Diss. (sammanfattning) Stockholm : Karolinska institutet, 2002. / Härtill 6 uppsatser.

Ο σκοπός της διδακτορικής διατριβής ήταν η μελέτη και η ανάπτυξη προσομοιωτή λειτουργίας του μέσου ωτός με σκοπό την υποστήριξη στη διάγνωση. Ο βασικός τρόπος διάγνωσης των παθολογιών του μέσου ωτός βασίζεται στην τυμπανομετρία. Εξέλιξη της τυμπανομετρίας είναι η τυμπανομετρία πολλαπλών συχνοτήτων, η οποία χρησιμοποιήθηκε για το σκοπό της διατριβής. Στις περισσότερες παθολογικές καταστάσεις, η διάγνωση βασίζεται εν μέρει σε αντικειμενικά κριτήρια. Το πρόβλημα έγκειται στη μετάφραση της κωδωνοειδούς καμπύλης του τυμπανογράμματος. Σε πολλές περιπτώσεις αυτό είναι αναποτελεσματικό για δύο λόγους. Πρώτον γιατί η καμπύλη ενδέχεται να συμπίπτει σε περισσότερες από μία παθολογικές καταστασεις και δεύτερον γιατί μπορεί να λειτουργούν στοιχεία του συστήματος κατά τέτοιο τρόπο ώστε να αλληλοεξουδετερώνονται τα αποτελέσματά τους. Η λειτουργία του προσομοιωτή βασίζεται στην αντιστοίχιση του βιολογικού συστήματος του μέσου ωτός (από τον τυμπανικό υμένα ως την ωοειδή και στρογγυλή θυρίδα) σε μηχανολογικό σύστημα και εν συνεχεία στην αντιστοίχιση του σε ισοδύναμο ηλεκτρικό κύκλωμα. Στο πλαίσιο της μελέτης εκφράστηκε η συνάρτηση μεταφοράς του ισοδύναμου κυκλώματος, αναπτύχθηκε η αρχιτεκτονική λειτουργίας του προσομοιωτή, διερευνήθηκαν αλγόριθμοι επεξεργασίας των μετρήσεων, λήφθηκαν κλινικές μετρήσεις φυσιολογικών και παθολογικών δειγμάτων και αξιολογήθηκαν τα αποτελέσματά τους. Εν τέλει αποδείχθηκε η ορθή λειτουργία του προσομοιωτή για φυσιολογική λειτουργία του μέσου ωτός και για την παθολογική λειτουργία του στις νόσους της ωτοσκλήρυνσης και της μέσης εκκριτικής ωτίτιδας. / The purpose of this doctoral dissertation was the study and development of a simulator of the function of middle-ear in order to support the diagnostic procedure. The basic diagnostic procedure for middle ear pathologies is based on tympanometry. The evolution of classic tympanometry is multi-frequency tympanometry, which was used for the purpose of this study. In most pathological situations, diagnosis is based partly on objective criteria. The problem lies with the translation of the bell-like curve of the tympanogram. In most cases this is not effective for two reasons. Firstly, because the curve may concur in more than one pathological situations and secondly, because elements of the system may function in such a way as to cancel each other out in their depiction. The operation of the simulator is based on the correlation of the biological system of the middle ear (tympanic membrane to round and oval windows) to the mechanical system and eventually to the equivalent electrical circuit. During thiw study, the transfer function of the system was generated, the architecture of the simulator was created, algorithms of manipulation of the measurements were investigated, clinical measurements were taken for both normal and pathological ears and their results were evaluated. Finally, the correct operation of the simulator was proven for normal operation of the middle ear and pathological operation in the cases of otosclerosis and secretory otitis media.

published_or_final_version / Speech and Hearing Sciences / Master / Master of Science in Audiology

<p>This thesis addresses the biomechanics of the human middle ear, that part of the auditory system which converts sound pressure waves in air to fluid pressure waves in the cochlea. The middle ear's mechanism is analysed in four papers, three main and one supporting; in the main papers the middle ear is treated as a multi-particle, multi-rigid body ensemble possessing a variable number of degrees of freedom depending upon the case being investigated.</p><p>It is confirmed, using the standard representation of a single fused incudo-malleal block, that the middle ear's motion is linear, but when this fused block restriction is lifted nonlinearity is present which significantly affects the mechanism's behaviour. In view of the linearity of the chain under the fused block conditions, the explanatory veracity of the conventionally accepted `fixed axis hypothesis' of ossicular motion is examined and found to be wanting as a realistic description of the chain's physical movement.</p><p>The nonlinear behaviour of the ossicular chain centres around the action of the incudo-malleal joint. This joint is shown to have preferential planes of operation, principally the pitch or longitudinal plane and in general to act as an efficient energy dissipator at high driving pressures and low frequencies. Providing the pressure is high enough, it is shown this energy dissipator effect eventually becomes independent of frequency.</p><p>The supporting paper discusses the dynamics of the imposition and removal of equation constraints justifying methods used to investigate the functioning of the incudo-malleal joint.</p>

Research was conducted on twenty-seven preoperative myringotomy patients to clarify the correlation between tympanometry type and the presence of middle ear effusion. Test results indicate that the relationship between tympanometry and middle ear effusion is dependent on the amount of fluid present. In impacted ears primarily Type B tympanograms were obtained whereas for less than impacted ears all tympanogram types were seen. Also suggested was that a combination of height of the tympanogram and the amount of negative pressure may be diagnostically more important than negative pressure alone as an indicator of effusion. It was recommended that other measures in addition to tympanometry be employed in the diagnosis of middle ear effusion and that further research is needed to achieve optimal use of impedance audiometry.

Includes bibliographies. / Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1977. / Microfiche copy available in the Institute Archives and Barker Engineering Library. / by William Mark Rabinowitz. / Ph.D.

The middle ear system is a vital component in the propagation mechanism of otoacoustic emissions. As such, investigation of the effect of variation in middle ear impedance on the measurement of emissions is warranted. Distortion product otoacoustic emissions (DPOAEs) have gained recognition as a means of gaining frequency specific information on auditory function. As the effects of changes in middle ear impedance will vary as a function of frequency, a clear definition of the relationship between middle ear impedance and DPOAE amplitude across the frequency spectrum is needed. Twenty adults (ages 20-37) with normal hearing and normal middle ear function were selected as subjects. Commercially available equipment (Virtual 330) was used to measure the DPOAEs on all subjects. The unit was modified to change canal pressure by coupling the probe to the pressure pump of a clinical acoustic immittance system. One ear from each subject was randomly selected for measurement and each subject was tested under five pressure conditions: +200, O, -200, -300, -400 daPa. The mean frequency of the fl/f2 tone pairs swept from 500 to 8000 Hz. Results indicate that changes in ear canal pressure can effect the amplitude of DPOAEs. Alteration of ear canal pressure resulted in decreased emission amplitude. This effect was found to differ as a function of eliciting frequency with the greatest reduction in amplitude with the mean of the primaries at 500 Hz. Less variation was noted across the ear canal pressures with the higher frequency stimuli. These results are consistent with previous findings reported regarding the effects of impedance changes on spontaneous and transiently evoked otoacoustic emissions.

Prior to this investigation, there appeared to be no published research data available on tympanometric configurations obtained from an older adult population. This study was designed to examine tympanograms obtained from an otologically normal, elderly population. Forty individuals, ranging in age from 59 to 83 years, participated in this study. All had a negative history of middle ear pathology and had normal tympanic membranes as determined by otologic examination. From the eighty ears tested, fifty were used in this survey. Conductance and susceptance at 220 and 660 Hz were obtained at each ear and ranges for admittance were computed from these components. Additionally, acoustic reflex thresholds were obtained from this population. The results obtained indicate that the values for the measures of conductance and susceptance are comparable to those from young adult groups. The reflex thresholds are slightly higher in the older group because their hearing thresholds are not as acute as those found in younger populations. Finally a larger percentage of the older population than might be expected was found to have evidence of healed perforations which were not discovered during otoscopic examination. The present investigation demonstrated that additional normative data are neededin order that the otoadmittance meter be fully utilized with older adult populations.

Acute otitis media is the most common illness diagnosed during early childhood that can cause significant morbidity (Brook, 1994) and sometimes can cause irreversible sequelae such as a hearing defect and subsequent learning difficulties (Klein, 1994). The aims of the research presented here were to study some aspects of the middle ear defence mechanisms in both immune and non-immune rats following experimental otitis media (OM) with two pathogens nontypeable Haemophilus influenzae (NTHi) and Moraxella catarrhalis (M. catarrhalis). This study also aimed at developing a suitable technique for preparing immunohistochemical staining of middle ear sections (chapter 2). A previous study has shown that a regime where rats received an IPP immunisation combined with an IT boost was effective in enhancing clearance of a middle ear infection with the same strain of NTHi and also in the presence of a concomitant viral infection (Moore et al, 2001). Results of this study have shown that for NTHi infection a distinct cellular influx to the middle ear in the immune rats was accompanied by an enhanced bacterial clearance compared to the non-immunised rats (chapter 3). This cellular influx was responsible for the remarkable reduction in the bacterial number. The sharp decline in PMNs numbers in the NTHi immunised rats that followed complete bacterial clearance at 72h post infection (Table 3.1) indicate a more effectively controlled down regulation of this cell infiltrate than the non-immunised rats. For M. catarrhalis infection, there was no difference in cell infiltrate between immune and non-immune rats, but enhanced clearance of the bacteria were observed for the immune animals. The histopathological changes in the middle ear mucosa of rats with experimentally induced infection were studied to provide a better understanding about the distribution of the inflammatory cells and changes in the mucosa during the first 24h post challenge with NTHi and M. catarrhalis (Chapter 4). These changes have not been previously studied for the two pathogens at 24h post challenge in rats. Induced infections with the two pathogens were found to produce similar histopathological changes but more inflammatory infiltration was observed within the infected mucosa with NTHi than that seen with M. catarrhalis. The infections were characterized by increased thickness of the middle ear mucosa, Eustachian tube mucosa, periosteum and tympanic membrane. There was also an increase in the number and size of small blood vessels at all sites, and these small blood vessels seem to be the source of the inflammatory infiltration into the middle ear mucosa and middle ear cavity during the infection. These findings provided an essential background to the immunohistochemical study. The effect of mucosal immunisation on the distribution of CD4+T cells and CD8+T cells has not been investigated previously. Results of the present study (Chapter 5) show the pattern of distribution of these cells during the first 48h post infection with NTHi in the rat. The number of CD4+and CD8+T cells peaked at 24h post infection in the nonimmunised animal and were highest at 48h post-infection in the immunised rats. The difference in response in the immunised rats may represent regulation of the inflammatory response by the immune system. The inflammatory response regulation is indicated by the difference in cellular influx into the immune rats and the response in the immune rats that corresponds to enhanced bacterial clearance prior to a decrease in numbers of inflammatory cells once the bacteria was no longer detected (Chapter 3). This resolution of the inflammatory mass would reduce the opportunity for continued damage to local tissue. These changes are also supported by the reduction in the thickness of the middle ear mucosa of the immunised rats especially at 24h and 48h post-infection (Chapter 5). This study has shown that there are distinct differences in the rate of bacterial clearance and cellular changes in the middle ear mucosa and tympanic bulla in immunised rats during a middle ear infection. Future studies are still required to gain a better understanding of differences in the inflammatory response for both pathogens, NTHi and M. catarrhalis.

This thesis addresses the biomechanics of the human middle ear, that part of the auditory system which converts sound pressure waves in air to fluid pressure waves in the cochlea. The middle ear's mechanism is analysed in four papers, three main and one supporting; in the main papers the middle ear is treated as a multi-particle, multi-rigid body ensemble possessing a variable number of degrees of freedom depending upon the case being investigated. It is confirmed, using the standard representation of a single fused incudo-malleal block, that the middle ear's motion is linear, but when this fused block restriction is lifted nonlinearity is present which significantly affects the mechanism's behaviour. In view of the linearity of the chain under the fused block conditions, the explanatory veracity of the conventionally accepted `fixed axis hypothesis' of ossicular motion is examined and found to be wanting as a realistic description of the chain's physical movement. The nonlinear behaviour of the ossicular chain centres around the action of the incudo-malleal joint. This joint is shown to have preferential planes of operation, principally the pitch or longitudinal plane and in general to act as an efficient energy dissipator at high driving pressures and low frequencies. Providing the pressure is high enough, it is shown this energy dissipator effect eventually becomes independent of frequency. The supporting paper discusses the dynamics of the imposition and removal of equation constraints justifying methods used to investigate the functioning of the incudo-malleal joint.