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Biomedical subjects

M W Skinner

Publications and source records attributed to M W Skinner.

At least 19 recordsLinked to original sources

Treatment for all: a vision for the future.

The World Federation of Hemophilia (WFH) has defined a new strategic plan which maps out where the organization is going and what it can do for our members. The plan embraces the vision of Treatment for All; i.e. one day, treatment will be available for all those with inherited bleeding disorders, regardless of where they live. Treatment for All means proper diagnosis, management, and care by a multidisciplinary team of trained specialists. It means safe, effective treatment products are available for all people with inherited bleeding disorders. It means expanding services beyond haemophilia, to those with von Willebrand's disease, rare factor deficiencies, and inherited platelet disorders. Today, more than 75% of the global bleeding disorders community receive either inadequate or no treatment whatsoever. Our mission is to improve treatment where it is limited or does not exist. At the same time, we must sustain the many gains we have achieved thus far. The challenge is immense. Making our vision a reality requires us to be focused and deliberate about the programmes we undertake and the commitments we make. Building on past strategic plans, this plan presents a vision for the continued success of the WFH over the next 3-5 years.

Blood Coagulation Disorders, Inherited↗

What is a cure and how do we get there?

The absence of adequate treatment for most of the world's 400 000 individuals with haemophilia makes the development of a cure compelling. Advances in the basic molecular sciences over the past 20 years have resulted in the feasibility of curing haemophilia through the application of gene therapy. However, the reality of this therapeutic strategy is highly complex. In addition, challenges to achieving a cure exist beyond the basic scientific hurdles. Thoughtful attention must also be given to a number of interrelated issues, including ethical considerations in patient recruitment, informed consent and geographical variables of global clinical trials. The global inequalities in healthcare mean that the ethics of international medical research, especially when it includes countries where people usually do not receive quality care, become much more complicated. The majority of haemophiliacs lives in developing countries and is a valuable resource of human subjects who could be enrolled in clinical trials. When recruiting subjects globally, investigators must be ever mindful that the patient population is a precious resource, which must be treated with respect and care. This presents a major challenge for investigators engaged in trials of haemophilia gene therapy to ensure that the informed consent process is current and comprehensive, that therapeutic misconceptions are appropriately managed, and that the roles of the researcher and physician are clear. Global clinical gene-therapy trials are an important and appropriate component in the quest to achieve a cure for haemophilia. When trials follow identical internationally accepted standards, a successful outcome can be achieved for trials including developing countries, if country specific cultural and economic aspects are considered.

Clinical Trials as Topic↗

Evaluation of the Intubating Laryngeal Mask Airway used by occasional intubators in simulated trauma.

This observational study assessed the potential role of the intubating laryngeal mask airway (ILMA) for use by emergency care givers with limited laryngoscopy skills. Six ambulance officers with advanced airway training, five doctors with intubation experience and five doctors without intubation experience were given a short instruction course on the use of the ILMA. They subsequently used the device on 80 consenting subjects anaesthetized for elective surgery after the application of cricoid pressure and manual in-line stabilization of the cervical spine. All patients were successfully ventilated via the ILMA. Mean (SD) times in seconds to ventilation were 27 (10), 33 (18) and 47 (22) respectively in the occasional intubator ambulance officers, occasional intubator doctor and naive intubator groups. The numbers (percentage) failures to intubate via the ILMA in each group were 2 (7%), 5 (20%) and 4 (16%) respectively. Mean (SD) times in seconds to intubation were 32 (23), 32 (17) and 36 (25). There was no evidence of "learning" with repeated use. The feedback forms were strongly supportive of a prehospital trial and also of having an ILMA available during all intubations. Participants almost universally rated the ILMA as easy to use. This study supports further evaluation of the ILMA in a large prehospital trial.

Adult↗

Cochlear implants: three-dimensional localization by means of coregistration of CT and conventional radiographs.

With use of radiopaque implanted objects as internal fiducial markers, the authors developed and evaluated a technique for coregistering computed tomographic (CT) and computed radiographic images to help determine three-dimensional location information for implant electrodes in the cochlea in phantoms and patients. Three-dimensional positional data from CT were assigned on a radiograph, which permitted identification of individual cochlear electrode locations that were not depicted at CT.

Adult↗

Do anaesthetists need to wear surgical masks in the operating theatre? A literature review with evidence-based recommendations.

Many operating theatre staff believe that the surgical face mask protects the healthcare worker from potentially hazardous biological infections. A questionnaire-based survey, undertaken by Leyland' in 1993 to assess attitudes to the use of masks, showed that 20% of surgeons discarded surgical masks for endoscopic work. Less than 50% did not wear the mask as recommended by the Medical Research Council. Equal numbers of surgeons wore the mask in the belief they were protecting themselves and the patient, with 20% of these admitting that tradition was the only reason for wearing them. Policies relating to the wearing of surgical masks by operating theatre staff are varied. This indicates some confusion about the role of the surgical mask in modern surgical and anaesthetic practice. This review was undertaken to collate current evidence and make recommendations based on this evidence.

Anesthesiology↗

The societal costs of severe to profound hearing loss in the United States.

OBJECTIVE: Severe to profound hearing impairment affects one-half to three-quarters of a million Americans. To function in a hearing society, hearing-impaired persons require specialized educational, social services, and other resources. The primary purpose of this study is to provide a comprehensive, national, and recent estimate of the economic burden of hearing impairment. METHODS: We constructed a cohort-survival model to estimate the lifetime costs of hearing impairment. Data for the model were derived principally from the analyses of secondary data sources, including the National Health Interview Survey Hearing Loss and Disability Supplements (1990-91 and 1994-95), the Department of Education's National Longitudinal Transition Study (1987), and Gallaudet University's Annual Survey of Deaf and Hard of Hearing Youth (1997-98). These analyses were supplemented by a review of the literature and consultation with a four-member expert panel. Monte Carlo analysis was used for sensitivity testing. RESULTS: Severe to profound hearing loss is expected to cost society $297,000 over the lifetime of an individual. Most of these losses (67%) are due to reduced work productivity, although the use of special education resources among children contributes an additional 21%. Lifetime costs for those with prelingual onset exceed $1 million. CONCLUSIONS: Results indicate that an additional $4.6 billion will be spent over the lifetime of persons who acquired their impairment in 1998. The particularly high costs associated with prelingual onset of severe to profound hearing impairment suggest interventions aimed at children, such as early identification and/or aggressive medical intervention, may have a substantial payback.

Adolescent↗

Digital X-ray stereophotogrammetry for cochlear implantation.

Multielectrode, intracochlear implant systems are effective treatment for profound sensorineural hearing loss. In some cases, these systems do not perform well, which may be partially due to variations in implant location within the cochlea. Determination of each electrode's position in a patient's inner ear provides an in vivo basis for both the cochlear modeling of electrical fields and the future design of electrode arrays that deliver electrical stimulation to surviving auditory neurons, and may improve speech processor programming for better speech recognition. We developed an X-ray stereophotogrammetric approach to localize implanted electrodes in three dimensions. Stereophotogrammetry of implanted electrodes is formulated in weak perspective geometry, with knowledge of a three-dimensional (3-D) reference structure and electrode positions in each of two digital stereo-images. The localization error is theoretically, numerically, and experimentally quantified. Both numerical and experimental results demonstrate the feasibility of the technique.

Biomedical Engineering↗

Three-dimensional modeling and visualization of the cochlea on the Internet.

Three-dimensional (3-D) modeling and visualization of the cochlea using the World Wide Web (WWW) is an effective way of sharing anatomic information for cochlear implantation over the Internet, particularly for morphometry-based research and resident training in otolaryngology and neuroradiology. In this paper, 3-D modeling, visualization, and animation techniques are integrated in an interactive and platform-independent manner and implemented over the WWW. Cohen's template shape with mean cross-sectional areas of the human cochlea is extended into a 3-D geometrical model. Also, spiral computer tomography data of a patient's cochlea is digitally segmented and geometrically represented. The cochlear electrode array is synthesized according to its specification. Then, cochlear implantation is animated with both idealized and real cochlear models. Insertion length, angular position, and characteristic frequency of individual electrodes are estimated online during the virtual insertion. The optimization of the processing parameters is done to demonstrate the feasibility of this technology for clinical applications.

Cochlea↗

Localization of cochlear implant electrodes in radiographs.

Multielectrode cochlear implantation is the most effective treatment for profound sensorineural hearing loss. In vivo three-dimensional 3-D localization of cochlear implant electrodes is important for modeling of the electrical field in the cochlea, design of electrode arrays, and may improve speech processor programming for better speech recognition. The prerequisite for 3-D localization of the electrodes is their 2-D localization in x-ray radiographs. In this paper, we develop a practical method to localize the electrodes with high efficiency, accuracy, and reproducibility. In this method, a priori knowledge of the electrodes and their approximate positions are utilized, an intelligent thresholding and segmentation mechanism is embedded, and the electrode center is computed as the weighted geometric center of segmented electrode pixels. Experiments with physical phantoms and human data demonstrate the feasibility and utility of this method. The PC-based program developed for this project is disseminated on the Web.

Cochlear Implants↗

Effect of stimulation rate on cochlear implant recipients' thresholds and maximum acceptable loudness levels.

Clinically, speech processor programs are created using electrical thresholds and maximum acceptable loudness levels (MALs) at several different stimulation rates to determine what rate will provide cochlear implant recipients with the best speech recognition when using fast-rate speech coding strategies. This study was designed to determine the difference in thresholds and MALs (expressed in the clinical unit, Current Level [CL]) for pairs of six rates spanning those available with the Nucleus 24 device (i.e., 250 to 2,400 pps/ch) using monopolar, 25 microsec/phase stimulation. Test-retest measures of threshold and MAL for each rate were obtained from seven adult Nucleus 24 recipients on each of 11 electrodes. The difference in threshold and in MAL between pairs of rates was dependent on the absolute CL. Below approximately 190 CL, thresholds and MALs decreased with increasing rate; above 210 CL, there was little change in threshold or MAL with increasing rate. Based on these findings, an approach to estimating threshold and MAL from one rate to another is suggested, pending further research.

Adult↗

Effect of speech processor program modifications on cochlear implant recipients' threshold and maximum acceptable loudness levels.

This study's purpose was to determine whether or not modifications in speech processor electrical stimulation levels were associated with changes in five Nucleus 22 cochlear implant recipients' thresholds or maximum acceptable loudness levels (MALs). These modifications in minimum and maximum stimulation levels were made to optimize hearing in everyday life. One threshold and one MAL were obtained on each active electrode during six, weekly test sessions, three before and three after program modification. Only one participant had a significant change in threshold after program modification; this participant and four others had significant changes in MAL. Participants' threshold variability was the same, but MAL variability was higher than that observed in other studies. Because these participants had no experience making MAL judgments prior to this study, this result suggests that implant recipients should be given sufficient practice in making MAL judgments to provide a stable clinical estimate of the upper boundary of the electrical dynamic range.

Acoustic Stimulation↗

Comparison of two methods for selecting minimum stimulation levels used in programming the Nucleus 22 cochlear implant.

Minimum stimulation levels for active electrodes in a Nucleus 22 cochlear implant were set at threshold (clinical default value) and raised levels (M = +2.04 dB) to determine if raised levels would improve recipients' understanding of soft speech sounds with the SPEAK speech coding strategy. Eight postlinguistically deaf adults participated in a 4-phase A1B1A2B2 test design. Speech recognition was evaluated with consonant-vowel nucleus-consonant (CNC) words in quiet and sentences in noise, both presented at 50, 60, and 70 dB SPL during 2 weekly sessions at the end of each phase. Group mean scores were significantly higher with the raised level program for words and phonemes at 50 and 60 dB SPL and for sentences at 50 and 70 dB SPL. All participants chose to use the raised level program in everyday life at the end of the study. The results suggest that clinical use of a raised level program for Nucleus 22 recipients has the potential to make soft sounds louder and, therefore, more salient in everyday life. Further research is needed to determine if this approach is appropriate for other cochlear implant devices.

Acoustic Stimulation↗

Identification of speech by cochlear implant recipients with the multipeak (MPEAK) and spectral peak (SPEAK) speech coding strategies II. Consonants.

OBJECTIVE: The major objective of this study was to evaluate differences in consonant recognition with the Multipeak (MPEAK) and the Spectral Peak (SPEAK) speech coding strategies of the Nucleus-22 Cochlear Implant System. This objective was addressed by comparison of acoustic and electrode activation analyses of consonants with cochlear implant recipients' responses to these same consonant tokens when they used the two speech coding strategies. DESIGN: Nine subjects identified 14 English consonants with the MPEAK and SPEAK speech coding strategies. These strategies were compared with an ABAB design. Evaluation occurred during two weekly sessions after subjects used each strategy for at least 3 wk in everyday life. RESULTS: Group medial consonant [aCa] identification scores with the SPEAK strategy were significantly higher than with the MPEAK strategy (76.2% versus 67.5%; p < 0.001). This improvement was largely due to the significant increase in information transmitted for the place feature (p < 0.001) through accurate tracking of second formant transitions and spectrally specific stimulation patterns to differentiate [s] from [symbol see text] and [n] from [m], and the stop consonant bursts. For this reason, more nasal consonants were correctly identified with SPEAK, but there also were more non-nasal error responses when the nasal murmur was of unusually low amplitude. Consequently, significantly less information was transmitted for the nasality feature with SPEAK than MPEAK (p < 0.001). CONCLUSIONS: Electrical stimulation with the SPEAK strategy provided better spectral representation of the stop consonant bursts, tracking formant transitions into the following vowel, frication in the consonant [symbol see text], and the formants for the nasals [m] and [n] than with the MPEAK strategy. The marked improvement in recognition of the velar consonants, [g] and [k], which cannot be seen during speechreading, should allow greater ease and accuracy of communication with SPEAK than MPEAK.

Adult↗

Optimization of speech processor fitting strategies for Chinese-speaking cochlear implantees.

OBJECTIVES: To compare speech recognition performance in Chinese-speaking cochlear implant patients with a speech processor program selected by the clinical audiologist in Taiwan and with a new speech processor program based on the Washington University clinical procedure developed by Skinner et al. STUDY DESIGN: Six adult Chinese-speaking patients implanted with the Nucleus cochlear implant system participated in this study. METHODS: A fitting procedure developed in 1995 by Skinner et al. at Washington University School of Medicine was used to create a new speech processor program to optimize each patient's hearing in everyday life. Speech tests (vowels, consonants, tones, and words), sound-field thresholds, and a self-report questionnaire were used to evaluate each patient's performance with his or her previous speech processor program and a new one. RESULTS: Four of the six patients had significant changes from the previous to the new speech processor program. These changes were associated with improvement in score on at least one speech test, more sensitive sound field thresholds, and reported improvement in some everyday listening situations on the questionnaire. CONCLUSIONS: These results suggest that use of this procedure with adult cochlear implantees may improve benefit in everyday life. Analysis of the speech test stimuli and patients' responses provides a basis for modification or creation of new Mandarin Chinese speech tests for preoperative and postoperative evaluation of adult cochlear implant patients.

Adolescent↗

Spiral CT image deblurring for cochlear implantation.

Cochlear implantation is the standard treatment for profound hearing loss. Preimplantation and postimplantation spiral computed tomography (CT) is essential in several key clinical and research aspects. The maximum image resolution with commercial spiral CT scanners is insufficient to define clearly anatomical features and implant electrode positions in the inner ear. In this paper, we develop an expectation-maximization (EM)-like iterative deblurring algorithm to achieve spiral CT image super-resolution for cochlear implantation, assuming a spatially invariant linear spiral CT system with a three-dimensional (3-D) separable Gaussian point spread function (PSF). We experimentally validate the 3-D Gaussian blurring model via phantom measurement and profile fitting. The imaging process is further expressed as convolution of an isotropic 3-D Gaussian PSF and a blurred underlying volumetric image. Under practical conditions, an oblique reconstructed section is approximated as convolution of an isotropic two-dimensional (2-D) Gaussian PSF and the corresponding actual cross section. The spiral CT image deblurring algorithm is formulated with sieve and resolution kernels for suppressing noise and edge artifacts. A typical cochlear cross section is used for evaluation, demonstrating a resolution gain up to 30%40% according to the correlation criterion. Physical phantoms, preimplantation and postimplantation patients are reconstructed into volumes of 0.1-mm cubic voxels. The patient images are digitally unwrapped along the central axis of the cochlea and the implanted electrode array respectively, then oblique sections orthogonal to the central axis formed. After deblurring, representation of structural features is substantially improved in all the cases.

Algorithms↗

In vivo measures of cochlear length and insertion depth of nucleus cochlear implant electrode arrays.

Three-dimensional cochlear canal lengths, electrode array intracochlear insertion depths, and characteristic frequency ranges were estimated for 20 Nucleus implant recipients on the basis of in vivo computed tomography (CT) scans. Ultra-high resolution images were reconstructed from spiral CT data with 0.1-mm slicing and expanded attenuation scales. Canal length estimates (mean 33.01 mm; SD 2.31) were consistent with previous findings for normal human temporal bones. Intracochlear array insertion depths estimated by 3-dimensional (3-D) spiral calculations (mean 20.19 mm; SD 2.86) and by a computerized array tracking algorithm (mean 20.36 mm; SD 2.66) were not significantly different. Estimates from surgical observations were significantly longer (mean 21.03 mm; SD 2.31) because array compressions were not detectable. Characteristic frequencies at apical electrodes estimated from Greenwood's equations ranged from 387 Hz to 2,596 Hz. The results show that significant variations in cochlear anatomy and array distribution among implant patients that may impact implant performance can be reliably detected and quantified by using in vivo high-resolution CT and 3-D reconstructions.

Adult↗

Parameter selection to optimize speech recognition with the Nucleus implant.

Speech coding strategy, frequency boundary assignment table, and speech processor program minimum and maximum stimulation levels are parameters of the Nucleus Cochlear Implant System whose selection affects speech recognition performance in adults and children. Research studies show that speech recognition is significantly better with (1) the Spectral Peak than with the Multipeak speech coding strategy and (2) frequency boundary assignment Table 7 than with Table 9 in an individual's speech processor program (MAP). Minimum and maximum stimulation levels in this MAP are based on psychophysical measurements on each electrode but often need to be modified for optimum use in everyday life. Many children and adults have increases, decreases, or fluctuations in electrical hearing that require changes in the MAP minimum and maximum levels to maintain their ability to recognize speech and other sounds.

Adult↗

Speech recognition with the MPEAK and SPEAK speech-coding strategies of the Nucleus Cochlear Implant.

The Spectra 22 Speech Processor and spectral peak (SPEAK) speech-coding strategy provide Nucleus 22 Channel Cochlear Implant (Cochlear, Corp., Englewood, Colo.) users with a better understanding of speech than the previous Mini Speech Processor and Multipeak (MPEAK) speech-coding strategy. On the NU-6 Monosyllabic Word Test, subjects scored 13% higher for words and 14% higher for phonemes with the SPEAK strategy than with the MPEAK strategy. On the Connected Speech Test and the CID Everyday Sentence Test, subjects scored 32% and 37% higher, respectively, with SPEAK than with MPEAK.

Adult↗