Search PubMed⌕ Search

Biomedical subjects

K Stephan

Publications and source records attributed to K Stephan.

At least 73 records · Page 4Linked to original sources

Changes in ventricular fibrillation threshold during repeated short-term coronary occlusion and release.

The time course of changes in VFT was determined during the 1st phase of arrhythmia following coronary occlusion and during consecutive reperfusion in five repeated periods of occlusion and reperfusion in 10 mongrel dogs (17--24 kg). VFT was determined using a square wave pulse series of 140 ms duration which was triggered by the R-wave of the ECG and placed into the vulnerable period of the cardiac cycle. After acute occlusion VFT decreased to a minimum level within a few minutes and then increased again slowly up to the control value which was reached about 20 min after the ligation. When the occlusions were repeated several times the extent of the decrease in VFT became increasingly less and its duration increasingly shorter until finally there was no significant decrease in VFT. Reperfusion after coronary occlusion led to an abrupt decrease in VFT within 1 min, followed by a rapid increase to the control value. This time course did not depend upon the number of prior occlusions. The results show that in the case of repeating short-term coronary occlusions one cannot expect comparable VFT time courses for the consecutive periods of occlusion except for the 1st and 2nd ones. Differing mechanisms leading to the occurrence of VF after coronary ligation and during reperfusion are discussed.

Animals↗

Comparison of the TEMPO+ ear-level speech processor and the cis pro+ body-worn processor in adult MED-EL cochlear implant users.

A study was conducted to compare the new MED-EL TEMPO+ ear-level speech processor with the CIS PRO+ body-worn processor in the COMBI 40/COMBI 40+ implant system. Speech tests were performed in 46 experienced subjects in two test sessions approximately 4 weeks apart. Subjects were switched over from the CIS PRO+ to the TEMPO+ in the first session and used only the TEMPO+ in the time between the two sessions. Speech tests included monosyllabic word tests and sentence tests via the telephone. An adaptive noise method was used to adjust each subject's scores to approximately 50%. Additionally, subjects had to complete a questionnaire based on their 4 weeks of experience with the TEMPO+. The speech test results showed a statistically significant improvement in the monosyllabic word scores with the TEMPO+. In addition, in the second session, subjects showed a significant improvement when using the telephone with the TEMPO+, indicating some learning in this task. In the questionnaire, the vast majority of subjects found that the TEMPO+ allows equal or better speech understanding and rated the sound quality of the TEMPO+ higher. All these objective and subjective results indicate the superiority of the TEMPO+ and are mainly attributed to a new coding strategy called CIS+ and its implementation in the TEMPO+. In other words, based on the results of this study, it appears that after switching over from the CIS PRO+ to the TEMPO+, subjects are able to maintain or even improve their own speech understanding capability.

Adult↗

A multicenter randomized double-blind study on the efficacy and safety of nicergoline in patients with multi-infarct dementia.

A 6-month double-blind, randomized, placebo-controlled clinical trial preceded by a 3-week single-blind, washout/run-in placebo phase was performed in male and female patients, 55-85 years of age with a clinical diagnosis of mild to moderate multi-infarct dementia according to DSM-III to evaluate the therapeutic efficacy and safety of nicergoline 30 mg b.i.d. Primary endpoints for efficacy were the changes in the Sandoz Clinical Assessment Geriatric Scale (SCAG) and Mini-Mental State Examination (MMSE) scores at the end of the treatment with respect to baseline. Secondary endpoints were Clinical Global Impression, 3 subtests of the Weschsler Adult Intelligence Scale and Blessed A scale for activities of daily living, and all endpoints in 2-month intervals. A total of 252 patients were screened, 136 patients entered the double-blind phase and were evaluated as intent-to-treat (ITT) patients. Fifteen patients were excluded from the efficacy analyses of valid cases (VC) due to protocol violations or because they dropped out of the study prematurely. Confirmatory efficacy analysis after 6 months of treatment revealed superiority of nicergoline treatment with p < 0.01 for both SCAG and MMSE scores (ITT and VC). Subsequent descriptive efficacy analysis resulted in significant differences in favor of nicergoline, in the majority of cases as early as 2 months after start of treatment. Nicergoline was well tolerated and a similar number of adverse events were observed in both the placebo and the nicergoline group.

Aged↗

Speech understanding in quiet and in noise with the CIS speech coding strategy (MED-EL Combi-40) compared to the multipeak and spectral peak strategies (nucleus).

This study compares sentence understanding in quiet and in noise with 3 different speech coding strategies for cochlear implants. The results show that the spectral-peak (SPEAK) and continuous-interleaved-sampling (CIS) coding strategies, based on spectral signal analysis, allow for better speech understanding in quiet as well as in noise, than the multipeak (MPEAK) coding strategy, which relys on speech feature extraction. In the intrasubject comparison of the MPEAK and SPEAK strategies, the SPEAK coding strategy provided a considerable improvement in quiet and in noise for the majority of patients using the Nucleus 22 Mini-implant. In the intersubject comparisons, the mean results in noise with the CIS strategy were superior to both the MPEAK and the SPEAK strategies. The difference was greatest for the most difficult tests in noise. Understanding in noise was least reduced for the CIS strategy. Understanding in quiet was not significantly different between the CIS and the SPEAK strategies; both strategies were significantly better than the MPEAK strategy in quiet. These results are still preliminary, due to the relatively small number of patients and the great inherent intersubject variability of results.

Adolescent↗

Evaluation of performance with the COMBI40 cochlear implant in adults: a multicentric clinical study.

The present multicentric clinical study involves 19 centres, 16 of them in German-speaking countries, 1 British, 1 Polish and 1 Hungarian. 60 postlingually deafened adults with a mean age of 47.5 years (20-70) and mean duration of deafness of 5.3 years (0.5-20) have been evaluated with the MED-EL COMBI 40 cochlear implant which implements a high-rate continuous-interleaved-sampling strategy with 8 channels. Safety and effectiveness data have been collected. Speech perception tests include a 16-consonant, an 8-vowel, a sentence and a monosyllabic-word test in all languages and a 2-digit figure test in all languages but English. Test intervals are 1, 3, 6 months and 1 year after first fitting. 41 of the 60 postlingually deafened adult study patients have completed their 6-month evaluation. While their pre-operative monosyllabic-word score was 0%, their mean monosyllabic-word score 6 months after first fitting was 48% (8-90) with a median of 50%. The mean sentence understanding was 84% (24-100) with a median of 90%. The respective values for the 1-year evaluations with 25 patients are a mean of 50% (5-85), with a median of 60% for the monosyllables and a mean of 89% (30-100), with a median of 97%, for the sentences.

Adult↗

Post-operative stapedius reflex tests with simultaneous loudness scaling in patients supplied with cochlear implants.

The estimation of the maximum comfort loudness levels (MCL) by measurements of the electrically elicited stapedius reflex was examined in six experienced cochlear implant users supplied with the COMBI 40 implant system. The stapedius reflex was tested and loudness scaling was performed simultaneously using an up/down stimulation protocol close to the reflex threshold with automated recording of both test procedures. The electrical stapedius reflex threshold (ESRT) and loudness scaling were evaluated separately. Scaling at the reflex threshold ranged between normal and loud. The range of stimulus intensities corresponding to ESRT is much smaller than that at a particular loudness category. The overall correlation between ESRT and MCL was high (r=0.92), with a similar dependence of ESRT and MCL on the channel stimulated. Thus, when the stapedius reflex can be detected post-operatively, the ESRT can be applied successfully for the fitting procedure of the speech processor. Simultaneous loudness scaling during the entire reflex test showed that overstimulation via the implant can be avoided effectively.

Adult↗

Effect of stimulus duration on stapedius reflex threshold in electrical stimulation via cochlear implant.

The effect of stimulus duration on the threshold of the contralateral stapedius reflex was investigated in patients supplied with a Vienna cochlear implant (analog stimulation via CI) and compared to results of a normal-hearing reference group in case of acoustic stimulation. Changes in reflex threshold were determined at four frequencies (125, 500, 1,000 and 2,000 Hz in case of electrostimulation and at 500, 1,000, 2,000 and 4,000 Hz for acoustic stimulation) and for five durations (30, 50, 100, 300 and 500 ms). The comparison of the two stimulation modes was accomplished by using the same instrumentation and procedure. Reflex threshold was evaluated according to an objective criterion based on the individual noise distribution of recordings without reflex and by subjective judgement. For both stimulation modes a strong effect of stimulus duration on reflex threshold was observed (p < 0.001). The amount of temporal integration reflected by the threshold difference between 500 and 50 ms was approximately 2-4 dB for electrical stimulation via CI and 6 dB for acoustic stimulation in normal-hearing individuals. In case of electrostimulation, the reflex threshold for stimuli of 30 ms was most often above the limit of uncomfortable loudness sensation; the increase in reflex threshold for acoustic stimulation between 500 and 30 ms was approximately 14 dB. There was no evidence of frequency effect on reflex threshold nor an interaction between frequency and stimulus duration for either stimulation mode.

Adult↗

Confirmation of transiently evoked otoacoustic emissions based on user-independent criteria.

Transiently evoked otoacoustic emissions (TEOAEs) were recorded from 525 ears (children, 3-11 years). Based on visual evaluation, the recordings were classified as TEOAEs present, absent or uncertain. Within each group the distribution of response level and reproducibility as well as of four derived parameters were calculated. The latter comprised: (1) corrected response level (difference between response level and approximated noise), (2) weighted response level (product of response level and correlation), (3) weighted sound pressure of the response (product of sound pressure and correlation) and (4) level of the weighted sound pressure of the response (weighted sound pressure of the response transformed to decibels). Based on these distributions, criteria to separate recordings with TEOAEs from recordings without TEOAEs were established. In this study the cutoff point is the parameter value where the amount of incorrectly identified recordings with TEOAEs is equal to the amount of correctly identified recordings without TEOAEs. The corresponding limiting values are: (a) response level 7.3 dB with 7.6% incorrect identifications for each group, (b) reproducibility 56% with 4.2% incorrect identifications, (c) corrected response level 2.4 dB with 5% incorrect identifications, (d) weighted response level 3.7 dB with 3.2% of incorrect identifications, (e) sound pressure of the response 0.027 mPa with 2% incorrect identifications and (f) level of the weighted sound pressure of the response 1.22 dB with 2% incorrect identifications.

Child↗

Age-specific doses of lormetazepam as a night sedative in cases of chronic sleep disturbance.

Lormetazepam, a new benzodiazepine derivative, was tested under double blind conditions in order to find the optimal dosage for different age groups of out-patients. 120 patients suffering from chronic sleep disturbance were included in the study: a younger group (age 20 to 55) and an older group (age 56 to 85 years). Four different doses were given to each age group: 0.5, 1.0, 2.0, and 3.0 mg to the younger group and 0.5, 1.0, 1.5, and 2.0 mg to the older group. A pre-placebo week (i.e. when all patients received placebo) in which baseline data were recorded preceded the two verum weeks, and these were followed by a post-placebo or withdrawal week (again all patients receiving placebo). The level of significance accepted for statistical decisions was alpha = 0.05. No differences in effects between the different doses were observed with regard to sleep pattern variables (sleep latency, sleep duration, frequency of awakenings, sleep quality, occurrence of 'bad' dreams) with the exception of sleep quality which was better in the older group than in the younger group after 0.5 mg in week 2. Considerable differences with regard to hangover feelings the next morning and during the next day (morning feelings, tranquility, alertness, and concentration), comparison of the effects of discontinuing therapy upon the above-mentioned sleep pattern variables and small differences in side effects--which were few--led to the following conclusion: --0.5 mg stood out as the best dose for the older group. --None of the dosages given to the younger group emerged clearly as superior. However, it would seem that the 1 mg dose should be the dose recommended, since fewer unfavourable scores and side effects appeared after this dose.

Adult↗