Acta Oto-Laryngologica

ISSN: 0001-6489 (Print) 1651-2251 (Online) Journal homepage: http://www.tandfonline.com/loi/ioto20

Pressure-dependent variation in volume of mucosal lining of the middle ear L. Andréasson, S. Ingelstedt, A. Ivarsson, B. Jonson & Ö. Tjernström To cite this article: L. Andréasson, S. Ingelstedt, A. Ivarsson, B. Jonson & Ö. Tjernström (1976) Pressure-dependent variation in volume of mucosal lining of the middle ear, Acta OtoLaryngologica, 81:5-6, 442-449, DOI: 10.3109/00016487609107499 To link to this article: http://dx.doi.org/10.3109/00016487609107499

Published online: 08 Jul 2009.

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Date: 13 April 2016, At: 20:12

Acta Otolaryngol81: 442449, 1976

PRESSURE-DEPENDENT VARIATION IN VOLUME OF MUCOSAL LINING OF THE MIDDLE EAR

L. AndrCasson, S. Ingelstedt, A. Ivarsson, B. Jonson and 0. Tjernstrom From the Department of Otolaryngology, Malmo General Hospital, Malmo of Clinical Physiology, University of Lund, Lund, Sweden

and the Department

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(Received July 5 , 1975)

Abstract. A method is described for studying pressuredependent variation in the volume of the mucosa of the middle ear. Studies were performed at different pressures in the middle ear as well as at different ambient pressures. It was found that the pressure-dependent volumetric changes of the mucosa were the same whether the pressure in the middle ear was changed directly by altering the intratympanic or indirectly by altering the ambient pressure. With the method described it is also possible to determine the middle ear volume without artefacts due to the middle ear mucosa. The volume-pressure relationship of the middle ear mucosa varied from 0.6 to I .7 pl/cm H20 and linearly with the volume of the middle ear. Comparisons between determinations of the middle ear volume with and without consideration of the mucosal compliance showed differences, especially in small middle ears. The effect on the volume of the mucosa caused by variation of posture was also studied. The physiological middle ear pressure depends on the functional state of the Eustachian tube, the middle ear volume, the tympanic membrane and the middle ear mucosa. Thus, knowledge of the mucosa compliance is important for calculating middle ear pressure as well as for determining the volume of the air-tilled middle ear space. The method might also prove a useful tool in the elucidation of the vascular bed both in health and in disease as well as the reaction of the mucosal vessels to drugs.

List of symbols Pa,,

P, Pch V,

atmospheric pressure (in the laboratory) pressure in the middle ear chamber pressure volume of the air-tilled middle ear

This study was supported by the Delegation for Applied Medical Defence Research (projects U87/1972. U95/1973, 010-10: 39 and 506H352). Acta Otolaryngol81

change in volume of middle ear due to tympanic membrane movements on increase or decrease of pressure applied, called volume displacement in the text. This displacement of the ear drum is given relative to its neutral position, outwards (+), inwards (-) volume of the mucous membrane lining the middle ear air-flow through resistor of the experimental system, i.e. system connected to patient, on compression or decompression of the gases in the middle ear air flow through resistor on compression or decompression of gases within the recording systems and within the external ear canal air-flow through resistor on compression or decompression of gas in the middle ear due to variation of the volume of the middle ear mucosa pressure gradient over the rubber disc in the external ear canal compliance of the middle ear mucosa AVmup/APch before a symbol indicates a change in a variable. Pressure is expressed in cm HzO.volume in pl or ml, and air-flow in pl/sec are relative to atmospheric pressure in the laboratory (considered constant during an experiment)

The bony walls of the middle ear are rigid but the tympanic membrane and the mucosal lining, however, are to a certain degree compliant to pressure variations (AVtm and AVmuc, Fig. 1). Hence the middle ear vanes in volume with the movements of the tympanic membrane (AVtm) and the volumetric changes of the middle ear mucosa. The variation in the

!=

AVtm

.”,

Vm

,

\,AVmu c,’

,

\

‘,+-,&



Pc h A

_,’‘.

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Fig. /. Middle ear model with tion of symbols. see text.

it5

virriables. For explana-

volume of the middle ear mucosa (AV,,,) is caused by variation in the amount of blood in the vessels of the mucosa. which in turn varies with the intratympanic pressure (P,) and vascular tone. I t was thought that investigation of the pressure-dependent variation of the volume of the mucosa might shed new light on the properties of the vascular bed in health and in disease and its reaction to drugs as well as on the widely assumed effect of the state of the mucosa on tuba1 function. Knowledge of the variation of the volume of the rnucosa with pressure is necessary for determining the volume of the middle ear (V,) both directly through a perfo rated ear drum (Flisberg et al.. 1963; Riu et al., 1966) as well as indirectly across an intact ear drum (Ingelstedt et al., 1967; Elner et al., 1971). Ingelstedt et al. (19671, who studied the effect of variation of venous pressure on the volume of the middle ear mucosa. found a linear correlation between AV,,, and the change in pressure within the range of 0 to + 10 cm H 2 0 ; AV,,, was, on the average, 0.42 pl/cm H 2 0 . They assumed that the variation in volume would be the same also when the vanation in P, was brought about by a change in the pressure acting directly on the mucosa. This assumption is important in the determination of V , . However, variation of P, affects all structures in the middle ear, including all blood and lymphatic vessels, while variation of the venous pressure affects mainly the veins and probably the capillaries. The aim of this investigation was threefold, viz.

( I ) to develop a method for quantitative determination of AV,,, on exposure of the mucosa to different pressures; ( 2 ) to elucidate the effect of variation of posture on AV,,,; ( 3 ) to devise a method for measuring the volume of the middle ear without interference by AVmuc.

MATERIAL The clinical material consisted of 5 subjects (4 women. I man) with traumatic perforation of the drum. Inspection with an operating microscope showed that the middle ear was completely dry and that the mucosa appeared normal in all 5 subjects. METHOD A N D EQUIPMENT The experiments were performed in a pressure chamber, in which it was possible to change any overpressure between 0 and SO cm H 2 0 to a corresponding underpressure within 25 seconds or vice versa. A polyethylene catheter running through a rubber disc was inserted airtight into the inner bony part of the external ear canal. The other end of the catheter was attached to a flowmeter (Fig. 2). This system, here called the test-system, records flow of air caused by the flow of air into and out of the middle ear, V m , and by compression or decompression of the gas within the recording system and within the can external ear canal. The latter flow, VSYst, be regarded as an artefact occurring on change of the pressure in the system. This artefact, VSYst,is determined and eliminated by a “reference-system”, i.e. a system with properties identical with those of the test-system and connected to a sham external ear canal with a volume of 0.3 ml. From the signal of the test-system, i.e. V,+VsYstr the signal from the reference-system, Vsvstris subtracted by an electronic circuit providing a signal corresponding to V,. The latter signal is integrated to obtain a signal corresponding to volumes entering or leaving the middle ear, AV,. The change in volume was recorded on Acra Otolaryngol8l

444 L . AndrPusson et al. d

a

b

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C

REFERENCE

The subjects were placed in a pressure chamber with a cap fixed airtight around the external ear. The pressure in the cap was the same as in the middle ear in order to avoid a pressure gradient across the rubber disc ( P c , d . I n the figure. ti-d are connected to atmospheric pressure. which corresponds to the experimental set-up for determination of AVmUcaccording to procedure A. When per-

forming experiments according to procedure C-E. 11-d were connected to chamber pressure or to an external pressure device. A middle ear model is seen ( / O M W right) connected to the test-system and the reference volume to the reference-system. Both systems consist of a flowmeter i.e. a resistor (pneumotachograph) and a pressure transducer (EMT32. Siemens-Elema). For more details. see text.

an X-Y recorder via a tape recorder as a function of the change in pressure prevailing in the chamber. In experiments when the chamber pressure was changed while the pressure in the middle ear was constant, the signals V , and AV, reflect changes in mucosal volume, i.e. $'i,c and AVmUc. In experiments with changes in the middle ear pressure and constant chamber pressure, AV,,, reflects any AV,,, inclusive volume compression or decompression of the middle ear gas. The use of two identical systems is of

fundamental importance as different errors caused by varying temperature and pressure affecting transducers and connecting lines are eliminated by subtraction of one signal from the other. I n order to avoid sliding of the ruhber disc in the external ear canal owing to a difference between the pressure in the ear and that in the chamber. caps were fixed over the subject's external ears. This prevented pressure gradients across the rubber disc (Pcurt,Fig. 2). For a more detailed description of the recording system, see Elner et al. (1971).

Fig. 2. Outline of the equipment used for the recordings.

Arm OtolawnRol81

Volunie cginiddle elir mucostil lining

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XV-RECORDER

bVmuc

-10

-io -io

6 + i o +io

b

Pch Cm H20

Fig. 3. ((0 Recordings of VmUc, AV,,, and Pch according to procedure A. ( b )Recordings of corresponding volumelpressure relationship (X-Y-recorder).

PROCEDURES AND RESULTS A. Deterinintition of AV,,, by chrrnging the umbient pressure ( P O The middle ear and the caps were connected to the atmospheric pressure. Lowering of the chamber pressure (Pch)to say, - 10 cm H,O. caused a relative overpressure in the middle ear and ;I decrease in volume of the middle ear mucosa (Fig. 3rr, h ) . When the chamber pressure was then changed from - 10 to + 10 cm H,O. the volume of the middle ear mucosa

M H 180706

XV-RECORDER

445

increased owing to the relative underpressure in the middle ear. AV,,, was continuously recorded during the pressure change as well as for another 10 sec during constant chamber pressure. At the end of each experiment it was checked that the volume signal of the middle ear mucosa had returned to the original value. The curve for the relation between volume and pressure was ellipsoid indicating a delay between the volumetric change in relation to the chamber pressure (Figs. 3 and 4). The wider the pressure variation the longer the delay. A purely static condition was never reached while the chamber pressure was constant (10 sec). A slow volume variation was observed even after 10 sec. The variations in volume seem to be of two kinds, one fast and quantitatively dominant and one slow (“slow type”). Fig. 5 shows static volume-pressure diagrams of the middle ear mucosa in all the patients. The values were measured from the end points of each loop (Fig. 4). When the pressure changes were small ( s10 cm H,O) the covariation of the volume was linear. When the pressure changes were larger ( > I 0 cm H,O) the correlation between AV,,, and Pch was nonlinear. The compliance ot the middle ear mucosa. C,,,. i.e. AV,,,,/AP,h, was de-

~ V r n U C

+10

- 10 - -20

+20

+30 +LO Pch cmH20

-20 A

-LO

-30

-20

-10 p,h

0 +10 cmH20

+20 *30 * L O

FJ,(,. 4 . Loops demonstrating the volume/pre\\ure relationship ;it different pressure changes according to procedure A . The endpoints of each loop were used when determining the di;igr:im presented in Fig. 5 . ill lh?’)l ~

1-30

F I , ~5., Diiigi-tim demonstl.ating the volumc/pressure r e h tionship according to procedure A . A linear relation u i ~ \ found within ;I pressure range of s +10 crn H,O. while ;I more varying relation was seen when the chamher pressure changes exceeded t 10 cm H,O. Aclcr Ololurynyol 81

446 L . AndrPasson et al. Table I. Compliance of the middle ear mucosa, C,,,, determined according to procedure A und calculated within a pressure range of sf10cm H 2 0 V,, according to procedure E without correction for AV,,, are compared to data with such a correction. The comparisons show that considerable errors may occur as concerns small middle ears, if no correction for AV,,, is made

V,, according to procedure D (ml)

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Cmuc

Case

W c m H,O)

IA 2 0 3 0 4 x

I .70 0.65 0.97 0.56

5.

0.61

V,, according to procedure E (ml) (not corrected for AVmuc)

V,, according to procedure E

(ml) (corrected for AVmuc)

24.0 2.7

21.0 I .7 10.0 I .2 3.0

22.0 2.2 10.0 I .2 2.9

11.0

I .8 3.5

termined within the pressure range of f10 cm H,O (Table I). The results showed a close relationship between C,,, and V, (Fig. 6).

C . Passive opening of Eustuchian tube in association with u fust und slow increase in middle ear pressure The experiments were performed in order to €3. Determination of AV,,, with change find out whether pressure-dependent changes in posture in the volume of the middle ear mucosa influThe flow of gas in and out of the middle ear ences the passive opening of the Eustachian caused by changes in volume of the middle ear tubes. The caps, the middle ear, and the mucosa with posture was recorded. The sub- reference-system (Fig. 2 u , b, d ) were exposed jects were seated in a "heart-chair", whose to the atmospheric pressure. The chamber back could be tilted from almost vertical (85") pressure was lowered and AV,,, was redown to a horizontal position (0"). corded. The sudden opening of the Eustachian Fig. 7 gives the individual AV,,, values on tube appeared clearly on the recording. This change of posture in relation to V,. The re- opening of the tube was not caused by any sults indicate that AV,,, is not directly pro- active manoeuvre by the subject, but by a portional to V,. relative overpressure in the middle ear high

B

0

CASE

A 1 0.51

0 0

AD

2 3

:;

0 0

5

10

15

20 V,

0

ml

5

10

15

20 25 V,ml

Fig. 6. The middle ear mucosa compliance was greater in

Fig. 7. Results from experiments according to procedure

middle ears with larger air-filled volumes. The relation has been calculated from the eq.: C,,,=0.45+0.061 x V,. Case symbols as in Fig. 5 .

B, i.c. the variation of AV,,, caused by the change of body posture in relation to the air-filled middle ear volumes.

Acla Otolaryngol81

rf12;

Volume of middle ear tnucosal lining

L B L70712

Pch ern H 2 0

AVmuc

-50 - c o 5cm HlYS

_----

-.......

-..-

1 2 L 5

5 5

5 0

_...: *

..fi- ;I ‘:I

::;

36 5 35 33 29 5 25 PASSIVE FORCING PRESSURE

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Fig. 8. Example of recordings of AV,,, during slow and fast pressure decreases in the pressure chamber starting at atmospheric pressure and continuing until the Eustachian tube was forced open passively (procedure C). For more details. see text.

enough to force the tube open. This pressure is called “passive forcing pressure”. Experiments with a varying rate of change in the chamber pressure were performed. Fig. 8 gives an example of the results from such experiments. Similar results were obtained in experiments on the other patients. When the middle ear pressure was increased slowly it caused a larger reduction in the volume of the mucosa, and the passive forcing pressure was lower than when the pressure changes were faster.

D.Determination of volume of middle ear (V,J without influence of AV,,, By connecting a , b and d (Fig. 2) to the chamber pressure, any change in chamber pressure caused an immediate and equal pressure change in the caps and the middle ear. The caps served no purpose in these experiments and the pressure in the middle ear was equal to the ambient pressure (Pch) throughout the experiment. An increase in chamber pressure caused an air-flow into the middle ear owing solely to compression of the gas (AV,). From the recording of AV, and AP,, V , was calculated according to Boyle’s law:

in which Pat, is the barometric pressure and 47 the pressure of water vapour at 37°C. The values recorded for V , (Table I) were not influenced by errors due to variation in volume of the middle ear mucosa or by slipping of the rubber disc in the external ear canal. The linear relationship (closed loop) between AV, and w c h was expected as the change in volume (AV,) was due solely to compression of the gas (Fig. 9).

E. Determination of V , and AV,,, By connecting a , b and d to an external pressure device it was possible to alter the pressure change in the middle ear, the caps and the reference-system (Fig. 2). The ambient pressure (chamber pressure) was constant during the experiments (atmospheric pressure). The pressure chamber served no purpose in these experiments . Changes in pressure cause volumetric displacements in the recording system partly because of compression or expansion of the middle ear gas and partly because of variation in the volume of the middle ear mucosa. When V , was calculated according to eq. 1, i.e. ignoring the variation in volume of the middle ear mucosa, the calculated figures were too high (Table I). When calculating V, after elimination of the individual V,,,-factor, i.e. according to eq. 11, the values were not

=

AV,(Pa1,-47 mmHg) APm

A Vm

M.H. 1 0 0 7 0 6

X V-R EC ORDE R

I

Pl 1+40 1+30

I

+20

-10 -20

-30 -0

V,

447

-6

-4

-2

0 ‘2 Pch cm H20

+4

+6

+0

(1) Fig. 9. Recording of AV,,, according to procedure D (see text). Acta Ololaryngol81

448 L . AndrPasson et al.

significantly different from the largely correct values found by procedure D.

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DISCUSSION The present material was small partly because of difficulties in finding suitable test subjects, i.e. healthy middle ears with a traumatic perforation, partly because of the technical difficulties. Ingelstedt et al. (1967) showed that the volume of the middle ear mucosa increased by, on the average, 0.42 pl/cm H,O of the venous pressure. In the present investigation corresponding values, i.e. the compliance of the mucosa, were about 60% higher than those found by Ingelstedt et a]. (1967), even when the patient with an unusually large middle ear was excluded. Since the data found in the two investigations showed no overlapping, the difference found appears to be a true one. The main part of the difference must apparently be due to the differences in the methods used for altering the pressure. In the present investigation the changes in pressure affected not only the veins and capillaries, as in the investigation done by Ingelstedt et al. (1967), but also the lymph vessels, the Eustachian tube and the round and oval windows. Volumetric changes of “slow type” might be responsible for part of the differences seen and might be due to displacement of intercellular fluid between the mucosa and the surrounding structures. The pressure applied were maintained for a shorter time in the earlier investigation. However, “slow type” changes in volume in the present investigation were responsible for only about 10% of the total volumetric change, which is only a minor fraction of the total difference (60%). What concerns volumetric changes contributed from the round and oval windows, these must be insignificant (Ivarsson & Pedersen, 1975). Acla Otolaryngol81

The tests with a slow and a rapid increase

in the pressure of the middle ear (procedure C, Fig. 81, showed that the slow pressure increase was associated with a large volume change of the mucosa, resulting in opening of the tube at relatively low pressures. These low forcing pressures mainly reflect decongestion of the mucosa but fatigue of the tissues operating the closure of the Eustachian tube might also be a contributory factor. The tests with change in posture showed somewhat larger volumetric changes than could be expected if the variation was caused by the increased venous pressure alone. The actual change of posture has been found to cause a venous pressure increase at the level of the middle ear (bulbus vena jugularis) of about 10 cm H,O (Jonson & Rundcrantz, 1969). If the recorded volumetric mucosa changes was caused only by a venous pressure increase, the minimum calculated pressure (mean 14.2, range 12.1-21.5 cm H,O) capable of causing these changes was higher than the above-mentioned venous pressure increase. However, the pressure changes on the arterial side must be substantially larger (20-30 cm H,O) than those on the venous side (10 cm H20)and this condition must contribute to the recorded volumetric changes on alteration of posture. A slow type of volumetric change was seen even after 10 sec in the recumbent position. The nature of this volumetric change as well as that seen taking place even after a 10 sec period of static pressure after a change in middle ear pressure must await future research. Determinations of the volume of the middle ear as in procedure D, are probably the first to have been made without any artefacts due to variation in volume of the mucosa (AVmUc). Table I clearly shows the risks of major errors when V, is estimated without taking AV,,c into consideration, especially when the middle ear volumes are small. This is because C,,, is high in relation to V, in such small middle ears, perhaps because the mucosa of the middle ear is well vascularized compared with

Volume of middle ear mucosal lining

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that of the air cell system. The factor AP,x C,,, constitutes a large part of AV,, eq. 2 . If V , is estimated according to procedure E, and Cm,c is taken into consideration as in eq. 2 , it will give adequate information about the true Vm. If in a given case C,,, is not known, it should be estimated, which was earlier done by lngelstedt et al. (1967). The best estimation known is the equation C,,c=0.4S+0.061 X V , (Fig. 7) though it was based on only the present S cases. Taking C,,, into consideration gives a closer estimation even when V , is determined indirectly (Ingelstedt et al., 1967).

ZUSAMMENFASSUNG Beschreibung einer Methode zum Studium der vom Druck abhingigen Verinderungen des Volumens der Mittelohrschleimhaut. Die Untersuchungen wurden bei unterschiedlichen Druckwerten im Mittelohr und in der Au\\enwelt durchgefuhrt. Die druckabhlngigen Volumeninderungen der Schleimhaut waren bei Druckverinderungen im Mittelohr durch Druckiinderung direkt in der Pauke oder indirekt in der Aussenwelt die gleichen. Mit der beschriebenen Methode kann auch das Paukenvolumen uber die Mittelohrschleimhaut ohne Artefakte bestimmt werden. Das Volumen-Druck-Verhlltnis in der Mittelohrschleimhaut variierte von 0.6-1.7 Fl/cm H,O und linear mit dem Volumen im Mittelohr. Vergleiche zwischen Bestimmungen des Mittelohrvolumens mit und ohne Beriicksichtigung der durch die Schleimhaut hervorgerufenen Complianz ergaben besonders bei kleinen Pauken deutliche Unterschiede. Der Einfluhs wechselnder

449

Stellungen auf das Volumen der Schleimhaut wurde ebenfalls studiert. Der physiologische Mitteldruck ist abhlngig von der Funktion der Eustachischen Tube, des Mittelohrvolumens. des Trommelfells und der Mittelohrschleimhaut. Deshalb ist die Bestimmung der Schleimhautcomplianz wichtig fur Berechnung des Mittelohrdrucks und auch fur das Studium des Volumens der luftgefullten Mittelohrraume. Die Methode kann auch zur Klarung der Gefassfunktion bei physiologischen und krankhaften Zustanden sowie der Reaktion der Schleimh a u t g e k s e auf Pharmaka beitragen.

REFERENCES Elner, A,. lngelstedt, S. & Ivarsson. A. 1971. A method for studies of the middle ear mechanics. Artrt Otolurvngol (Stockh) 72, 191. Flisberg. K.. lngelstedt, S . & Ortegren. U. 1963. Clinical volume determination of the air-tilled ear space. Arta Otolrtryngol (Stockh), Suppl. 182. lngelstedt. S . . Ivarsson, A . & Jonson. B. 1967. Mechanics of the human middle ear. Acrct Otolrtryngol (Stockh). Suppl. 228. lvarsson, A. & Pedersen, K. 1975. The volume-pressure characteristics of the membranes in the round and oval windows. To be published. Jonson. B. & Rundcrantz, H. 1969. Posture and pressure within the internal jugular vein. A r m Otol~ryngol (Stockh)68. 271. Riu. R.. Flottes, L.. Bouche. J . & LeDen, R. 1966. Lri physiologic de la trotripe d’Eusttiche. Applications cliniques et therapeutiques. Arnette. Paris.

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Actu Oroluryngol8i

Pressure-dependent variation in volume of mucosal lining of the middle ear.

A method is described for studying pressure-dependent variation in the volume of the mucosa of the middle ear. Studies were performed at different pre...
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