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Biomedical subjects

R A Dobie

Publications and source records attributed to R A Dobie.

At least 19 recordsLinked to original sources
PubMed2001

Otologic injuries from airbag deployment.

Airbags became available as an optional passive restraint system in motor vehicles in 1973. The National Highway Traffic Safety Administration mandated placement of driver and right passenger airbags in all passenger vehicles and light trucks beginning in model year 1997. An estimated 2.1 million airbags have been deployed from the late 1980s until the present. There have been several case reports of hearing loss after exposure to airbag deployments in drivers and passengers since 1995. Members of the American Academy of Otolaryngology-Head and Neck Surgery submitted case reports on 71 patients with otologic symptoms after airbag deployment.

Adolescent↗
PubMed2000

Efficacy of 3 commonly used hearing aid circuits: A crossover trial. NIDCD/VA Hearing Aid Clinical Trial Group.

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</=.001). All 3 circuits significantly reduced the frequency of problems encountered in verbal communication. Some test results suggested that CL and WDRC circuits provided a significantly better listening experience than PC circuits in word recognition (P =.002), loudness (P =.003), overall liking (P =.001), aversiveness of environmental sounds (P =.02), and distortion (P =.02). In the rank-order ratings, patients preferred the CL hearing aid circuits more frequently (41.6%) than the WDRC (29.8%) and the PC (28.6%) (P =.001 for CL vs both WDRC and PC). CONCLUSIONS: Each circuit provided significant benefit in quiet and noisy listening situations. The CL and WDRC circuits appeared to provide superior benefits compared with the PC, although the differences between them were much less than the differences between the aided vs unaided conditions. JAMA. 2000;284:1806-1813.

Adult↗
PubMed1999

A review of randomized clinical trials in tinnitus.

OBJECTIVES: Review reports of randomized clinical trials (RCTs) in tinnitus to identify well-established treatments, promising developments, and opportunities for improvement in this area of clinical research. STUDY DESIGN: Literature review of RCTs (1964-1998) identified by MEDLINE and OLD MEDLINE searches and personal files. METHODS: Studies were compared with the RCT criteria of Guyatt et al. for quality of design, performance, and analysis; "positive" results were critically examined for potential clinical relevance. RESULTS: Sixty-nine RCTs evaluated tocainide and related drugs, carbamazepine, benzodiazepines, tricyclic antidepressants, 16 miscellaneous drugs, psychotherapy, electrical/magnetic stimulation, acupuncture, masking, biofeedback, hypnosis, and miscellaneous other nondrug treatments. No treatment can yet be considered well established in terms of providing replicable long-term reduction of tinnitus impact, in excess of placebo effects. CONCLUSIONS: Nonspecific support and counseling are probably helpful, as are tricyclic antidepressants in severe cases. Benzodiazepines, newer antidepressants, and electrical stimulation deserve further study. Future tinnitus therapeutic research should emphasize adequate sample size, open trials before RCTs, careful choice of outcome measures, and long-term follow-up.

Antidepressive Agents, Tricyclic↗
PubMed1998

Low-level steady-state auditory evoked potentials: effects of rate and sedation on detectability.

Steady-state auditory evoked potentials (SSAEPs) in alert adults are most detectable at stimulus or modulation rates of about 40 Hz. Sedation reduces the detectability of 40-Hz SSAEPs and increases it for higher rate SSAEPs. This study examined whether rates higher than 40 Hz would be preferable for detecting responses to low-intensity tones in sedated adults. Fourteen normal adults listened to 640-Hz tones at modulation rates (and toneburst rates) of 20-160 Hz, in 10-Hz steps, at levels of 38 and 58 dB peak equivalent sound-pressure level (peSPL) (20 and 40 dB normal hearing level (nHL) for amplitude-modulated (AM) tones), both alert and sedated (1-2 g chloral hydrate). Sedation reduced both signal (SSAEP) power and noise power at all rates, but noise power reduction was greater for higher rates. Detectability in the alert condition was always greatest at 40 Hz. Under sedation, a second detectability peak was present at 90 Hz for 58-dB peSPL tones, approximately equal to that seen at 40 Hz. At 38 dB peSPL (sedated), peak detectability moved from 40 to 50 Hz. These results suggest that presentation/modulation rates around 40 Hz may be optimal for SSAEP detectability at low levels in adults, whether alert or sedated.

Adult↗
PubMed1998

Evaluation of posturography in the detection of malingering subjects.

OBJECTIVE: This study aimed to test the performance of proposed methods for detecting malingering subjects on computerized dynamic posturography using one subject group in three situations (normal, malingering, vestibular weakness). STUDY DESIGN: The study design was a prospective, blinded study. SETTING: The study was conducted at a university hospital. PATIENTS: Volunteer subjects aged 20-59 years of age participated. INTERVENTIONS: Computerized dynamic posturography was performed under three situations: best effort, faking vestibular weakness, and transient induced vestibular weakness with bilateral simultaneous caloric irrigation. MAIN OUTCOME MEASURES: Measured was identification of situation (normal, malingering, induced vestibular weakness) by each of three detection methods: blinded clinical scoring, a set of formulae, and a set of variables (the latter two methods proposed previously by other investigators). RESULTS: Each method performed well. In three-way discrimination, the formulae and clinical scoring each correctly identified approximately 75% of trials. In two-way discrimination (malingering vs. induced vestibular weakness), the best combination of variables slightly outperformed clinical scoring (0.93 vs. 0.88 ROC [receiver operating characteristic] curve area). CONCLUSIONS: Computerized dynamic posturography can distinguish malingering in normal subjects from trials performed with best effort or after binaural simultaneous caloric irrigation. The accuracy of blinded clinical scoring was comparable to that of two objective detection methods.

Adult↗
PubMed1997

Impact of a laryngectomy on quality of life: perspective of the patient versus that of the health care provider.

This study retrospectively assesses the impact of laryngectomy on the quality of life of 46 patients as compared to the perception of the impact of laryngectomy of 13 health care providers (HCPs). Employing the "time trade-off" methodology, we assessed patient and HCP preferences and calculated estimated utilities. We found that 20% of patients would be willing to compromise anticipated life expectancy to preserve voice or preoperative quality of life. By comparison, 46% of the HCPs perceived that their patients would be willing to accept a reduced life span in order to preserve their larynx and quality of life. In conclusion, the percentage of HCPs who believed their patients would compromise survival was substantially higher than the percentage of actual patients who expressed this preference. This perception may influence physicians' attitudes toward recommending laryngeal preservation therapy for their patients. For most laryngectomy patients, treatments attempting laryngeal preservation, particularly if associated with compromised survival, may not be warranted.

Adult↗
PubMed1996

A comparison of t test, F test, and coherence methods of detecting steady-state auditory-evoked potentials, distortion-product otoacoustic emissions, or other sinusoids.

Sinusoids in background noise can conveniently be detected using unsegmented power spectra, comparing power at the signal frequency to average power at several neighbor frequencies. In this case, the F test is preferable to t tests based on rms or dB values, because of the skewed distributions of rms and dB when signal-to-noise ratio (SNR) = 0. F-test performance improves as the number of frequencies increases, to about 15, but can be degraded if the background noise is not white, with a slope exceeding about 10 dB for the range of frequencies sampled. Segment analysis, using magnitude-squared coherence (MSC) or related statistics, has equivalent statistical power; MSC and F each yield unbiased SNR estimates that have identical distributions when SNR = 0. Selection of F or MSC for detection of sinusoids will usually be a matter of convenience.

Evoked Potentials, Auditory↗
PubMed1995

Prevention of noise-induced hearing loss.

OBJECTIVES: To review the evidence suggesting that occupational hearing conservation programs prevent noise-induced hearing loss; to describe the features, prevalence, and handicap associated with noise-induced hearing loss; and to describe the otolaryngologist's role in prevention of noise-induced hearing loss. DATA SOURCES: Recent statements from the American College of Occupational Medicine, the National Institutes of Health, and the International Organization for Standardization are supplemented by published articles known to the author (no formal literature search was done). STUDY SELECTION: Articles that purported to measure the effects of occupational hearing conservation programs on preventing noise-induced hearing loss. DATA EXTRACTION: Each article was separately critiqued without a priori assessment criteria. DATA SYNTHESIS: Several studies suggest that occupational hearing conservation programs prevent noise-induced hearing loss, but none of these are conclusive. No randomized clinical trial has been reported, of which I am aware, and previously reported data suffer from one or more of the following shortcomings: failure to match treatment and control groups for age, nonoccupational noise exposure, and/or prior hearing loss; failure to control for audiometric learning effects; and inclusion of workers who had already worked long careers without hearing protection (and thus had little risk of additional noise-induced loss). CONCLUSION: Although noise reduction for individuals obviously can prevent noise-induced hearing loss, to my knowledge, no single study offers convincing evidence of the efficacy of occupational hearing conservation programs, primarily due to methodologic flaws.

Hearing Loss, Noise-Induced↗
PubMed1995

Coherence analysis of envelope-following responses (EFRs) and frequency-following responses (FFRs) in infants and adults.

The frequency-following response (FFR) and the envelope-following response (EFR) were recorded in 1-month-old infants and in adults to examine the development of temporal coding. The stimuli were amplitude-modulated (AM) tones. A modulation frequency of 80 Hz was used in infants; modulation frequencies of 40 and 80 Hz were used in adults. The effects of intensity, carrier frequency, and modulation frequency on these responses were studied. Responses were analyzed using magnitude-squared coherence. The effect of intensity on the growth of FFR- and EFR-coherence were similar in infants and adults. In addition, the growth functions were not affected by the carrier frequency or the modulation frequency of the stimulus. FFR thresholds did not differ across age groups. 'Best frequency' (i.e., infant 80 Hz and adult 40 Hz) EFR thresholds were the same for infants and adults at 500 and 1000 Hz, but infant EFR thresholds were poorer than adult thresholds at 2000 Hz. Thus, although FFRs and EFRs are primarily adult-like at 1 month of age, there are some age differences in the EFR that deserve further study.

Acoustic Stimulation↗
PubMed1995

Comparison of objective threshold estimation procedures for 40-Hz auditory evoked potentials.

OBJECTIVE: Objective threshold estimation is possible using statistics such as magnitude-squared coherence (MSC) and responses such as the 40-Hz auditory evoked potential (AEP). The purpose of this paper is to compare three general methods of threshold estimation using MSC. DESIGN: Using 500-Hz amplitude-modulated tones and 40-Hz AEPs from 10 paid-volunteer young adults with normal hearing, we compared three MSC-based threshold estimation methods--extrapolation, intensity series, and adaptive. RESULTS: The extrapolation method yielded low thresholds but unacceptable variability. The intensity series method was insensitive and time-consuming. Two adaptive methods displayed good performance in terms of precision and sensitivity. The first employed an MSC criterion with a 13.5% false positive rate (per trial), but achieved overall false positive rates under 5% after 5 to 7 runs, requiring 30 to 40 minutes test time (a run is a single set of ascending or descending trials, terminated by a reversal). The second, which performed better overall, included only a single run, but collected more data at intensities near threshold than at higher intensities; test time could be further reduced (from 22 to 18 minutes) by using a stopping rule based on initial MSC and noise power estimates at each test intensity. If speed is paramount, a simple single-run method achieved threshold estimates in about 9 minutes, starting at 40 dB nHL, with acceptable precision but less sensitivity. CONCLUSIONS: A single-run adaptive method, with or without collection of additional data near threshold, yielded the best results, in terms of statistical performance and data collection time.

Adult↗
PubMed1995

Objective versus human observer detection of 40-Hz auditory-evoked potentials.

Magnitude-squared coherence (MSC) was used to detect 40-Hz auditory-evoked potentials (AEPs) in a two-alternative forced-choice experiment. MSC performance was found to be better than that of ten human observers. Experienced observers did not perform better than naive observers. In a "yes-no" experiment, observers demonstrated large differences in criterion, with false-positive rates of 2%-20%. Observers also performed better when AEPs were presented in a 50-ms window (two response cycles) than when presented in a 205-ms window (eight response cycles), although total test time was the same; MSC performed equally well in both cases. MSC provides a useful and objective adjunct to visual detection of 40-Hz AEPs.

Adult↗