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Biomedical subjects

M E Lutman

Publications and source records attributed to M E Lutman.

At least 19 recordsLinked to original sources
PubMed2005

Influence on the mechanisms of generation of distortion product otoacoustic emissions of mobile phone exposure.

Mobile phones have become very commonly used throughout the world within a short period of time. Although there is no clear evidence to show harmful physiological effects of electromagnetic fields (EMF) at the levels used by mobile phones, there is widespread public concern that there may be potential for harm. Because mobile phones are usually held close to the ear, it is appropriate to study effects on hearing. In this study, the outer hair cell function of 15 subjects was assessed by DPOAE recording before and after a controlled EMF exposure. To increase the sensitivity of DPOAE recording to identify even small changes in hearing function, an inverse fast Fourier transform (IFFT) analysis and time-domain windowing was applied to separate the two generation mechanisms of DPOAE, the so-called place-fixed and wave-fixed mechanisms, in order to verify if EMF can affects the two DPOAE emission mechanisms. Statistical analysis of the data showed that 10 min of EMF exposure at the maximum power (2 W at 900 MHz or 1 W at 1800 MHz) does not induce any changes in either DPOAE generation mechanism.

Adolescent↗
PubMed2005

Effect of aspirin on phase gradient of 2F1-F2 distortion product otoacoustic emissions.

It is well known that aspirin consumption temporarily reduces overall otoacoustic emission (OAE) amplitude in humans. However, little is known about changes in the separate components of distortion product otoacoustic emissions (DPOAE), which may be distinguished by examining phase gradients. The effects of aspirin on the phase gradient of the DPOAE 2F1-F2 obtained with fixed frequency ratio sweeps were studied longitudinally in a group of twelve subjects in whom a temporary hearing loss was induced by aspirin consumption. DPOAE were recorded daily for two days pre-aspirin consumption, during the three days of aspirin consumption and two days afterwards. DP-grams were recorded over a restricted frequency range centered on 2,3,4 and 6 kHz with the following stimulus levels: L1/L2 of 60/50-80/70 in 10-dB steps. The effects of aspirin on the phase gradients varied between the subjects and across frequency: the general trend was that the phase gradient became steeper across successive sessions for the higher frequencies, while no significant effect was found at the lower frequencies. These results suggest that aspirin may have more persistent effects on cochlear function than are disclosed by measurements of hearing threshold level or DPOAE amplitude. Particularly, DPOAE phase gradient appears to be increased by aspirin consumption and has not recovered two days after cessation of aspirin intake, despite almost complete recovery of DPOAE amplitude and hearing threshold levels. These findings may suggest differential effects on the distortion and reflection mechanisms considered to underlie DPOAE generation.

Acoustic Stimulation↗
PubMed2005

Demystifying biomedical signals: a student centred approach to learning signal processing.

The processing and analysis of physiological signals has become firmly established in clinical medicine and biomedical research. Many of the users of this technology however do not come from an engineering or science background, and traditional approaches in teaching signal processing are thus not appropriate for them. We have therefore developed a series of modular courses that are aimed specifically at an audience with a background in medicine, health-care or the life-sciences. In these courses, we focus on the concepts, principles and rationale of applying signal processing methods, rather than the mathematical foundations of the techniques. Thus, we aim to remove some of the perceived 'mystery' often surrounding this subject. The very practical approach, with hands-on experience using the MATLAB software, has been well received, with strong evidence that students have learnt to apply their knowledge. This paper describes the learning and teaching approach taken, and some of the experience acquired.

Algorithms↗
PubMed2001

Communication development in young deaf children: review of the video analysis method.

It is widely recognised that preverbal communication skills underpin development of spoken language. This historical review outlines the establishment of a quantitative methodology for assessing preverbal communication skills in children with hearing aids and cochlear implants. The method is shown to be reliable and free from observer bias. The review also summarises findings from a series of cross-sectional and longitudinal observational studies utilising the methodology. Profoundly deaf young children, either with cochlear implants or successful users of hearing aids, show similar patterns of preverbal communication development that contrast with those of unsuccessful hearing-aid users. Preverbal measures obtained 12 months after implantation are predictive of late performance on speech perception tasks. Moreover, there is a significant association between the preverbal measure of 'autonomy' obtained before implantation and later speech perception performance. This latter finding has important theoretical implications for understanding of language development and suggests that intervention that promotes autonomy in adult-child interaction may lead to improved outcomes. Such intervention could be commenced as soon as deafness is discovered.

Child, Preschool↗
PubMed2001

The reliability of the SCAN test: results from a primary school population in the UK.

The SCAN test utilizes a pre-recorded tape, with carrier phrase and target words spoken by an American English speaker, to screen for central auditory processing disorders in children. The aim of the present study was to establish whether the normative data, derived from American school children, are applicable to a UK primary school population. The SCAN test was administered to 133 British primary school children with normal hearing, stratified into one-year age bands. Mean scores from the UK sample were found to be significantly lower than US mean scores for the most of the age bands. Analysis of word errors indicates accent and word familiarity effects. This evaluation of the SCAN indicates that the test is not directly applicable to British children as currently normalized. The present study provides interim norms for the American recording for age bands six to 11 years. It is recommended that the test material is recorded by a UK English speaker, with substitution of high error-rate target words, followed by normative data collection for the new test material.

Child↗
PubMed2001

Static input-output non-linearity as the source of non-linear effects in maximum length sequence click-evoked OAEs.

The application of the maximum length sequence (MLS) technique to the recording of click-evoked otoacoustic emissions (CEOAEs) allows for a reduction in test time by one to two orders of magnitude. This is because the technique permits the use of extremely high click rates, as inter-click intervals are not constrained to be greater than the duration of the response. However, increasing the click rate also causes a progressive reduction in amplitude, or 'suppression', of the CEOAE. The origin of this suppression is unclear, with diverse suggestions in the literature as to its nature and mechanism. This paper presents a simple model of the well-known compressive non-linearity of the CEOAE level function, based on a static amplitude non-linearity within each of a number of narrowband frequency channels. The response of the model to MLS stimulation demonstrates suppression broadly of the form and magnitude previously reported in experimental studies. Furthermore, the model exhibits the generation of additional non-linear components that have been speculated on in connection with CEOAE recordings using the MLS technique. It is concluded that the MLS suppression phenomenon is derived largely, if not entirely, from the static non-linearity of the CEOAE level function. The approach to modelling the phenomenon as described here also bears promise for understanding various aspects of non-linearity in MLS-based CEOAE recordings.

Cochlea↗
PubMed2001

The feasibility of maximum length sequences to reduce acquisition time of the middle latency response.

Maximum length sequences (MLS) have been used to improve the signal-to-noise ratio (SNR) of otoacoustic emissions [Thornton, J. Acoust. Soc. Am. 94, 132-136 (1993)] and the auditory brainstem response [Thornton and Slaven, Br. J. Audiol. 27, 205-210 (1993)]. By implication, a shorter recording time would be required to give equal signal-to-noise ratio (SNR). This study aimed to establish whether it is also possible to improve the SNR of the auditory-evoked potential termed the middle latency response (MLR) using maximum length sequences (MLS). Recordings of 180 s each were made using a conventional recording rate and MLS rates of 42, 89, and 185 clicks/s. Three different stimulus intensities were used in the range 30 to 70 dB nHL. The rate of 89 clicks/s was found to produce most improvement in SNR for both the Na-Pa region of the MLR and the Na-Pb region. This improvement in SNR using MLS implies that an MLS rate of 89 clicks/s would produce a fourfold reduction in recording time for equal SNR over conventional recording for the Pa-Nb region of the MLR at a stimulus intensity of 70 dB nHL. The latency of the Nb wave was found to reduce significantly using MLS. An MLR could not be recorded from every subject in this study, but more subjects had an identifiable response for MLS than for conventional recordings. Use of MLS to record the MLR appears to offer the potential for reduction in test time and better wave identification.

Adult↗
PubMed2001

Patient-assessed outcomes after excision of acoustic neuroma: postoperative symptoms and quality of life.

OBJECT: The aim of this study was to assess whether outcomes from excision of acoustic neuroma vary among patients and have a material impact on their quality of life (QOL). METHODS: A questionnaire concerning postoperative symptoms and the Short Form 36 (SF-36) QOL instrument were mailed to 97 consecutive patients who had undergone acoustic neuroma surgery via the translabyrinthine approach. The survey response rate was 78% and the symptomatology was consistent with other reports, supporting the representativeness of the sample. The respondents' QOL was rated significantly below published norms and their work capacity was reportedly reduced. Specifically, the following SF-36 dimensions were reduced: physical functioning and role-physical, together with vitality, general health, and social functioning. Greater numbers of postoperative symptoms and larger tumors were associated with a worse rating of physical functioning. More severe balance problems were associated with lower ratings of social functioning. The disparity between the patient's self-estimate and self-measurement and the clinician's assessment of the patient's facial functioning raises doubts about the validity of subjective reports and assessment. CONCLUSIONS: The present study supports the use of generic QOL measures to assess outcome and to draw comparisons between different populations.

Adolescent↗
PubMed2000

Nonlinear temporal interactions in click-evoked otoacoustic emissions. I. Assumed model and polarity-symmetry.

Click-evoked otoacoustic emissions (CEOAEs) are reduced in amplitude by the presentation of 'suppressor' clicks that either closely lead or follow the stimulus ('test') clicks. This suppression of the response represents nonlinear temporal interactions between the test and suppressor clicks and/or the CEOAEs they evoke. There are some discrepancies amongst previous reports of the phenomenon, and the underlying mechanisms are not understood. In particular, it is unclear whether the suppression reported simply reflects the compressive nonlinearity of the CEOAE input-output (I-O) function. This paper presents a simple model of the nonlinear interactions between CEOAEs evoked by two closely-spaced clicks. The model shows that suppression as reported may be entirely derived from CEOAE I-O nonlinearity, in combination with the extended duration of the cochlear responses to click stimuli. It is also shown experimentally that suppression is insensitive to the polarities of test and suppressor clicks, which is consistent with the model based on I-O nonlinearity. A companion paper (Kapadia and Lutman, Hear. Res. 146 (2000)) presents experimental findings from a detailed parametric study of nonlinear temporal interactions in CEOAEs in human subjects with normal hearing. The findings are compared with the pattern of results generated by the above model, in order to assess the role of I-O nonlinearity in these nonlinear interactions.

Acoustic Stimulation↗
PubMed2000

Nonlinear temporal interactions in click-evoked otoacoustic emissions. II. Experimental data.

Click-evoked otoacoustic emissions (CEOAEs) are reduced in amplitude by the presentation of 'suppressor' clicks that either closely lead or follow the stimulus ('test') clicks. A model described in a companion paper (Kapadia and Lutman, Hear. Res. 146 (2000) 89-100) shows that such nonlinear temporal interactions, as previously reported, may be explained in terms of the compressive non-linearity of the CEOAE input-output (I-O) function. This paper presents the results of a detailed parametric investigation into such nonlinear interactions, studied in 12 normal adult ears over a wide range of test and suppressor click levels and inter-click intervals. The results differ from those generated by the model in a number of respects. Principally, maximum suppression is generally obtained for suppressors presented in advance of test clicks, rather than co-incident with the test clicks. The amount of advance depends systematically on the two click levels. The measured suppression can also exceed the theoretical maximum allowed by the model. It is concluded that the nonlinear temporal interactions measured do not simply reflect CEOAE I-O function non-linearity. They may, instead, arise from disturbance of the generator elements from their resting state prior to generation of the CEOAE. These results may also have general implications relating to cochlear responses to transient stimuli and indicate the potential of CEOAEs in probing aspects of cochlear mechanics.

Acoustic Stimulation↗
PubMed2000

Guidelines on the diagnosis of noise-induced hearing loss for medicolegal purposes.

These guidelines aim to assist in the diagnosis of noise-induced hearing loss (NIHL) in medicolegal settings. The task is to distinguish between possibility and probability, the legal criterion being 'more probable than not'. It is argued that the amount of NIHL needed to qualify for that diagnosis is that which is reliably measurable and identifiable on the audiogram. The three main requirements for the diagnosis of NIHL are defined: R1, high-frequency hearing impairment; R2, potentially hazardous amount of noise exposure; R3, identifiable high-frequency audiometric notch or bulge. Four modifying factors also need consideration: MF1, the clinical picture; MF2, compatibility with age and noise exposure; MF3, Robinson's criteria for other causation; MF4, complications such as asymmetry, mixed disorder and conductive hearing impairment.

Audiometry↗
PubMed2000

What is the risk of noise-induced hearing loss at 80, 85, 90 dB(A) and above?

Regulations regarding risk from exposure to noise at work entail action at levels of 85 dB(A) and above. At 80 dB(A) there is no material risk in the vast majority of individuals. At 85 dB(A) there is a marginal risk with susceptible individuals accruing a significant hearing impairment from a lifetime of exposure. At 90 dB(A) and above the risk becomes material, with the majority of individuals accruing a significant hearing impairment.

Hearing Loss, Noise-Induced↗
PubMed2000

Preimplant measures of preverbal communicative behavior as predictors of cochlear implant outcomes in children.

OBJECTIVE: Comparison of preverbal communication behavior in young children before receiving cochlear implants with outcomes 3 yr after implantation on speech identification and speech production tasks, to assess whether outcomes can be predicted from characteristics inherent to the child before implantation. DESIGN: Video recordings of preverbal communicative behavior were examined before use of the implant to quantify turn-taking and demonstration of autonomy by the child. Speech identification ability was measured 3 yr after implantation based on the Iowa Closed-Set Speech Perception Sentence Test, continuous discourse tracking, and an observational measure of telephone use. Speech production ability was measured 3 yr after implantation by the Edinburgh Articulation Test. Associations between the preimplant measures and the 3-yr outcomes were assessed by correlation analysis of data from 33 children. RESULTS: The 3-yr performance measures of speech identification were correlated with the preimplant measure of autonomy. Telephone use and speech production ability were not significantly associated with the preimplant measures. CONCLUSIONS: Up to a fourth of the variance in speech identification performance 3 yr after cochlear implantation of young children may be predicted from characteristics that are inherent to the child before implantation. Those characteristics are represented by the demonstration of autonomy in preverbal communicative interactions, whether by means of vocalization or by gesture. If those characteristics are acquired during infancy, outcomes in children with auditory prostheses including cochlear implants may be enhanced by activities that encourage autonomy in early years.

Child Behavior↗
PubMed2000

Approach to communication, speech perception and intelligibility after paediatric cochlear implantation.

The aim of this study was to explore the relationship between approach to communication, speech perception and speech intelligibility after cochlear implantation of young children with profound early deafness. A prospective speech perception and speech intelligibility assessment was undertaken on a consecutive group of implanted children. There were 46 children at the three-year, 26 at the four-year and 20 at the five-year intervals. All had been born deaf or deafened before the age of three and received cochlear implants before the age of seven. Their speech perception ability and the intelligibility of their speech were measured before cochlear implantation and annually thereafter. The children's communication had been classified by their teachers of the deaf at each interval into one of two categories: those using an oral approach and those using a signing approach. Results revealed that at all intervals, those children classified as using oral communication significantly exceeded those using signed communication on measures of speech perception and intelligibility (p<0.05). When those children who had changed from signed to oral communication were compared at the three-year interval with those who used oral communication throughout, there was no significant difference in their results. However, it remains to be explored whether children use oral communication after cochlear implantation because they are doing well, or whether they do well because they are using oral communication.

Child↗
PubMed1998

Categories of auditory performance: inter-user reliability.

Categories of Auditory Performance (CAP) describes a scale used to rate outcomes from paediatric cochlear implantation in everyday life. It differs from more technical measures by being readily applied and easily understood by non-specialist professionals and by parents. Being based on subjective assessments, there is a need to establish whether ratings by different persons are comparable. Therefore, an analysis of inter-user reliability was undertaken using ratings from 23 children followed up at various intervals after implantation. Analysis relating scores by local teachers of the deaf and the teachers of the deaf at the implant centre revealed very high inter-user reliability (correlation coefficient 0.97). This result establishes the reliability of CAP as an outcome measure for use in cochlear implant programmes.

Child, Preschool↗