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Biomedical subjects

P Avan

Publications and source records attributed to P Avan.

At least 73 records · Page 4Linked to original sources
PubMed1992

[Secondary auditory risks from listening to portable digital compact disc players].

The recent availability of portable high-performance digital disc-players in addition to cassette players, and with an increased dynamical range, has enhanced the risk to hearing for their users. The present study aimed at attempting to evaluate this hazard. After selection of a digital player, 12 normally-hearing voluntary subjects were exposed to listening to two records (classical music and hard-rock) at an acoustic level complying with safety regulations. Their temporary threshold shifts (TTS) were determined at 4 and 6 kHz just after exposure. The 0.5 kHz auditory thresholds were also measured as a control. At 4 and 6 kHz, the average value of TTS was 5 dB (standard deviation 3.1 to 5.9 dB). There was no statistically significant difference neither between the TTS at 4 and 6 kHz (p > > 0.05), not between TTS for the two types of music. A voluntary subject, suffering from a mild high-frequency hearing loss, was also tested. His TTSs were higher than average and may have corresponded to slower recovery (may be non monotonous). Therefore special caution should be recommended in such cases. The measurements have pointed out that very high acoustic levels could be reached (125 to 127 dBA) with a Leq (1 hour) od 110 dBAi.e. much higher than tolerable levels. Thus there is a serious risk to hearing, possibly increased by high level transients. Moreover, better headphones are likely to provoke TTS also above 8 kHz, which might be evaluated by high-frequency audiometry.(ABSTRACT TRUNCATED AT 250 WORDS)

Equipment Safety↗
PubMed1992

[Acoustic distorsion products. A systematic analysis of technical parameters. How to explain the results?].

The aim of this study was to define the most interesting parameters useful for a clinical application of acoustic distortion products (mainly, F1 and F2 primaries frequencies and levels). The most interesting F1 and F2 primaries level in order to separate subjects with a normally-hearing function and patients with a sensorineural hearing loss is 50 dBHL. This result can be explained by some physiological properties of cochlear mechanisms.

Acoustic Stimulation↗
PubMed1992

[Deafness screening in children by otoacoustic emissions. Current data].

Hearing impairment should be detected in early childhood. Among available screening techniques, acoustic oto-emission testing is a rapid, reliable, noninvasive method which specifically investigates peripheral hearing but does not provide data on auditory nerve centers. This functional test should be carried out within a few days of birth in infants with risk factors for hearing impairment.

Hearing Disorders↗
PubMed1991

Objective low-frequency audiometry by distortion-product acoustic emissions.

The aim of this study was to measure distortion-product otoacoustic emissions (DPOEs) in a clinical setting. First, DPOE input-output functions were automatically realized to determine the ratio of the pure tones (primaries) f2 and f1 that would elicit the most significant DPOE input-output function. The DPOE input-output functions presented two separate portions for the f2/f1 ratio, ranging from 1.18 to 1.26: (1) below 60-dB sound pressure level (SPL), a saturating portion with a DPOE detection threshold at 36-dB SPL; and (2) above 66-dB SPL, a linear portion. For other f2/f1 ratios, DPOE input-output functions had a more linear behavior. The DPOEs generated by primary intensities below 60-dB SPL, which show saturating behavior, probably have their origin in the properties of outer hair cells. This indicates that DPOE measurements in a clinical setting must be realized with precise stimulus values: (1) f2/f1 ratio near 1.22, and (2) primary intensities below 60-dB SPL. Second, DPOE input-output functions were realized for DPOEs varying from 707.5 to 342 Hz. No more saturating plateau could be observed with DPOEs below 512.5 Hz, suggesting that active mechanisms are absent below 725 Hz within the human cochlea. These data permit us to establish the bases of an objective low-frequency audiometric test.

Acoustic Stimulation↗
PubMed1991

Quantitative assessment of human cochlear function by evoked otoacoustic emissions.

The amplitudes of evoked otoacoustic emissions (EOE) and their detection threshold were measured in 44 normal young adults and 118 patients with two categories of cochlear dysfunction, acoustic trauma and presbycusis. A different method was used for each category: detection of click EOE or of stimulus frequency emissions. A partial correlation and multivariate analysis was performed for both groups of results to investigate the relations between EOE threshold one pure tone audiometric thresholds (250 to 8000 Hz). Only one significant correlation was found, linearly relating EOE threshold and hearing threshold at 2 kHz (P less than 0.001), independently of the origin of cochlear dysfunction. It suggests that EOE threshold is not frequency-specific since the frequency of EOE at threshold was nearly always close to 1 kHz. A simple model is proposed, based on the assumption that EOE amplitudes and threshold are proportional to the total number of residual active sites in the organ of Corti, i.e. to the total length of active basilar membrane. It is shown that this model accounts for the results disclosed by the statistical analysis and fits the experimental data. It can be used for quantitatively predicting the residual cochlear activity of a patient. However, the EOE threshold is only sensitive to already important cochlear alterations and this parameter does not seem to allow a follow-up of early stages of cochlear dysfunction.

Adolescent↗
PubMed1991

[Acoustic distortion products. Clinical values and limitations in the study of low frequencies].

Distortion products are otoemissions produced when the cochlea is stimulated by two pure, continuous sounds f1 and f2. The most ample distortion product in Man corresponds to a frequency of 2f1-f2. The aim of our work is to appreciate the possibilities to study the distortion products for the exploration of low frequencies in Man. Three populations of subjects have been studied: young subjects have been studied: young subjects with a normal hearing, subjects with pathological otoscopic findings in spite of a normal hearing, subjects with pathological otoscopic findings in spite of a normal audiometric study, and subjects with endocochlear perceptive deafness. The major result of this study was to demonstrate that the lowest frequency that can be explored with distortion products is 750 Hertz.

Acoustic Stimulation↗
PubMed1991

Progressive hereditary deafness with predominant inner hair cell loss.

This paper presents the first case of human genetic hearing loss due to predominant inner hair cell damage investigated by psychoacoustic audiometry, auditory brainstem responses (ABR), evoked acoustic emissions (EAEs), and distortion product otoacoustic emissions (DPOEs). The genetic transmission was an autosomal dominant inheritance. The audiogram pattern was a dominant high-frequency hearing loss. EAE and DPOE properties were normal. Bronx waltzer mutant mouse with genetically determined predominant inner hair cell defects provide an interesting model to study this congenital deafness. This rare congenital deafness with predominant damage to inner hair cells cannot be detected by neonatal screening techniques using EAEs or DPOEs.

Adult↗
PubMed1991

[Study of the cochlea by evoked otoemissions. Physiological interpretation of results].

Amplitudes and detection thresholds of evoked otacoustic emissions (EOE) were measured in various groups of subjects: 44 normal young adults, 80 patients with presbycusis and 38 patients with acoustic trauma. Relations between these EOE parameters and tonal audiogram were analyzed. Surprisingly, EOE detection threshold at 1 kHz was strongly correlated with auditory threshold at 2 kHz and no other one. This result demonstrates that some EOE parameters are not frequency-specific. A simple model is implemented in which it is assumed that EOE amplitudes are proportional to the global cochlear activity. This model fits very well experimental data and allows a quantitative evaluation of the residual cochlea. The domain of validity of EOE test in clinics has therefore been precised.

Audiometry↗
PubMed1990

Evoked otoacoustic emissions in guinea pig: basic characteristics.

Different types of evoked otoacoustic emissions (EOAEs) such as stimulus frequency emissions, tone burst and click EOAEs, were investigated in the guinea pig. Their correlates on cochlear microphonic potential were also recorded. Although it was confirmed that click EOAEs are difficult to detect in the guinea pig, partly because their delay (2 to 3 ms, measured on tone burst EOAEs) is much shorter than in man, other types of OAE were found in the interval (1.5-5 kHz) for almost every normal animal. Many of their properties were quite different from man, for instance their small number, low level, and the wide frequency range of some of them (up to 500 Hz), suggesting that they represent a sort of continuum. It is proposed that these particularities may not arise from different generating mechanisms but should be correlated with the well-known differences in hair cells patterns.

Acoustic Stimulation↗
PubMed1990

Clinical significance of otoacoustic emissions: a perspective.

The aim of this paper is to review the properties of otoacoustic emissions from a clinical point of view and to discuss the perspective interest of this test. In adults, the clinical significance of evoked otoacoustic emissions seems to be limited either in endocochlear hearing losses or for detecting retrocochlear diseases. In infants, evoked otoacoustic emissions seem to be a reliable, simple, non-invasive, and precise method for estimating auditory sensitivity for midfrequencies (1-4 kHz). Then, EOEs could be considered as an interesting way for screening auditory dysfunction in infants.

Adult↗
PubMed1990

[Acoustic distorsion products: technic, reproducibility and audiometric value. A new technic for the clinical evaluation of hearing].

Acoustic distorsion products are sounds emitted by the cochlea, in relation with the outer hair cell properties and the micromechanical properties of the Organ of Corti, in response to an acoustic stimulation by two primairies F1 and F2. Acoustic distorsion product 2F1-F2 have been recorded in two populations: 10 normally-hearing subjects and 10 subjects with pure sensorineural hearing losses. Three points are discussed: (i) the test-retest reliability, (ii) the clinical tolerance and (iii) the clinical applications of this test.

Adolescent↗
PubMed1988

Effect of elevated potassium concentration in the perilymph on the nonlinearity of cochlear microphonics in the guinea-pig cochlea.

Various characteristics of cochlear microphonic responses (CM) were measured in the guinea-pig after perfusing scala tympani with KCl solutions. In addition to a decrease of CM magnitude, the nonlinearity and the symmetry of waveform showed typical modifications suggesting, in addition to a depolarization of hair cells, some mechanical alterations.

Animals↗
PubMed1988

[Active cochlear mechanisms. Significance of a clinical study of acoustic emissions].

Recent studies in inner ear physiology clearly show that active cochlear mechanisms play an important role in the normal auditory perception. One of the effects of these mechanisms is that the inner ear can emit acoustic energy towards the outer ear canal. Oto-emissions are currently recorded by various techniques adaptable to usual audiological devices. It is expected that more precise diagnoses to inner ear diseases might be deduced from their study.

Acoustic Stimulation↗
PubMed1986

Modifications of cochlear microphonic frequency responses following transient changes of hydrostatic pressure in the perilymph.

Cochlear microphonic potential was recorded with differential electrodes implanted in the various turns of the guinea-pig cochlea. Isointensity frequency responses were plotted in normal conditions and after excessive displacements of the cochlear partition. These displacements were provoked by changes of hydrostatic pressure in the perilymph of scala tympani or scala vestibuli. Typical modifications of the frequency response were observed. The most noticeable was a division in two parts of the response zone which suggested the existence of two resonance peaks. Scanning electron microscopy revealed that changes of hydrostatic pressure provoked alterations of the stereocilia in the outer rows of external hair cells, probably in relation with a decoupling of the tectorial membrane from the organ of Corti. These results are discussed in terms of possible alterations of cochlear micromechanics.

Animals↗
PubMed1985

Role of suppressive interactions in the cochlear microphonic response to wide-band clicks.

Cochlear microphonic responses (CM) were recorded from the guinea pig cochlea with conventional differential electrodes implanted in the first and second turns. The CM frequency functions were determined by calculating the Fast Fourier Transform of responses to wide-band clicks. These frequency functions appeared to be dependent upon the spectrum of the click. This effect was interpreted as resulting from suppressive interactions between the various components of the click. It is suggested that such CM interactions are related to corresponding effects reported previously concerning cochlear nerve responses.

Acoustic Stimulation↗