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OBJECTIVES: To determine the effects of long-term, low-dose difluoromethylornithine (DFMO) on audiometric thresholds and distortion product otoacoustic emission (DPOAE) levels in humans. DESIGN: A prospective, randomized, placebo-controlled phase 2 clinical trial of DFMO in participants with a prior adenomatous colonic polyp. SETTING: Academic tertiary care referral center. PARTICIPANTS: One hundred twenty-three volunteer subjects with colorectal polyps and normal hearing for the frequencies 250 through 2000 Hz. INTERVENTIONS: Subjects were randomized to receive placebo or oral DFMO at daily dosages between 0.075 and 0.4 g/m(2) of body surface area for 12 months. OUTCOME MEASURES: Pure-tone audiometric thresholds for the frequencies 250, 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz and DPOAE levels were measured at baseline and 1, 3, 6, 9, and 12 months after starting treatment with DFMO or placebo and 3 months after cessation of treatment if there was a suggestion of possible changes at the 12-month measurement. RESULTS: At these low dosages, there was little evidence for shifts in auditory pure-tone thresholds, and there were no statistically significant shifts in DPOAE levels. For auditory pure-tone thresholds, there was a subtle, approximately 2- to 3-dB hearing level decrease in hearing sensitivity for the 2 higher DFMO dosages, but only at the 2 lowest frequencies, 250 and 500 Hz. CONCLUSIONS: Administration of low-dose DFMO for 12 months did not produce hearing loss, in contrast to prior studies that used higher dosages.

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CONTEXT: Numerous studies have demonstrated that hearing aids provide significant benefit for a wide range of sensorineural hearing loss, but no carefully controlled, multicenter clinical trials comparing hearing aid efficacy have been conducted. OBJECTIVE: To compare the benefits provided to patients with sensorineural hearing loss by 3 commonly used hearing aid circuits. DESIGN: Double-blind, 3-period, 3-treatment crossover trial conducted from May 1996 to February 1998. SETTING: Eight audiology laboratories at Department of Veterans Affairs medical centers across the United States. PATIENTS: A sample of 360 patients with bilateral sensorineural hearing loss (mean age, 67.2 years; 57% male; 78.6% white). INTERVENTION: Patients were randomly assigned to 1 of 6 sequences of linear peak clipper (PC), compression limiter (CL), and wide dynamic range compressor (WDRC) hearing aid circuits. All patients wore each of the 3 hearing aids, which were installed in identical casements, for 3 months. MAIN OUTCOME MEASURES: Results of tests of speech recognition, sound quality, and subjective hearing aid benefit, administered at baseline and after each 3-month intervention with and without a hearing aid. At the end of the experiment, patients ranked the 3 hearing aid circuits. RESULTS: Each circuit markedly improved speech recognition, with greater improvement observed for soft and conversationally loud speech (all 52-dB and 62-dB conditions, P

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Three methods for compensating multiple frequency acoustic admittance measurements for ear canal volume were studied in 26 men with normal middle ear transmission systems. Peak compensated static acoustic admittance (magnitude of y) and phase angle (phi) were calculated from sweep frequency tympanograms (226-1243 Hz in 113 Hz increments). Of the procedures used to compensate for volume in rectangular form, the ear canal pressure used to estimate volume had the largest effect on the estimate of middle ear resonance. Median resonance was 800 Hz for admittance measurements compensated at 200 daPa versus 1100 Hz for measurements compensated at -350 daPa. The remaining two methods, compensation of susceptance only versus both susceptance and conductance and compensation using the minimum volume versus separate volumes at each frequency, did not affect estimates of middle ear resonance. Estimates of middle ear resonance from compensated phase angle measurements also were compared with estimates of resonance from admittance and phase difference curves. Although resonance could not be estimated from the phase difference curve, resonance estimated from the admittance difference curve agreed with the estimate from compensated phase angle.

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Pre- and postoperative equivalent ear canal volume measures were obtained from a group of 334 children ranging in age from 6 weeks to 6.7 years. The purpose of the study was to develop volumetric guidelines for the determination of tympanostomy tube patency. For children 4 years and older, almost no ambiguity existed in making this determination accurately. For younger children, the pre- and postoperative distributions overlap. A criterion value of greater than or equal to 1.0 cm3 as an indicator of a tympanic membrane perforation appears to yield the lowest possible error rate. When both pre- and postoperative measures are available, a difference of greater than or equal to 0.4 cm3 can be used in conjunction with the absolute value to identify a patent tympanostomy tube.

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The Department of Veterans Affairs recently produced a compact disc of speech audiometry materials. The compact disc, which is available commercially, includes the W-1 spondaic words recorded by a female speaker. Two experiments were conducted. The purposes of experiment 1 were to obtain normative detection and recognition data on the female recording of the spondaic words and to compare the detection and recognition functions for the original male speaker version of the W-1 words. No significant differences were found between the recognition functions for each speaker. The recognition functions for both speakers were displaced to higher sound-pressure levels by 8 dB above the detection functions. Clinically, the two versions of the W-1 spondaic words should produce equivalent results. In experiment 2, slopes of the individual spondaic word recognition functions for the female speaker were obtained from two listeners and are discussed in terms of interstimulus, intertrial, and intersubject variability.

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Two descriptive experiments were performed on a version of the Northwestern University Auditory Test No. 6 (NU No. 6) recorded by a female speaker that is included on an audio compact disc recently produced by the Department of Veterans Affairs. In Experiment 1, normative psychometric functions for the female speaker version of the NU No. 6 materials were established on 24 young adults for three monaural listening conditions (in quiet, in 60-dB SPL broadband noise, and in 60-dB SPL competing message). The 60-dB SPL broadband noise shifted the psychometric function for the NU No. 6 words 33 dB, whereas the 60-dB SPL competing message shifted the function only 18-22 dB. In contrast to the slopes of the quiet and noise conditions (4.5%/dB), the slope of the competing message function was more gradual (3.5%/dB). In Experiment 2, comparisons between the psychometric functions for the female and the original male speaker versions of NU No. 6 in quiet and in broadband noise were made on 8 young adults. In comparison to the psychometric functions for the male speaker version of NU No. 6, the functions for the female speaker version of NU No. 6 were displaced between the 10-90% correct points to higher sound-pressure levels by 10-13 dB in quiet and by 12-16 dB in noise. The difference in performance on the two versions of NU No. 6 is attributed to spectral differences between the two sets of materials that produced a calibration anomaly.

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The Vanhuyse, Creten, and Van Camp (1975) model for analyzing high frequency tympanograms predicts the shapes of conductance, susceptance, and admittance tympanograms from the relationship between resistance and reactance tympanograms at the tympanic membrane. This model has been applied primarily to low impedance middle-ear pathologies but has not been applied extensively to the more commonly occurring high impedance pathologies. The purpose of this study was to extend the Vanhuyse et al. (1975) model to high impedance pathologies and to identify tympanometric parameters associated with otosclerosis, secretory otitis media, and lateral ossicular fixation. Data from previous experiments on the shape and absolute values of resistance and reactance tympanograms were used to calculate 678-Hz admittance tympanograms that were unique to each of the three high impedance pathologies. Guidelines for differentiating among the middle-ear pathologies on the basis of high frequency tympanometric shapes are presented.

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The effects of the direction (ascending and descending) and rate (12.5, 25.0, and 50.0 daPa/s) of ear-canal pressure changes on three tympanometric measures (peak static admittance, shape, and tympanometric peak pressure) were studied in 24 adults with normal middle-ear transmission systems. Susceptance, conductance, admittance, and phase angle data for the six conditions both at 226 and 678 Hz were obtained using a general purpose computer. Peak static admittance was significantly affected by both the rate and direction of pressure change as evidenced by a decrease in phase angle for ascending and for fast rates of ear-canal pressure change. Tympanometric shape was broader for descending pressure changes with less frequent notching both for descending and for slow rates of pressure change. Finally, the difference in peak pressure for the two directions of pressure change increased with the rate of ear-canal pressure change.

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This research note describes an earphone-coupling technique that can be used to measure the temporal characteristics of acoustic-immittance instruments. The primary advantage of the earphone-coupling procedure in comparison with the procedure described by Popelka and Dubno (1978) is that the temporal measures are not contaminated by delays and irregularities in the coupler sound-pressure level associated with the pressure system. The latencies of two instruments (Grason-Stadler, Model 1723) were compared using this earphone-coupling procedure and the Popelka-Dubno procedure. The latency measures were in good agreement following a correction for the delay associated with the pressure tubing in the latter procedure. The technique described is offered as an alternative to the Popelka-Dubno procedure in the absence of a modified 2-cm3 coupler, particularly for instruments with complex pressure systems.

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The basic principles essential for interpreting two-component, multiple frequency tympanograms first are reviewed. These principles then are applied to an analysis of tympanometric shape (conductance, susceptance, and admittance tympanograms) as a function of probe frequency in subjects with normal middle ear transmission systems. The final section presents tympanometric data from patients with confirmed middle ear pathologies that produce an increase in resonant frequency (e.g., middle ear effusion, otosclerosis, ossicular adhesions, and tympanic membrane retraction) or a decrease in resonant frequency (e.g., otitis externa, serous otitis media, tympanic membrane pathology, and ossicular discontinuity). The advantages and disadvantages of a particular probe frequency and/or admittance component are illustrated with individual cases. The cases further demonstrate that the same tympanometric pattern can be recorded from ears with different pathologies (e.g., tympanic membrane perforation with cholesteatoma, tympanic membrane retraction, ossicular adhesions, and middle ear effusion), and conversely, that the same pathology can result in different tympanometric shapes (e.g., tympanic membrane perforation, middle ear effusion, and otosclerosis). Caution, therefore, must be exercised in ascribing a tympanometric abnormality to a specific middle ear lesion.

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The influence that repeated tympanometric trials have on the aural-acoustic admittance characteristics of the middle-ear transmission system was studied in 24 young adults. The 226-Hz and 678-Hz data were generated by concurrently digitizing the conductance and admittance tympanograms at 25 daPa/s for both ascending and descending pressure directions. Ten successive trials for each frequency and direction of pressure change were made. Changes in admittance corrected for ear canal volume across the 10 tympanometric trials were computed. The results demonstrated that generally admittance increases as the number of trials increases. For many subjects, the complexity of the tympanometric configuration also increases across trials. The results from eight subjects with single-peaked 678-Hz tympanograms were compared with the results from eight subjects with notched 678-Hz tympanograms to explain the mean decrease in susceptance across tympanometric trials. Finally, the pressure peak locations of the conductance, susceptance, and admittance tympanograms were evaluated and are discussed. The effects that differences in peak pressure location have on the computed static admittance values are presented.

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Psychometric functions for the S omicron N omicron and S pi N omicron conditions and masking level differences were obtained for a subgroup of 10 words having the largest masking-level differences of 36 CID W-1 spondaic words. The mean masking-level difference obtained from 36 young normal adults was 9.4 dB with a standard deviation of 1.2 dB. The smallest masking-level difference of 7.4 dB was suggested as the low cut-off for normalcy. A shorter version of the masking-level difference procedure was suggested for clinical implementation. The subgroup of 10 words may permit a wider separation between normal and abnormal performance, and thus may enhance the clinical utility of the masking-level difference task for speech recognition. Because the magnitude of the masking-level difference will vary with the materials and procedures used, each clinic must establish its own norms.

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The accuracy of tympanometric estimates of ear canal volume was evaluated by testing the following two assumptions on which the procedure is based: (a) ear canal volume does not change when ear canal pressure is varied, and (b) an ear canal pressure of 200 daPa drives the impedance of the middle ear transmission system to infinity so the immittance measured at 200 daPa can be attributed to the ear canal volume alone. The first assumption was tested by measuring the changes in ear canal volume in eight normal subjects for ear canal pressures between +/- 400 daPa using a manometric procedure based on Boyle's gas law. The data did not support the first assumption. Ear canal volume changed by a mean of .113 ml over the +/- 400 daPa pressure range with slightly larger volume changes occurring for negative ear canal pressures than for positive ear canal pressures. Most of the volume change was attributed to movement of the probe and to movement of the cartilaginous walls of the ear canal. The second assumption was tested by comparing estimates of ear canal volume from susceptance tympanograms with a direct measurement of ear canal volume adjusted for changes in volume due to changes in ear canal pressure between +/- 400 daPa. These data failed to support the second assumption. All tympanometric estimates of ear canal volume were larger than the measured volumes. The largest error (39%) occurred for an ear canal pressure of 200 daPa at 220 Hz, whereas the smallest error (10%) occurred for an ear canal pressure of -400 daPa at 660 Hz. This latter susceptance value (-400 daPa at 660 Hz) divided by three is suggested to correct the 220-Hz tympanogram to the plane of the tympanic membrane. Finally, the effects of errors in estimating ear canal volume on static immittance and on tympanometry are discussed.

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Bilateral measurements of the aural acoustic-immittance characteristics of the middle-ear transmission system of 48 subjects were made with an acoustic-admittance meter. The measurements, including static acoustic-immittance, acoustic-reflex thresholds, and acoustic-reflex growth functions, were made using a 220-Hz probe. The contralateral reflex data for three pure tones (500, 1000, and 2000 Hz) and for broadband noise were acquired in 2-dB steps at sound-pressure levels from 84-116 dB (tones) and 66-116 dB (noise) during ascending- and descending-intensity level runs. For all acoustic-immittance measurements, right ear and left ear comparisons were made and found not to be significantly different. The individual subject data then were expressed as the absolute differences between ears. In this manner normative inter-aural immittance differences were defined. The peak static immittance data were analyzed in terms of median inter-aural differences and upper 80% cut-off values. The 80% ranges for normal immittance values were smaller for a within subject versus an across subject comparison. For acoustic-reflex thresholds, a disparity between ears of greater than 10 dB was suggested as indicative of an abnormality in the auditory mechanism. Finally, the reflex-growth data indicated mean inter-aural absolute differences that ranged to .040-.043 acoustic mmhos (300-400 acoustic ohms) at the higher reflex activator sound-pressure levels.

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