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Pumping and clearancefunction of the eustachian tube
Am J OtoIarynsol 6:241-244, 1985
Pumping and Clearance Function of the Eustachian Tube IWAO HONJO, M.D., MASAHIKOHAYASHI,M.D., SHINSUKEITO, M.D., AND HARUO TAKAHASHI,M.D. The purpose of this study was to clarify the relationship between mucociliary and muscular clearance in the eustachian tube. Displacement of various viscosities and volumes of a colored fluid through the tube was observed endoscopically in cats. To test ciliary clearance, the fluid was placed in either the tympanum or the mastoid bulla. The interval between the instillation and beginning of discharge of the fluid from the pharyngeal orifice of tube was measured. Clearance time was prolonged with fluids having high viscosities, and the clearance time from the tympanum was shorter than that from the mastoid bulla. To test muscular clearance, the tensor veil palatini muscle was stimulated electrically to simulate swallowing, and the number of contractions necessary for massive discharge of the fluid was counted. Massive discharge occurred only with low viscosity fluid placed in the tympanum, whereas small amounts of highly viscous fluid were cleared by linear discharge. The authors concluded that when the volume of middle ear effusion was small, the fluid was cleared by mucociliary clearance. When the volume of fluid was large, the low viscosity fluid was cleared by muscular clearance only, while highly viscous fluid was cleared both by ciliary and muscular clearance.
To understand the pathogenesis and therapy of otitis media with effusion, it is necessary to clarify the clearance of fluid from the t y m p a n u m via the eustachian tube. Two mechanisms are involved in such clearance: mucociliary clearance and muscular clearance. Ciliary clearance of the tube plays an important role in expulsion of fluid from the middle ear. On the other hand, we reported that muscular clearance, i.e., p u m p i n g function of the tube, causes massive discharge of fluid when the t y m p a n u m is not closed. 1 In the present study, the two clearance f u n c t i o n s were evaluated u n d e r various viscosities and volumes of test fluid in the middle ear.
muscle was severed to minimize muscular function. A hole was made in the mastoid bulla, into which 0.05 ml of a colored fluid was instilled (Fig. 1). The pharyngeal orifice of the tube was observed using an endoscope through a small hole in the midline of the soft palate. The interval between the instillation and beginning of the discharge of the fluid from the pharyngeal orifice of the tube was measured. The viscosities of the colored fluid used in this study are shown in Table 1. They had been measured with a Btype rotating viscometer. The results are p l o t t e d in Figure 2, w h i c h shows the viscosity on a common logarithmic scale. Clearance time t e n d e d to increase with Tympanic Orifice
METHODS AND RESULTS
Tube
Experiment 1: Mucociliary clearance of fluid in the mastoid bulla. Nine cats were used.
~
\ ~
Under general anesthesia with pentobarbital sodium, each cat was t r a c h e o t o m i z e d and connected to a respirator. The tensor well palatini ~ From the Department of Otolaryngology,Faculty of Medicine, KyotoUniversity,KyotoCity,Japan. Presented at the International Conference on Current Aspects of Basic and Clinical Ear Research, January 20, 1985, Oita, Japan. Accepted for publication at that time. Address correspondenceand reprint requests to Dr. Honjo: Department of Otolaryngology,Faculty of Medicine, Kyoto University, Sakyo-ku,KyotaCity, 606, Japan.
Mastoid Bulla
Figure 1. Fluidis placed in the mastoid bulla. Tensor veli palatini muscle (TVPM) is transected.
241
EUSTACHIAN TUBE FUNCTION
The clearance time was markedly shortened compared with that in experiment 1, especially those of highly viscous fluids. There was significant regression between the viscosity and the clearance time (P < 0.02) (Fig. 3).
TABLE 1. Viscosity and Composition of C o l o r e d F l u i d Used VISCOSITY (CP*)
COMPOSITION
1 80 230 570 1,200 3,100 3,600 9,000 76,000
Indigocarmine 0.25% SCMC,t 0.1% Evans blue 0.50% SCMC, 0.1% Evans blue 0.75% SCMC, 0.1% Evans blue 1.00% SCMC, 0.1% Evans blue 1.25% SCMC, 0.1% Evans blue 1.50% SCMC, 0.1% Evans blue 2.00% SCMC, 0.1% Evans blue 3.00% SCMC, 1.0% Evans blue
Experiment 3: Muscular (pumping) clearance
* Centipoise. t Sodium carboxyl methylcellulose.
higher viscosities. There is significant regression between viscosity and clearance time (P < 0.001). The fluid with a viscosity of 76,000 centipoise was not expelled within 90 minutes after instillation. In the dead animal, the fluids with viscosities of 1 and 1,200 centipoise were not expelled within 90 minutes after instillation. Autopsy revealed that the fluid had reached the isthmus of the eustachian tube.
Experiment 2: Mucociliary clearance of fluid in the tympanum. Six cats were used. Colored fluid of various viscosities (0.02 ml) was placed in the tympanum. Measurement of the clearance time was made in the same way as in experiment 1.
of a large volume of fluid. Ten cats were used. The tympanic cavity was filled with the fluid, and the pharyngeal orifice of the tube was observed endoscopically. In order to simulate swallowing, the tensor veli palatini muscle was stimulated using a bipolar hooked electrode inserted into the muscle (Fig. 4). Conditions of electrical stimulation were 0.3-second duration, 5-V amplitude, and lO0-Hz square wave pulse. The number of contractions necessary for the massive discharge of fluid from the orifice was counted. When the fluid was not expelled by the muscle contractions, the interval between the instillation and the beginning of the linear (ciliary) discharge was measured. Massive discharge was observed with fluids having viscosities up to 570 centipoise (Table 2). Only linear discharge was observed at viscosities of at least 1,200 centipoise. There was significant regression between the viscosity and the clearance time (P < 0.05) (Fig. 5).
Experiment 4: Muscular clearance of a small volume of fluid. A small volume (0.02 ml) of
1-~'
t-
7O
E~
60
E I'-
50
O
Jr Dead
Figure 2. M u c o c i l i a r y clearance time and viscosity of fluid (centipoise [cp]) placed in the mastoid bulla. The regression line was Y ~ 2.53557 + 10.67846 X. Dead animals are indicated by crosses.
0
0 Alive
(3 c
40
9
3o 20 IC I
1
lO
1'o'
I
1'o'
lo'
I
lo'
Viscosity(cp)
C vE
f:: 30
~ 2o C
American Journal of Otolaryngology 242
~ lO
9 I 10
9
102
o$ 1103
Viscosity(cp)
|'O4
I
10s
Figure 3. M u c o c i l i a r y clearance time and viscosity of fluid (centipoise [cp]) placed in the tympanum. The r e g r e s s i o n line was Y = 0.17336 + 3.49764 X.
HONJO ET AL.
the fluid (80, 1,200, 3,100, and 3,600 centipoise) was placed in the tympanum, and the tensor muscle was stimulated electrically. Two cats were used. During electrical stimulation of the muscle, the pharyngeal orifice was observed endoscopically. No massive discharge was observed even after many muscle contractions, only a linear discharge (Table 3). DISCUSSION AND CONCLUSION
Clearance function of the eustachian tube and the role it plays in expelling middle ear effusions is not well understood. Several studies on the clearance function using roentogenography,2 fluorescein, 3 saccharin, 4'5 and radioactive isotopes 6 were mainly conducted as tests for clinical use. In those reports, differences between ciliary and muscular clearance were not adequately described. On the other hand, animal experiments conducted by Shibata 7 or endoscopic observation of human beings by Fukamachi 8 revealed that there are two mechanisms of tubal clearance in the eustachian tube: ciliary (linear) and muscular (massive). It is reasonable to assume that fluid expulsion from the tympanum through the eustachian tube depends on the viscosity of the fluid. However, this relationship is not well investigated. Sade 9 and McCall 1~ measured mucociliary transport rates of mucoid samples using the palatal membrane of frogs. The present study revealed that the ciliary clearance time from the tympanum was significantly shorter than that from the mastoid bulla. No marked difference in the clearance time was noted between the fluid of low and high viscosTympanic Orifice Tube
IIIVIIfl r
~
/
,
Y
~ Electrical Stimulation
Figure 4. Electrical stimulation of tensor ve]i palatini
muscle (TVPM).
TABLE 2. Viscosity and Muscular Clearance Function VISCOSITY (CP*) 1 80 230 570 1,200 3,100 3,600 9,000 76,000
MASSIVEDISCHARGEr LINEARDISCHARGE +,1
-
+, I +, 1 +, 3 -
+ + + +
-
+
* Centipoise. t Numeral indicates number needed for massive discharge.
of muscular
contractions
ities. This indicates that the mucociliary function of the tube is slightly affected by the viscosity of the fluid. These findings coincide well with the morphologic observations that the density of ciliated cells in the tube and hypotympanum is considerably higher than that in the mastoid bulla. 11'12 On the other hand, the mucociliary discharge from the mastoid is markedly influenced by the viscosity of the fluid. This indicates that pus or effusion in the mastoid antrum is not readily cleared. The absence of ciliary discharge in dead animals implies that the clearance of the tube in this experiment is not caused by a gravity or pressure difference. In a previous study, we reported that contractions and relaxations of the tensor muscle cause a pumping function of the tube, which expels fluid from the t y m p a n u m into the pharynx. 1 However, the influence of viscosity or volume of the fluid on this function had not been investigated. The present study revealed that massive discharge of fluid occurs by muscle contraction when the viscosity of the fluid is low. In contrast, only linear discharge is observed with highly viscous fluids. These results indicate that the serous fluid is expelled by the pumping function of the tube, while the mucous fluid is expelled by the cilia. Even with highly viscous fluids, however, muscular clearance may be involved to some extent, because the time for linear discharge in this condition was significantly shorter than when the tensor veli palatini muscle was severed. Muscular discharge was influenced by the volume of the fluid. When the volume of the middle ear effusion is small, the fluid is not cleared by muscular function even at low viscosities. The present study confirmed the presence of two mechanisms of fluid clearance in the eustachian tube. When the volume of middle ear effusion is small, the fluid is cleared by muco-
Volume 6 Number 3 May 1985 243
EUSTACHIAN TUBE FUNCTION
E
30
i:
Figure 5. Muscular clearance time and viscosity of fluid (centipoise [cp]) placed in the tympanum. The regression line was Y = -1.68766 + 1.84151 X.
20
0 E
10
A
A
I
O'
A--t--------~
IO
-~.'~'~
A
103
102
I
10'~
10 6
Viscosity(cp)
TABLE 3. Viscosity and Muscle Clearance F u n c t i o n for Fluid (0.02 ml) Placed in the Tympanum VISCOSITY(CP*) 80 1,200 3,100 3,600
MASSIVEDISCHARGE LINEARDISCHARGE --
-
+
+ + +
* Centipoise.
ciliary clearance, which is not affected by increase of viscosity. When the volume of fluid is large, clearance depends on the viscosity. Serous fluid is cleared by muscular clearance, while mucous is cleared both by ciliary and muscular clearance. As massive fluid discharge is caused only by the muscular clearance, it appears important for effective clearance to reduce the viscosity of fluid.
References 1. Honjo I, Okazaki N, Nozoe T, et ah Experimental study of the pumping function of the eustachian tube. Acta Otolaryngol 91:85-89, 1981
American Journal of Otolaryngology 244
2. Compere WE Jr: Tympanic cavity clearance studies. Trans Am Acad Ophthalmol Otolaryngol 62:444-454, 1958 3. Rogers RL, Kirchner FR, Proud GO: The evaluation of -eustachian tubal function by fluorescent dye studies. Laryngoscope 72:456-467, 1962 4. Elbrend O, Larsen E: Mucociliary function of the eustachian tube. Arch Otolaryngol 102:539-541, 1976 5. Hadas E, Sade J: Clearance by the mucociliary system in simple chronic otitis media. J Laryngol Otol 93:781783, 1979 6. Karja J, Nuutinen J, Karjalainen P: Mucociliary function in children with secretory otitis media. Acta Otolaryngol 95:544-546, 1983 7. Shibata S: Experimental study of the evacuating function of the eustachian tube. Pract Otol Kyoto 35:560-578, 1940 8. Fukamachi M: Clinical observation on the evacuating function of the human eustachian tube. J Otolaryngol Jpn 57:1114-1119, 1954 9. Sade J, Meyer FA, King M, et ah Clearance of middle ear effusions by the mucociliary system. Acta Otolaryngol 79:277-282, 1975 10. McCall AL, Potsic WP, Shih CK, et ah Physiochemical properties of human middle ear effusions (mucus) and their relation to ciliary transport. Laryngoscope 88:729-738, 1978 11. Sade J: Ciliary activity and middle ear clearance. Arch Otolaryngol 86:128-135, 1967 12. Shimada T, Lim DJ: Distribution of ciliated cells in the human middle ear. Ann Otol Rhinol Laryngol 81:203211, 1972
Pumping and Clearance Function of the Eustachian Tube IWAO HONJO, M.D., MASAHIKOHAYASHI,M.D., SHINSUKEITO, M.D., AND HARUO TAKAHASHI,M.D. The purpose of this study was to clarify the relationship between mucociliary and muscular clearance in the eustachian tube. Displacement of various viscosities and volumes of a colored fluid through the tube was observed endoscopically in cats. To test ciliary clearance, the fluid was placed in either the tympanum or the mastoid bulla. The interval between the instillation and beginning of discharge of the fluid from the pharyngeal orifice of tube was measured. Clearance time was prolonged with fluids having high viscosities, and the clearance time from the tympanum was shorter than that from the mastoid bulla. To test muscular clearance, the tensor veil palatini muscle was stimulated electrically to simulate swallowing, and the number of contractions necessary for massive discharge of the fluid was counted. Massive discharge occurred only with low viscosity fluid placed in the tympanum, whereas small amounts of highly viscous fluid were cleared by linear discharge. The authors concluded that when the volume of middle ear effusion was small, the fluid was cleared by mucociliary clearance. When the volume of fluid was large, the low viscosity fluid was cleared by muscular clearance only, while highly viscous fluid was cleared both by ciliary and muscular clearance.
To understand the pathogenesis and therapy of otitis media with effusion, it is necessary to clarify the clearance of fluid from the t y m p a n u m via the eustachian tube. Two mechanisms are involved in such clearance: mucociliary clearance and muscular clearance. Ciliary clearance of the tube plays an important role in expulsion of fluid from the middle ear. On the other hand, we reported that muscular clearance, i.e., p u m p i n g function of the tube, causes massive discharge of fluid when the t y m p a n u m is not closed. 1 In the present study, the two clearance f u n c t i o n s were evaluated u n d e r various viscosities and volumes of test fluid in the middle ear.
muscle was severed to minimize muscular function. A hole was made in the mastoid bulla, into which 0.05 ml of a colored fluid was instilled (Fig. 1). The pharyngeal orifice of the tube was observed using an endoscope through a small hole in the midline of the soft palate. The interval between the instillation and beginning of the discharge of the fluid from the pharyngeal orifice of the tube was measured. The viscosities of the colored fluid used in this study are shown in Table 1. They had been measured with a Btype rotating viscometer. The results are p l o t t e d in Figure 2, w h i c h shows the viscosity on a common logarithmic scale. Clearance time t e n d e d to increase with Tympanic Orifice
METHODS AND RESULTS
Tube
Experiment 1: Mucociliary clearance of fluid in the mastoid bulla. Nine cats were used.
~
\ ~
Under general anesthesia with pentobarbital sodium, each cat was t r a c h e o t o m i z e d and connected to a respirator. The tensor well palatini ~ From the Department of Otolaryngology,Faculty of Medicine, KyotoUniversity,KyotoCity,Japan. Presented at the International Conference on Current Aspects of Basic and Clinical Ear Research, January 20, 1985, Oita, Japan. Accepted for publication at that time. Address correspondenceand reprint requests to Dr. Honjo: Department of Otolaryngology,Faculty of Medicine, Kyoto University, Sakyo-ku,KyotaCity, 606, Japan.
Mastoid Bulla
Figure 1. Fluidis placed in the mastoid bulla. Tensor veli palatini muscle (TVPM) is transected.
241
EUSTACHIAN TUBE FUNCTION
The clearance time was markedly shortened compared with that in experiment 1, especially those of highly viscous fluids. There was significant regression between the viscosity and the clearance time (P < 0.02) (Fig. 3).
TABLE 1. Viscosity and Composition of C o l o r e d F l u i d Used VISCOSITY (CP*)
COMPOSITION
1 80 230 570 1,200 3,100 3,600 9,000 76,000
Indigocarmine 0.25% SCMC,t 0.1% Evans blue 0.50% SCMC, 0.1% Evans blue 0.75% SCMC, 0.1% Evans blue 1.00% SCMC, 0.1% Evans blue 1.25% SCMC, 0.1% Evans blue 1.50% SCMC, 0.1% Evans blue 2.00% SCMC, 0.1% Evans blue 3.00% SCMC, 1.0% Evans blue
Experiment 3: Muscular (pumping) clearance
* Centipoise. t Sodium carboxyl methylcellulose.
higher viscosities. There is significant regression between viscosity and clearance time (P < 0.001). The fluid with a viscosity of 76,000 centipoise was not expelled within 90 minutes after instillation. In the dead animal, the fluids with viscosities of 1 and 1,200 centipoise were not expelled within 90 minutes after instillation. Autopsy revealed that the fluid had reached the isthmus of the eustachian tube.
Experiment 2: Mucociliary clearance of fluid in the tympanum. Six cats were used. Colored fluid of various viscosities (0.02 ml) was placed in the tympanum. Measurement of the clearance time was made in the same way as in experiment 1.
of a large volume of fluid. Ten cats were used. The tympanic cavity was filled with the fluid, and the pharyngeal orifice of the tube was observed endoscopically. In order to simulate swallowing, the tensor veli palatini muscle was stimulated using a bipolar hooked electrode inserted into the muscle (Fig. 4). Conditions of electrical stimulation were 0.3-second duration, 5-V amplitude, and lO0-Hz square wave pulse. The number of contractions necessary for the massive discharge of fluid from the orifice was counted. When the fluid was not expelled by the muscle contractions, the interval between the instillation and the beginning of the linear (ciliary) discharge was measured. Massive discharge was observed with fluids having viscosities up to 570 centipoise (Table 2). Only linear discharge was observed at viscosities of at least 1,200 centipoise. There was significant regression between the viscosity and the clearance time (P < 0.05) (Fig. 5).
Experiment 4: Muscular clearance of a small volume of fluid. A small volume (0.02 ml) of
1-~'
t-
7O
E~
60
E I'-
50
O
Jr Dead
Figure 2. M u c o c i l i a r y clearance time and viscosity of fluid (centipoise [cp]) placed in the mastoid bulla. The regression line was Y ~ 2.53557 + 10.67846 X. Dead animals are indicated by crosses.
0
0 Alive
(3 c
40
9
3o 20 IC I
1
lO
1'o'
I
1'o'
lo'
I
lo'
Viscosity(cp)
C vE
f:: 30
~ 2o C
American Journal of Otolaryngology 242
~ lO
9 I 10
9
102
o$ 1103
Viscosity(cp)
|'O4
I
10s
Figure 3. M u c o c i l i a r y clearance time and viscosity of fluid (centipoise [cp]) placed in the tympanum. The r e g r e s s i o n line was Y = 0.17336 + 3.49764 X.
HONJO ET AL.
the fluid (80, 1,200, 3,100, and 3,600 centipoise) was placed in the tympanum, and the tensor muscle was stimulated electrically. Two cats were used. During electrical stimulation of the muscle, the pharyngeal orifice was observed endoscopically. No massive discharge was observed even after many muscle contractions, only a linear discharge (Table 3). DISCUSSION AND CONCLUSION
Clearance function of the eustachian tube and the role it plays in expelling middle ear effusions is not well understood. Several studies on the clearance function using roentogenography,2 fluorescein, 3 saccharin, 4'5 and radioactive isotopes 6 were mainly conducted as tests for clinical use. In those reports, differences between ciliary and muscular clearance were not adequately described. On the other hand, animal experiments conducted by Shibata 7 or endoscopic observation of human beings by Fukamachi 8 revealed that there are two mechanisms of tubal clearance in the eustachian tube: ciliary (linear) and muscular (massive). It is reasonable to assume that fluid expulsion from the tympanum through the eustachian tube depends on the viscosity of the fluid. However, this relationship is not well investigated. Sade 9 and McCall 1~ measured mucociliary transport rates of mucoid samples using the palatal membrane of frogs. The present study revealed that the ciliary clearance time from the tympanum was significantly shorter than that from the mastoid bulla. No marked difference in the clearance time was noted between the fluid of low and high viscosTympanic Orifice Tube
IIIVIIfl r
~
/
,
Y
~ Electrical Stimulation
Figure 4. Electrical stimulation of tensor ve]i palatini
muscle (TVPM).
TABLE 2. Viscosity and Muscular Clearance Function VISCOSITY (CP*) 1 80 230 570 1,200 3,100 3,600 9,000 76,000
MASSIVEDISCHARGEr LINEARDISCHARGE +,1
-
+, I +, 1 +, 3 -
+ + + +
-
+
* Centipoise. t Numeral indicates number needed for massive discharge.
of muscular
contractions
ities. This indicates that the mucociliary function of the tube is slightly affected by the viscosity of the fluid. These findings coincide well with the morphologic observations that the density of ciliated cells in the tube and hypotympanum is considerably higher than that in the mastoid bulla. 11'12 On the other hand, the mucociliary discharge from the mastoid is markedly influenced by the viscosity of the fluid. This indicates that pus or effusion in the mastoid antrum is not readily cleared. The absence of ciliary discharge in dead animals implies that the clearance of the tube in this experiment is not caused by a gravity or pressure difference. In a previous study, we reported that contractions and relaxations of the tensor muscle cause a pumping function of the tube, which expels fluid from the t y m p a n u m into the pharynx. 1 However, the influence of viscosity or volume of the fluid on this function had not been investigated. The present study revealed that massive discharge of fluid occurs by muscle contraction when the viscosity of the fluid is low. In contrast, only linear discharge is observed with highly viscous fluids. These results indicate that the serous fluid is expelled by the pumping function of the tube, while the mucous fluid is expelled by the cilia. Even with highly viscous fluids, however, muscular clearance may be involved to some extent, because the time for linear discharge in this condition was significantly shorter than when the tensor veli palatini muscle was severed. Muscular discharge was influenced by the volume of the fluid. When the volume of the middle ear effusion is small, the fluid is not cleared by muscular function even at low viscosities. The present study confirmed the presence of two mechanisms of fluid clearance in the eustachian tube. When the volume of middle ear effusion is small, the fluid is cleared by muco-
Volume 6 Number 3 May 1985 243
EUSTACHIAN TUBE FUNCTION
E
30
i:
Figure 5. Muscular clearance time and viscosity of fluid (centipoise [cp]) placed in the tympanum. The regression line was Y = -1.68766 + 1.84151 X.
20
0 E
10
A
A
I
O'
A--t--------~
IO
-~.'~'~
A
103
102
I
10'~
10 6
Viscosity(cp)
TABLE 3. Viscosity and Muscle Clearance F u n c t i o n for Fluid (0.02 ml) Placed in the Tympanum VISCOSITY(CP*) 80 1,200 3,100 3,600
MASSIVEDISCHARGE LINEARDISCHARGE --
-
+
+ + +
* Centipoise.
ciliary clearance, which is not affected by increase of viscosity. When the volume of fluid is large, clearance depends on the viscosity. Serous fluid is cleared by muscular clearance, while mucous is cleared both by ciliary and muscular clearance. As massive fluid discharge is caused only by the muscular clearance, it appears important for effective clearance to reduce the viscosity of fluid.
References 1. Honjo I, Okazaki N, Nozoe T, et ah Experimental study of the pumping function of the eustachian tube. Acta Otolaryngol 91:85-89, 1981
American Journal of Otolaryngology 244
2. Compere WE Jr: Tympanic cavity clearance studies. Trans Am Acad Ophthalmol Otolaryngol 62:444-454, 1958 3. Rogers RL, Kirchner FR, Proud GO: The evaluation of -eustachian tubal function by fluorescent dye studies. Laryngoscope 72:456-467, 1962 4. Elbrend O, Larsen E: Mucociliary function of the eustachian tube. Arch Otolaryngol 102:539-541, 1976 5. Hadas E, Sade J: Clearance by the mucociliary system in simple chronic otitis media. J Laryngol Otol 93:781783, 1979 6. Karja J, Nuutinen J, Karjalainen P: Mucociliary function in children with secretory otitis media. Acta Otolaryngol 95:544-546, 1983 7. Shibata S: Experimental study of the evacuating function of the eustachian tube. Pract Otol Kyoto 35:560-578, 1940 8. Fukamachi M: Clinical observation on the evacuating function of the human eustachian tube. J Otolaryngol Jpn 57:1114-1119, 1954 9. Sade J, Meyer FA, King M, et ah Clearance of middle ear effusions by the mucociliary system. Acta Otolaryngol 79:277-282, 1975 10. McCall AL, Potsic WP, Shih CK, et ah Physiochemical properties of human middle ear effusions (mucus) and their relation to ciliary transport. Laryngoscope 88:729-738, 1978 11. Sade J: Ciliary activity and middle ear clearance. Arch Otolaryngol 86:128-135, 1967 12. Shimada T, Lim DJ: Distribution of ciliated cells in the human middle ear. Ann Otol Rhinol Laryngol 81:203211, 1972