Higher rates of pressure decrease in inflamed compared with noninflamed middle ears

Presentation and eustachian tube function test results in children evaluated at a specialty clinic

OBJECTIVES/HYPOTHESIS

Interest in eustachian tube (ET) dysfunction (ETD) has increased with the recent Food and Drug Administration approval of a new device for balloon dilation of the ET (BDET) in adults. However, children have been receiving BDET treatment with ET-specific or sinus balloons around the world and off-label in the United States for years. It is important, therefore, to understand the manifestations of and methods to verify ETD in children.

STUDY DESIGN

Retrospective cross-sectional study.

METHODS

This is a retrospective study of clinical presentations and results of ET function (ETF) tests in children referred to the ETD clinic. An otorhinolaryngology exam, nasopharyngeal videoendoscopy of the ET orifices during swallow and maneuvers, and ETF tests, including inflation deflation, forced response test, and pressure chamber tests, were performed as applicable.

RESULTS

Data for 30 children aged 6.2 to 17.3 years (mean = 12.9 ± 2.8 years) were analyzed. Of 60 ears, 19 (31.7%) had an intact tympanic membrane (TM), 16 (26.7%) had a patent and two had a blocked ventilation tube, and 23 (38.3%) had a TM perforation. Endoscopy of the nasopharynx revealed a large amount of secretions in 19/45 (42.2%); ET orifices and mucosal inflammation in 22/45 (48.8%); a large amount of adenoid tissue in the fossa of Rosenmuller was noted in 21/45 (46.7%). ETF tests revealed abnormal active function in 43/54 ears (79.6%) and abnormal passive function in 40/54 ears (74.1%).

CONCLUSIONS

ETD in children is often associated with residual or regrowth of adenoids and inflammation. Caution should be taken assigning a uniform phenotype and treatment prior to thorough evaluation and testing.

LEVEL OF EVIDENCE

4 Laryngoscope, 129:1218-1228, 2019.

Oral pseudoephedrine decreases the rate of transmucosal nitrous oxide exchange for the middle ear

OBJECTIVES/HYPOTHESIS

Determine if oral treatment with a vasoconstrictor decreases the blood to middle ear exchange rate of the perfusion-limited gas, nitrous oxide (N2O).

STUDY DESIGN

Randomized, double-blind, crossover study.

METHODS

Ten adult subjects with and 10 without past middle ear disease completed paired experimental sessions, identical except for oral treatment with either pseudoephedrine hydrochloride or lactose placebo. At each session, subjects were fitted with a nonrebreathing mask and breathed room air for 20 minutes (acclimation period), 50% N2O:50% O2 for 20 minutes (experimental period), and 100% O2 for 10 minutes (recovery period). Throughout, heart rate, blood pressure, and O2 saturation were monitored, and bilateral middle ear pressures were recorded by tympanometry every minute. The primary outcome was the slope of the middle ear pressure-time function for the experimental period, which estimates the volume N2O exchange rate. Using repeated measures analysis of variance, the effects of group (disease history), treatment (active vs. placebo), and period (1 vs. 2) on the recorded vital signs, and of group, treatment, and ear (left/right) on the middle ear pressure-time slope were evaluated for statistical significance.

RESULTS

Statistically significant effects of period on O2 saturation (period 2 > period 1) and of treatment on heart rate (active > placebo) were documented. Only treatment was statistically significant for the middle ear pressure-time slope, with a shallower slope characterizing the active treatment session.

CONCLUSIONS

The volume exchange rate across the middle ear mucosa of perfusion-limited gases can be modulated pharmacologically. Theoretically, similar drugs can be used to reduce the requisite eustachian tube opening efficiency for adequate middle ear pressure regulation.

LEVEL OF EVIDENCE

1b.

The mastoid as a functional rate-limiter of middle ear pressure change

INTRODUCTION

The physiological function of the mastoid air cell system (MACS) with respect to middle ear (ME) pressure-regulation remains controversial because predictive mathematical models and experimental data to formulate and test hypotheses are lacking.

OBJECTIVE

A mathematical description of MACS volume effects on the rate of ME pressure change is presented; the agreement between published data and model prediction is examined for consistency with the hypothesis that the MACS acts as a functional rate-limiter of ME pressure change, and an explanation for the relationship between MACS volume and otitis media is discussed.

METHODS

The mathematical description shows that the value of a single, free parameter, termed the "MACS buffering efficiency" (M) determines if MACS volume affects the rate of ME pressure change caused by diffusive gas exchange. The MACS serves no rate-limiting function for M=0, acts as a gas sink for M>1 and acts as a gas reserve (rate-limiter) for M<1.

RESULTS

Fitting the model equation to published adult human data yielded an estimate for M of 0.2. This implies that larger MACS volumes are associated with lesser rates of change in ME pressure caused by diffusive gas exchange and lesser required frequencies of effective Eustachian tube openings to maintain near ambient ME pressures.

CONCLUSION

If well-controlled studies confirm M<1 for children and adults, larger MACS volumes will increase the time required to develop sufficient ME underpressures to cause otitis media by hydrops ex vacuo during transient or prolonged periods of Eustachian tube dysfunction.

Middle ear gas loss in inflammatory conditions: The role of mucosa thickness and blood flow

Several middle ear (ME) pathologies are associated with ME gas deficit. These include in particular the chronic otitis media diseases that are associated with inflammation (hence, increased ME mucosal blood flow) and/or reduced Eustachian tube (ET) function. The present study models the trans-mucosal gas exchange in normal and inflamed middle ears of rats. The model evaluates the role of the gas diffusion path in the ME mucosa using mucosa thickness as its index and the role of the mucosal blood flow rate on ME gas economy in order to compare between normal and inflamed MEs. An experimental method employing ME gas volume changes at constant pressure due to trans-mucosal gas exchange, and blood gas values from the literature, was used in anaesthetized rats to corroborate the model. Mucosa thickness was measured as an index of the gas diffusion path between the ME space and the ME circulation. ME inner surface area was estimated from its measured gas volume. Inflammation was inflicted by applying lipopolysaccharide (LPS) into one ear. The contralateral ear served as control. ME gas volume decreased significantly faster with time (p=0.02) in inflamed ears (-0.107 microL min(-1) +/- 0.034 S.D., n=10) versus control ears (-0.067 microL min(-1) +/- 0.036 S.D., n=10). Mucosa thickness was significantly thicker in inflamed ears (48.4 microm +/- 11.0 S.D.) versus controls (20.5 microm +/- 10.1 S.D.). The mathematical model, the experimental results, and the blood gas values were used to estimate the relative effective mucosal blood flow rate. The model predicts that in spite of almost doubling mucosa thickness in LPS treated ears, the increased gas loss in inflamed ears may be explained by increased mucosal blood flow rate. We suggest that the ability to estimate ME blood flow as obtained by applying the model to the measurements, is relevant to medical management of inflamed ME.

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.

Behaviour of middle ear cleft mucosa during inflammation: histo- morphometric study

CONCLUSION

This histo-morphometric study shows a significant reduction in the distance between the blood vessel's centre and the basal membrane of the middle ear cleft mucosa during inflammatory process. This could suggest that gaseous exchange is faster and more abundant in inflamed mucosa. The distance is significantly shorter in the postero-superior compartment of the middle ear cleft, possibly favouring a specific gas exchange function.

OBJECTIVES

The aim was to try to understand the morphologic changes that occur when the middle ear cleft mucosa suffers from chronic inflammation.

MATERIALS AND METHODS

Light microscopic computerized morphometry was used to measure the distance between the centre of the blood vessels and the basement membrane of the middle ear cleft mucosa.

RESULTS

In inflammation, the distance from blood vessel to mucosa is reduced in all five regions of the middle ear cleft. This distance is statistically the shortest in the postero-superior compartment of the middle ear cleft.

Studies in otitis media: Children's Hospital of Pittsburgh-University of Pittsburgh progress report--2004

OBJECTIVES/HYPOTHESIS

The present Progress Report has summarized the key otitis media clinical trials and laboratory studies conducted since 1969 by investigators at the Children's Hospital of Pittsburgh-University of Pittsburgh (Pittsburgh, PA).

STUDY DESIGN

Review.

METHODS

Included in the discussion are the following: 1) studies of the epidemiology and risk factors; 2) anatomy and pathology of the eustachian tube-middle ear from human temporal bone histopathological specimens; 3) physiology and pathophysiology of the eustachian tube-middle ear in humans and animal models; 4) pathogenesis; 5) otitis media in special populations (e.g., patients with cleft palate, Native Americans, patients with Down syndrome); 6) microbiology; 7) diagnosis; 8) outcomes of randomized clinical trials that evaluated efficacy of nonsurgical and surgical methods of treatment and prevention; 9) studies of certain complications and sequelae (e.g., effect of middle-ear effusion on hearing, early child development, and the vestibular system; chronic suppurative otitis media). Also included are relevant summary tables and 256 references.

Barotrauma during air travel: predictions of a mathematical model

Middle ear barotrauma during flight is a painful disorder experienced by passengers who cannot properly regulate their middle ear pressure in response to the changing cabin pressures during ascent and descent. Previous reports emphasized the important role of poor eustachian tube function in disease pathogenesis but paid little attention to other moderating factors. Here we describe a mathematical model of middle ear pressure regulation and simulate the pressure response to the changes in cabin pressure experienced over typical flights. The results document buffering mechanisms that decrease the requisite efficiency of active, muscle-assisted eustachian tube opening for disease-free flight. These include the relative difference between destination and departure elevations and the ratio of maximum tympanic membrane volume displacement to middle ear volume, where greater absolute values require lesser efficiencies for disease-free flight. Also, the specific type of functional deficit is important since ears with a completely obstructed eustachian tube can be less susceptible to barotrauma than those with a eustachian tube that passively opens but fails to dilate in response to muscle activity. These buffering systems can explain why some children and adults with poor eustachian tube function do not experience middle ear barotrauma.

Middle ear inflation for diagnosis and treatment of otitis media with effusion

An adult (18 years), healthy, male subject with persistent bilateral middle ear (ME) underpressure and a history of recurrent otitis media into his teen years was identified. The response of his MEs to air inflation was evaluated and showed an immediate pressure increase after a Valsalva maneuver followed by a rapid pressure drop to approach the pre-inflation levels. That response is consistent with the presence of ME effusion, which was not diagnosed by otoendoscopy or tympanometry, but was visualized bilaterally within the mastoid regions using magnetic resonance imaging (MRI). The patient was treated for 25 days with ME inflation (3/day) and then re-examined. On each treatment day, he recorded his ME pressure using tympanometry before and after one inflation maneuver. The patient's compliance with the treatment protocol was high, and successful gas transfers were documented on most days. Over the course of treatment, pre-inflation ME pressure became more normal bilaterally. When compared to the pre-treatment test, the post-treatment inflation test showed a similar rate of ME pressure decrease, but significantly higher terminal pressures. On follow-up but not during the pre-treatment period, discrete changes in ME pressure attributable to ET openings were noted during test sessions. MRI documented lesser amounts of effusion in the mastoid, but not complete disease resolution. The significance of these observations to the design of a well controlled clinical trail of ME inflation as a treatment for otitis media is discussed.