: 1894-1904. Kirchner FR, Robinson R, Smith RF. Study of the ventilation of middle ear using radioactive xenon. Ann Otol Rhinol Laryngol 1976; Suppl 25: 165-8. Elner A. Gas diffusion through the tympanic membrane. A model study in the diffusion chamber. Acta Otolaryngol (Stockh) 1970; 69: 185-91. Elner A. Indirect determination of gas absorption from the middle ear. Acta Otolaryngol (Stockh) 1972; 74: 191-6. Ingelstedt S , Jonsson B. Mechanisms of the gas exchange in the normal human middle ear. Acta Otolaryngol (Stockh) 1967; Suppl 224: 452-61.

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Middle ear ventilation mechanism.

The ventilation mechanism of the middle ear is very important as regards the pathogenesis of middle ear disease, but its mode of function is still obs...
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