Biomedical subjects

Raymond M Bonnet

Publications and source records attributed to Raymond M Bonnet.

3 recordsLinked to original sources

PubMed2004

Speech recognition with a cochlear implant using triphasic charge-balanced pulses.

OBJECTIVE: Typically, symmetrical charge-balanced biphasic current pulses are used in cochlear implants to ensure biological safety. Theoretically, monophasic pulses are more effective, but potentially noxious, stimuli. In this study we charge-balanced such monophasic pulses during selected non-stimulated intervals, effectively leading to triphasic pulses with a 4:1 amplitude ratio between the cathodic and anodic phases. Apart from ensuring safety, this is also expected to reduce power consumption and channel interaction. MATERIAL AND METHODS: Seven experienced Clarion CII cochlear implant users with a multichannel (12-16 channels) monopolar continuous interleaved sampling (CIS) strategy participated in the study. Three different CIS strategies were fitted using the Clarion Research Interface (CRI-2). The reference was an implementation of each subject's own CIS program. The two strategies tested used triphasic pulses on the same channels, one with half-wave rectification (TP-HWR) and one without rectification (TP-NoR) at the input. Directly after fitting (i.e. without any training), speech perception (phoneme score on consonant-vowel-consonant words) was measured in silence (sound-only) and in speech-shaped background noise with signal:noise ratios (SNRs) of +5 and 0 dB. RESULTS: Speech perception with the reference via the CRI-2 was equal to that of the free-field condition with the subjects' own speech processor. With the TP-NoR strategy, speech perception improved significantly (from 89% to 93%) in silence and in the 0-dB SNR condition (from 43% to 49%). With a SNR of +5 dB, performance was stable at approximately 66%. With the TP-HWR strategy, performance increased significantly in the 0- and +5-dB SNR conditions, to 55% and 74%, respectively. Power consumption was reduced in both strategies, to 30% and 36% for TP-HWR and TP-NoR, respectively. CONCLUSION: The new triphasic strategies are most promising, with respect to both their improved speech perception and reduced power requirements. The optimal parameters will have to be identified following long-term use.

Adult↗

PubMed2004

Clinical ototoxicity of teicoplanin.

No strong evidence of ototoxicity of teicoplanin can be found in the literature, possibly because of conservative definitions of ototoxicity. We performed audiometry over time to compare the ototoxicity of teicoplanin with that of cloxacillin as a non-ototoxic standard. The data were analyzed with a linear mixed-effects model. The hearing thresholds of 12 patients who were treated with teicoplanin for severe staphylococcal infections showed a slight but significant increase over time, whereas the thresholds of 5 patients treated with cloxacillin decreased significantly during treatment. This improvement in hearing with cloxacillin may be attributed to improvement of the clinical condition. This outcome implies that previous reports that suggest a lack of ototoxicity of teicoplanin potentially underestimate the risk and should be interpreted accordingly.

Anti-Bacterial Agents↗

PubMed2003

Optimizing the number of electrodes with high-rate stimulation of the clarion CII cochlear implant.

OBJECTIVE: This blind crossover study evaluates the effect of the number of electrodes of the Clarion CII cochlear implant on speech perception in silence and in noise using a "high-rate" continuous interleaved sampling (CIS) strategy. MATERIAL AND METHODS: Nine users of this implant with 3-11 months of experience of an 8-channel CIS strategy [833 pulses per second (pps)/channel, 75 micros/phase] were fitted in a random order with 8-, 12- and 16-channel CIS strategies (+/- 1,400 pps/channel, 21 micros/phase). After 1 month of exclusive use of each strategy the performance was tested with consonant-vowel-consonant words in silence (sound only) and in speech-shaped background noise with signal-to-noise ratios (SNRs) of + 10, + 5, 0 and -5 dB. RESULTS: With "high-rate" strategies most patients' speech understanding in noise improved, although the optimum number of electrodes was highly variable. Generally, faster performers benefited from more active electrodes, whilst slower performers deteriorated. If each patient's optimal strategy was determined by a weighted sum of the test results at +10, + 5 and 0 dB SNR, the average phoneme score improved from 57% to 72% at a SNR of + 5 dB, and from 46% to 56% at a SNR of 0 dB. The average phoneme score in silence was approximately 85% for all strategies. CONCLUSION: We conclude that speech perception (especially in noise) can improve significantly with "high-rate" speech processing strategies, provided that the optimum number of electrodes is determined for each patient individually.

Acoustic Stimulation↗