Tympanometry accurately measures middle ear underpressures in monkeys

Tympanometry is useful for evaluating middle ear (ME) status, but its accuracy in estimating true ME pressure has been questioned. We evaluated the accuracy of tympanometry in 6 monkeys. Direct application and measurement of ME pressure were achieved with a probe introduced into the mastoid antrum, and tympanometry was done over a large range of applied ME pressures. For all ears, tympanometric pressure was a linear function of applied pressure. At large overpressures, the tympanometric pressure was approximately 40 mm H2O greater than the applied pressure, but there was little error in the measurement for applied underpressures. The measurement error was proportional to the ME pressure multiplied by the ratio of the extant volume displacement of the tympanic membrane to ME volume. These results show that in monkeys, tympanometry provides an accurate, relatively unbiased estimate of ME underpressure and suggest that the measurement error for tympanometry can be predicted for MEs of other species.     

Morning pressure in the middle ear

Tympanograms were taken in the early morning in 25 persons with healthy ears. A first tympanogram was obtained shortly after waking up while the subject was still recumbent, and a second tympanogram was taken in the upright position after chewing and swallowing. Positive middle-ear pressure was found in a majority of ears, and the pressure was reduced after swallowing. The present results indicate that gas absorption from the middle ear is not important in quantitative terms during sleep. Otherwise the morning pressure would be expected to be negative. Two other experiments showed that the middle-ear pressure increased during shallow "sleep-type" breathing, and decreased during hyperventilation. The present results can be explained by diffusion of carbon dioxide over the middle-ear mucosa, the direction of gas transfer being dependent on the breathing pattern.     

Effects of inflammatory changes in the middle ear mucosa on middle ear total pressure

CONCLUSIONS: Inflammation of the middle ear mucosa leads to inhibition of transmucosal carbon dioxide (CO2) diffusion. Furthermore, CO2 diffusion is inhibited more severely in ears with a histologically higher grade of inflammation. OBJECTIVES: To investigate the effect of inflammatory changes in the middle ear mucosa on transmucosal gas exchange, and the relationship between the histologic inflammation grade of the middle ear mucosa and the middle ear total pressure (METP). MATERIALS AND METHODS: Twenty-six rabbits were used for this study. Changes in the METP and the oxygen partial pressure in the middle ear (PmO2) were measured in the otitis media group and the untreated group, and were compared between the two groups. Inflammatory changes in the middle ear mucosa were classified into four grades histologically, and the relationship between the histologic inflammatory grade and the maximum METP was examined. RESULTS: The maximum METP in the otitis media group was significantly decreased compared with the untreated group (p < 0.05), but there was no difference between the two groups in the rate of decrease of the PmO2. Furthermore, the maximum METP in grade III inflammation was significantly decreased compared with that in grade II inflammation (p < 0.05).     

Effects of inflammatory changes in the middle ear mucosa on middle ear total pressure

Conclusions. Inflammation of the middle ear mucosa leads to inhibition of transmucosal carbon dioxide (CO₂) diffusion. Furthermore, CO₂ diffusion is inhibited more severely in ears with a histologically higher grade of inflammation. Objectives. To investigate the effect of inflammatory changes in the middle ear mucosa on transmucosal gas exchange, and the relationship between the histologic inflammation grade of the middle ear mucosa and the middle ear total pressure (METP). Materials and methods. Twenty-six rabbits were used for this study. Changes in the METP and the oxygen partial pressure in the middle ear (PmO₂) were measured in the otitis media group and the untreated group, and were compared between the two groups. Inflammatory changes in the middle ear mucosa were classified into four grades histologically, and the relationship between the histologic inflammatory grade and the maximum METP was examined. Results. The maximum METP in the otitis media group was significantly decreased compared with the untreated group (p<0.05), but there was no difference between the two groups in the rate of decrease of the PmO₂. Furthermore, the maximum METP in grade III inflammation was significantly decreased compared with that in grade II inflammation (p<0.05).     

Inner ear disturbances following inoculation of endotoxin into the middle ear

Inner ear function was assessed by a frequency-specific (+/-100 Hz) auditory brainstem response (ABR) technique after a single instillation of a suspension of purified E. coli lipopolysaccharide in sterile water into the round window (RW) niche in rats. Instillation of endotoxin caused a transient concentration and tonotopically dependent dysfunction of the inner ear. The largest threshold impairment occurred in the high-frequency region anatomically located close to the RW. At 31.5 kHz the threshold impairment persisted throughout the study. Morphologic damage to the inner ear was not detected at the light microscopic level when using serial sections from decalcified specimens. Our study supports the clinical hypothesis that remnants of non-viable bacteria such as endotoxins, when trapped in the middle ear, can promote middle ear effusion and dysfunction of the inner ear.     

Monitoring middle ear pressure by tympanometry. A study of middle ear pressure variation through seven hours

The aim of this investigation was to monitor fluctuations in middle ear pressure, to study tympanometric signs of Eustachian tube functioning and to assess the validity of the tympanometric readings. In 20 patients with a low initial middle ear pressure (-150 daPa or lower) and 5 normals, impedance tympanometry was performed every 3 min through 7 h. Median pressure for the patients was -150 daPa (range 100 to -400 daPa) and for the normals 0 daPa (range 50 to -50 daPa). A remarkable pressure increase was seen after changing the body position to the supine. The patients were arranged into three groups according to the lowest middle ear pressure registered. Median pressures for the groups were running at a rather constant level. However, the individual pressure fluctuations in many patients were so great that a single tympanometric reading has to be considered unreliable when selecting patients for insertion of ventilation tubes. Thirteen patients never equalized their negative middle ear pressure, indicating that their Eustachian tube did not open during the test period. In spite of this the pressure did not decrease to lower values, indicating that maintaining a relative constant middle ear pressure is independent of opening of the Eustachian tube.     

Chloral hydrate and middle ear pressure

Middle ear pressure and tympanic membrane compliance were measured in 34 infants and young children (66 ears) with normal middle ears under oral choral hydrate hypnosis. Tympanograms were performed before and 40 to 60 minutes after administration of the drug. Results showed that the middle ear pressure increased significantly in all cases and in both sexes. This increase ranged between +19 and +219 mm H2O. In all cases the pressure returned to its prehypnotic values after recovery. Results of tympanic membrane compliance showed significant increase in males and not significant decrease in females.     

Mucosal immunity of the middle ear: analysis at the single cell level

OBJECTIVE: Studies have suggested that the middle ear is a potential site of immunological regulation and that the middle ear mucosa constitutes a part of the mucosal immune system. We clarify the characteristics of the middle ear mucosa with respect to immune potential. STUDY DESIGN: We investigated lymphocyte subsets, mRNA of cytokines, and induction of antigen-specific IgA-producing cells in the middle ear mucosa in specific pathogen-free C57BL/6 mice. RESULTS: Flow cytometric analysis showed a certain amount (10%-15%) of gammadelta T cells among CD3+ T cells. P6-specific IgA-producing cells were induced by intranasal immunization with P6 together with cholera toxin. RT-PCR assay of mucosal T cells detected mRNA of Th2 type cytokines such as IL-5 and IL-10. CONCLUSION: These findings support the fact that the middle ear is potentially an effector site of the mucosal immunity.     

Effects of desflurane on middle ear pressure

OBJECTIVE: To evaluate the effects of desflurane on middle ear pressure. STUDY DESIGN: A prospective clinical study. METHODS: In this study, 38 ears of 19 male children that were scheduled for circumcision were included. Baseline tympanometry reading was performed on each ear just before anesthesia. After induction anesthesia with propofol a laryngeal mask was applied and desflurane administration was started. The next tympanometry reading was taken at 5th, 10th and 15th minute after administration and at the 10th minute after the cessation of desflurane. Data were analysed using Wilcoxon test. RESULTS: Mean MEP values before anesthesia in 38 ears of 19 boys were -10.32+/-33.14. After starting the administration of desflurane 5th minute mean value was 71.15+/-60.42, at the 10 th minute 111.56+/-59.03 and at the 15th minute it increased to 120.50+/-54.14, and these measurements were significantly higher than the starting value (p<0.001). After cessation of desflurane mean MEP value dropped to 57.56+/-79.06, but compared with the starting value this was also significantly higher (p<0.001). CONCLUSION: Desflurane may increase the middle ear pressure and it may be unsuitable for certain middle ear surgeries.     

Transient pressure changes in the middle ear.

Transient increases in total pressure in the ear (1) during sleep, after hypoventilating in a supine position with a closed eustachian tube, and (2) after the partial pressures in middle-ear gas are lowered by a total pressure decrease and the eustachian tube is voluntarily maintained closed can be accounted for quantitatively on the basis of the standard mucosal gas exchange model and the following data: (1) partial pressures in tissue: pN2* = 573 mm Hg (7621 decaPascals [daPa]), pO2* = 40 mm Hg (532 daPa), pCO2* = 46 mm Hg (612 daPa), and pH2O* R = 47 mm Hg (625 daPa); (2) partial pressures in the nasopharynx: pN2' = 566 mm Hg (7528 daPa), pO2' = 120 mm Hg (1596 daPa), pCO2' = 27 mm Hg (359 daPa), and pH20' = 47 mm Hg (625 daPa); (3) a middle-ear gas space of 2 x 10(-5) m3; (4) an absorption rate for nitrogen, when the partial pressure difference is 1 atm, of 3 x 10(15) molecules per second; and (5) mucosal absorption rates for oxygen and carbon dioxide 1.8 and 34 times larger, respectively, than for nitrogen.     

The significance of negative middle ear pressure

An increasing body of experience is defining the value of the impedance bridge for the detection and diagnosis of otologic disorders. In this study the audiometric status of 1,133 ears is correlated with the tympanometric configuration and middle ear pressure. It is noted that the air-bone gap systematically increases as the middle ear pressure decreases from 0 to — 400 mm H₂O. Mildly negative middle ear pressure (Jerger's Type A Tympanogram) produces air-bone gaps statistically greater than at atmospheric pressure. These data demonstrate the magnitude of the adverse effect of negative middle ear pressure upon middle ear auditory function.     

Localization of endotoxin in the inner ear following inoculation into the middle ear

Sensorineural hearing loss is known to be a significant sequela of otitis media (OM). The pathophysiology of such hearing loss in OM is thought to be due to transmission of toxins and other bacterial products through the round window membrane, damaging the hair cells of the basal turn of the cochlea. Other routes, such as those involving the oval window, blood vessels and lymphatics, may also be involved. The purpose of this study was to elucidate the routes from the middle ear cavity to the inner ear and also the distribution pattern of endotoxin in the inner ear after injection of fluorescence-labelled endotoxin into the tympanic cavity and detection of fluorescence in the cochleae, vestibular end organs and facial nerves. This fluorescence was far more intense in the lower turns of the cochlea. These findings suggest that endotoxin can reach the inner ear by various routes, e.g. the round window, blood vessels or lymphatics, and/or interscala exchange, resulting in a disturbance not only of the cochlea but also of the vestibular end organs.     

The cell-mediated response of the guinea pig's middle ear

In this project, we studied the cell-mediated response of guinea pig's middle ear. The specific objective was to characterize rejection of skin grafts on the back (allo- and iso-grafts) after primary stimulation (iso- or allo-) in the ear or on the back. The method used was the mixed lymphocyte response with and without phytohemagglutinin (PHA). Preliminary results showed that the middle ear is able to mount a normal immune response, both locally and systemically. Such basic studies will help us to understand the otologic immune response as a whole and may shed some light on the immune phenomena observed in middle ear transplantations.