CHAPTER IV. ETIOLOGY, PATHOGENESIS AND PATHOLOGY
CLEARANCE OF MIDDLE EAR EFFUSIONS AND MIDDLE EAR PRESSURES
J. A.
HALEVY,
SAnE, M.D.
M.D.
E.
HAnAS,
M.D.
KFAR SABA, ISRAEL
SUMMARY - Twenty-six children presenting bilateral secretory otitis media (SOM) had ventilating tubes inserted into both middle ears. Mucus was, however, aspirated only from one ear, the right side. The vast majority of ears right and left were seen to have cleared their effusion equally well regardless of whether they were aspirated on not. This experiment points toward the essential intactness of the mucociliary system and the patency of the lumen of the Eustachian tube in SOM. Promotion of middle ear clearance through ventilation, which reminds one of the second opening in a beer can, does obviously suggest the relief of some negative pressure. Direct manometric measurements of SOM middle pressure were performed in 41 ears showing negative pressure averaging -1.7 mm H 20, this range being two orders of magnitude less than tympanometric measurements. Normal ears did not have even such a small negative pressure. The validity of these direct manometric measurements was checked against a model of the middle ear. Tympanometry, which is a valid diagnostic tool, does indicate in all probability the presence of middle ear effusion due to its rheologic effects on the drum and ossicles rather than the measure of actual middle ear pressures. This is determined by the fact that direct needling of the middle ear, or even the insertion of a ventilating tube, did not change tympanometric values but aspiration of part of the effusion did: indeed the latter tended to bring manometry to normal values.
Secretory otitis media (SaM) is characterized by the presence of an effusion in the middle ear. The origin of the effusion was shown by Sade' to be the middle ear lining, a true respiratory mucosa which secretes mucus and bears cilia." This mucociliary system clears the secreted mucus into the nasopharynx through the Eustachian tube under normal conditions." Among the questions still to be answered are, 'Why is there excessive mucus secretion and why is this excessive mucus not cleared?" To elucidate the question as to what extent the middle ear mucociliary system and the Eustachian tube lumen are affected we inserted ventilating tubes into both ears of 26 children with bilateral SaM. The effusion was aspirated from all the right ears and was not aspirated from the left ears. The left ear
served as a control. Our follow-up, using the microscope, was done the evening after the operation, the next day, and 72 hours after the operation. Audiograms were undertaken on all children preoperatively and compared with postoperative audiograms. Table I summarizes the results of this experiment showing that there was practically no difference between ears aspirated or not aspirated. The majority of the ears in both groups have cleared the effusion at the same rate and attained the same hearing level. The ears designated as dry contained no mucus as viewed through the ventilating tube with the microscope. The few ears designated as wet did not contain mucus either - rather a certain brownish fluid, slightly viscous, was to be seen filling or covering the ventilating tube. This brownish effusion was probably inflammatory in nature.
---From the Meir Hospital, Kfar Saba, Israel, Weizmann Institute of Science, Rehovot, Israel, and the University of Iowa, Iowa City, Iowa.
58
59
CLEARANCE AND PRESSURES
TABLE I RESULTS OF INSERTION OF VENTILATION TUBES 52 Ears (26 Patients)
Ear R (asp.) L (not asp.)
Average Audiometry Pre Post 40 dB 47 dB
12.3 dB 14.4 dB
12 Hours
Wet
Dry
6
20
5
21
24 Hours Wet Dry 3 2
23
24
72 Hours Wet Dry 2 2
24
24
asp. - Aspirated
The conclusion from the above experi- taking all the precautions to ensure rement is that in these patients the muco- liable direct measurements of the intraciliary system is essentially intact and so tympanic pressure. This included: 1 ) is the patency of the Eustachian tube, checking our method of direct pressure which resumes its function promptly on measurement on a model, the model ventilating this system. representing a middle ear; and 2) tymThe second question to follow was, panometry was done on our patients be'What is the mechanism of the favorable fore and after the direct manometric effect of ventilation on middle ear clear- measurements. The direct manometric measurements ance?" It is traditionally assumed that nega- were undertaken with a 22 gauge needle tive pressure in the middle ear is the coated from the inside with hydrophobic pathogenetic factor in SaM, the venti- silicone, and from the outside with a lating tube equalizing this negative pres- hydrophilic detergent. The tympanic sure with the atmospheric pressure. Pro- membrane was covered with water to ponents of the vacuum theory base their avoid gas leak. The manometer's inner claim on the following observations in diameter was 0.8 mm, as was the 25 mm SOM: 1 ) the presence of a retracted long polyethylene tube connecting the tympanic membrane; 2) water covering needle to the manometer. The manomthe tympanic membrane is supposed to eter contained methanol stained with a be sucked into the tympanic cavity on grain of mercurochrome. The free space incision of the latter; and 3) tympano- in the manometer from the tip of the metric measurements show negative needle up to the methanol was 0.16 em, pressure of 100-300 mm. These measure- which is about 6% of the middle ear ments are supposed to represent intra- space (2 cc ); this in the case of a sclerotic or diploic mastoid, is the rule in tympanic negative pressure. SaM children. However, retracted tympanic memThe middle ear model was a 2 cc branes are found only in the minority of chamber made of transparent perspex SaM patients" (less than 10%) and we (Fig. 1) and had a circular opening into have never observed water being sucked into the tympanic cavity, even when which a cadaver tympanic membrane looking for it purposely in many patients. (or some other membrane) could be fastened with a screw (arrow). Leading Lately Buckingham and Ferrar- pub- directly into this chamber was a syringe lished important data on direct measure- with a micrometric device to create negments of intratympanic pressure showing ative pressures as well as a manometer no negative pressure in 25% of their pa- to measure simultaneously the created tients, and a negative pressure averaging negative pressure - comparing it with about 5 mm of water in the rest; this be- the measurements obtained with the ing about two orders of magnitude less trans-tympanic manometer. than measured tympanometrically. When water covered the tympanic In view of the conflicting information membrane as a protection for gas leak, we thought it might be useful to repeat experiments on the model could be carthe direct manometric measurements, ried on until a negative pressure of 20
60
SAIJP. ET AL. 100 -
Manometry Average (-) 1.7 (+)5-(-)12.06
--0
Tymponometry Average (-)130 (+)100-(-)260
i.
15
!:
:1
10
" "
ft" "" "
I
11 I
r
,
'I i!
t
I, I I J I
-'5
II
1\
:I II
I
I
I
I
I:I I
I
I
I
I
I
I
A
I
I~,
r I
-100
\ \,
J
\:
200
Fig. 1. Middle ear model. A-Transtympanic manometer. B-Manometer in direct connection with the middle ear cavity model. C-Micrometric syringe to create negative pressures in middle ear model. Arrow-Region of middle ear model into which an artificial tympanic membrane can be fastened with a screw.
mm H 20 was created. Below this pressure the water leaked into the model. However when antibiotic ointment (Terramycinw") was used, as a seal, the procedure could be carried out satisfactorily up to negative pressures of 140 mm H 20. In both instances the trans-tympanic manometric (A) measurements corresponded to the indwelling manometry (B). The mucus-like substance introduced into the artificial ear did not alter the measurement, whether the needle penetrated it or not. Having satisfied ourselves that direct manometric measurements with a needle through an artificial drum represent faithfully the pressure existing in the artificial middle ear, we undertook manometric measurements in patients, the procedure being as follows:
1. Measurements were carried out on 41 ears with effusion. 2. The patients had preoperative audiograms and tympanograms. 3. Anesthesia: Local used in adults; in children, ketamine hydrochloride was used. No ventilation was performed. 4. Tympanogram was repeated with the patient asleep, or having local anesthesia.
t
/\ " \
..
"
Y
a /, I
~ f\
\:
1}
\ o~..
I)
1 I
b'
..
\"r
I
..
/\i
j
/
~
::
.
I'
,0- :
;\!
v,!!
' ..
'o..J
,
\~ \, ,
\
p
~\ f
\1~
300
Fig. 2. Results of manometric measurements in 36 SOM ears - compared with tympanometric measurements in the same ears.
5. Water (saline) was instilled into the external ear canal to cover the tympanic membrane. 6. A manometric needle was inserted into the middle ear and reading undertaken. 7. Needle was removed, water removed, and tympanogram repeated. 8. Grommet was inserted; mucus was not aspirated. 9. Tympanogram was repeated once again. 10.. Five ears had tympanograms repeated after some mucus was aspirated and grommet inserted. RESULTS
1. In no case was water seen to be sucked into the tympanic cavity on introduction of the needle into the tympanic cavity. 2. In 36 ears with effusion, tympanometry showed an average of 130 mm H 2 0 (ranging from + 100 to - 260) before and after anesthesia, and was the same before and after the manometric measurement, i.e., the insertion of the needle did not alter the tympanometric measurement (Fig. 2).1 3. Manometric measurements on these 36 ears with effusion showed an
"Pfizer Laboratories Division, Pfizer Inc., New York, N. Y.
61
CLEARANCE AND PRESSURES ___ Tympanametry Pre e. Past Manometry Average (-)152 (-)80-H200 100
.......... Manometry Average (-) 1.12 (+)0.8-(-)3.2 0---0
Past Aspiration Tympanametry / AverageH 52 (+)80-(-) 160 , "
,
o
TABLE II TYMPANOMETRIC VALUES (mm H 2 0 )
~""""""""""""'~'-"""""""""""'3'····················...4..;/+~_············· 5
,,
-100
"
"
/
,,
,0' /
"
-200
Fig. 3. Tympanometric results in five SOM ears before and after mucus aspiration.
average of -1.7 mm H 20 (ranging from +5 to -12.06) (Fig. 2). 4. Tympanometric measurements did not change after insertion of the ventilating tube either, if mucus was not aspirated. However, once some mucus was aspirated, in five ears, it came up from an average of -152 mm H 20 to an average of - 52 mm H 20 (Fig. 3). 5. Manometric measurements on 11 ears with no effusion; seven with otosclerosis and four others showed an average of + 0.4 mm H 20. DISCUSSION
From our experiments we can see that the reason for the delay of middle ear clearance is apparently not because of "breakdown" of the mucociliary system. The prompt mucus clearance on ventilation, which occurs whether the effusion is aspirated or not, also confirms our previous histological? observation showing no real organic tubal obstruction in SOM. At the same time, clearance was obviously promoted or triggered through the ventilating procedure. It is, of course, natural to view the mechanism by which ventilation facilitates clearance as being connected with equalization of pressures, the middle ear having an under pressure. Our direct measurements of intratympanic pressures
SOM Adults (12) Children (20) Otosclerosis Adults (18)
Normal Adults (20)
-100 to -400 -120 to -380
'" '"
Av. -240 Av. -255
80
Av. -
20
to -190
Av. -
13
to -
have in essence confirmed Buckingham and Ferrar's" data, the pressures measured by US showing negative value, being slightly below zero and having an average of about -1.7 rom H 20. It should be noted that normal controlled ears without effusions do not show even this small negative pressure. While tympanometry is a very good diagnostic indicator for SOM (Table II) it would seem that this indirect measurement does not reflect in these cases the real intratympanic pressures. The meticulous studies of Eliachar et al7 , 8 do indeed demonstrate that artificially created intratympanic pressures in otherwise normal ears can be accurately measured with the aid of a tympanometer. However, it would seem from our study that similar tympanometric measurements can be obtained as a result of other factors, such as the presence of intratympanic effusion. This we can deduce from the alternation of tympanometry and its return to near normal averages on aspiration of part of the effusion. Tympanometry was apparently feasible under all our experimental conditions because some mucus was always present in the tympanic cavity to seal the grommet openings. From our studies as well as those of Buckingham and Ferrar," it would seem that the actual negative middle ear pressure in SOM is only a few millimeters of water, being two orders of magnitude less than indicated with tympanometric indirect measurements. '" What is the mechanism that brings about minimal underpressures?
"When oxygen is absorbed from a "closed pocket," equilibrium with capillary blood is eventually reached. This will create a difference of about - 40 mm Hg which corresponds to -550 mm H 20. An organic Eustachian tube obstruction is expected to turn the middle ear into a "closed pocket" with such underpressures.
62
SAD!; ET AL.
The answer should be looked for in Hilding's" experiments which show that an advancing mucus mass in a mucociliary cylinder may create a negative pressure behind it, of an order of magnitude compatible with our experiments. The middle ear is in effect such a cylinder closed on one side. Mucus is a cross linked material'"" and when acting en
mass as one huge interlinked molecule will apparently leave, on being cleared, some vacuum behind it. Indeed a reduced capacity of the Eustachian tube to ventilate the middle ear' will probably be an enhancing factor. Animal experiments mimicking such a situation in the ear should resolve the matter and are currently in progress.
REFERENCES 1. Sade J: The biopathology of secretory otitis media. Ann Otol Rhinol Laryngol 83 (Suppl 11 :59-71 ), 1974 2. Sade J: Middle ear mucosa. Arch Otolaryngol 84:137-143, 1966
3. Sade J: Ciliary activity and middle ear clearance. Arch Otolaryngol 86: 128-135, 1967 4. Cohen D: Secretory Otitis Media, thesis. Hebrew University, Jerusalem, 1968 5. Buckingham RA, Ferrar JL: Middle ear pressure in Eustachian tube malfunction: manometric studies. Laryngoscope 83: 15851593, 1973 . 6. Sade J: Pathology and pathogenesis of serous otitis media. Arch Otolaryngol 84:292305, 1960 7. Eliachar I, Northern JL: Studies in
tympanometry: validation of the present technique for determining intra-tympanic pressure through the intact eardrum. Laryngoscope 84:247-255, 1974 8. Eliachar I, Sando I, Northern JL: Measurement of middle ear pressure in guinea pigs. Arch Otolaryngol 99: 171-176, 1974 9. Hilding AC: Role of ciliary action in production of pulmonary atelectasis. Vacuum in paranasal sinuses and in otitis media. Trans Am Acad Ophthalmol Otolaryngol July-August, 7-12, 1944 10. Sade J: Mucociliary flow in the middle ear. Ann Otol Rhinol Laryngol 80:336372, 1971 11. Meyer FA, Eliezer N, Silberberg A, et al: An approach to the biochemical basis for transport function of epithelial mucus. Bull Physiopathol Resp 9:259-269, 1973
REPRINTS - J. Sade, M.D., Meir Hospital, Kfar Saba, Israel. Dr. Sade is an Established Investigator of the Chief Scientist's Bureau, Ministry of Health, Meir Hospital and Weizmann Institute of Science, Israel. He is Visiting Professor in the Department of Otolaryngology and Maxillofacial Surgery, University Hospitals, University of Iowa, Iowa City, Iowa, until July 1, 1976. ACKNOWLEDGMENT - The manometric equipment and artificial ear were constructed at the Weizmann Institute of Science with the collaboration and help of Prof. E. Frie and Doctor Jerushalmi.
CLEARANCE OF MIDDLE EAR EFFUSIONS AND MIDDLE EAR PRESSURES
J. A.
HALEVY,
SAnE, M.D.
M.D.
E.
HAnAS,
M.D.
KFAR SABA, ISRAEL
SUMMARY - Twenty-six children presenting bilateral secretory otitis media (SOM) had ventilating tubes inserted into both middle ears. Mucus was, however, aspirated only from one ear, the right side. The vast majority of ears right and left were seen to have cleared their effusion equally well regardless of whether they were aspirated on not. This experiment points toward the essential intactness of the mucociliary system and the patency of the lumen of the Eustachian tube in SOM. Promotion of middle ear clearance through ventilation, which reminds one of the second opening in a beer can, does obviously suggest the relief of some negative pressure. Direct manometric measurements of SOM middle pressure were performed in 41 ears showing negative pressure averaging -1.7 mm H 20, this range being two orders of magnitude less than tympanometric measurements. Normal ears did not have even such a small negative pressure. The validity of these direct manometric measurements was checked against a model of the middle ear. Tympanometry, which is a valid diagnostic tool, does indicate in all probability the presence of middle ear effusion due to its rheologic effects on the drum and ossicles rather than the measure of actual middle ear pressures. This is determined by the fact that direct needling of the middle ear, or even the insertion of a ventilating tube, did not change tympanometric values but aspiration of part of the effusion did: indeed the latter tended to bring manometry to normal values.
Secretory otitis media (SaM) is characterized by the presence of an effusion in the middle ear. The origin of the effusion was shown by Sade' to be the middle ear lining, a true respiratory mucosa which secretes mucus and bears cilia." This mucociliary system clears the secreted mucus into the nasopharynx through the Eustachian tube under normal conditions." Among the questions still to be answered are, 'Why is there excessive mucus secretion and why is this excessive mucus not cleared?" To elucidate the question as to what extent the middle ear mucociliary system and the Eustachian tube lumen are affected we inserted ventilating tubes into both ears of 26 children with bilateral SaM. The effusion was aspirated from all the right ears and was not aspirated from the left ears. The left ear
served as a control. Our follow-up, using the microscope, was done the evening after the operation, the next day, and 72 hours after the operation. Audiograms were undertaken on all children preoperatively and compared with postoperative audiograms. Table I summarizes the results of this experiment showing that there was practically no difference between ears aspirated or not aspirated. The majority of the ears in both groups have cleared the effusion at the same rate and attained the same hearing level. The ears designated as dry contained no mucus as viewed through the ventilating tube with the microscope. The few ears designated as wet did not contain mucus either - rather a certain brownish fluid, slightly viscous, was to be seen filling or covering the ventilating tube. This brownish effusion was probably inflammatory in nature.
---From the Meir Hospital, Kfar Saba, Israel, Weizmann Institute of Science, Rehovot, Israel, and the University of Iowa, Iowa City, Iowa.
58
59
CLEARANCE AND PRESSURES
TABLE I RESULTS OF INSERTION OF VENTILATION TUBES 52 Ears (26 Patients)
Ear R (asp.) L (not asp.)
Average Audiometry Pre Post 40 dB 47 dB
12.3 dB 14.4 dB
12 Hours
Wet
Dry
6
20
5
21
24 Hours Wet Dry 3 2
23
24
72 Hours Wet Dry 2 2
24
24
asp. - Aspirated
The conclusion from the above experi- taking all the precautions to ensure rement is that in these patients the muco- liable direct measurements of the intraciliary system is essentially intact and so tympanic pressure. This included: 1 ) is the patency of the Eustachian tube, checking our method of direct pressure which resumes its function promptly on measurement on a model, the model ventilating this system. representing a middle ear; and 2) tymThe second question to follow was, panometry was done on our patients be'What is the mechanism of the favorable fore and after the direct manometric effect of ventilation on middle ear clear- measurements. The direct manometric measurements ance?" It is traditionally assumed that nega- were undertaken with a 22 gauge needle tive pressure in the middle ear is the coated from the inside with hydrophobic pathogenetic factor in SaM, the venti- silicone, and from the outside with a lating tube equalizing this negative pres- hydrophilic detergent. The tympanic sure with the atmospheric pressure. Pro- membrane was covered with water to ponents of the vacuum theory base their avoid gas leak. The manometer's inner claim on the following observations in diameter was 0.8 mm, as was the 25 mm SOM: 1 ) the presence of a retracted long polyethylene tube connecting the tympanic membrane; 2) water covering needle to the manometer. The manomthe tympanic membrane is supposed to eter contained methanol stained with a be sucked into the tympanic cavity on grain of mercurochrome. The free space incision of the latter; and 3) tympano- in the manometer from the tip of the metric measurements show negative needle up to the methanol was 0.16 em, pressure of 100-300 mm. These measure- which is about 6% of the middle ear ments are supposed to represent intra- space (2 cc ); this in the case of a sclerotic or diploic mastoid, is the rule in tympanic negative pressure. SaM children. However, retracted tympanic memThe middle ear model was a 2 cc branes are found only in the minority of chamber made of transparent perspex SaM patients" (less than 10%) and we (Fig. 1) and had a circular opening into have never observed water being sucked into the tympanic cavity, even when which a cadaver tympanic membrane looking for it purposely in many patients. (or some other membrane) could be fastened with a screw (arrow). Leading Lately Buckingham and Ferrar- pub- directly into this chamber was a syringe lished important data on direct measure- with a micrometric device to create negments of intratympanic pressure showing ative pressures as well as a manometer no negative pressure in 25% of their pa- to measure simultaneously the created tients, and a negative pressure averaging negative pressure - comparing it with about 5 mm of water in the rest; this be- the measurements obtained with the ing about two orders of magnitude less trans-tympanic manometer. than measured tympanometrically. When water covered the tympanic In view of the conflicting information membrane as a protection for gas leak, we thought it might be useful to repeat experiments on the model could be carthe direct manometric measurements, ried on until a negative pressure of 20
60
SAIJP. ET AL. 100 -
Manometry Average (-) 1.7 (+)5-(-)12.06
--0
Tymponometry Average (-)130 (+)100-(-)260
i.
15
!:
:1
10
" "
ft" "" "
I
11 I
r
,
'I i!
t
I, I I J I
-'5
II
1\
:I II
I
I
I
I
I:I I
I
I
I
I
I
I
A
I
I~,
r I
-100
\ \,
J
\:
200
Fig. 1. Middle ear model. A-Transtympanic manometer. B-Manometer in direct connection with the middle ear cavity model. C-Micrometric syringe to create negative pressures in middle ear model. Arrow-Region of middle ear model into which an artificial tympanic membrane can be fastened with a screw.
mm H 20 was created. Below this pressure the water leaked into the model. However when antibiotic ointment (Terramycinw") was used, as a seal, the procedure could be carried out satisfactorily up to negative pressures of 140 mm H 20. In both instances the trans-tympanic manometric (A) measurements corresponded to the indwelling manometry (B). The mucus-like substance introduced into the artificial ear did not alter the measurement, whether the needle penetrated it or not. Having satisfied ourselves that direct manometric measurements with a needle through an artificial drum represent faithfully the pressure existing in the artificial middle ear, we undertook manometric measurements in patients, the procedure being as follows:
1. Measurements were carried out on 41 ears with effusion. 2. The patients had preoperative audiograms and tympanograms. 3. Anesthesia: Local used in adults; in children, ketamine hydrochloride was used. No ventilation was performed. 4. Tympanogram was repeated with the patient asleep, or having local anesthesia.
t
/\ " \
..
"
Y
a /, I
~ f\
\:
1}
\ o~..
I)
1 I
b'
..
\"r
I
..
/\i
j
/
~
::
.
I'
,0- :
;\!
v,!!
' ..
'o..J
,
\~ \, ,
\
p
~\ f
\1~
300
Fig. 2. Results of manometric measurements in 36 SOM ears - compared with tympanometric measurements in the same ears.
5. Water (saline) was instilled into the external ear canal to cover the tympanic membrane. 6. A manometric needle was inserted into the middle ear and reading undertaken. 7. Needle was removed, water removed, and tympanogram repeated. 8. Grommet was inserted; mucus was not aspirated. 9. Tympanogram was repeated once again. 10.. Five ears had tympanograms repeated after some mucus was aspirated and grommet inserted. RESULTS
1. In no case was water seen to be sucked into the tympanic cavity on introduction of the needle into the tympanic cavity. 2. In 36 ears with effusion, tympanometry showed an average of 130 mm H 2 0 (ranging from + 100 to - 260) before and after anesthesia, and was the same before and after the manometric measurement, i.e., the insertion of the needle did not alter the tympanometric measurement (Fig. 2).1 3. Manometric measurements on these 36 ears with effusion showed an
"Pfizer Laboratories Division, Pfizer Inc., New York, N. Y.
61
CLEARANCE AND PRESSURES ___ Tympanametry Pre e. Past Manometry Average (-)152 (-)80-H200 100
.......... Manometry Average (-) 1.12 (+)0.8-(-)3.2 0---0
Past Aspiration Tympanametry / AverageH 52 (+)80-(-) 160 , "
,
o
TABLE II TYMPANOMETRIC VALUES (mm H 2 0 )
~""""""""""""'~'-"""""""""""'3'····················...4..;/+~_············· 5
,,
-100
"
"
/
,,
,0' /
"
-200
Fig. 3. Tympanometric results in five SOM ears before and after mucus aspiration.
average of -1.7 mm H 20 (ranging from +5 to -12.06) (Fig. 2). 4. Tympanometric measurements did not change after insertion of the ventilating tube either, if mucus was not aspirated. However, once some mucus was aspirated, in five ears, it came up from an average of -152 mm H 20 to an average of - 52 mm H 20 (Fig. 3). 5. Manometric measurements on 11 ears with no effusion; seven with otosclerosis and four others showed an average of + 0.4 mm H 20. DISCUSSION
From our experiments we can see that the reason for the delay of middle ear clearance is apparently not because of "breakdown" of the mucociliary system. The prompt mucus clearance on ventilation, which occurs whether the effusion is aspirated or not, also confirms our previous histological? observation showing no real organic tubal obstruction in SOM. At the same time, clearance was obviously promoted or triggered through the ventilating procedure. It is, of course, natural to view the mechanism by which ventilation facilitates clearance as being connected with equalization of pressures, the middle ear having an under pressure. Our direct measurements of intratympanic pressures
SOM Adults (12) Children (20) Otosclerosis Adults (18)
Normal Adults (20)
-100 to -400 -120 to -380
'" '"
Av. -240 Av. -255
80
Av. -
20
to -190
Av. -
13
to -
have in essence confirmed Buckingham and Ferrar's" data, the pressures measured by US showing negative value, being slightly below zero and having an average of about -1.7 rom H 20. It should be noted that normal controlled ears without effusions do not show even this small negative pressure. While tympanometry is a very good diagnostic indicator for SOM (Table II) it would seem that this indirect measurement does not reflect in these cases the real intratympanic pressures. The meticulous studies of Eliachar et al7 , 8 do indeed demonstrate that artificially created intratympanic pressures in otherwise normal ears can be accurately measured with the aid of a tympanometer. However, it would seem from our study that similar tympanometric measurements can be obtained as a result of other factors, such as the presence of intratympanic effusion. This we can deduce from the alternation of tympanometry and its return to near normal averages on aspiration of part of the effusion. Tympanometry was apparently feasible under all our experimental conditions because some mucus was always present in the tympanic cavity to seal the grommet openings. From our studies as well as those of Buckingham and Ferrar," it would seem that the actual negative middle ear pressure in SOM is only a few millimeters of water, being two orders of magnitude less than indicated with tympanometric indirect measurements. '" What is the mechanism that brings about minimal underpressures?
"When oxygen is absorbed from a "closed pocket," equilibrium with capillary blood is eventually reached. This will create a difference of about - 40 mm Hg which corresponds to -550 mm H 20. An organic Eustachian tube obstruction is expected to turn the middle ear into a "closed pocket" with such underpressures.
62
SAD!; ET AL.
The answer should be looked for in Hilding's" experiments which show that an advancing mucus mass in a mucociliary cylinder may create a negative pressure behind it, of an order of magnitude compatible with our experiments. The middle ear is in effect such a cylinder closed on one side. Mucus is a cross linked material'"" and when acting en
mass as one huge interlinked molecule will apparently leave, on being cleared, some vacuum behind it. Indeed a reduced capacity of the Eustachian tube to ventilate the middle ear' will probably be an enhancing factor. Animal experiments mimicking such a situation in the ear should resolve the matter and are currently in progress.
REFERENCES 1. Sade J: The biopathology of secretory otitis media. Ann Otol Rhinol Laryngol 83 (Suppl 11 :59-71 ), 1974 2. Sade J: Middle ear mucosa. Arch Otolaryngol 84:137-143, 1966
3. Sade J: Ciliary activity and middle ear clearance. Arch Otolaryngol 86: 128-135, 1967 4. Cohen D: Secretory Otitis Media, thesis. Hebrew University, Jerusalem, 1968 5. Buckingham RA, Ferrar JL: Middle ear pressure in Eustachian tube malfunction: manometric studies. Laryngoscope 83: 15851593, 1973 . 6. Sade J: Pathology and pathogenesis of serous otitis media. Arch Otolaryngol 84:292305, 1960 7. Eliachar I, Northern JL: Studies in
tympanometry: validation of the present technique for determining intra-tympanic pressure through the intact eardrum. Laryngoscope 84:247-255, 1974 8. Eliachar I, Sando I, Northern JL: Measurement of middle ear pressure in guinea pigs. Arch Otolaryngol 99: 171-176, 1974 9. Hilding AC: Role of ciliary action in production of pulmonary atelectasis. Vacuum in paranasal sinuses and in otitis media. Trans Am Acad Ophthalmol Otolaryngol July-August, 7-12, 1944 10. Sade J: Mucociliary flow in the middle ear. Ann Otol Rhinol Laryngol 80:336372, 1971 11. Meyer FA, Eliezer N, Silberberg A, et al: An approach to the biochemical basis for transport function of epithelial mucus. Bull Physiopathol Resp 9:259-269, 1973
REPRINTS - J. Sade, M.D., Meir Hospital, Kfar Saba, Israel. Dr. Sade is an Established Investigator of the Chief Scientist's Bureau, Ministry of Health, Meir Hospital and Weizmann Institute of Science, Israel. He is Visiting Professor in the Department of Otolaryngology and Maxillofacial Surgery, University Hospitals, University of Iowa, Iowa City, Iowa, until July 1, 1976. ACKNOWLEDGMENT - The manometric equipment and artificial ear were constructed at the Weizmann Institute of Science with the collaboration and help of Prof. E. Frie and Doctor Jerushalmi.
