Prediction of successful hearing aid treatment in first-time and experienced hearing aid users: Using the International Outcome Inventory for Hearing Aids.

OBJECTIVE: Primarily to understand whether clinically relevant factors affect the International Outcome Inventory (IOI-HA) scores and to examine if IOI-HA scores improve when renewing the hearing aids (HA) for experienced users. Secondly, to estimate the overall HA effectiveness using the IOI-HA. DESIGN: A prospective observational study. STUDY SAMPLE: In total, 1961 patients with hearing loss were included. All patients underwent a hearing examination, were fitted with HAs, and answered the IOI-HA. Factor analysis of IOI-HA separated the items into a Factor 1 (use of HA, perceived benefits, satisfaction, and quality of life) and Factor 2 (residual activity limitation, residual participation restriction and impact on others) score. RESULTS: Degree of hearing loss, word recognition score, motivation, HA usage time, tinnitus, asymmetry, and sex were significantly associated with total IOI-HA, Factor 1, or Factor 2 scores. The seven IOI-HA items increased on average by 0.4 (p < 0.001) when renewing HAs. The total median IOI-HA score at follow-up was 29 (7) for experienced (n = 460) and first-time users (n = 1189), respectively. CONCLUSIONS: Degree of hearing loss, word recognition score, motivation, tinnitus, asymmetry, and sex may be used to identify patients who require special attention to become successful HA users.

The influence of endotoxin upon middle ear fibroblasts cultured in normal middle ear gas and atmospheric air.

Otitis media represents a continuum of inflammatory stages frequently in association with bacteria and/or endotoxin. Furthermore, the disease is often treated with insertion of ventilation tubes, which causes hyperoxia relative to the physiological state in the tympanic cavity. The present study was undertaken to quantitate the interaction between endotoxin and relative hyperoxia in cultures of rabbit middle ear fibroblasts incubated in normal middle ear gas and atmospheric air, respectively. Growth was monitored by determination of DNA, cell protein and cell division. The synthetic activity was estimated by collagen production. The antioxidant defense was determined by measuring the intra-and extracellular concentrations of superoxide dismutase (SOD). The results demonstrated that hyperoxia significantly impaired the growth of middle ear fibroblasts, which was compensated for by addition of endotoxin stimulating the growth. The collagen synthesis increased significantly in atmospheric air with a synergistic effect of endotoxin. Hyperoxia induced intracellular SOD formation, while endotoxin tended to reduce the synthesis. Finally, exposure to atmospheric air caused significantly larger amounts of reducing agents extracellularly in cultures without endotoxin compared to endotoxin incubated cultures. It is suggested that endotoxin possess both synergistic and antagonistic potential as regards the effects of relative hyperoxia, and that the interaction between endotoxin and hyperoxia may be an important factor in otitis media.

Tympanometric preconditioning of the tympanic membrane.

Preconditioning is a general biomechanical phenomenon, where tissue characteristics change due to repetitive loading-unloading experiments, resulting in an increased compliance. Increasing compliance by repetitive tympanometric measurements has previously been described and may be related to rate of pressure change during recordings. Presently, 9 tympanometries were performed in a group of normal adults (n = 103 ears) at 4 different rates: 50, 100, 200, and 400 daPa/s. Compliance showed an initial larger increase from trial to trial, tending to reach a steady state during later trials, and the pattern was found identical in all 4 groups. However, stratifying data according to compliance at 1st trial of each ear, the preconditioning effect was found significantly correlated to compliance (P < 0.001), so that low compliance was associated with low preconditioning and vice versa. Stratification also illustrated that, while most ears reached a steady state, some ears with high compliance (> or = 1.04 cm3) did not. In this way identification is possible of tympanic membranes, which are less resistant to pressure loads and therefore may be susceptible to development of retraction pockets. Repeatable measures of compliance with insignificant effect of preconditioning could be obtained after 5 tympanometries, and measures of precision of compliance are reported.

Atmospheric air vs. normal middle ear gas: effects on in vitro growth and collagen synthesis in normal middle ear fibroblasts.

The present study was undertaken to quantitate the effects of atmospheric air and normal middle ear gas on cultured fibroblasts obtained from normal rabbit middle ear mucosa. The cells were exposed to three different gas compositions: 7% O2:5% CO2:88% N2, 21% O2:5% CO2:74% N2, and 75% O2:5% CO2:20% N2. The growth was monitored by measuring the total content of cell protein, the amount of DNA, and the cell division activity. The activity of the synthetic apparatus was determined by the collagen synthesis. For comparison, rabbit skin fibroblasts were grown under identical conditions. The results demonstrated significantly higher replication rate of middle ear fibroblasts at 7% oxygen than at atmospheric air whereas the collagen synthesis was significantly lower at 7%. Furthermore, the responses varied significantly between rabbit middle ear and rabbit skin fibroblasts. Thus the present study substantiates the hypothesis of an influence of atmospheric air on the middle ear mucosa which might be of importance, e.g., in relation to insertion of ventilation tubes or longstanding perforations of the tympanic membrane in otitis media.

Sequelae of secretory otitis media: changes in middle ear biomechanics.

A new method previously introduced investigating the pressure volume relationship of the middle ear system describes dynamic mechanical properties of the system: the variables measured are hysteresis, compliance, and P(ec0) expressing the zero position of the tympanic membrane. The present study investigates the mechanical properties in 69 adolescents treated with ventilation tubes during childhood due to secretory otitis media. The tympanic membranes displayed various degrees of atrophy, sclerosis, and retraction of the pars flaccida. Atrophy was quantitatively related to decreasing hysteresis and increasing compliance, while myringosclerosis showed opposite effects. P(ec0) was significantly lower for the group of former secretory otitis media than for normals (p < 0.001). This reflects a retraction pattern of the tympanic membrane, which may be explained by a low opening pressure of the eustachian tube or previous pressure load of the drum. Signs of retraction were not found by tympanometry. Treatment with ventilation tubes was associated with a dramatic increase of tympanic membrane pathology (66%) compared to untreated ears (12%), as assessed by otomicroscopy (p < 0.001). However, these changes specific to treatment were not found in the corresponding mechanical variables of the middle ear system, as the effects of combined atrophy and myringosclerosis tend to counterbalance.

Biomechanical characteristics of the middle ear system measured by a new method. III: Comparisons with tympanometric measurements.

A new method for studying middle ear mechanics is reported in which we measured ear canal pressure changes due to tympanic membrane volume displacements. One feature of this pressure-volume relationship (PVR) is the determination of dynamic compliance of the middle ear system (MES). We found a significant correlation between dynamic compliance expressed by the PVR and static acoustic compliance by tympanometry. Another feature of the PVR was determination of the mechanical zero position of the tympanic membrane (TM) defined in terms of minimum hysteresis, which correlated significantly with the neutral position of the TM determined by tympanometry, but indicates a retracted position of the TM relative to tympanometry. Finally the hysteresis effect of the MES measured with the PVR was compared and found to fall within the range of peak difference found in bidirectional tympanometric recordings, which is also influenced by phase delay and semi-dynamic conditions.

The biochemical characteristics of the middle ear system measured by a new method. I: Instrumentation.

A frequent finding in patients with earlier otitis media is the sequelae of tympanic membrane atrophy and sclerosis. A major number of these patients nevertheless present with normal audiometric and tympanometric findings. In search of an objective and quantitative description of these pathological changes a new instrument has been developed to measure pressure changes in the ear canal as a function of dynamic tympanic membrane volume displacement. This pressure-volume relationship of the middle ear system expresses non-linear behaviour and hysteresis, which is due to loss of energy under dynamic conditions. Hysteresis can be measured and is here introduced as a new mechanical variable of the middle ear system along with dynamic compliance. Hysteresis is expressed in microJ and compliance in microliter/cmH2O. Analytical measurements of the instrument were found to be small compared with clinical values (< 2.8%). This paper will be succeeded by another study presenting the clinical application of the method and a normal material.

The biomechanical characteristics of the middle ear system measured by a new method. II: Clinical application and normal material.

An instrument for measuring the pressure-volume relationship of the middle ear system was introduced earlier. This paper describes the practical application of the instrument and presents a normal material of 45 healthy young adults. Reflecting a slight increase in pressure in the ear canal during the measuring procedure, a series of curves is obtained, each representing a different position of the tympanic membrane. From these curves the zero curve is defined, representing the zero position of the drum. This curve is used to determine the variables of the pressure-volume relationship of the middle ear system: hysteresis, pressure range, Pec0, and compliance. The variables express objective and dynamic measures of the mechanical properties of the middle ear. The method had an acceptable repeatability and was found to be consistent with earlier investigations. It is easy to perform and causes the subject no discomfort. It is therefore considered useful for further investigation of middle ear physiology and pathophysiology.

Precision of tympanometric measurements.

In both scientific and clinical investigations, precision of instruments is demanded. Precision of tympanometric measures has been reported in the literature rarely, and studies are generally not comparable. This study introduces a new method of determining precision of tympanometric variables. Forty-three participants in good health were investigated. Static compliance, middle ear pressure, and gradient were recorded in test-retest design. Plots of test versus retest measurements were constructed for each variable, after which differences between measurements were plotted against their means. The standard deviation of the distribution of differences provides a measure of precision: the coefficient of repeatability. Static compliance showed a significant disagreement between measurements; hence repeatability was poor, which can be explained by preconditioning of the tympanic membrane. Middle ear pressure and gradient showed good agreement between measurements, and comparable measures of precision are reported. The method is simple and based on two repeated measurements in each subject; the design is ethical and practical in clinical investigations.

Middle ear volume and pressure effects on tympanometric middle ear pressure determination: model experiments with special reference to secretory otitis media.

OBJECTIVE: Middle ear pressure (P(m)) measured by tympanometry has revealed high negative values in patients with secretory otitis media (SOM) in contrast to direct measurement. This may be explained by errors in tympanometry caused by volume displacement of the tympanic membrane (TM) affecting the volume of the middle ear (V(m)) and the P(m) according to Boyle's Law. Such errors are susceptible to the size of V(m). METHODS: A realistic middle ear model based on previous clinical studies of normal pressure-volume relations of the middle ear system (MES) was constructed. In this model non-linear behaviour and hysteresis of the MES was imitated and P(m) as well as V(m) could be controlled. RESULTS: Tympanometrically estimated P(m) decreased on average 38 daPa, when V(m) was changed from 21 to 1 cm(3). The decrease was most pronounced, when V(m) became smaller than 5 cm(3). Moreover, tympanometry showed a linear numerical overestimation of P(m) by a factor 2.31 compared with model P(m). CONCLUSION: A curve fit was derived describing the tympanometric P(m) as a function of V(m). This demonstrated that tympanometric P(m) approached -infinity daPa, when middle ear volume approached 0 cm(3), which indicates that negative tympanometric recordings and B curves can be found in ears with normal P(m) entirely due to very small V(m)'s. This explains the discrepancy between direct and tympanometric measurements of P(m) in SOM, since the effusion replaces the air filled expandable volume resulting in a very small 'functional' V(m). Numerical overestimation of P(m) by tympanometry was explained by hysteresis, which reflected the viscoelastic properties of the MES. These results question the significance of negative P(m)'s as a pathogenetic factor in SOM.

Mechanics of the middle ear system: computerized measurements of its pressure-volume relationship.

A new method is described measuring the pressure-volume relationship of the middle ear system (MES). These measurements express the dynamic mechanical properties of the MES. Ear canal pressure changes are measured in response to tympanic membrane (TM) volume displacements in a material of 39 younger normal adults. During one recording procedure several displacements curves are obtained from which one curve is isolated representing the neutral position of the TM. From this curve the following variables are determined: hysteresis (microJ) describing the viscoelastic properties of the MES, compliance (mm3/kPa) describing its elasticity, Prange (kPa) describing the pressure range of the curve, and Pec0 (kPa) describing the ear canal pressure for the neutral position of the TM. Normative data are presented and compared with tympanometric measurements. Compliance correlates significantly to static admittance (P<0.001), while Pec0 correlates significantly to middle ear pressure (P<0.001). Further, data on repeatability and sources of measurement errors are reported, which support a high reliability of the method. Compared with tympanometry the method is more detailed and has several advantages, which are discussed, and it has been found valuable for future mechanical studies of the MES. These studies include possibilities for diagnostics of middle ear disorders and derivation of pressure-volume equations useful in modeling of the MES.

Positional changes and stabilization of middle ear pressure.

Middle ear pressure has been shown to increase when body position is shifted from the erect to the supine position, which is explained by an increased volume of the middle ear mucosa due to an increased hydrostatic pressure. The increase in the volume of middle ear mucosa consists of a fast major response followed by slow minor increase, which is reflected by a similar pattern in the increase of middle ear pressure. Since many otological experiments may be performed with subjects in the supine position, it is of interest to analyse these changes in middle ear pressure, as results may be affected by changes in middle ear pressure. The present study investigated the middle ear pressure changes due to a shift in body position from sitting to supine at time intervals of 15 s over a period of 120 s in a group of 20 normal adults. The middle ear pressure was found to increase 22 daPa (mean; S.D. = 12.1), whereas a stable middle ear pressure was reached after 30 s, indicating a steady state concerning the increase in volume of the middle ear mucosa. Thus, it is recommended that experiments with subjects in the supine position should be carried out only after assuming the position for 30 s. The increase in pressure did not correlate to the prevailing middle ear pressure or to the body height.

Mechanical properties of the middle ear system investigated by its pressure-volume relationship. Introduction to methods and selected preliminary clinical cases.

A new method is presented for the measurement of ear canal pressure changes in response to tympanic membrane volume displacements, i.e. the pressure-volume relationship (PVR) of the middle ear system. This method has several advantages when compared to tympanometry; for example, it avoids phase delay and hysteresis can be used as a variable thanks to bidirectional recordings. Moreover, dynamic compliance is registered physically as changes in volume relative to pressure. Normative data for 39 subjects are summarized along with preliminary data from patients exhibiting various clinical conditions. The major findings are that secretory otitis media with middle ear effusion results in significantly increased hysteresis (leading to large errors when middle ear pressure is determined by tympanometry), two types of ossicular discontinuity may be distinguished by this method and that myringoplasty leads to a linear PVR in contrast to the nonlinearity found in normal subjects.

Agreement between two tympanometers. A methodological study of instrument comparison.

When old instruments are replaced by new ones, agreement between them becomes important when comparing measurements. Their precision, too, is important. A common, however inappropriate, statistical approach in these cases is correlation analysis. As an alternative, a simple statistical method is suggested, in which differences between measurements of either instrument are plotted against their means. The distribution of the differences is tested against 0 (one-sample t-test), and for good agreement P > 0.05. This statistical method was used in a group of 32 adults in which measurements taken with an older automatic tympanometer and a new digital one were compared. Static compliance and and gradient showed good agreement, while middle ear pressure showed a significant bias between instruments explained by phase delay. This disagreement was insignificant for clinical purposes, but may be important in scientific studies. The same statistical principle applies determining the precision of each instrument. The new digital instrument showed higher precision than the older one.

Mechanics of the middle ear system: age-related changes in viscoelastic properties.

Morphological studies of age-related changes in the tympanic membrane have suggested a decreased elasticity for increasing age, whereas age-related changes in admittance measured by tympanometry have revealed inconsistent results. In this study we report on the viscoelastic properties of the middle ear system by means of a new method in two different age groups. This method measures hysteresis (microJ), which describes the viscous properties of the system, and compliance (mm(3)/kPa) reflecting its elasticity. Moreover, P(ec0) (kPa) was recorded, which corresponds to middle ear pressure measured by tympanometry. Recordings were made in a group of 30 older normal subjects (mean age 77 years) and results were compared to previous findings in a group of 39 younger normal subjects (mean age 29). Hysteresis was markedly decreased in the older normal group compared to the younger one (p = 0.057). This may reflect morphological changes previously reported in the tympanic membrane and can be related to theoretical considerations on tympanic membrane rupture pressures. Compliance and P(ec0) were not influenced by variation in age (p = 0.645 and 0.966).

In vitro growth and collagen synthesis in fibroblasts from the rabbit middle ear mucosa.

The present methodological study was undertaken to introduce a model system in which individual cells of the middle ear mucosa could be studied under controlled conditions allowing standardized sampling and different manipulations using quantitative methods. The method is based upon isolation and culture of fibroblasts from normal rabbit middle ear mucosae. The growth pattern of the cells was determined by measurement of the total content of cell protein, DNA content and cell division activity. Collagen synthesis was also estimated and results compared with normal skin fibroblasts. Finally, fibroblasts derived from rabbit middle ear mucosae with otitis media were cultured under similar conditions. Results demonstrated the method to be valid and reproducible. Evaluated by any of the parameters applied, growth initially increased exponentially, followed by a stationary phase with a constant cell mass. The growth potentials in middle ear fibroblasts appeared to differ significantly from skin fibroblasts. Except for a decreased cell proliferation, fibroblasts from diseased mucosae did not demonstrate any major differences from the normal fibroblasts probably because the original inflammatory stimuli in vivo were lost in vitro. These findings suggest that future investigations of a model system of otitis media in vitro require the addition of inflammatory mediators.

The effect of N-acetylcysteine on the in vitro growth of normal rabbit middle ear fibroblasts.

In the present study the effect of N-acetylcysteine on the growth pattern and collagen synthesis of cultures of rabbit middle ear fibroblasts was determined. The growth pattern was evaluated by cell counting, measurements of the total content of cell protein and mitotic activity by incorporation of 3H-thymidine. Collagen synthesis was estimated by incorporation of 3H-proline. The results demonstrate a dose-dependent reduction in both normal cell proliferation and collagen production. Thus, N-acetylcysteine seems to possess properties desirable and useful in the treatment of secretory otitis media.

Preconditioning the tympanic membrane: identification of cholesteatoma prone ears?

Preconditioning refers to changes in the mechanical properties of tissues due to repeated stress-strain experiments. Generally, after a number of cyclic deformation, a steady state is reached, where the experiment becomes repeatable, and the specimen is preconditioned. Tympanometric measurements of middle ear compliance also show increasing values for repeated trials until after 5 or 6 measurements, where steady state is reached. However, in some normal cases with high compliance it has previously been found that the tympanic membrane is not always able to reach a steady state, but displays larger and larger compliance over trials. This property may be characterized as a decreased resistance against pressure loads, which may lead to retractions, atelectasis, and cholesteatomas. Preconditioning was investigated in a group of 21 patients with cholesteatomas. Due to perforations and discharge the contralateral ear was measured. Nine tympanometries were recorded in one sequence. The increase in compliance between trials showed a complete overlap with a group of 25 normal subjects. For both groups good repeatability between trials with insignificant effect of preconditioning can be obtained after 4 trials.

Stereologic, histopathologic, flow cytometric, and clinical parameters in the prognostic evaluation of 74 patients with intraoral squamous cell carcinomas.

BACKGROUND AND METHODS: A consecutive series of all 78 incident cases of intraoral squamous cell carcinoma occurring during a 2-year period in a population of 1.4 million inhabitants were evaluated by histologic score (the modified classification of Jacobsson et al.), flow cytometry, stereology, tumor size, and the TNM classification. RESULTS: The investigation showed a significant difference between the volume-weighted mean nuclear volume (nuclear vv) of oral leukoplakia (n = 29) and oral squamous cell carcinomas (P = 0.001). The value of the parameters as prognostic indicators of survival and recurrence was tested with Kaplan-Meier plots and Cox multiple hazard regression analysis. Tumor size, T-stage, stereologically estimated nuclear vv, and mean nuclear profile area were all of significant prognostic value in single factor analysis with reference to both survival and recurrence. The histologic parameters of mitotic activity, morphologic nuclear dedifferentiation, and histologic mean malignancy score and the DNA ploidy level had no prognostic value. A prognostic index based on the results of the Cox analysis that included T-stage and nuclear vv was correlated highly with survival (P = 0.00001) and recurrence (P = 0.002). CONCLUSION: These findings may contribute to optimal and individualized therapy.

Tympanometric hysteresis effect and errors in middle ear pressure determination--a preliminary study in children with secretory otitis media.

Previous tympanometric studies on middle ear pressure (MEP) have revealed the hysteresis effect, which is illustrated in bidirectional tympanometries by the different peak pressures for either direction. This leads to an error in determination of MEP, which has been reported to be 10-25 daPa in normal ears, but experimental data have suggested that this error may be increased in ears with secretory otitis media (SOM). This was investigated in a group of 18 children with SOM by bidirectional tympanometries. The peak pressure difference (PPD) was calculated and found to be 75 daPa in the group of SOM, which was significantly larger than in normal ears (mean = 3 daPa) (p < 0.001). The maximum PPD in the SOM group was 205 daPa, indicating an error in MEP determination of more than 100 daPa. Hysteresis is related to the viscous properties of the middle ear system, and the increased hysteresis in SOM ears can be explained by the additional viscosity of the middle ear effusion. In order to improve the accuracy of MEP estimation it is suggested that in ears with SOM, the mean pressure of bidirectional tympanometries should be applied.