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D K Kessler

Publications and source records attributed to D K Kessler.

At least 19 recordsLinked to original sources
PubMed1999

The CLARION Multi-Strategy Cochlear Implant.

The Clarion cochlear implant is the result of many years of research and development, first at the University of California, San Francisco and the Research Triangle Institute of North Carolina, and then at Advanced Bionics Corporation in Sylmar, California. Approved by the US Food and Drug Administration after carefully monitored investigational clinical trials in both the adult and pediatric populations, it has now been implanted in approximately 3,000 patients worldwide. A fully flexible, programmable system, the Clarion offers multiple strategies and options in speech processing. The coupling mode, the stimulating waveform, and the temporal pattern of stimulation can be selected to allow each patient an opportunity to be fitted with the strategy that offers the highest level of performance. This paper describes the current status of the Clarion system. However, Clarion development has been a dynamic process, and from its initial introduction in 1991, the system has been modified and continually improved. The process of improvement and advancement is ongoing. New speech processing strategies and hardware developments are briefly summarized at the conclusion of this paper.

Cochlear Implants↗
PubMed1995

Ambulatory electrocardiography. A cost per management decision analysis.

BACKGROUND: This study evaluated the current clinical use and costs of ambulatory electrocardiographic (AECG) monitoring for arrhythmia detection based on a cost per management decision analysis. METHODS: Consecutive inpatient and outpatient 24-hour AECGs (n = 650) performed during the calendar year 1991 were retrospectively reviewed for clinical indication, arrhythmia detection, diary information, and whether a management decision that might alter patient outcome was derived from the data. The cost per management decision (based on a representative reimbursement of $550 per AECG) and the cost index (CI) (all tests divided by useful tests) were calculated. RESULTS: Although arrhythmias were identified in 91% of the patients, management decisions were indicated in only 18% (cost per decision, $2974; CI = 5.4). Management decisions were most often derived from the data in patients being evaluated for arrhythmia therapy (37 of 37 patients; cost per decision, $550; CI = 1). Symptoms and arrhythmias were correlated in only 11 patients (2%). More often typical clinical symptoms were present (26 patients) in the absence of an arrhythmia. Of 101 AECGs following a cerebrovascular event, four had unsuspected atrial fibrillation (cost per decision, $13,888; CI = 25.0). Dizziness or lightheadedness associated with other cardiac symptoms was more likely to lead to a management decision than the same symptoms in isolation (29% vs 7%; P < .05). No patient had central nervous system symptoms correlated with an arrhythmia during the recording period or unsuspected ventricular tachycardia. CONCLUSION: Ambulatory electrocardiography has a highly variable and indication-dependent effectiveness and cost. The results suggest a strategy for improving the use of AECG based on knowing what testing indications are more likely to lead to useful clinical information.

Aged↗
PubMed1995

Is ambulatory electrocardiography useful in the evaluation of patients with recent stroke?

This study was designed to determine whether ambulatory electrocardiography in patients with recent stroke would lead to a change in clinical management or outcome and to express these findings in terms of cost benefit. A prospective, consecutive sample of patients (n = 100) with recent stroke referred from the neurology or medical services for ambulatory electrocardiography was identified. Ambulatory electrocardiograms were reviewed to identify patients with potentially important bradyarrhythmias, tachyarrhythmias, or atrial fibrillation. Patients were then followed up without interference with ongoing care to determine whether these findings led to changes in clinical management that might influence patient outcome. Of the 100 patients, 16 had an index "important" arrhythmia. No significant bradyarrhythmias were noted. Nonsustained ventricular tachycardia (> or = 6 complexes) in two patients and supraventricular tachycardia (> or = 10 complexes) in seven patients did not lead to management changes. Four patients had a history of atrial fibrillation who were in sinus rhythm; anticoagulation had been addressed in three; the fourth patient died before the issue could be addressed. Of three patients in atrial fibrillation, there was a history of atrial fibrillation and a decision regarding anticoagulation in each before monitoring. The cost of these 100 ambulatory electrocardiograms was about $55,000. In conclusion, these findings do not support the routine use of ambulatory electrocardiography in the evaluation of patients with stroke.

Aged↗
PubMed1993

Clarion cochlear implant: phase I investigational results.

Under phase I of an FDA-approved Investigational Device Exemption (IDE), six patients at the University of California, San Francisco (UCSF) have been implanted with the Clarion, a new multichannel, multiprogrammable cochlear implant system. Over a period of 5 years, the Clarion has been collaboratively developed by UCSF, the Research Triangle Institute (RTI) of North Carolina, and the device manufacturer and sponsor, MiniMed Technologies of Sylmar, California. For UCSF, it represents the culmination of 21 years of cochlear implant research. The Clarion incorporates the 16-contact electrode array developed at UCSF. This electrode is designed with a gentle curve and an elastic memory that allow it to hug the modiolar wall of the scala tympani. In addition, the electrode has mechanical features that prevent it from rotating upward and injuring the basilar membrane. One of the innovations necessary to allow broad clinical application of this device has been the development of an electrode insertion tool to assist the surgeon in safe placement. In each of the six UCSF cases, the insertion tool was used and electrode placement was achieved with ease. With the availability of a variety of speech processing strategies, the Clarion has also provided the opportunity for all of the patients tested to date to achieve some degree of open-set, auditory-only speech recognition. Surgical considerations and preliminary audiologic data demonstrate that the design rationale and objectives of the Clarion have been met.

Aged↗
PubMed1992

Preliminary results with the Clarion cochlear implant.

A new cochlear implant has become available. This device, called the Clarion Multichannel Cochlear Implant, is the result of collaborative efforts between the University of California, San Francisco (UCSF), the Research Triangle Institute (RTI), Research Triangle Park, North Carolina, and the device manufacturer and sponsor, MiniMed Technologies of Sylmar, California. The Clarion represents a new generation of multi-programmable cochlear implant systems. Options in waveform, the stimulation mode, and the temporal distribution of the signal permit the device to be optimally customized for each individual patient. The speech coding scheme offering the greatest opportunity for speech recognition can be selected. The first Clarion recipient has recently been implanted at UCSF, initiating the Clarion's investigational clinical trials. A description of the device and preliminary patient results are presented.

Aged↗
PubMed1989

State of the art of cochlear implants. The UCSF experience.

Clinical trials with the University of California, San Francisco (UCSF)/Storz multichannel cochlear implant began in February 1985. A total of 16 patients were implanted with this four channel unit, a vocoder-based, compressed-analog system. Twelve of the 16 patients have had their 1-year postoperative evaluations, which permitted observations of their performance over time. Of these 12 patients, 10 (83%) are able to obtain a considerable degree of speech recognition. This represents the achievement of some level of auditory-only understanding in a very high proportion of the implant population. Results are measured with a battery of speech reception tests, including monosyllabic word recognition (the standard clinical "speech discrimination" list), the recognition of key words in sentences, and connected discourse tracking. Conventional audiologic test procedures are used. The objective of the clinical trial was to evaluate the strategies developed by the UCSF implant team through neurophysiologic, histopathologic, and psychophysical investigations over the past 18 years. The UCSF/Storz trials have helped to clarify and to define the specifications for our next generation implant, an electrically transparent eight (bipolar) or 16 (monopolar) channel system.

Adult↗
PubMed1987

Surgical considerations and hearing results with the UCSF/Storz cochlear implant.

Sixteen patients have been implanted with the UCSF/Storz multichannel implant, 11 of whom have been fitted with their external speech processors and transmitters and administered postoperative audiological evaluations. Both the surgical procedures used and the hearing results for these patients are presented. The potential medical/surgical complications of implant surgery and the future direction of research and development within the UCSF/Storz implant program are discussed.

Adult↗
PubMed1987

The UCSF/Storz cochlear implant: patient performance.

Clinical trials of the UCSF/Storz multichannel cochlear implant were initiated in February 1985, under the sponsorship of Storz Instrument Company. This four-channel device uses simultaneous bipolar, radial stimulation and a vocoder-based speech processing scheme. To date, eighteen patients have been implanted with the UCSF/Storz implant at four clinical centers in the United States. Based on data accumulated through June 1986, fifteen of these patients had received their speech processors and were given at least an initial evaluation of their performance with the implant. Results have been very encouraging, with all but two of these patients obtaining some degree of open-set auditory-only speech recognition. Most patients have demonstrated improvement over time without extensive rehabilitative intervention and all patients have attained an enhancement in lip-reading ability, as measured with a tracking procedure. According to a self-rated performance scale, all patients have experienced improvement in general communicative function since receiving the implant.

Adult↗
PubMed1986

The UCSF/Storz multichannel cochlear implant: patient results.

Using the four channel cochlear implant system with a vocoder-based processor developed at UCSF over an extensive period of research, clinical trials of the UCSF/Storz device were initiated in February 1985, under the sponsorship of Storz Instrument Company. To date, 13 patients have been implanted with this device, nine of whom have been fitted with their external processor and transmitter and have received at least their initial postoperative evaluation. Patient results have been extremely promising, with eight of the nine patients obtaining some open-set auditory only speech understanding. Most patients have demonstrated improvement over time and all patients have attained an enhancement in lipreading ability with the use of the UCSF/Storz device.

Adult↗
PubMed1986

The University of California, San Francisco/Storz cochlear implant program.

Using a four-channel implant system with a vocoder-based processor developed at UCSF over an extensive period of research, clinical trials of the UCSF/Storz device were initiated in February 1985 under the sponsorship of Storz Instrument Company. To date, 13 patients have been implanted with the UCSF/Storz device, 10 of whom have been fitted with their external processor and transmitter and have received at least their initial postoperative evaluations. Of these 10 patients, nine are able to use all four channels of their implant system. The device fitting/adjusting process for these patients has been remarkably easy, requiring only approximately 30 to 60 minutes. Patient results have been extremely good, with eight of the 10 patients obtaining some open-set auditory only speech understanding. Without extensive rehabilitation and training, most patients have demonstrated an improvement in speech reception over time. Lip-reading and tracking results indicate that all patients have attained an enhancement of lip-reading ability with the use of the device, suggesting that improved general communication skills have been provided for each UCSF/Storz patient.

Adult↗