Biomedical subjects

Michelle L Hughes

Publications and source records attributed to Michelle L Hughes.

5 recordsLinked to original sources

PubMed2006

The relation between electrophysiologic channel interaction and electrode pitch ranking in cochlear implant recipients.

The primary goal of this study was to examine the relation between electrophysiologic measures of channel interaction and the ability to discriminate pitch between electrodes in a psychophysical pitch-ranking task. It was hypothesized that cochlear implant recipients should perform better on an electrode pitch-ranking task when using electrodes with less channel interaction as measured with the electrically evoked compound action potential (ECAP). The width of the ECAP channel interaction function was compared with the slope of the pitch-ranking function for 10 adult Nucleus 24 recipients. Results showed no significant correlation between electrode pitch-ranking ability and width of the ECAP channel interaction function for individual subjects or for group data. Additionally, there was no significant correlation between speech perception performance and either pitch-ranking ability or width of the ECAP channel interaction function. These results suggest that the width of the ECAP interaction function may not be an accurate predictor of the ability to discriminate between electrodes on the basis of pitch.

Action Potentials↗

PubMed2006

Electrophysiologic channel interaction, electrode pitch ranking, and behavioral threshold in straight versus perimodiolar cochlear implant electrode arrays.

The primary goal of this study was to examine electrophysiologic measures of channel interaction, electrode pitch discrimination ability using a pitch-ranking task, and behavioral threshold levels in individuals implanted with a straight electrode array versus a perimodiolar array. It was hypothesized that perimodiolar arrays should yield lower thresholds, less channel interaction as measured with the electrically evoked compound action potential (ECAP), and better electrode pitch-ranking ability. Results from ten adult Nucleus 24 recipients (N=5 straight array, N=5 perimodiolar Contour array) showed no significant difference in threshold between the two electrode designs; however, there was significantly better electrode pitch-ranking ability and less channel interaction as measured with the ECAP for perimodiolar electrodes. Additionally, there was a significant positive correlation between behavioral threshold and width of the ECAP interaction function for Contour group data. There was no significant correlation between behavioral threshold and electrode pitch-ranking ability. These data suggest that electrode design and/or perimodiolar position may reduce physiologic channel interaction in the cochlea and improve electrode pitch discrimination ability; however, this positive finding did not translate into significantly better speech perception ability for Contour subjects.

Action Potentials↗

PubMed2004

Sensitivity and specificity of averaged electrode voltage measures in cochlear implant recipients.

OBJECTIVE: The primary purpose of this study was to evaluate the diagnostic accuracy of averaged electrode voltages (AEVs) for identifying malfunctioning electrodes in cochlear implant users. DESIGN: AEVs were measured using common ground (N = 33 ears) and monopolar stimulation modes (N = 40 ears) in adult subjects implanted with the Nucleus 24M or Nucleus 24R(CS) cochlear implant. AEV measures were then compared with common ground electrode impedance measures as well as to subjective judgments of electrode sound quality to determine the sensitivity and specificity of AEVs. RESULTS: Results showed excellent specificity for both modes of AEV testing: 97.9% for common ground and 99.8% for monopolar. Sensitivity for common ground AEV testing was 91.7%; however the sensitivity of monopolar AEVs was very poor, at 7.7%. Monopolar AEVs accurately identified open circuits but missed all short circuits. These results are consistent with the sensitivity of impedance measures made with each of the two stimulation modes. CONCLUSIONS: Common ground AEVs are more reliable than monopolar AEVs for identifying malfunctioning electrodes.

Adolescent↗

PubMed2003

Can we see more outpatients without more doctors?

A reduction in the number of return patients attending general cardiology clinics, if achievable without harm, would improve access for newly referred patients. Outpatient clinic letters (525) sent to general practitioners over a three-month period were reviewed. Simultaneously, physicians' opinions were collected by questionnaire. A subset of 30 clinic patients who attended three local general practitioners were studied to identify how many were assessed in primary care, and how often, in a six-month period. The hospital records of these patients were reviewed to determine whether information about these visits to the general practitioner was documented in the hospital notes. From the outpatient clinics the discharge rates were only 26% and the reason for further clinic review was often not clear. The fact that many patients had no intervention or treatment change performed at the clinic (42%) indicates that patients are reviewed to assess symptom change rather than to receive further interventions. The use of fixed times for review appointment (six months or 1 year) suggests that the intervals are determined by habit rather than clinical indication. A high proportion of patients (28/30) were reviewed at least once in primary care by general practitioners between hospital clinic visits and 20/30 were seen three or more times. There was poor documentation of these consultations in the hospital case notes, and so hospital physicians may be unaware that symptoms are under regular review in primary care. This study suggests that a substantial proportion of current cardiology return outpatients do not require regular outpatient review. However, alternative management demands good communication and exchange of information between secondary and primary care, development of formal written discharge planning in outpatient letters and other forms of follow-up.

Aged↗

PubMedDate not supplied

Channel interaction in cochlear implant users evaluated using the electrically evoked compound action potential.

One likely determinant of performance with a cochlear implant is the degree of interaction that occurs when overlapping subsets of nerve fibers are stimulated by various electrodes of a multielectrode array. The electrically evoked compound action potential (ECAP) can be used to assess physiological channel interaction. This paper describes results from two different methods of analysis of ECAP channel interaction measures made by the Nucleus neural response telemetry system. Using a forward-masking stimulus paradigm, masker and probe pulses are delivered through different electrodes. The response to the probe is then dependent on the extent of overlap in the stimulated neural populations. The amplitude of response to the probe as a function of masker electrode position then reflects the degree of overlap between the population of neurons responding to the masker and those stimulated by the probe. Results demonstrate large variations across individual implant users as well as across electrodes within an individual. In general, the degree of interaction is shown to be dependent on stimulus level.

Action Potentials↗