Influence of surface condition of mucosa of eustachian tube on tubal compliance

Eustachian Tube Function

The fibrocartilaginous eustachian tube is part of a system of contiguous organs including the nose, palate, rhinopharynx, and middle ear cleft. The middle ear cleft consists of the tympanic cavity, which includes the bony eustachian tube (protympanum) and the mastoid gas cells system. The tympanic cavity and mastoid gas cells are interconnected and allow gaseous exchange and pressure regulation. The fibrocartilaginous eustachian tube is a complex organ consisting of a dynamic conduit with its mucosa, cartilage, surrounding soft tissue, peritubal muscles (ie, tensor and levator veli palatine, salpingopharyngeus and tensor tympani), and superior bony support (the sphenoid sulcus).

Investigation of middle ear pressure changes during prone position under general anesthesia without using nitrous oxide

PURPOSE

The effects of different body positions on the middle ear were reported in several studies, but there are no data about the effects on patients under general anesthesia. The aim of this study is to determine the effect of prone position on middle ear pressure (MEP) during general anesthesia without using nitrous oxide.

METHODS

Twenty patients under general anesthesia during prone position were included in the study. The performed anesthesia method was the same for all patients. Remifentanil was used for analgesia instead of nitrous oxide. MEPs were measured 5 times with a middle ear analyzer: before induction (BI), after intubation (AI), after turned to the prone position (PP1), at the end of the prone position (PP2), and after returned to the supine position (SP). Duration of prone position was also recorded.

RESULTS

Of the 20 patients were 11 women and 9 men with a 49 ± 13 mean age. BI-AI, AI-PP1, PP1-PP2, and PP2-SP comparisons of both MEPs were statistically significant (P < 0.0001). Right mean MEPs were BI, -1 ± 23 daPa; AI, 41 ± 51 daPa; PP1, 124 ± 76 daPa; PP2, 152 ± 59 daPa; and SP, 63 ± 29 daPa; whereas left mean MEPs were BI, -24 ± 55 daPa; AI, 28 ± 34 daPa; PP1, 132 ± 67 daPa; PP2, 162 ± 48 daPa; and SP, 70 ± 89 daPa. Significant increases were detected at the start and continuation of the prone position. The mean duration of prone position was 98 ± 51 per minute.

CONCLUSIONS

The significant MEP increases during the prone position under general anesthesia depend on a number of reasons. Among them are inhaler agents, pressure changes in mucosal blood vessels due to venous congestion, and the mastoid bone volume. Further researches are required to determine and explain the mechanisms of increase in MEP during prone position.

Effect of exogenous surfactant on ventilatory and clearance function of the rat's eustachian tube

HYPOTHESIS AND BACKGROUND

The Eustachian tube has three important functions with respect to the middle ear: ventilation, clearance, and protection. Surfactants are assumed to be important to maintain these functions. The administration of exogenous surfactant may therefore be effective to improve the function of the Eustachian tube. This randomized, double-blind, placebo-controlled study was designed to investigate the effect of exogenous surfactant on the function of the Eustachian tube in rats.

MATERIALS AND METHODS

Exogenous surfactant was administered into the middle ear of 10 otologically healthy rats, and 10 other rats received placebo. The effect on the opening and closing pressure (passive ventilatory function) and the dye clearance time (clearance function) of the rat's Eustachian tube was measured.

RESULTS

A significant decrease in the opening pressure was seen after the administration of surfactant. Both surfactant and placebo caused an increase in the closing pressure. A serious disturbance of the dye clearance time was induced in 13 rats, and the test failed in 1 rat. In the remaining 6 rats, no significant differences in the dye clearance time were observed between the two groups.

CONCLUSIONS

Exogenous surfactant decreased the closing forces of the Eustachian tube even in otologically healthy rats. No significant effect on the mucociliary clearance was observed, but this may have resulted from the small number of rats. Additional randomized, double-blind, placebo-controlled trials should be conducted to determine the clinical relevance of these changes and to further assess the effect of surfactant on the function of the Eustachian tube.

Effect of surface tension and surfactant administration on Eustachian tube mechanics

Development of otitis media has been related to abnormal Eustachian tube (ET) mechanics. ET is a collapsible tube that is periodically opened to regulate middle ear pressure and to clear middle ear fluid into the nasopharynx. The ability to perform these physiological functions depends on several mechanical properties, including the ET's opening pressure (P(open)), compliance (ETC), and hysteresis (eta). In this study, a previously developed modified force-response protocol was used to determine ET mechanical properties after experimental manipulation of the mucosal surface condition. Specifically, these properties were measured in the right ear of six cynomologous monkeys under baseline conditions after "washing out" the normal ET mucous layer and after instillation of a pulmonary surfactant, Infasurf. Removal of the normal mucosa did not significantly alter P(open) but did result in a decrease in ETC and eta (P < 0.05). Treatment of the mucosa with Infasurf was effective in reducing P(open) and increasing both ETC and eta to baseline values (P < 0.05). These results indicate that the mucosa-air surface tension can affect the overall ETC and eta properties of the ET. In addition, this study indicates that surfactant therapy may only be beneficial in patients with rigid or inelastic ETs (large P(open) and low ETC and eta).

Measurement of the viscoelastic compliance of the eustachian tube using a modified forced-response test

OBJECTIVES

Eustachian tube compliance (ETC) was suggested to be an important determinate of function. Previous attempts to quantify ETC used summary measures that are not clearly related to the physical properties of the system. Here, we present a new method for measuring ETC that conforms more closely to the engineering definition of compliance.

METHODS

The forced response test was modified to include oscillations in applied flow after the forced tubal opening. Pressure and flow were recorded during the standard and modified test in 12 anesthetized cynomolgus monkeys. The resulting pressure-flow, hysteresis loops were compared with those predicted by a simple fluid-structure model of the Eustachian tube with linear-elastic or viscoelastic properties. The tubal compliance index (TCI) and a viscoelastic compliance (C(v)) were calculated from these data for each monkey.

RESULTS

The behavior of a viscoelastic, but not a linear elastic model accurately reproduced the experimental data for the monkey. The TCI and C(v) were linearly related, but the shared variance in these measures was only 63%.

CONCLUSIONS

This new method for measuring ETC captures all information contained in the traditional TCI, but also provides information regarding the contribution of wall viscosity to Eustachian tube mechanics.

Variability of Eustachian tube function in children with secretory otitis media. Evaluations at tube insertion and at follow-up

OBJECTIVE

Despite the variable clinical course of diseases related to Eustachian tube function, the variability of tubal function has been less focused than outcomes of single tests. This study aimed to compare the passive and active tubal function and its variability in children with secretory otitis media (SOM) at tube insertion and at follow-up.

METHOD

Thirty-eight ears in 19 children aged 4-10 years (mean 7.0 years) with long-standing SOM were examined 4-6 h after tube insertion, at 4 months and at 9 months. The pressure in the middle ear and the nasopharynx were recorded while performing (1) forced opening test, (2) equalization of +100 and -100 daPa, (3) Valsalva test, and (4) sniff test. The procedure was repeated after 30 min. Relationships were analyzed by uni- and multi-variate analysis of variance.

RESULTS

From tube insertion to 4 months, the mean forced opening pressure increased from 282+/-128 to 355+/-153 daPa (P<0.01), and the mean closing pressure from 91+/-51 to 126+/-82 daPa (P<0.01). There was no further change at 9 months. Female gender, serous effusion (in contrast to mucoid), and more than three previous episodes of acute otitis media were related to higher opening and closing pressures. At tube insertion, 60% and 16% equalized +100 and -100 daPa, respectively, and 28% succeeded in performing Valsalva inflation. The sniff test was positive in 32%, indicating a closing failure. These rates did not change significantly over time. For individual ears, outcomes of all tests varied considerably when retested after 30 min; P(o) changed by +/-12% and P(c) by +/-26%, and 9-29% of the ears changed from a positive to negative response, or vice versa, in the equalization, Valsalva, and sniff tests.

CONCLUSIONS

The unexpected finding of weaker closing forces at the day of tube insertion and increased tubal resistance at follow-up might be ascribed to changes in the muco-adhesive forces related to the disease and tube treatment. The pronounced intra-individual variability of test outcomes indicates that tubal function is dynamic and variable in ears prone to SOM, which emphasizes that results of single tubal function tests have very low prognostic value.

Influence of the upper respiratory tract infection on tubal compliance in children with otitis media with effusion

To clarify the influence of inflammation on tubal compliance in children with otitis media with effusion (OME), we investigated the change of compliance of the ET by upper respiratory tract infection (URTI) in 18 children (23 ears) with OME using the forced response test. The tubal compliance index (TCI), the ratio of passive tubal resistances at two different airflow rates, significantly increased during URTI represented by acute rhinitis or paranasal sinusitis in comparison with non-URTI periods (paired t-test: t = 4.14, p < 0.001). In nine ears, the TCI could be followed for some months after that, during which the children had had URTI several times. A clear reproducible correlation was found between the presence or absence of URTI and the TCI values; the TCI values increased again during URTI and decreased after the URTI periods. These results seemed to support our hypothesis that compliance of the ET may depend not only on the property of the cartilaginous framework of the ET but also upon the mucosal condition.