ORL 40 : 319 -324 (1978)
Pressure-Regulating Mechanisms in the Inner Ear1 0. Densert, B. Carlborg and J. Stagg Department of Otolaryngology, Department of Biomedical Engineering and Department of Experimental Research, University of Lund, Malmö General Hospital, Malmö
Key Words. Inner ear pressure • Inner ear nonlinearities • Infrasound Abstract. The perilymphatic pressure was studied in relation to pressure step variations in the external ear canal and in the middle ear. The transfer of pressure via the ossicular chain reached its limiting value at quite low pressures. When pressure steps were applied directly to the middle ear, there was almost a direct transfer of pressure for positive changes. Nonlinearities were shown between positive and negative pressure steps. The pressure-regulating ability of the inner ear was illustrated by means of calculating the time constants of the pressure transfer curves.
In spite of extensive experimental and clinical research in Meniere’s disease the pathogenesis of the disease is still controversial. Hallpike and Cairns’ ( 1938) histological findings directed the attention to the endolymphatic hydrops as a critical factor. Evidence exists that faults in the pressure-regulating ability in the inner ear might be a causal factor in the development of Meniere’s disease. Exposing the inner ear to pressure changes has revealed a direct influence on hearing thresholds and vestibular symptoms (Densert ct al, 1975; Ingelstedt et aL, 1976). In order to increase our knowledge of the hydrodynamics of the inner ear, experimental studies concerning the perilymphatic pressure in cats were undertaken in our laboratory. In the present paper, an account of data is given concerning the effect of ear canal and middle ear pressure changes on the perilymphatic pressure. For measurement of perilymphatic pressure, an extra-aural approach via the skull
Downloaded by: Kings's College London 137.73.144.138 - 10/31/2017 2:19:57 PM
' Paper presented at the Barany Society Meeting in Uppsala, June 1-3, 1978.
Densert/Carlborg/Stagg
320
Cannula for registration of inner ear pressure
and temporal bones was chosen. In this way the perilymph could be reached behind the top of the oval window. The middle ear was kept intact and no other structures were damaged. Pressure measurement was performed with the help of micro-tip transducers of the Millar & Gaeltec type. In order to prevent volume displacement errors, a very short adaptor was used between the metallic cannula inserted in the bone and the micro-tip transducer. For details see Carlborg et al. (in press). The method for application and measurement of pressures in the ear canal and in the middle ear is shown schematically in figure 1. The pressures in the ear canal and middle ear were varied in the form of square waves in the range of ± 70 mm Hg. A registration example of pressure transfer from the ear canal to the inner ear is shown in figure 2. The perilymphatic pressure reacts instantaneously to a change in ear canal pressure. After the initial perilymphatic pressure change it returns to its original level, in spite of a steady ear canal pressure. When pressure was applied to the middle ear, a similar transfer was noted (fig. 3). Then the degree of transfer was much larger, since most of the transfer occurred across the very elastic round window membrane. When the pressure was applied via the ossicular chain, the transfer reached a limiting value at quite low pressures. Such a severe limitation was not seen for the middle to inner ear transfer. In fact, for positive changes, there was almost a direct transfer of pressure.
Downloaded by: Kings's College London 137.73.144.138 - 10/31/2017 2:19:57 PM
Fig. 1. Schematic diagram of ear, showing experimental access points.
Pressure-Regulating Mechanisms in the Inner Ear
321
Fig. 2. A registration example of pressure transfer from the ear canal to the inner ear. The top curve shows the applied rectangular pressure pulses.
Changes in the ear canal (fig. 4) and middle ear pressure (fig. 5) produced in both cases initial perilymph pressure steps that were different for positive and negative pressure changes. The pressure transfer curves had a general form which is well known in electronics when a signal passes through a first-order linear system. This allowed
Downloaded by: Kings's College London 137.73.144.138 - 10/31/2017 2:19:57 PM
Fig. 3. A registration example of pressure transfer from the middle to the inner ear. Calibration is shown to the left.
322
Densert/Carlborg/Stagg
mm Hg
2°
inner ear pressure step
APp ••
10 o—
80
i-
-60
o—
8-
-20
-40
H----1—
■ i------ 1------ 1-------H
— I--------- 1 -
20
-I
60
40
80 mm Mg
Ear canal pressure step APec
-10
-20
Fig. 4. A graphic plot of the inner ear pressure as a function of pressure step changes in the ear canal. APp = Perilymphatic pressure step changes; APec = ear canal pressure step changes.
mm Hg 80 Inner ear pressure step
o>
A \
o
w
X
7
/• o
o
x
APp
* •
x-S X
• 20 -80
-60
-40
-20
A ■ -20
20
A0
60
80 mm Hg
Middle ear pressure step
APm -A0
•60
Fig. 5. A graphic plot of the inner ear pressure (APp) as a function of pressure step changes in the middle ear (APm).
Downloaded by: Kings's College London 137.73.144.138 - 10/31/2017 2:19:57 PM
--80
Pressure-Regulating Mechanisms in the Inner Ear
323
(APptime constant)“’
us to use standard curve analysis methods to obtain an understanding of the hydrodynamic characteristics of the inner ear. By means of calculating the time constants in the perilymph pressure curves, the pressure-regulating ability of the inner ear could be illustrated. Comparisons could be made between individuals. Often two time constants were seen, one of which was much longer than the other. By analyzing the shorter time constant, it was found that it is most often longer for positive pulses than for negative ones. Furthermore, it was to some extent proportional to the applied pressure. In figure 6 the inverted value of the short time constant was plotted. It gives a measure of the stiffness of the inner ear system. Biological differences in the properties of different cat ears were observed. Besides, fundamental differences were occasionally seen, such as shorter time constants for positive changes instead of the reverse. The similarity with a first-order linear system was used to build a simple electronic model in order to simulate the hydrodynamic characteristics of the ear. Thus two kinds of nonlinearity were shown: (1) Dissimilarity in transfer of positive and negative pressure pulses to the inner ear. (2) Dissimilarity between time constants for positive and negative pulses.
Downloaded by: Kings's College London 137.73.144.138 - 10/31/2017 2:19:57 PM
Fig. 6. The inverted value of the short time constants at pressure changes in the inner ear (APp) when pressure step changes are applied to the ear canal (APec).
Densert/Carlborg/Stagg
324
These properties of low-frequency pressure transfer to the inner ear are thought to be of fundamental importance when the influence of infrasound on the inner ear is considered.
References Carlborg, B.; Densert, O., and Stagg, J.: Perilymphatic pressure in the cat. I (to be published). Densert, O.; Ingelstedt, S.; Ivarsson, A., and Pedersen, K.: Immediate restoration of basal sensorineural hearing (Mb Meniere) using a pressure chamber. Acta oto-lar. 80 : 93-100 (1975) . Hallpike, C.S. and Cairns, H.: Observations on pathology of Meniere’s syndrome. J. Lar. Otol. 53 : 625-564 (1938). Ingelstedt, S.; Ivarsson, A., and Tjemstrom, O.: Immediate relief of symptoms during acute attacks of Meniere’s disease, using a pressure chamber. Acta oto-lar. 82 : 368-378 (1976) .
Ove Densert, MD, Department of Otolaryngology, Lasarettet, S-301 85 Halmstad (Sweden)
Downloaded by: Kings's College London 137.73.144.138 - 10/31/2017 2:19:57 PM
Received: December 14, 1978; accepted: December 21, 1978
Pressure-Regulating Mechanisms in the Inner Ear1 0. Densert, B. Carlborg and J. Stagg Department of Otolaryngology, Department of Biomedical Engineering and Department of Experimental Research, University of Lund, Malmö General Hospital, Malmö
Key Words. Inner ear pressure • Inner ear nonlinearities • Infrasound Abstract. The perilymphatic pressure was studied in relation to pressure step variations in the external ear canal and in the middle ear. The transfer of pressure via the ossicular chain reached its limiting value at quite low pressures. When pressure steps were applied directly to the middle ear, there was almost a direct transfer of pressure for positive changes. Nonlinearities were shown between positive and negative pressure steps. The pressure-regulating ability of the inner ear was illustrated by means of calculating the time constants of the pressure transfer curves.
In spite of extensive experimental and clinical research in Meniere’s disease the pathogenesis of the disease is still controversial. Hallpike and Cairns’ ( 1938) histological findings directed the attention to the endolymphatic hydrops as a critical factor. Evidence exists that faults in the pressure-regulating ability in the inner ear might be a causal factor in the development of Meniere’s disease. Exposing the inner ear to pressure changes has revealed a direct influence on hearing thresholds and vestibular symptoms (Densert ct al, 1975; Ingelstedt et aL, 1976). In order to increase our knowledge of the hydrodynamics of the inner ear, experimental studies concerning the perilymphatic pressure in cats were undertaken in our laboratory. In the present paper, an account of data is given concerning the effect of ear canal and middle ear pressure changes on the perilymphatic pressure. For measurement of perilymphatic pressure, an extra-aural approach via the skull
Downloaded by: Kings's College London 137.73.144.138 - 10/31/2017 2:19:57 PM
' Paper presented at the Barany Society Meeting in Uppsala, June 1-3, 1978.
Densert/Carlborg/Stagg
320
Cannula for registration of inner ear pressure
and temporal bones was chosen. In this way the perilymph could be reached behind the top of the oval window. The middle ear was kept intact and no other structures were damaged. Pressure measurement was performed with the help of micro-tip transducers of the Millar & Gaeltec type. In order to prevent volume displacement errors, a very short adaptor was used between the metallic cannula inserted in the bone and the micro-tip transducer. For details see Carlborg et al. (in press). The method for application and measurement of pressures in the ear canal and in the middle ear is shown schematically in figure 1. The pressures in the ear canal and middle ear were varied in the form of square waves in the range of ± 70 mm Hg. A registration example of pressure transfer from the ear canal to the inner ear is shown in figure 2. The perilymphatic pressure reacts instantaneously to a change in ear canal pressure. After the initial perilymphatic pressure change it returns to its original level, in spite of a steady ear canal pressure. When pressure was applied to the middle ear, a similar transfer was noted (fig. 3). Then the degree of transfer was much larger, since most of the transfer occurred across the very elastic round window membrane. When the pressure was applied via the ossicular chain, the transfer reached a limiting value at quite low pressures. Such a severe limitation was not seen for the middle to inner ear transfer. In fact, for positive changes, there was almost a direct transfer of pressure.
Downloaded by: Kings's College London 137.73.144.138 - 10/31/2017 2:19:57 PM
Fig. 1. Schematic diagram of ear, showing experimental access points.
Pressure-Regulating Mechanisms in the Inner Ear
321
Fig. 2. A registration example of pressure transfer from the ear canal to the inner ear. The top curve shows the applied rectangular pressure pulses.
Changes in the ear canal (fig. 4) and middle ear pressure (fig. 5) produced in both cases initial perilymph pressure steps that were different for positive and negative pressure changes. The pressure transfer curves had a general form which is well known in electronics when a signal passes through a first-order linear system. This allowed
Downloaded by: Kings's College London 137.73.144.138 - 10/31/2017 2:19:57 PM
Fig. 3. A registration example of pressure transfer from the middle to the inner ear. Calibration is shown to the left.
322
Densert/Carlborg/Stagg
mm Hg
2°
inner ear pressure step
APp ••
10 o—
80
i-
-60
o—
8-
-20
-40
H----1—
■ i------ 1------ 1-------H
— I--------- 1 -
20
-I
60
40
80 mm Mg
Ear canal pressure step APec
-10
-20
Fig. 4. A graphic plot of the inner ear pressure as a function of pressure step changes in the ear canal. APp = Perilymphatic pressure step changes; APec = ear canal pressure step changes.
mm Hg 80 Inner ear pressure step
o>
A \
o
w
X
7
/• o
o
x
APp
* •
x-S X
• 20 -80
-60
-40
-20
A ■ -20
20
A0
60
80 mm Hg
Middle ear pressure step
APm -A0
•60
Fig. 5. A graphic plot of the inner ear pressure (APp) as a function of pressure step changes in the middle ear (APm).
Downloaded by: Kings's College London 137.73.144.138 - 10/31/2017 2:19:57 PM
--80
Pressure-Regulating Mechanisms in the Inner Ear
323
(APptime constant)“’
us to use standard curve analysis methods to obtain an understanding of the hydrodynamic characteristics of the inner ear. By means of calculating the time constants in the perilymph pressure curves, the pressure-regulating ability of the inner ear could be illustrated. Comparisons could be made between individuals. Often two time constants were seen, one of which was much longer than the other. By analyzing the shorter time constant, it was found that it is most often longer for positive pulses than for negative ones. Furthermore, it was to some extent proportional to the applied pressure. In figure 6 the inverted value of the short time constant was plotted. It gives a measure of the stiffness of the inner ear system. Biological differences in the properties of different cat ears were observed. Besides, fundamental differences were occasionally seen, such as shorter time constants for positive changes instead of the reverse. The similarity with a first-order linear system was used to build a simple electronic model in order to simulate the hydrodynamic characteristics of the ear. Thus two kinds of nonlinearity were shown: (1) Dissimilarity in transfer of positive and negative pressure pulses to the inner ear. (2) Dissimilarity between time constants for positive and negative pulses.
Downloaded by: Kings's College London 137.73.144.138 - 10/31/2017 2:19:57 PM
Fig. 6. The inverted value of the short time constants at pressure changes in the inner ear (APp) when pressure step changes are applied to the ear canal (APec).
Densert/Carlborg/Stagg
324
These properties of low-frequency pressure transfer to the inner ear are thought to be of fundamental importance when the influence of infrasound on the inner ear is considered.
References Carlborg, B.; Densert, O., and Stagg, J.: Perilymphatic pressure in the cat. I (to be published). Densert, O.; Ingelstedt, S.; Ivarsson, A., and Pedersen, K.: Immediate restoration of basal sensorineural hearing (Mb Meniere) using a pressure chamber. Acta oto-lar. 80 : 93-100 (1975) . Hallpike, C.S. and Cairns, H.: Observations on pathology of Meniere’s syndrome. J. Lar. Otol. 53 : 625-564 (1938). Ingelstedt, S.; Ivarsson, A., and Tjemstrom, O.: Immediate relief of symptoms during acute attacks of Meniere’s disease, using a pressure chamber. Acta oto-lar. 82 : 368-378 (1976) .
Ove Densert, MD, Department of Otolaryngology, Lasarettet, S-301 85 Halmstad (Sweden)
Downloaded by: Kings's College London 137.73.144.138 - 10/31/2017 2:19:57 PM
Received: December 14, 1978; accepted: December 21, 1978
