Observations of middle ear pressures. Commentary with movie

Nitric Oxide Is Locally Produced in the Human Middle Ear and Is Reduced by Acquired Cholesteatoma

OBJECTIVE

To find out if nitric oxide (NO) can be locally produced in the middle ear and if chronic otitis media (COM) and acquired cholesteatoma affect the production.

DESIGN

Case-control study.

SETTING

Two tertiary-referral hospitals.

PATIENTS

Gaseous NO from 11 patients with unilateral perforations or grommet openings was measured with chemiluminescence. Middle ear mucosa from 48 patients with COM and 26 patients with cholesteatoma was investigated.

MAIN OUTCOME MEASURES

Detection of NO. Expression of nitric oxide synthase (NOS) mRNA, in mucosa from COM, cholesteatoma and healthy controls, quantified using polymerase chain reaction.

RESULTS

The gaseous NO from ears with a unilateral tympanic membrane perforation or a grommet was higher (9 ± 3 ppb, n = 11) than among the controls (4 ± 1 ppb, n = 11, p = 0.04). Lower levels of eNOS (2.64 ± 0.86 mol/100,000 mol ACTB) were detected in the pooled samples from the COM group (n = 48), compared with the control group (140.48 ± 92 mol/100,000 mol ACTB, n = 45, p = 0.010). In the cholesteatoma group (n = 26), a lower expression of nNOS (5.78 × 10-6 ± 1.13 × 10-6 ΔCt) was found in comparison with the controls (1.23 × 10-4 ± 3.18 × 10-5 ΔCt, n = 15, p = 0.011).

CONCLUSIONS

NO is likely a natural and permanent part of the gas mixture in the human middle ear. The presence of NOS enzymes in the middle ear mucosa indicates an ongoing NO production and the reduction of NOS in ears with cholesteatoma, and pooled samples from ears with COM, suggest a role for locally produced NO in middle ear disease.

A formal description of middle ear pressure-regulation

INTRODUCTION

Middle ear (ME) pressure-regulation (MEPR) is a homeostatic mechanism that maintains the ME-environment pressure-gradient (MEEPG) within a range optimized for "normal" hearing.

OBJECTIVE

Describe MEPR using equations applicable to passive, inter-compartmental gas-exchange and determine if the predictions of that description include the increasing ME pressure observed under certain conditions and interpreted by some as evidencing gas-production by the ME mucosa.

METHODS

MEPR was modeled as the combined effect of passive gas-exchanges between the ME and: perilymph via the round window membrane, the ambient environment via the tympanic membrane, and the local blood via the ME mucosa and of gas flow between the ME and nasopharynx during Eustachian tube openings. The first 3 of these exchanges are described at the species level using the Fick's diffusion equation and the last as a bulk gas transfer governed by Poiseuille's equation. The model structure is a time-iteration of the equation: P^ME_{g(t=(i+1)Δt)} = ∑^s(P^ME_s(t=iΔt)+(1/(β^ME_sV^ME)∑^P(Қ^P_s(P^C_s(t=(iΔt)-P^ME_s(t=(iΔt))). There, P^ME_g(t=iΔt) and P^ME_s(t=iΔt) are the ME total and species-pressures at the indexed times, P^C_s(t=iΔt) is the species-pressure for each exchange-compartment, β^ME_sV^ME is the product of the ME species-capacitance and volume, Қ^P_s is the pathway species-conductance, and ∑^S and ∑^P are operators for summing the expression over all species or exchange pathways.

RESULTS

When calibrated to known values, the model predicts the empirically measured ME species-pressures and the observed time-trajectories for total ME pressure and the MEEPG under a wide variety of physiologic, pathologic and non-physiologic conditions.

CONCLUSIONS

Passive inter-compartmental gas exchange is sole and sufficient to describe MEPR.

Ventilation and clearance of the middle ear

OBJECTIVE

To investigate the ventilation and drainage mechanism of the middle ear.

STUDY DESIGN

Prospective.

SETTING

We observed 304 (of 337) middle ears with tympanic membrane perforation or myringotomy (102 normal, 90 with otitis media with effusion and 112 with chronic otitis media); 912 observations were recorded overall. Perforations were covered with solution, creating a fluid film, and inspected for gas bubbling at rest, and for outward and inward movement of the fluid film during swallowing. We also noted the inflammatory condition of the ear (i.e. dry, wet or purulent) and the perforation size.

RESULTS

Ears sometimes reacted differently in various sessions. Due to these differences, reactions were classified as 'types' of reactions rather than 'ears'. We refer to 449 'types' of 304 ears. Spontaneous gas bubbling at rest (indicating gas production) was observed in 98 per cent of normal types, 68 per cent of otitis media with effusion types and 65 per cent of chronic otitis media types. Evacuation towards the eustachian tube was observed in 47 per cent, no movement in 46 per cent and outward movement in 9 per cent. During swallowing, inward movement of the fluid film was observed in 74 per cent of normal types, 41 per cent of otitis media with effusion types and 32 per cent of chronic otitis media types.

CONCLUSIONS

We found no support for the theory that the eustachian tube supplies air to the middle ear during swallowing. The normal middle ear produces gas which is evacuated by the Eustachian tube. In ears with otitis media, this mechanism appears to be impaired.

Role of grommet in otitis media with effusion: A necessity or nuisance? A comparative study

Otitis media with effusion is one of the commonest otological problems in paediatric age group. The condition occurs in childhood as overt or covert hearing loss presenting as an educational or behavioural problem. As there is widespread controversy regarding its precise aetiology, natural history and pathogenesis a treatment dilemma still persists. The main goal of this study is to compare the efficacy of different modalities of medical and surgical treatment designed for this condition and analysis of the results statistical.

Experimental results do not support a gas reserve function for the mastoid

The mastoid is an aerated extension of the middle ear gas pocket whose state of development was shown to be an indicator of past and future otitis media experience. While the function(s) of the mastoid is not known, a number of hypotheses has been advanced to explain the reported association between mastoid size and middle ear disease. These include the hypotheses that, with respect to the middle ear, the mastoid functions as a pressure buffer, a gas reserve, and/or a pressure regulator. In this paper, a physical model of the mastoid is presented that makes specific predictions against which the validity of the hypothesized gas reserve function could be tested. Data from three published clinical experiments were evaluated for consistency with the predictions of the model, and the hypothesis was rejected. Also, when reinterpreted within the context of the model, the published data do not support a pressure-regulating function for the mastoid.

Pneumatization of the tympanic bulla after blockage of the ventilation route through the eustachian tube in the pig

To examine whether gas exchange occurs in the middle ear air cell system independent of the eustachian tube (ET), we occluded the middle ear clefts of piglets, whose tympanic bullae closely resemble the human mastoid air cell system, and investigated subsequent changes in the air cell system. We anticipated that pneumatization and development of the air cell system would continue if gas were exchanged through the mucosa lining the air cell system. If, on the other hand, mastoid air cells depend on the ET, mastoid development would be impaired or arrested. In noninflamed ears, pneumatization was maintained, and development of the air cell system continued after the middle ear cleft had been occluded with an acrylate adhesive and the bullar air cell system was thus excluded from any communication with the ET. These results indicate that the normal middle ear air cell system has the capacity to perform gas exchange independently of the ET, with gas exchange appearing to occur through the submucosal capillary network.

The effect of postural change and upper respiratory tract infection on middle ear pressure

The effect of a change in posture from sitting erect to lying supine and horizontal on middle ear pressure was investigated in 5 healthy adults and 5 adults with symptoms of an acute upper respiratory tract infection (URTI). The change in posture had no significant effect on middle ear pressure in the healthy subjects (p greater than 0.05). In those with URTI mean middle ear pressure increased from -39.5 daPa (erect) to -16.9 daPa (supine) (p = 0.026, n = 10). In the supine posture the middle ear pressure in subjects with URTI was raised. The cause of the increase in middle ear pressure is discussed in terms that the postural change may alter middle ear physiology such that in the supine posture there is a net production of middle ear gas as opposed to a net reabsorption in the erect posture. This may indicate that an increase in jugular venous pressure causes a net positive production of middle ear gas.

Middle ear gas generation in myringoplasties

No Gelfoam was used to support the vein in 10 simple underlay vein graft myringoplasties. Computed tomographic studies 24 hours postoperatively showed gas filling 75% to 100% of the middle ears in three ears. The epitympanum and mastoid were also evaluated. Apparently, in some ears the middle ear generates gas in the immediate postoperative period to support fresh vein grafts.

The motor innervation of the tympanic muscles in the guinea pig

The number and the location of the motor neurons innervating the stapedius or tensor tympani muscles in the guinea pig were identified by retrograde axonal transport of the tracer horseradish peroxidase. Tracer injections were made either into the stapedius or tensor tympani muscle and effected the retrograde labeling of neurons in the ipsilateral brain stem. These findings showed that the stapedius motor neurons lie outside the traditionally recognized facial nucleus and are present in two cell columns: ventromedial and dorsomedial to the facial nucleus. These labeled neurons are dissimilar to cells within the facial nucleus, i.e. they are smaller and more fusiform in shape. The tensor tympani motor neurons were found outside the trigeminal motor nucleus. At a rostral level they were located in a region ventral and ventrolateral to the latter nucleus. These labeled neurons were smaller than the trigeminal motor neurons and polygonal in shape. In the animals studied there were about six times more tensor tympani motor neurons than stapedius motor neurons.

Middle ear effusion--a theoretical neuro mechanical hypotheses

An alternative theoretical neuro-mechanical hypothesis is presented in the pathogenesis of middle ear effusion, along with a review.

Pathophysiology of otitis media with effusion: clinical evaluation through some qualitative methods

In an attempt to elucidate the pathophysiology of otitis media with effusion (OME), systematic clinical investigations were undertaken. The high resolution computed tomography, tympanogram, tubal inflation and our qualitative tubal functioning test were routinely applied to cases of OME, both in children and adults. Through these studies, following was concluded: 1. The primary pathology involved may be obstructive lesion somewhere in the tubotympanic cleft including the epitympanum and the mastoid, which in turn results in negative pressure in the middle ear. 2. This negative middle ear pressure may mainly constitute the Eustachian tube dysfunction, which is considered to play an important role in the pathogenesis of OME. Discussed in detail further will be the importance of correcting the negative middle ear pressure substantially for the treatment of OME, and also the essence of our qualitative tubal functioning test.

Gas absorption in serous otitis. A clinical aspect

Animal experiments have shown that gas absorption can produce a considerable intratympanic underpressure when the gas composition of the middle ear is disturbed. A similar phenomenon was observed in children with serous otitis. In 12 ears with underpressures exceeding -150 mm H2O, Valsalva inflation or politzerization produced a transient improvement followed by a rapid return to subatmospheric pressures ranging from -130 to -300 mm H2O. In four cases with middle ear pressures between -65 and -135 mm H2O, the same procedure did not result in any significant underpressures. These findings suggest that inflation of the middle ear in the presence of a deep underpressure serves no purpose. It is also possible that a negative pressure, once established, can be maintained in this way.