CHAPTER VII. PHYSIOLOGY AND PATHOPHYSIOLOGY
PHYSIOLOGY OF THE EUSTACHIAN TUBE SVEN INGELSTEDT,
M.D.
MALMO, SWEDEN
SUMMARY - A method for studying the middle ear mechanics is described. The method permits continuous recording of the volume deviation of the drum in relation to the neutral position, both on change in the ambient pressure and in the pressure in the middle ear. One hundred and two volunteers with normal hearing, i.e., a normal audiogram and normal ear findings, were tested repeatedly. This is the most detailed and extensive investigation hitherto performed on healthy volunteers with the aid of a sophisticated, reliable scientific method not suitable for clinical use.
Several studies on the mechanics of the middle ear have been presented by our research group since 1963.1 , 2 We have succeeded in revealing the mechanics of the human middle ear indirectly, i.e., without interfering with the function of the ear. However, some of the methods used require the ability of the subject to equilibrate the pressure in the middle ear with the ambient pressure by opening the Eustachian tube during deglutition. For describing the mechanics of the middle ear, it is convenient to start with a standardized model, as shown in Fig. 1. In this model the middle ear is provided with an ear drum and consists of a tympanic cavity and the airfilled cell system lined by mucosa. We have succeeded in quantitatively determining all these variables in normal human middle ears with a method which permits recording of the volume displacement of the tympanic membrane caused by changes in pressure across the membrane. Today I will describe some experiments on normal human tubal function under static as well as dynamic pressure.v' The investigations have been performed on 102 students, aged 21-30 years. Only volunteers were used in whom the audiogram, the otoscopic findings, and the mobility of the drum were
normal, and who had no history of ear disease or symptoms or signs of catarrhal infections of the upper airways. The apparatus, illustrated in Fig. 2, consisted of a flowmeter, which was hermetically connected to the inner bony part of the external ear canal by a cuffcatheter-system. Airflow caused by the movement of the drum is recorded by the flowmeter. The flow signal is integrated with respect to time, and the volume deviation of the drum is recorded. This volume deviation is correctly recorded by only one flowmeter when the deviation is produced by pressure changes in the middle ear, i.e., when the ambient pressure (Pch), is kept constant. If, however, for example, Pch is increased, two components are recorded by the flowmeter, one component is caused by the inward movement of the ear drum and the other by compression of air within the ear canal and the flowmeter system. Selective recording of the volume deviation of the drum requires elimination of the volume flow by compression of air within the system up to the drum. This can be done by using another identical flowmeter system, i.e., a reference system. The volume of the reference system can be adjusted to be exactly equal to that of the ear flowmeter system up to the tympanic membrane. On change of ambient pressure
From the Department of Otolaryngology, University of Lund, Malmo General Hospital, Malmo, Sweden.
156
157
PHYSIOLOGY OF EUSTACHIAN TUBE
Pee
/
v
,
/
I
\
~I
-->,
Vtm
Pm
I I
\
/
.f" ".
l' I
A
/1~~ Fig. 1. Pec: Pressure in the external ear canal. Pm: Middle ear pressure. Ptm: Pressure across the tympanic membrane, i.e., Pm-Pec. ~ Vtm: Volume displacement of the tympanic membrane. t::,. Vt: Volume of gas portion passing the tube. Vm: Volume of gas enclosed in the middle ear spaces. t::,. Vmuc: Volume changes of the mucosa lining the ear spaces. t::,. Vdiff: Gas volume leaving the cavity and entering the blood by diffusion.
. ---~
'---.J! '
,
Peh
the signals from both flowmeters are subtracted. The subtracted flow signal is integrated with respect to time, and then only the volume deviation of the drum is recorded. Thus, the basic principle of the method is the recording of the volume deviation of the tympanic membrane during and after changes in the ambient pressure as well as in the intratympanic pressure. In functional studies it is most important to realize that the methods used must not interfere with the physiological function of the ear.
- - - - - - lime - -
o
cmHfJ -5
Fig. 2. Block diagram of the apparatus for isolated recording of the movement velocity of the ear drum, Vtm, and its volume deviation, t::,. Vtm. Vtm-curve illustrates the recorded volume displacement of the drum outward (+) and inward (-). Arrows denote dsglutitions. Pch-curve: Pressure change in a pressure chamber and ear canal.
NB,CASES 80
VARIOUS PHYSIOLOGICAL TEST SITUATIONS
Equilibration of Static Pressure Differences Across the Tympanic Membrane. A change in the pressure in a pressure chamber (Pch), by 10 em H 2 0 , creates a pressure difference across the drum. The drum thereby moves outward or inward. The test subject is then allowed to equilibrate the pressure difference by ten deglutitions during three minutes. The material was divided into four groups according to the subjects' ability to equilibrate a static relative over- and underpressure in the middle ear. As seen in Figure 3, group I equilibrated pressure differences completely, group II with small residual pressure in the middle ear. Of the subjects examined, 93% belonged to these groups. Group III could equilibrate relative
60
.
~
40
ttttttttlt
m
20
I
D
m
Fig. 3. Grouping of the material with regard to equilibration capacity of static relative over- and underpressure in the middle ear (102 cases). NB: Number.
SVEN INGELSTEDT
158
ASCENT
NB,CASES
DESCENT
+10
97°'0
VIm 0
60
,ul -10 +50
40
Pch 0
cmHzO
20 61"10
-50
39"10 100"10
3"10 +Grupp)
+Grupp D
+Grupp m
100"10 +Grupp m
Fig. 4. Results of Tcynbee's test in ~e lation to the different tubal function groups (94 cases).
overpressure, but not underpressure, and group IV could not equilibrate any pressure by deglutition. There were thus seven subjects, groups III and IV, who at repeated tests performed at intervals of several months, had poor tubal function or none at all during deglutition, but who nevertheless had normal hearing, normal otoscopic findings,. and. no symptoms or signs of catarrhal infection, We found that these individuals unconsciously used a different equilibration technique, such as movement of the mandible, yawning, Valsalva maneuver or blowing of the nose. It is thus important for the examiner to be aware of these techniques, for otherwise tubal function may easily be regarded as impaired. NB,CASES
87°'0 60
40
20
76% 100"10
+-.Grupp)
Grupp ll
100"10
+-
+-
Gruppm
GruppN
Fig. 5. Results of Valsalva .test in relation to different tubal function groups (101 cases).
25 sec.
Fig. 6. Equilibration of dynaO?!c rela,: tive over- and underpressure, ascent and "descent." Upper curve illustrates the recorded volume deviation of the drum outward (+) and inward (-) . Lower curve: Pressure change in the pressure chamber and the ear canal.
The Better the Tubal Function, the More Positive Toynbee's Test. The test was positive in 97% of group I and negative in all cases in group III and IV (Fig. 4). No Correlation Between the Valsalva Test and the Different Tubal Funct~on Groups. The test is not a tubal function test in a physiological sense, b.ecause opening of the tube does not .re~Ulr~ any active muscle activity. Yet, It IS evident from the results that all the subjects who could not equilibrate a negative middle ear pressure, groups. III:IV.' ha? a positive Valsalva test. This fmdmg IS important from a therapeutic point of view (Fig. 5). Equilibration of Dynamic Pressure Differences Across the .Tympanic Membrane. The volume displacement of the drum (Vtm ), is recorded during changing pressure in the pressure chamber, "ascent" and "descent" from + 50 to - 50 em H 2 0 or the reverse in 25 seconds, during which time the sub1ects are instructed to swallow as many times as possible (Fig. 6). Equilibration. of the dynamic pressure changes, as durl;llg "descent," is the most difficult function test. It can only be performed by d~ glutition in subjects in group I, i.e., ill 64% out of 89 tested persons with no experience of flying. The rest of the subjects lacked this capacity. completely and had to use the Valsalva maneuver for equilibration.
PHYSIOLOGY OF EUSTACHIAN TUBE Nb. Cas••
/
39 cases
,
A ?ch=4GmH~Oh
12
/
l' 20
159
r--: ~
10
/
g-
.:
/
X o
/
E
/
.,... "..... .. ..... /
I--,-~
n -79 Me.n - 43.9
/
50-16.5 5E -1.9
..
/
~
!TTl I I I 1
/ ' ~.:. ./ /
....
o
/
10
20
30
Ptm means cmH20 Descent, max. freq. deglut.
Fig. 7. Relation between the mean pressure across the tympanic membrane during "ascent" and "descent" during maximum number of deglutitions. Pch: Ambient pressure. Ptm: Pressure across tympanic membrane.
Figure 7 shows that the mean pressure across the tympanic membrane, (Ptm mean), was calculated for a complete "ascent" and "descent," respectively, and both these pressures in 39 subjects belonging to tubal function group I were compared. Every point in the diagram represents Ptm mean in a single subject. If the subject's capacity to equilibrate dynamic over- and underpressure were equal, the Ptmmean-relation would fall on the dotted line. It is clear from the figure, however, that nearly all subjects could equilibrate dynamic overpressure better than underpressure. This PaS5iY~ forcing
+ 20 +
10
Vtm
time
..ul - 10 - 20
+
45
Pch 0 cm H20
t. Pch
time
- 45 I
25 sec.
Fig. 8. The tube is forced open passively only at "ascent," i.e., the forcing pressure. The chamber pressure is lowered and the subject is forbidden to swallow until the tube is passively forced open at .6Pch 50 ern H 2 0 . Then arrows denote deglutitions.
I I
o
+20
I I I I +40 +60 +80 Passive forcing-pressure
+100 em H20
Fig. 9. Distribution of 79 subjects in relation to the passive forcing pressure of the Eustachian tube. Only one ear of each subject has been investigated.
phenomenon has long been known. But there was no such difference when these individuals in group I were tested with static over- and underpressure. In Figure 8 the recorded chamber pressure (L.Pch) is seen, at which the tube is forced open during "ascent." Figure 9 gives the results in 79 subjects tested. The forcing pressure is expressed as that pressure change in the chamber at which the tube is passively forced open. Broadly speaking, this pressure change denotes the relative overpressure in the middle ear at which the tube is forced open. All the experiments were performed when the chamber pressure was lowered at a constant rate of 4 em H 20/second. Interesting findings were made in subjects with a high forcing pressure. In these it was possible to record so-called altemobaric vertigo."
Effect of Change in Posture on the Function of the Eustachian Tube. From our experiments it has become evident that the pressure equalizing ability of the tube is reduced in recumbent position, even in healthy persons. When describing findings made in the Eustachian tube, one should always state the position of the patient, because in the recumbent position the tubal function is always reduced by engorgement of, among other things, the tubal mucosa by an increased venous pressure in the head."
160
SVEN INGELSTEDT
REFERENCES 1971 On the function of middle ear and Eustachian 4. Elner A, Ingelstedt S, Ivarsson A: The tube. Acta Otolaryngol [Suppl] (Stockh) 182, normal function of the Eustachian tube. A 1963 study of 102 cases. Acta Otolaryngol (Stockh) 2. Ingelstedt S, Ivarsson A, Jonson B: Me72:320-328, 1971 5. Ingelstedt S, Ivarsson A, Tjernstrorn o. chanics of the human middle ear. Pressure regulation in aviation and diving. A nonVertigo due to relative overpressure in the traumatic method. Acta Otolaryngol [Suppl] middle ear. Acta Otolaryngol (Stockh) 78: 1(Stockh) 228, 1967 14, 1974 3. Elner A, Ingelstedt S, Ivarsson A: A 6. Rundcrantz H: Posture and Eustachian method for studies of the middle ear mechan- tube function. Acta Otolaryngol (Stockh) 68: ics. Acta Otolaryngol (Stockh) 72: 191-200, 279-292, 1969 1. Flisberg K, Ingelstedt S, Ortegren U:
REPRINTS - Sven Ingelstedt, M.D., Dept. of Otolaryngology, University of Lund, Malmo General Hospital, Malmo, Sweden.
PHYSIOLOGY OF THE EUSTACHIAN TUBE SVEN INGELSTEDT,
M.D.
MALMO, SWEDEN
SUMMARY - A method for studying the middle ear mechanics is described. The method permits continuous recording of the volume deviation of the drum in relation to the neutral position, both on change in the ambient pressure and in the pressure in the middle ear. One hundred and two volunteers with normal hearing, i.e., a normal audiogram and normal ear findings, were tested repeatedly. This is the most detailed and extensive investigation hitherto performed on healthy volunteers with the aid of a sophisticated, reliable scientific method not suitable for clinical use.
Several studies on the mechanics of the middle ear have been presented by our research group since 1963.1 , 2 We have succeeded in revealing the mechanics of the human middle ear indirectly, i.e., without interfering with the function of the ear. However, some of the methods used require the ability of the subject to equilibrate the pressure in the middle ear with the ambient pressure by opening the Eustachian tube during deglutition. For describing the mechanics of the middle ear, it is convenient to start with a standardized model, as shown in Fig. 1. In this model the middle ear is provided with an ear drum and consists of a tympanic cavity and the airfilled cell system lined by mucosa. We have succeeded in quantitatively determining all these variables in normal human middle ears with a method which permits recording of the volume displacement of the tympanic membrane caused by changes in pressure across the membrane. Today I will describe some experiments on normal human tubal function under static as well as dynamic pressure.v' The investigations have been performed on 102 students, aged 21-30 years. Only volunteers were used in whom the audiogram, the otoscopic findings, and the mobility of the drum were
normal, and who had no history of ear disease or symptoms or signs of catarrhal infections of the upper airways. The apparatus, illustrated in Fig. 2, consisted of a flowmeter, which was hermetically connected to the inner bony part of the external ear canal by a cuffcatheter-system. Airflow caused by the movement of the drum is recorded by the flowmeter. The flow signal is integrated with respect to time, and the volume deviation of the drum is recorded. This volume deviation is correctly recorded by only one flowmeter when the deviation is produced by pressure changes in the middle ear, i.e., when the ambient pressure (Pch), is kept constant. If, however, for example, Pch is increased, two components are recorded by the flowmeter, one component is caused by the inward movement of the ear drum and the other by compression of air within the ear canal and the flowmeter system. Selective recording of the volume deviation of the drum requires elimination of the volume flow by compression of air within the system up to the drum. This can be done by using another identical flowmeter system, i.e., a reference system. The volume of the reference system can be adjusted to be exactly equal to that of the ear flowmeter system up to the tympanic membrane. On change of ambient pressure
From the Department of Otolaryngology, University of Lund, Malmo General Hospital, Malmo, Sweden.
156
157
PHYSIOLOGY OF EUSTACHIAN TUBE
Pee
/
v
,
/
I
\
~I
-->,
Vtm
Pm
I I
\
/
.f" ".
l' I
A
/1~~ Fig. 1. Pec: Pressure in the external ear canal. Pm: Middle ear pressure. Ptm: Pressure across the tympanic membrane, i.e., Pm-Pec. ~ Vtm: Volume displacement of the tympanic membrane. t::,. Vt: Volume of gas portion passing the tube. Vm: Volume of gas enclosed in the middle ear spaces. t::,. Vmuc: Volume changes of the mucosa lining the ear spaces. t::,. Vdiff: Gas volume leaving the cavity and entering the blood by diffusion.
. ---~
'---.J! '
,
Peh
the signals from both flowmeters are subtracted. The subtracted flow signal is integrated with respect to time, and then only the volume deviation of the drum is recorded. Thus, the basic principle of the method is the recording of the volume deviation of the tympanic membrane during and after changes in the ambient pressure as well as in the intratympanic pressure. In functional studies it is most important to realize that the methods used must not interfere with the physiological function of the ear.
- - - - - - lime - -
o
cmHfJ -5
Fig. 2. Block diagram of the apparatus for isolated recording of the movement velocity of the ear drum, Vtm, and its volume deviation, t::,. Vtm. Vtm-curve illustrates the recorded volume displacement of the drum outward (+) and inward (-). Arrows denote dsglutitions. Pch-curve: Pressure change in a pressure chamber and ear canal.
NB,CASES 80
VARIOUS PHYSIOLOGICAL TEST SITUATIONS
Equilibration of Static Pressure Differences Across the Tympanic Membrane. A change in the pressure in a pressure chamber (Pch), by 10 em H 2 0 , creates a pressure difference across the drum. The drum thereby moves outward or inward. The test subject is then allowed to equilibrate the pressure difference by ten deglutitions during three minutes. The material was divided into four groups according to the subjects' ability to equilibrate a static relative over- and underpressure in the middle ear. As seen in Figure 3, group I equilibrated pressure differences completely, group II with small residual pressure in the middle ear. Of the subjects examined, 93% belonged to these groups. Group III could equilibrate relative
60
.
~
40
ttttttttlt
m
20
I
D
m
Fig. 3. Grouping of the material with regard to equilibration capacity of static relative over- and underpressure in the middle ear (102 cases). NB: Number.
SVEN INGELSTEDT
158
ASCENT
NB,CASES
DESCENT
+10
97°'0
VIm 0
60
,ul -10 +50
40
Pch 0
cmHzO
20 61"10
-50
39"10 100"10
3"10 +Grupp)
+Grupp D
+Grupp m
100"10 +Grupp m
Fig. 4. Results of Tcynbee's test in ~e lation to the different tubal function groups (94 cases).
overpressure, but not underpressure, and group IV could not equilibrate any pressure by deglutition. There were thus seven subjects, groups III and IV, who at repeated tests performed at intervals of several months, had poor tubal function or none at all during deglutition, but who nevertheless had normal hearing, normal otoscopic findings,. and. no symptoms or signs of catarrhal infection, We found that these individuals unconsciously used a different equilibration technique, such as movement of the mandible, yawning, Valsalva maneuver or blowing of the nose. It is thus important for the examiner to be aware of these techniques, for otherwise tubal function may easily be regarded as impaired. NB,CASES
87°'0 60
40
20
76% 100"10
+-.Grupp)
Grupp ll
100"10
+-
+-
Gruppm
GruppN
Fig. 5. Results of Valsalva .test in relation to different tubal function groups (101 cases).
25 sec.
Fig. 6. Equilibration of dynaO?!c rela,: tive over- and underpressure, ascent and "descent." Upper curve illustrates the recorded volume deviation of the drum outward (+) and inward (-) . Lower curve: Pressure change in the pressure chamber and the ear canal.
The Better the Tubal Function, the More Positive Toynbee's Test. The test was positive in 97% of group I and negative in all cases in group III and IV (Fig. 4). No Correlation Between the Valsalva Test and the Different Tubal Funct~on Groups. The test is not a tubal function test in a physiological sense, b.ecause opening of the tube does not .re~Ulr~ any active muscle activity. Yet, It IS evident from the results that all the subjects who could not equilibrate a negative middle ear pressure, groups. III:IV.' ha? a positive Valsalva test. This fmdmg IS important from a therapeutic point of view (Fig. 5). Equilibration of Dynamic Pressure Differences Across the .Tympanic Membrane. The volume displacement of the drum (Vtm ), is recorded during changing pressure in the pressure chamber, "ascent" and "descent" from + 50 to - 50 em H 2 0 or the reverse in 25 seconds, during which time the sub1ects are instructed to swallow as many times as possible (Fig. 6). Equilibration. of the dynamic pressure changes, as durl;llg "descent," is the most difficult function test. It can only be performed by d~ glutition in subjects in group I, i.e., ill 64% out of 89 tested persons with no experience of flying. The rest of the subjects lacked this capacity. completely and had to use the Valsalva maneuver for equilibration.
PHYSIOLOGY OF EUSTACHIAN TUBE Nb. Cas••
/
39 cases
,
A ?ch=4GmH~Oh
12
/
l' 20
159
r--: ~
10
/
g-
.:
/
X o
/
E
/
.,... "..... .. ..... /
I--,-~
n -79 Me.n - 43.9
/
50-16.5 5E -1.9
..
/
~
!TTl I I I 1
/ ' ~.:. ./ /
....
o
/
10
20
30
Ptm means cmH20 Descent, max. freq. deglut.
Fig. 7. Relation between the mean pressure across the tympanic membrane during "ascent" and "descent" during maximum number of deglutitions. Pch: Ambient pressure. Ptm: Pressure across tympanic membrane.
Figure 7 shows that the mean pressure across the tympanic membrane, (Ptm mean), was calculated for a complete "ascent" and "descent," respectively, and both these pressures in 39 subjects belonging to tubal function group I were compared. Every point in the diagram represents Ptm mean in a single subject. If the subject's capacity to equilibrate dynamic over- and underpressure were equal, the Ptmmean-relation would fall on the dotted line. It is clear from the figure, however, that nearly all subjects could equilibrate dynamic overpressure better than underpressure. This PaS5iY~ forcing
+ 20 +
10
Vtm
time
..ul - 10 - 20
+
45
Pch 0 cm H20
t. Pch
time
- 45 I
25 sec.
Fig. 8. The tube is forced open passively only at "ascent," i.e., the forcing pressure. The chamber pressure is lowered and the subject is forbidden to swallow until the tube is passively forced open at .6Pch 50 ern H 2 0 . Then arrows denote deglutitions.
I I
o
+20
I I I I +40 +60 +80 Passive forcing-pressure
+100 em H20
Fig. 9. Distribution of 79 subjects in relation to the passive forcing pressure of the Eustachian tube. Only one ear of each subject has been investigated.
phenomenon has long been known. But there was no such difference when these individuals in group I were tested with static over- and underpressure. In Figure 8 the recorded chamber pressure (L.Pch) is seen, at which the tube is forced open during "ascent." Figure 9 gives the results in 79 subjects tested. The forcing pressure is expressed as that pressure change in the chamber at which the tube is passively forced open. Broadly speaking, this pressure change denotes the relative overpressure in the middle ear at which the tube is forced open. All the experiments were performed when the chamber pressure was lowered at a constant rate of 4 em H 20/second. Interesting findings were made in subjects with a high forcing pressure. In these it was possible to record so-called altemobaric vertigo."
Effect of Change in Posture on the Function of the Eustachian Tube. From our experiments it has become evident that the pressure equalizing ability of the tube is reduced in recumbent position, even in healthy persons. When describing findings made in the Eustachian tube, one should always state the position of the patient, because in the recumbent position the tubal function is always reduced by engorgement of, among other things, the tubal mucosa by an increased venous pressure in the head."
160
SVEN INGELSTEDT
REFERENCES 1971 On the function of middle ear and Eustachian 4. Elner A, Ingelstedt S, Ivarsson A: The tube. Acta Otolaryngol [Suppl] (Stockh) 182, normal function of the Eustachian tube. A 1963 study of 102 cases. Acta Otolaryngol (Stockh) 2. Ingelstedt S, Ivarsson A, Jonson B: Me72:320-328, 1971 5. Ingelstedt S, Ivarsson A, Tjernstrorn o. chanics of the human middle ear. Pressure regulation in aviation and diving. A nonVertigo due to relative overpressure in the traumatic method. Acta Otolaryngol [Suppl] middle ear. Acta Otolaryngol (Stockh) 78: 1(Stockh) 228, 1967 14, 1974 3. Elner A, Ingelstedt S, Ivarsson A: A 6. Rundcrantz H: Posture and Eustachian method for studies of the middle ear mechan- tube function. Acta Otolaryngol (Stockh) 68: ics. Acta Otolaryngol (Stockh) 72: 191-200, 279-292, 1969 1. Flisberg K, Ingelstedt S, Ortegren U:
REPRINTS - Sven Ingelstedt, M.D., Dept. of Otolaryngology, University of Lund, Malmo General Hospital, Malmo, Sweden.
