Accuracy of CO2 conductance predicted using a morphometric model of the middle ear mucosa.

CONCLUSION: These results hold promise that morphometric analysis can be used to generate transMEM (middle ear mucosa) gas conductance estimates for MEM geometries representative of the shift from healthy to pathologic states (e.g. increased MEM thickness and capillary density). OBJECTIVES: Novel strategies to treat otitis media with effusion require a better understanding of how MEM geometry affects gas transport. Earlier studies developed techniques to empirically measure transMEM gas conductance and to estimate conductance using morphometric models of MEM geometry. We used chinchillas to determine the correspondence between experimentally measured transMEM CO2 conductance and that predicted by morphometric study of the MEM. MATERIALS AND METHODS: TransMEM CO2 conductance was measured unilaterally in 10 chinchillas; the animals were killed and the ME was removed and processed for morphometric analyses of MEM geometry. RESULTS: The average measured and estimated transMEM CO2 conductances were 4.87+/-2.30 x 10-10 and 1.75+/-0.29 x 10-10 mol/s/mmHg, respectively. The magnitude and direction of the estimate error were similar for all ears, suggesting a fixed, negative bias to the estimate. A theoretically consistent source for this bias was identified as the representation of the true diffusional length within a 3-D geometry using a 2-D modeling platform. Best estimate correction for this effect based on available data significantly reduced the estimate bias.

Sensitivity and specificity of eustachian tube function tests in adults.

IMPORTANCE: The study demonstrates the utility of eustachian tube (ET) function (ETF) test results for accurately assigning ears to disease state. OBJECTIVES: To determine if ETF tests can identify ears with physician-diagnosed ET dysfunction (ETD) in a mixed population at high sensitivity and specificity and to define the interrelatedness of ETF test parameters. DESIGN, SETTING, AND PARTICIPANTS: Through use of the forced-response, inflation-deflation, Valsalva, and sniffing tests, ETF was evaluated in 15 control ears of adult subjects after unilateral myringotomy (group 1) and in 23 ears of 19 adult subjects with ventilation tubes inserted for ETD (group 2). Data were analyzed using logistic regression including each parameter independently and then a step-down discriminant analysis including all ETF test parameters to predict group assignment. Factor analysis operating over all parameters was used to explore relatedness. EXPOSURES: ETF testing. MAIN OUTCOMES AND MEASURES: ETF parameters for the forced response, inflation-deflation, Valsalva, and sniffing tests measured in 15 control ears of adult subjects after unilateral myringotomy (group 1) and in 23 ears of 19 adult subjects with ventilation tubes inserted for ETD (group 2). RESULTS: The discriminant analysis identified 4 ETF test parameters (Valsalva, ET opening pressure, dilatory efficiency, and percentage of positive pressure equilibrated) that together correctly assigned ears to group 2 at a sensitivity of 95% and a specificity of 83%. Individual parameters representing the efficiency of ET opening during swallowing showed moderately accurate assignments of ears to their respective groups. Three factors captured approximately 98% of the variance among parameters: the first had negative loadings of the ETF structural parameters; the second had positive loadings of the muscle-assisted ET opening parameters; and the third had negative loadings of the muscle-assisted ET opening parameters and positive loadings of the structural parameters. CONCLUSIONS AND RELEVANCE: These results show that ETF tests can correctly assign individual ears to physician-diagnosed ETD with high sensitivity and specificity and that ETF test parameters can be grouped into structural-functional categories.

Relationship between the electromyographic activity of the paratubal muscles and eustachian tube opening assessed by sonotubometry and videoendoscopy.

OBJECTIVE: To determine the role played by the tensor veli palatini and levator veli palatini muscles (mTVP and mLVP, respectively) in eustachian tube (ET) opening. DESIGN: Prospective study. SETTING: Research laboratories at a tertiary care hospital. PATIENTS: Fifteen healthy adults with normal middle ears and documented ET openings. INTERVENTIONS: Submental and ground surface electrodes were placed. After anesthetizing and decongesting the nasal passages, paired electromyographic needle electrodes were inserted into both the mTVP and mLVP on the test side. A microphone was placed into the ipsilateral ear canal and the probe from a sound generator was introduced into the opposite nostril. A 45° telescope was used on the test side to video-record the soft palate and ET movements while the individual swallowed. MAIN OUTCOME MEASURES: Concurrent recordings of the ET openings by sonotubometry, the electromyographic activity for the LVP, TVP, and submental muscles, and video of the nasopharyngeal orifice of the ET during swallowing. RESULTS: During swallowing, the median peak amplitude and duration of ET openings by sonotubometry were 30.6 mV and 196 milliseconds, respectively. For the mLVP and mTVP, the median peak amplitudes were 0.33 and 0.82 mV, and peak durations were 131 and 85 milliseconds, respectively. The mean onsets of muscle activity referenced to the sonotubometry peak amplitude were -0.28, -0.24, and -0.14 milliseconds for the mLVP, mTVP, and submental muscles, respectively. Video recording of ET movements were consistent with the timing of these events. CONCLUSIONS: The mTVP activity had a shorter duration but greater amplitude than the mLVP activity and was associated with peak ET opening by sonotubometry. The mLVP activity occurred before that of the mTVP, the submental muscle group, and peak ET opening. The mLVP contractions were associated with movements of the soft palate, anterior ET orifice, and rotation of the ET cartilage.

In vivo measurement of O(2) and CO(2) gas exchange across the human tympanic membrane.

CONCLUSION: The hypothesis that the human tympanic membrane (TM) is permeable to CO(2) and O(2) at physiologic pressure gradients is supported but additional experiments need to be done to validate this methodology. OBJECTIVE: Gas exchange between the middle ear and adjacent compartments determines the trajectory of middle ear pressure change. Little information is available regarding the permeability of the TM to physiological gases. This study aimed to determine in vivo if the human TM is permeable to O(2) and CO(2) at physiologic transTM pressure gradients. SUBJECTS AND METHODS: An ear canal (EC) probe (ECP) constructed from a custom-fitted acrylic body, a glass capillary tube enclosing an oil meniscus to maintain ambient ECP + EC pressure and a silica glass microtube linked to a mass spectrometer (MS) for measuring gas composition was hermetically sealed within one EC in each of 15 adults. ECP + EC volume was measured and gas samples were taken at 10 min intervals for 1 h. Epinephrine (1:100 000) was applied topically to the ipsilateral TM to decrease blood flow and the experiment was repeated. The ECP + EC pressures of O(2) (32 AMU) and CO(2) (44 AMU) were regressed on time and the slope divided by the predicted transTM partial-pressure gradients to yield estimates of transTM O(2) and CO(2) conductance. RESULTS: Consistent with expectations for transTM gas exchange, ECP + EC O(2) decreased and CO(2) increased during the experiments. CO(2) increase was faster after application of epinephrine to the TM. The ratio of O(2)/CO(2) conductances was not consistent with the gas exchange through a primarily water or lipid diffusion barrier.