Juliane Banks

Repair of the tympanic membrane with urinary bladder matrix

To test urinary bladder matrix (UBM) as a potential treatment for tympanic membrane (TM) healing and regeneration.

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.

Eustachian tube function in young children without a history of otitis media evaluated using a pressure chamber protocol.

Abstract Conclusions: Protocol limitations were identified and accounted for in the analysis. Percent gradient equilibrated (PGE) was affected by driving gradient direction in a similar manner to other efficiency measures. A finer resolution of possible age-related changes in eustachian tube opening efficiency is expected with the application of more sophisticated statistical models to the complete dataset at study end. Objective: To report the results of an interim analysis for an ongoing study designed to characterize the age-related changes in eustachian tube opening efficiency measured using a pressure chamber protocol in children without a history of middle ear disease. Methods: To date, 41 children aged 3 years without a history of otitis media have been enrolled in a longitudinal study of the age-related changes in eustachian tube function and evaluated at yearly intervals between 3 and 7 years of age. Eustachian tube opening efficiency, the percent of the applied pressure gradient equilibrated by swallowing, was measured by repeat tympanometry during a pressure chamber protocol. Data (120 tests) were analyzed using an ANOVA with variance partitioned by age (3 through 6 years), gradient direction (positive/negative), and ear (left/right). Results: PGE was higher for left ears and positive driving gradients, but was not different among age groups.

Rate of nitrous oxide exchange across the middle ear mucosa in monkeys before and after blockage of the mastoid antrum.

OBJECTIVES We tested the hypothesis that mastoid volume buffers the rate of change in middle ear pressure caused by transmucosal, inert gas exchange. STUDY DESIGN Twelve monkeys were randomly assigned to group 1 or group 2. Right ears of group 1 had sham surgery and of group 2 had obstruction of the mastoid antrum. Before and after surgery, the time constant for transmucosal N(2)O exchange was estimated from N(2)O breathing experiments. The hypothesis predicts that the postoperative time constant measured for right ears of group 2 but not group 1 is greater than that measured before surgery. RESULTS Mastoid antrum block significantly decreased right middle ear volume but did not affect the time constant for transmucosal N(2)O exchange. CONCLUSION A mastoid gas-reserve function is not supported by the experimental data. SIGNIFICANCE These results for monkeys and the theory developed to explain the effect of mastoid volume on transmucosal inert gas exchange suggest that the results for previous experiments in humans interpreted as evidencing a mastoid gas-reserve function are consistent with alternative explanations.

Directional asymmetry in the measured nitrous oxide time constant for middle ear transmucosal gas exchange.

Objectives: Simple, 2-compartment mathematical models of middle ear (ME) transmucosal gas exchange reproduce observed ME pressure behavior. These models require input of an experimentally determined, lumped-parameter exchange constant for each represented gas species. Previous model applications assumed directional asymmetry for those parameters, which has not been experimentally validated. Methods: As a surrogate for the inert gas nitrogen (N2), for which exchange is too slow to be measurable, the nitrous oxide (N2O) transmucosal exchange constant for 16 ears of 8 monkeys was measured for positive and negative ME blood N2O gradients. Results: The paired exchange constants for each ear were highly correlated, but the ME-blood/blood-ME exchange constant ratio was approximately 13. Modeling shows this asymmetry to depend on the value of the arterial-venous/arterial-ME ratio, a variable in the exchange constant for perfusion-limited gases. Conclusions: These results support an asymmetric rate of transmucosal N2O and, by extension, N2 exchange for the ME. Because the primary controlling parameter for ME pressure behavior in the absence of eustachian tube opening is the rate of transmucosal N2 exchange, this effect needs to be incorporated into the simple 2-compartment exchange models for predictive accuracy. The gradient ratio dependence suggests that parameter-free modeling may require treating the ME mucosa as having a distributed gradient for certain gas species.

Middle ear gas exchange in the air phase

Objective - The rate of gas exchange between the tympanum and mastoid is important for middle ear pressure regulation. The best-studied model of middle ear pressure regulation is the cynomolgus monkey. The aim of this study was to determine the time required for the equilibration of tympanum and mastoid partial pressures for two inert gases, argon and helium, in cadaveric cynomolgus monkey middle ears. Material and Methods - In separate experiments on 5 air-dried temporal bones from monkeys, helium or argon was introduced into the tympanum to bring the total pressure to 300 mmH₂O above ambient and the partial pressures of a ll relevant gases in the tympanum and mas to id were measured using mass spectrometry at 0, I, 3, 5, 10 or 15 min. Results - The average ratios of tympanum:mastoid partial pressure at 0 min were 4.7±1.9 and 3.9±2.0 for helium and argon, respectively. By 5 min those ratios had decreased to 1.2±0.2 and 1.1±0.1, respectively, suggesting approximate equilibrium. Conclusions: Air-phase gas exchange between the tympanum and mastoid is rapid. Partial-pressure gradients across the middle ear will be dissipated quickly and a re not an important contributor to middle ear pressure regulation in the studied model.

Transmucosal O2 and CO2 exchange rates for the human middle ear.

OBJECTIVE Estimate the transmucosal CO(2) and O(2) rate-constants for adult middle ears (MEs). METHODS Ten adults with healthy MEs had a unilateral myringotomy. A custom-fitted acrylic mold with a valved line to a mass spectrometer (MS) and central tube coupled to a 3-way valve and connected to a pressure transducer (the probe) was sealed with adhesive glue within the ipsilateral ear-canal. A second 3-way valve was attached to the probe valve, a flow-regulated tank gas source and paired syringes. Volumes of the ME and probe were measured. On sequential days, the probe+ME was washed for 15-min with 6% O(2), Balance N(2) and 25% O(2), 6% CO(2), Balance N(2) to create transmucosal CO(2) and O(2) gradients, respectively. After washing, the probe+ME was isolated from the gas source, and baseline and 10-min gas samples were obtained for MS analysis of gas partial-pressures. The rates of change in ME CO(2) and O(2) pressures were divided by their established transmucosal gradients to yield CO(2) and O(2) rate-constants. RESULTS The average (±STD) transmucosal CO(2) and O(2) rate-constants were 0.062 ± 0.034 (N=10, range: 0.032-0.119) and 0.011 ± 0.009 (N=8, range: 0.002-0.032)mmHg/min/mmHg, respectively. The average half-life for the CO(2) and O(2) gradient was 11.1 and 61.6 min. The average CO(2):O(2) rate-constant ratio was 8.1 ± 4.0 (N=8, range: 3.6-14.6). CONCLUSIONS For adult human MEs, transmucosal CO(2) exchange is rapid and much faster than transmucosal O(2) exchange. The estimated CO(2)/O(2) rate-constant ratio for the human ME is not consistent with that predicted for diffusion-limited gas exchange across a water-based barrier.

Multimodal Assessment of Normal Eustachian Tube Function

Objective: Evaluate normal human Eustachian tube (ET) function during swallowing and other maneuvers that open the ET using a variety of modalities including EMG of the Tensor veli palatini (mTVP), Levator veli palatini (mLVP), and submental muscles, videoendoscopy, and sonotubometry; and compare these results with ET function tests in a pressure chamber. Method: In adult volunteers surface electrodes and needle EMG electrodes were placed into the mTVP and mLVP muscles. A 45° telescope was used to video-record the ET orifice, and sonotubometry recorded the ET openings. A subset was also tested in a pressure chamber. Results: Seventeen subjects were enrolled. EMG data was recorded from both the mTVP and mLVP in 15 subjects but from only one muscle in 2 subjects. In 9 subjects ET functions tests were performed in the pressure chamber. Video recording of ET opening was consistent with the EMG activity and ET openings by sonotubometry. mTVP activity had a shorter duration but a greater amplitude than mLVP activity. mLVP activity occurs before that of mTVP and the submental muscle group. Tests conducted in the pressure chamber demonstrated ET function consistent with the multimodal test results. Conclusion: Multimodal assessment of ET openings by monitoring the EMG of the paratubal and submental muscles, video recordings of the ET, and sonotubometry with ET function testing in the pressure chamber in adult volunteers is a novel and promising method for expanding our knowledge of middle ear physiology and pathophysiology.