Maternal arrhythmia and perinatal outcomes.

OBJECTIVE: The objective of this study was to determine whether arrhythmia in the setting of maternal cardiac disease (MCD) affects perinatal outcomes. STUDY DESIGN: This is a retrospective cohort study of pregnant women with MCD who delivered during 2008 to 2013. Perinatal outcomes among women with an arrhythmia were compared with those without. RESULTS: Among 143 women, 36 (25%) had an arrhythmia. Those with an arrhythmia were more likely to have a spontaneous vaginal delivery (64 vs 43%, P<0.05) and required fewer operative vaginal births (8 vs 27%, P=0.02). Pregnancies were more likely to be complicated by intrauterine growth restriction (IUGR) (17 vs 5%, P<0.05), although there were no differences in the rate of small for gestational age. The risk of IUGR remained increased after controlling for confounding (adjusted odds ratio 6.98, 95% confidence interval 1.59 to 30.79, P=0.01). Two cases of placental abruption were identified among mothers with arrhythmia while none were identified in the controls (P<0.05). CONCLUSION: Patients with arrhythmias were more likely to have a spontaneous vaginal delivery. Our data suggest that these pregnancies were an increased risk for IUGR.

Suitcase lab measurement of digital cellphone interference levels on hearing aids.

A low-cost, "real-life" method for measuring the interference caused by digital wireless (cell-phones) telephones in hearing aids is proposed. Data would be valid for specific telephone and hearing aid models. The estimated equipment cost is $500.

Pericardial angiosarcoma after mediastinal irradiation for seminoma. A case report and a review of the literature.

BACKGROUND: Second malignancies are a well recognized complication of radiation therapy. METHODS: We performed a computer search of the literature using the Medline Database for Pericardial Tumors and Post-Irradiation Sarcomas. RESULTS: The case history of a patient who developed a radiation-induced pericardial angiosarcoma is described. We present a detailed review of pericardial sarcomas. CONCLUSIONS: We believe this to be the first report of a radiation-induced pericardial sarcoma. The importance of continued long-term observation for patients who receive mediastinal irradiation is stressed.

Comparison of two hearing aid receiver-amplifier combinations using sound quality judgments.

Sound quality judgments were obtained on two binaural pairs of laboratory hearing aids with similar battery drain. One pair had a traditional low-current-drain "starved Class A" output stage. The other had a new (at the time) "Class D" output stage. Speech and music reproduction was rated, for seven input levels between 70 and 100 dB SPL, on an overall quality scale by juries of normal-hearing and hearing-impaired subjects. The same subjects also were asked to assign a dollar value to each condition by answering the question "What would you pay for a hearing aid that sounded like that?" Both subject groups rated the hearing aids with the Class D output stage as having superior sound quality across a variety of input levels and test materials, consistent with objective distortion measurements. On the average, each one-percentage point increase in sound quality rating corresponded to a $6.75 increase in perceived value in these experiments.

New knowledge about the function of the human middle ear: development of an improved analog model.

Conventional teaching regarding the acoustic function of the human middle ear is that it serves as an impedance matching system to offset the loss that occurs when sound passes from the low-impedance sound field to the high-impedance cochlear fluid. A transformer analogy is often used with the pressure transformation produced by the eardrum; footplate area ratio and the lever ratio considered to be approximately 27 dB. Recent data on middle ear function has shown this to be only partially correct. A transformer analogy is not appropriate since the pressure gain of the middle ear decreases above 1000 Hz and does not depend on the cochlear load at all frequencies. Experiments are described of umbo, malleus short process, and stapes displacement in human temporal bones using a laser Doppler measuring system (LDS). The measurements support previous studies that indicate that in addition to a roll-off in tympanic membrane function above 1000 Hz, there is slippage in the ossicular lever system that causes an increasing "lever ratio" above 1000 Hz, thought to be caused by translational movement of the ossicular rotation axis near the short process. An improved analog circuit model of the external and middle ear has been developed that produces results equivalent to those found in the temporal bones.

Improving the reliability of the auditory middle latency response by monitoring EEG delta activity.

The auditory middle latency response (MLR), a useful tool in the assessment of low-frequency auditory sensitivity, can be consistently recorded in young children during wakefulness, stages 1 and 2, and REM sleep. Responses are often absent or questionable during stage 4. An on-line measure indicating favorable periods for recording MLR during sleep is important for interpretation of absent potentials. Here, for children 5 to 7 years old, the reliability and detectability of MLR was compared to sleep state and the dominance of delta activity (0-3 Hz) in the EEG frequency spectrum. Dominance of delta activity, a characteristic of stage 4, was expressed in a "delta ratio," a measure of relative EEG energy in the 0 to 3 Hz frequency spectrum. A fixed delta ratio (DR = 9) allowed the differentiation of periods favorable for MLR. MLR wave Pa amplitude and latency also varied with delta ratio. Results indicate that on-line monitoring of the delta ratio will allow reliable testing of MLR in clinical situations.

The K-Amp Hearing Aid: An Attempt to Present High Fidelity for Persons With Impaired Hearing.

The reason no one wants to be seen wearing hearing aids is probably that they don't work well, or at least they didn't. When the problems with such hearing aids are solved, a new/old problem arises: Background noises are often blamed on the hearing aid. The problem is that the user has lost ABONSO (automatic brain-operated noise suppressor option), and the problem persists until the user relearns how to recognize and localize background noises (at which time the brain automatically performs as a highly effective noise suppressor option). Ongoing attempts to replace the brain with a tiny circuit that will somehow reject noises we don't want to hear are unlikely to result in useful devices.

Sound exposures and hearing thresholds of symphony orchestra musicians.

To assess the risk of noise-induced hearing loss among musicians in the Chicago Symphony Orchestra, personal dosimeters set to the 3-dB exchange rate were used to obtain 68 noise exposure measurements during rehearsals and concerts. The musicians' Leq values ranged from 79-99 dB A-weighted sound pressure level [dB(A)], with a mean of 89.9 dB(A). Based on 15 h of on-the-job exposure per week, the corresponding 8-h daily Leq (excluding off-the-job practice and playing) ranged from 75-95 dB(A) with a mean of 85.5 dB(A). Mean hearing threshold levels (HTLs) for 59 musicians were better than those for an unscreened nonindustral noise-exposed population (NINEP), and only slightly worse than the 0.50 fractile data for the ISO 7029 (1984) screened presbycusis population. However, 52.5% of individual musicians showed notched audiograms consistent with noise-induced hearing damage. Violinists and violists showed significantly poorer thresholds at 3-6 kHz in the left ear than in the right ear, consistent with the left ear's greater exposure from their instruments. After HTLs were corrected for age and sex, HTLs were found to be significantly better for both ears of musicians playing bass, cello, harp, or piano and for the right ears of violinists and violists than for their left ears or for both ears of other musicians. For 32 musicians for whom both HTLs and Leq were obtained, HTLs at 3-6 kHz were found to be correlated with the Leq measured.

Comparison of the noise attenuation of three audiometric earphones, with additional data on masking near threshold.

The noise-excluding properties of a standard supra-aural audiometric earphone, a widely used circumaural-supra-aural combination, and an insert earphone sealed to the ear with a vinyl foam eartip were measured in a diffuse-field room complying with ANSI S12.6-1984. Data on attenuation were obtained monaurally with the nontest ear plugged and muffed. Results for the supra-aural earphones generally agreed well with previously reported measurements. A broadband masking noise was used to directly test the ANSI S3.1-1977 permissible background noise levels for measuring to audiometric zero using standard audiometric earphones. This "ANSI noise" raised the average thresholds of 15 normal-hearing test subjects by 3 to 5 dB at the octave frequencies from 500 to 4000 Hz. With a noise conforming to the less stringent OSHA-1983 regulation, average thresholds were elevated 9 to 17 dB. An "ENT office noise" with an overall sound level of 54 dBA raised average thresholds even further, by as much as 29 dB at 500 Hz. Use of the circumaural system in the office noise limited the threshold elevation to 11, 5, 2, and 0 dB at the four octave frequencies tested. With the fully ("deeply") inserted foam eartips, the threshold elevation in the simulated office noise was 2 dB or less at all test frequencies. Actual threshold elevations agreed closely with predictions based on a critical ratio calculation utilizing measured sound field noise levels and measured earphone attenuation values.

Comments on "Earphones in Audiometry" [Zwislocki et al., J. Acoust. Soc. Am. 83, 1688-1689 (1988)].

The Zwislocki et al. ["Earphones in Audiometry," J. Acoust. Soc. Am. 83, 1688-1689 (1988)] Letter to the Editor states that insert earphones have some unresolved technical problems, such as limited frequency response, limited dynamic range and power handling capability, intersubject variability, and hygiene safety. In evaluating circumaural earphones, Zwislocki et al. say that the lack of a standard coupler disqualifies them for audiometry. Since this letter carries the weight of a CHABA committee recommendation, these issues are commented on herein. Section I was written primarily by Mead Killion and Sec. II primarily by Edgar Villchur. For brevity throughout, the authors of the Zwislocki et al. letter will be referred to as "the authors."

Reference thresholds for the ER-3A insert earphone.

Several recent studies have demonstrated that the ER-3A insert earphone may sometimes be directly substituted, without recalibrating, for a TDH-39/MX-41AR earphone. However, most available data have not been reduced to a form suitable for establishing a revised estimate of the reference threshold levels. This article reports such a data analysis performed on the results of five recent studies. The mean data from the five studies are typically within 1 dB of the provisional reference threshold SPLs given by the ER-3A manufacturer for calibration in a (HA-1) 2-cc coupler. After converting the mean data to equivalent Zwislocki-coupler-type ear simulator SPLs at each of the reported audiometric frequencies (125, 250, 500, 1000, 2000, 3000, 4000, 6000, and 8000 Hz), agreement within 1.5 dB was seen with the revised estimate of minimum audible pressures given by Killion [J. Acoust. Soc. Am. 63, 1501-1508 (1978)]. Either the manufacturer's provisional SPLs or the average results from this study may be used with little noticeable difference for most purposes.

Insertion gain repeatability versus loudspeaker location: you want me to put my loudspeaker where?

The traditional 0 degree (straight-ahead) location of the loudspeaker during insertion gain measurements is a poor choice, based on theoretical considerations, from the standpoint of measurement repeatability. In a series of experiments, we were able to demonstrate that a location 45 degrees to the side, or 45 degrees up and 45 degrees to the side, provided a much more repeatable measurement of basically the same insertion gain response.

Clinical use of an insert earphone.

There are several applications of and advantages to using an insert earphone. An insert earphone has three parts: a transducer to convert electrical energy to sound, a conduit to deliver the sound into the ear canal, and a coupler connecting the device to the canal. The data from this study indicate that there is a distinct advantage in using insert earphones over TDH-49 phones (standard headphones) in the attenuation of low frequency ambient noise. The use of insert earphones will permit one to test hearing in areas of higher ambient noise than was previously possible. Insert earphones are used to shorten the hearing aid selection process. A technique is described in which only one real ear measurement is required for an accurate hearing aid fitting. Most, but not all, of the masking dilemmas that are encountered with standard headphones are circumvented or eliminated by using insert earphones. In brain stem auditory evoked response testing, the insert earphone reduces the stimulus artifact without influencing the acoustic signal. Finally, the insert earphone solves the collapsing ear canal problem.

Evaluation of high-fidelity hearing aids.

An essential building block for any high-fidelity hearing aid is an amplifier-transducer-coupling combination that does not audibly degrade the sound, that is, provides high-fidelity sound reproduction as judged by someone with normal hearing. To demonstrate that such a combination is possible, two binaural pairs of hearing aids were assembled using available hearing aid transducers and electronic components, one pair of Over-The-Ear hearing aids with 8-kHz bandwidth and one pair of In-The-Ear hearing aids with 16-kHz bandwidth. Objective insertion-gain measurements on these aids, obtained with a KEMAR manikin in a diffuse sound field, revealed a frequency-response accuracy comparable to that available in expensive high-fidelity loudspeakers. Subjective fidelity ratings obtained from three groups of listeners judging prerecorded A-B-A comparisons (made from equalized eardrum-position microphones in a KEMAR manikin) produced a similar conclusion. We conclude that the important question for hearing aid research is no longer "What can a hearing aid be designed to do?" but "What should a hearing aid be designed to do for the hearing impaired?"

Earmold options for wideband hearing aids.

A summary of recent developments in earmold constructions for wideband hearing aids is presented. Earmold modification techniques, special earmolds, and temporary earmolds are discussed. The appendix contains the results from transmission line theory as applied to earmold acoustics and some sources for useful earmold supplies.

Revised estimate of minimum audible pressure: where is the "missing 6 dB"?

Eardrum pressures at hearing threshold have been calculated from both earphone data (ISO R389-1964 and ANSI S3.6-1969) and free-field data (ISO R226-1961). When head diffraction, external-ear resonance, and an apparent flaw in ISO R226 are accounted for in the free-field data, and real-ear versus coupler differences and physiological noise are accounted for in the earphone data, the agreement between the two derivations is good. At the audiometric frequencies of 125, 250, 500, 1000, 2000, 4000, and 8000 Hz, the estimated eardrum pressures at absolute threshold are 30, 19, 12, 9, 15, 13, and 14 dB SPL, respectively. Except for the effects of physiological noise at low frequencies, no evidence of the "missing 6 dB" is seen, an observation consistent with the experimental results of several recent studies.