Recommendations on the utilization of telemedicine in cardiology

The enormous progress made in recent years in the field of information and communication technology and also in sensor and computer technology has affected numerous fields of medicine and is capable of inducing even radical changes in diagnostic and therapeutic processes. This is particularly true for cardiology, where, for example, telemetric monitoring of cardiac and circulatory functions has been in use for many years. Nevertheless, broad application of newer telemedical processes has not yet been achieved to the extent one would expect from the encouraging results of numerous clinical studies in this field and the state of the art of the underlying technology. In the present paper, the Working Group on Rhythmology of the Austrian Cardiological Society aims to provoke a critical discussion of the digital change in cardiology and to make recommendations for the implementation of those telemedical processes that have been shown to exert positive effects on a wide variety of medical and economic parameters. The greatest benefit of telecardiological applications is certainly to be found in the long-term care of patients with chronic cardiovascular diseases. Accordingly, follow-up care of patients with cardiological rhythm implants, management of chronic heart failure and secondary prevention following an acute cardiac event during rehabilitation are currently the most important fields of application. Telemedicine is intended to enable high-quality and cost-efficient care for an increasing number of patients, whose care poses one of the greatest challenges to our healthcare system. Not least of all, telemedicine should make a decisive contribution to improving the quality of life of this segment of the population by favorably influencing mortality, morbidity and hospitalization as well as the patient's contribution to treatment.

Conceptualization of an ICU Infrastructure for Simulation Based Education in Medical Engineering & eHealth

The use of simulation-based training is gaining importance in medical as well as engineering related education. The complex environment of an intensive care unit is characterized by a high need of interaction between clinical as well as technical components and views. These diverse interactions and the connected requirements are the focus for the presented simulation infrastructure, enabling research, education and training. The presented concept of a modular and flexible intensive care environment provides a high degree of interoperability and flexibility for individual research questions and full support of connectivity for typical clinical workflows. The presented simulation and testing bed will allow both, education for engineering and medical students using patient simulation and simultaneous data transfer as well as research on medical workflows, infrastructural demands and connectivity conformance questions.

Evaluation of Standards for Access Control Enabling PHR-S Federation

The adoption of the Internet of Things (IoT) and mobile applications in the healthcare may transform the healthcare industry by offering better disease tracking and management as well as patient empowerment. Unfortunately, almost all of these new systems set up their own ecosystem and to be really valuable for the care process they need to be integrated or federated with user managed access control services based on international standards and profiles to enable interoperability. Thus, this work presents the results of an evaluation of available specifications for federated authorization, based on a set of basic requirements.

Biosignals, Standards and FHIR - The Way to Go?

BACKGROUND

Standards have become available to share semantically encoded vital parameters from medical devices, as required for example by personal healthcare records. Standardised sharing of biosignal data largely remains open.

OBJECTIVES

The goal of this work is to explore available biosignal file format and data exchange standards and profiles, and to conceptualise end-to-end solutions.

METHODS

The authors reviewed and discussed available biosignal file format standards with other members of international standards development organisations (SDOs).

RESULTS

A raw concept for standards based acquisition, storage, archiving and sharing of biosignals was developed. The GDF format may serve for storing biosignals. Signals can then be shared using FHIR resources and may be stored on FHIR servers or in DICOM archives, with DICOM waveforms as one possible format.

CONCLUSION

Currently a group of international SDOs (e.g. HL7, IHE, DICOM, IEEE) is engaged in intensive discussions. This discussion extends existing work that already was adopted by large implementer communities. The concept presented here only reports the current status of the discussion in Austria. The discussion will continue internationally, with results to be expected over the coming years.

Development of a Multidisciplinary and Telemedicine Focused System Database

BACKGROUND

Tele-rehabilitation at home is one of the promising approaches in increasing rehabilitative success and simultaneously decreasing the financial burden on the healthcare system.

OBJECTIVES

Novel and mostly mobile devices are already in use, but shall be used in the future to a higher extent for allowing at home rehabilitation processes at a high quality level. The combination of exercises, assessments and available equipment is the basic objective of the presented database.

METHODS

The database has been structured in order to allow easy-to-use and fast access for the three main user groups. Therapists - looking for exercise and equipment combinations - patients - rechecking their tasks for home exercises - and manufacturers - entering their equipment for specific use cases.

RESULTS

The database has been evaluated by a proof of concept study and shows a high degree of applicability for the field of rehabilitative medicine. Currently it contains 110 exercises/assessments and 111 equipment/systems.

CONCLUSION

Foundations of presented database are already established in the rehabilitative field of application, but can and will be enhanced in its functionality to be usable for a higher variety of medical fields and specifications.

Propose of Standards Based IT Architecture to Enrich the Value of Allergy Data by Telemonitoring Data

Interoperability is a key requirement for any IT-System to be future proof and cost efficient, due to the increasing interaction of IT-Systems in Healthcare. This feasibility study is part of a larger project focusing on the conceptualization and evaluation of interoperable and modular IT-Framework components for exchanging big data information sets. Hence, this project investigates the applicability of a standard based IT-Architecture for the integration of Personal Health Devices data and open data sources. As a proof of concept use case, pollen forecast data from the Medical University of Vienna were combined with Personal Health Device data and a data correlation was investigated. The standards were identified as well as selected in expert's reviewed and the Architecture was designed based on a literature research. Subsequently the prototype was implemented and successfully tested in interoperability tests. The study shows that the architecture meets the requirements. It can be flexibly extended according to further requirements due to its generic setup. However, further extensions of the Interoperability-Connector and a full test setup needs to be realized in future.

Bluetooth Low Energy Peripheral Android Health App for Educational and Interoperability Testing Purposes

Based on recent telemonitoring activities in Austria for enabling integrated health care, the communication interfaces between personal health devices (e.g. blood pressure monitor) and personal health gateway devices (e.g. smartphone, routing received information to wide area networks) play an important role. In order to ease testing of the Bluetooth Low Energy interface functionality of the personal health gateway devices, a personal health device simulator was developed. Based on specifications from the Bluetooth SIG a XML software test configuration file structure is defined that declares the specific features of the personal health devices simulated. Using this configuration file, different scenarios are defined, e.g. send a single measurement result from a blood pressure reading or sending multiple (historic) weight scale readings. The simulator is intended to be used for educational purposes in lectures, where the number of physical personal health devices can be reduced and learning can be improved. It could be shown that this simulator assists the development process of mHealth applications by reducing the time needed for development and testing.

Development of a virtual lab for practical eLearning in eHealth

In recent years an ongoing development in educational offers for professionals working in the field of eHealth has been observed. This education is increasingly offered in the form of eLearning courses. Furthermore, it can be seen that simulations are a valuable part to support the knowledge transfer. Based on the knowledge profiles defined for eHealth courses a virtual lab should be developed. For this purpose, a subset of skills and a use case is determined. After searching and evaluating appropriate simulating and testing tools six tools were chosen to implement the use case practically. Within an UML use case diagram the interaction between the tools and the user is represented. Initially tests have shown good results of the tools' feasibility. After an extensive testing phase the tools should be integrated in the eHealth eLearning courses.

Development of Knowledge Profiles for International eHealth eLearning Courses

Professionals working in the multidisciplinary field of eHealth vary in their educational background. However, knowledge in the areas of medicine, engineering and management is required to fulfil the tasks associated with eHealth sufficiently. Based on the results of an analysis of national and international educational offers a survey gathering user requirements for the development of knowledge profiles in eHealth was conducted (n=75) by professionals and students. During a workshop the first results were presented and discussed together with the network partners and the attendees. The resulting knowledge profiles contain knowledge areas of all three thematic content categories including fundamentals of medical terminology, standards and interoperability and usability as well as basics of all three content categories. The knowledge profiles are currently applied in a master's degree programme at the UAS Technikum Wien and will be developed further.

The impact of adherence on costs and effectiveness of telemedical patient management in heart failure: a systematic review

OBJECTIVE

This paper analyzes evidence of the impact of patients' adherence to pharmacological and non-pharmacological recommendations on the treatment costs of heart failure (HF) patients.

METHODS

A systematic review was performed based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement. Papers were searched using various combinations of the following keywords: 'telemedicine', 'telemonitoring', 'telehealth', 'eHealth', 'remote monitoring', 'adherence', 'compliance', 'cost-effectiveness', 'cost-benefit', 'heart failure', 'healthcare costs', 'hospitalization', and 'drug costs'. We included only papers written in English or German, published between 1998 and 2014, and having one of our search terms in the title.

RESULTS

Initially, 73 papers were selected. After a detailed review, these were narrowed done to 9 that reported an association between adherence and/or compliance and costs. However, none established a quantitative relationship between adherence and total healthcare costs.

CONCLUSION

A model-based cost-effectiveness analysis that appropriately considers adherence has not been carried out so far, but is needed to fully understand the potential economic benefits of telehealth.

Education for eHealth--a status analysis

eHealth is not only a growing market, but also an important factor for new healthcare systems. National and European initiatives implicitly demand a higher level of knowledge in the areas of healthcare, engineering and management. As part of the eLearning4eHealth project an initial web based study was performed concentrating on European and global eHealth related educational programs. The results show that eHealth related courses do not evenly exist for the identified professions. 43% of the offered programs are focused on the engineering sector, whereas only 21% are available for the management sector. In order to offer compatible and comparable state of knowledge in the identified fields of profession and knowledge, further educational programs may be necessary. Despite the found shortcomings, results have shown that international activities have started in order to close the gaps and improve the quality of knowledge in the interdisciplinary field of eHealth.

Bedside patient data viewer using RFID and e-Ink technology

In the daily routine of hospitals, which work with paper based medical records, the staff has to find the appropriate patient file if it needs information about the patient. With the introduction of ELGA the Austrian hospitals have to use specific standards for their clinical documentation. These structured documents can be used to feed an e-Ink reader with information about every patient in a hospital. Combined with RFID and security measures, the clinical staff is supported during the patient file searching process. The developed experimental setup of the Bedside Patient Data Viewer demonstrates a prototype of such a system. An Amazon Kindle Paperwhite is used to display processed data, supplied by a Raspberry Pi with an attached RFID module for identification purposes. Results show that such a system can be implemented, however a lot of organizational and technical issues remain to be solved.

Security challenges in integration of a PHR-S into a standards based national EHR

Health related data provided by patients themselves is expected to play a major role in future healthcare. Data from personal health devices, vaccination records, health diaries or observations of daily living, for instance, is stored in personal health records (PHR) which are maintained by personal health record systems (PHR-S). Combining this information with medical records provided by healthcare providers in electronic health records (EHR) is one of the next steps towards "personal care". Austria currently sets up a nationwide EHR system that incorporates all healthcare providers and is technically based on international standards (IHE, HL7, OASIS, ...). Looking at the expected potential of merging PHR and EHR data it is worth to analyse integration approaches. Although knowing that an integration requires the coordination of processes, information models and technical architectures, this paper specifically focuses on security issues by evaluating general security requirements for a PHR-S (based on HL7 PHR-S FM), comparing them with the information security specifications for the Austrian's national EHR (based on ISO/IES 27000 series) and identifying the main challenges as well as possible approaches.

LUMOR: an app for standardized control and monitoring of a porcine lung and its nutrient cycle

The outcome of the EU-funded project ElBik has been the lung simulator 'iLung', which imitates an actively breathing human lung with a porcine lung. In order to keep the explanted lung in a nearly physiological state during transportation from the slaughterhouse to the ventilation laboratory the tissue needs to be nourished and temperature controlled. The Project AlveoPic designs a mobile transport vehicle implementing an ISO/IEEE 11073-20601 compliant communication interface for the exchange of the physical parameters, alert messages and setpoint-values. An appropriate 11073 domain information model is designed and limitations of the defined services and attributes are identified. For monitoring purposes the Android App LUMOR is implemented providing a user with an easy-to-handle GUI. It was found, that alert capabilities and remote set features are not well supported in ISO/IEEE 11073-20601 at the moment and possible workarounds are discussed.

Certification programs for eHealth--status quo

The skills of the workforce are a core factor for the quality of healthcare systems. On top of the basic education, postgraduate training is an important factor for continuously maintaining as well as improving the workforce qualification level. Advanced training often provides certification of the acquired skills. This paper analyses the status quo of international certification programs in the sector of eHealth (EU, US, Global). It uses available literature and observations from international educational expert's workgroups. It identifies gaps regarding certifications in eHealth and suggests steps for solutions. Despite little attention to legal and financial eHealth related content in certification programs in the EU as well as a low degree of harmonization of international certifications in general, there are strong activities especially in the international scope towards personal certification programs in eHealth. Major changes are to be expected within the coming years.

Usage of international standards for integrating extramural monitoring and personal health device data into medical information infrastructure

Integrating extramural measured devices data into medical information systems is becoming more and more attractive for integrated medical care. A lot of devices already have the ability to transfer measured data to mobile devices or computers and a few systems offer submitting data to a centralized information database or information system. Unfortunately, all of these devices use proprietary protocols and processes which makes integration into other systems a major problem. To address this problem the Healthy Interoperability project has been created with the objective of creating a framework for transferring health data based on international standards. The paper outlines how the framework architecture takes full advantage from the definitions of the international standards ISO 11073, HL7, IHE and CEN 13606. Even the definition of the user profiles and the security framework is based on standards from ETSI, ISO and CEN. By using these standards the framework can also perfectly be used for intramural communication.

Irregularity of the ventricular rhythm during atrial fibrillation: effect of slow atrioventricular nodal pathway ablation

BACKGROUND

The contribution of dual atrioventricular (AV) nodal pathway physiology to the irregularity of the ventricular rhythm during atrial fibrillation has not been clarified.

HYPOTHESIS

This study was performed to assess the effects of slow AV nodal pathway ablation on the irregularity of the ventricular rhythm during atrial fibrillation.

METHODS

Irregularity of the ventricular rhythm was quantified using analysis of heart rate variability. In 20 patients with AV nodal reentrant tachycardia, absolute heart rate variability during atrial fibrillation was quantified before and after slow AV nodal pathway ablation by the standard deviation of all NN intervals (SDNN). Relative heart rate variability was determined by computing the coefficient of variation, SDNN normalized for the standard deviation of the mean ventricular cycle length (MVCL-AF).

RESULTS

The slope of the regression between MVCL-AF and SDNN was significantly more gradual after slow pathway ablation (slope 0.39 vs. 0.23, p < 0.001). Coefficient of variation increased in 12 patients with heart rates > 120 beats/min at baseline (18.6 +/- 3.9 vs. 22.1 +/- 2.7% MVCL-AF, p < 0.05), but decreased in 8 patients with heart rates < 120 beats/min at baseline (25.6 +/- 3.1 vs. 22.2 +/- 2.2% MVCL-AF, p = 0.05). Furthermore, coefficient of variation correlated with MVCL-AF only at baseline (slope 0.034, r = 0.66), but no relation was found after slow pathway ablation (slope 0, r = 0).

CONCLUSIONS

Slow AV nodal pathway ablation alters the relation between absolute heart rate variability and mean ventricular rate during atrial fibrillation and eliminates cycle length dependency of relative heart rate variability. These data indicate that dual AV nodal pathway physiology contributes to the irregularity of the ventricular rhythm during atrial fibrillation.

Objective assessment of the fusion frequency in functional electrical stimulation using the fast Fourier transform

In functional electrical stimulation (FES) the dynamics of tetanic muscle contractions is often described by the fusion frequency (FF), as determined by palpation: contractions elicited by stimulation frequencies above the FF appear smooth. To contribute to a more objective assessment of this important FES parameter, we have developed a dedicated signal analysis method based on fast Fourier transformation (FFT). The ripple to peak ratio (R(rpFFT)) - the relation between ripple amplitude and peak force value of a recorded tetanic muscle force in relation to the applied stimulation frequency - was determined automatically by analysing a 0.2-s interval in the steady state of a stimulation burst. The method was tested on simulated data and on force recordings from isolated tibialis anterior muscles of six rabbits. The results were compared to manual estimates. The robustness of the method was tested by adding noise and hum. Simulated noise at 100% of the ripple force increased R(rpFFT) by 4%. Hum at 20 Hz away from the stimulation frequency caused changes of less than 0.5%. The results of the automated analysis of recorded signals matched the manual estimates sufficiently well, especially for stimulation frequencies near or above FF. R(rpFFT) therefore seems suitable for automated, objective and robust assessment of the ripple and the FF of electrically stimulated muscle.

Kinematic evaluation in Parkinson's disease using a hand-held position transducer and computerized signal analysis

BACKGROUND

The objective of this work was to develop a device for quantification of akinesia in Parkinson's disease, for the use in home monitoring of PD patients, as a part of home telecare programs. For this purpose a simple movement task is to be preferred, and the measurement devices must be small, lightweight, and easy to use, so patients may perform the measurements unattended. Another intended application was optimisation of the electrode position during implantations of neuromodulation systems for treatment of Parkinson.

METHOD

A hand held transducer was used to measure the position of the thumb while the patient repeatedly flexed and extended the thumb. The position data was sampled and stored on a personal computer with a plug in converter card and software. Measurements were performed on 15 PD patients and 6 age-matched controls. Signal analysis procedures were developed in order to automatically derive numerical parameters that quantify the movement performance. In order to select the most relevant parameters, they were correlated to Unified Parkinson Disease Rating Scale (UPDRS) motor scores (Spearman's rank, single sided, p < 0.05).

FINDINGS

In reviews of the raw position signals the amplitude and frequency was found to be lower in patients than in controls. In patients the movement was frequently interrupted by short periods of hesitation. The calculated parameters of covered distance (correlation coefficient r = -0.63), hesitation (r = 0.64) and frequency (r = -0.6) were found to be most relevant, as they correlated best to the UPDRS hand pronation/supination score.

DISCUSSION

The equipment proved to be fast to setup and easy to use. The signal analysis methods provided meaningful numerical parameters for quantification of akinesia, represented in hand pronation/supination. These results suggest that the described methods may be useful for telemedicine and intraoperative use.

The Vienna functional electrical stimulation system for restoration of walking functions in spastic paraplegia

An eight-channel stimulation system, currently intended for stimulation of lower extremities, was developed and is introduced. The major development goals were easy handling, modularity to make the system easily adaptable for other functional electrical stimulation (FES) applications, and a wide stimulation parameter range for application-specific parameter optimization. For paraplegic stepping, the system worn by the patient consists of 2 four-channel stimulation modules, a central unit holding the battery and circuitry for power management and communication control, a wireless remote control unit, and a palmtop computer as the main control and input device. A software package for Microsoft Windows supports the design and optimization of stimulation sequences in the rehabilitation center. First tests with patients familiar with FES showed smoother movements during stepping and acceptable good handling. In combination with the PC software, the required stimulation sequences could be created in a very short time.

Basic design and construction of the Vienna FES implants: existing solutions and prospects for new generations of implants

We can distinguish 3 generations of FES implants for activation of neural structures: 1. RF-powered implants with antenna displacement dependent stimulation amplitude; 2. RF-powered implants with stabilised stimulation amplitude; and 3. battery powered implants. In Vienna an 8-channel version of the second generation type has been applied clinically to mobilisation of paraplegics and phrenic pacing. A 20-channel implant of the second generation type for mobilisation of paraplegics and an 8-channel implant of the third generation type for cardiac assist have been tested in animal studies. A device of completely new design for direct stimulation of denervated muscles is being tested in animal studies. There is a limited choice of technologically suitable biocompatible and bioresistant materials for implants. The physical design has to be anatomically shaped without corners or edges. Electrical conductors carrying direct current (D.C.) have to be placed inside a hermetic metal case. The established sealing materials, silicone rubber and epoxy resin, do not provide hermeticity and should only embed DC-free components. For electrical connections outside the hermetic metal case welding is preferable to soldering; conductive adhesives should be avoided. It is advisable to use a hydrophobic oxide ceramic core for telemetry antenna coils embedded in sealing polymer. Cleaning of all components before sealing in resin is of the utmost importance as well as avoidance of rapid temperature changes during the curing process.

Preparation of a skeletal muscle ventricle in sheep: severe damage to the Latissimus dorsi muscle due to mobilization before preconditioning

As part of a study examining the use of a skeletal muscle ventricle for cardiac assistance in sheep, a new concept of muscle preconditioning was put into practice. We aimed to produce a latissimus dorsi muscle (LDM) capable of performing chronic work immediately after the construction of a skeletal muscle ventricle. The left LDM was detached from the thoracic wall, divided longitudinally and reattached in situ to achieve vascular delay. The right LDM was left unaffected. Thereafter, preconditioning of both LDM was started according to the clinically approved stimulation protocol for cardiomyoplasty. Preconditioning of the unaffected right LDM in situ resulted in a complete muscle fiber transformation with no signs of degeneration or necrosis. Mobilization of the left LDM before preconditioning led to a distinct damage of the muscle. During conditioning, the increase in burst duration from 2 to 3 impulses in sheep A and from 3 to 5 impulses in sheep B resulted in a homogenous degeneration of the muscle fibers of the left LDM. Histomorphological analysis showed a dramatic increase in the percent perimysial and endomysial connective tissue. The applied concept of muscle prefabrication proved to be a failure. Muscle splitting and mobilization followed by vascular delay and in situ conditioning as a concept of muscle prefabrication should be strictly avoided.

Long-term electromyogram recording from the posterior cricoarytenoid muscle as a potential biological trigger for phrenic pacing: results of an animal study

Diaphragm pacing has been used to restore respiration in approximately 1,000 patients worldwide suffering from high quadriplegia or from central alveolar hypoventilation syndrome. Compared with conventional mechanical ventilation, electrophrenic respiration (EPR) reduces the risk of pulmonary infections and increases the mobility of patients. Voluntary activation of the pacemaker during speech would improve patients' quality of life and allow application of EPR in a more physiological way. An animal study was performed to investigate the electromyogram (EMG) of the posterior cricoarytenoid (PCA) muscle and the movement of the glottis via impedance measurement (electroglottography) with the aim to examine reproducibility and stability of the recordings from the PCA muscle as a potential biological trigger for a phrenic pacemaker. The EMG of the PCA muscle was recorded via implanted electrodes for a 200 day period. The EMG signal proved stable for that period, artifacts caused by movements can be suppressed, and swallowing can be detected. In contrast, impedance measurement to detect movement of the glottis proved not useful. Based on the results of this study, the use of the PCA EMG as a biological trigger for a phrenic pacemaker has to be considered a realistic option.

MYOSTIM-FES to prevent muscle atrophy in microgravity and bed rest: preliminary report

Long-term flights in microgravity cause atrophy and morphological changes of skeletal muscles. Training with mechanical devices is insufficient regarding the required time to exercise and space for devices. The objective of this project is to develop a passive training method based on functional electrostimulation (FES) to preserve muscle mass and fiber composition with minimal impairment to the cosmonaut. For a pilot experiment on the MIR space station, a suitable 8 channel FES device was developed. It consists of electrode trousers that carry surface electrodes and cables, 2 interconnected 4 channel stimulators, and a laptop personal computer (PC) for stimulator programming and processing compliance data. An automatic extensive training of 4 muscle groups of the lower extremities is performed for 6 h/day, with 1 s on and 2 s off tetanic contractions at 20-30% of maximum tetanic muscle force. The synchronous activation of antagonists of the thigh and lower leg prevents uncoordinated movements.

Battery-powered miniature implant for electrical nerve stimulation

The range of application of implantable stimulators in functional electrical stimulation (FES) for therapeutic purposes and for the restoration of lost or damaged functions has steadily grown within the last 20 years. Each time a clinically used method is improved, a new field of FES application explored or basic research conducted, animal experiments are needed to check and evaluate the findings and results. It is precisely for this use that the stimulation system described in this paper was developed. The battery-powered single-channel stimulator can be used for the excitation of motor and sensory nerves with monophasic or biphasic impulses. All parameters and functions are programmable via the bidirectional telemetry circuit. Implant programming is achieved by a laptop computer, supported by a graphical user interface, instead of by a specially designed programmer. The maximum settings of the stimulation parameters are: frequency 100 Hz, monophasic pulse duration 0.8 ms, biphasic pulse duration 1.6 ms, stimulation current 3 mA. The implant volume was reduced to 2 cm3 (length 23 mm, width 13 mm, height 7.5 mm), lowering the weight to 3.6 g. Due to this small volume the implant can be used in small animals. The power supply via battery obviates the need for transcutaneous tunneling or permanent external high-frequency senders and facilitates the keeping of the animals.

Battery-powered implantable nerve stimulator for chronic activation of two skeletal muscles using multichannel techniques

Chronic activation of skeletal muscle is used clinically in representative numbers for diaphragm pacing to restore breathing and for dynamic graciloplasty to achieve fecal continence. The 3 different stimulation techniques currently used for electrophrenic respiration (EPR) all apply high frequency powered implants. It was our goal to make these stimulation methods applicable for EPR by a battery-powered nerve stimulator that would maximize the patient's freedom of movement. Additionally, the system should allow the implementation of multichannel techniques and alternating stimulation of 2 skeletal muscles as a further improvement in graciloplasty. Generally, the developed implantable nerve stimulator can be used for simultaneous and alternating activation of 2 skeletal muscles. Stimulation of the motor nerve is achieved by either single channel or multichannel methods. Carousel stimulation and sequential stimulation can be used for graciloplasty as well as for EPR. For EPR we calculated an operating time of the implant battery of 4.1 years based on the clinically used stimulation parameters with carousel stimulation. The multichannel pulse generator is hermetically sealed in a titanium case sized 65 x 17 mm (diameter x height) and weighs 88 g.

Personal computer supported eight channel surface stimulator for paraplegic walking: first results

Today functional electrical stimulation (FES) is used among other treatments to restore hand and arm function, to restore mobility of the lower extremities, for phrenic pacing, and in cardiomyoplasty. Common to all FES applications is that they require careful setup of stimulation parameters. To improve these tasks, personal computer (PC) based software for stimulation parameter evaluation and data acquisition was written. First, the described software was used to mobilize paraplegic patients in conjunction with an 12C bus controlled 8 channel surface stimulator. Electrodes were placed on each leg on the m. quadriceps and m. gluteus for hip and knee extension and the peroneal nerve to elicit flexion reflex. The fourth channel was used to correspond to subjects' individual needs. The stimulation patterns for standing up, walking, and sitting down easily could be set up and optimized by adjusting up to 128 stimulation parameters in a task-specific way.

Multifunctional implantable nerve stimulator for cardiac assistance by skeletal muscle

Different methods are used, clinically and experimentally, to assist severely impaired heart function by means of skeletal muscle. The efficiency of these methods is restricted by skeletal muscle losing strength after transpositioning and during conditioning and not being sufficiently resistant to fatigue. This is mainly due to the nonphysiological activation of the nerves by electrical stimulation. We have developed a battery operated, ECG triggered multichannel implant that is capable of implementing various advanced stimulation techniques. The stimulator can activate 2 skeletal muscles via the motor nerves. It allows for application of multichannel stimulation methods, i.e., carousel stimulation and sequential stimulation, as well as the programming of optimized pulse trains. Synchronization delay and burst duration can be automatically and dynamically adapted to the heart rate. The multichannel stimulator is hermetically sealed in a titanium case. Its calculated life span on the basis of the integrated battery is 3-5 years, depending on the programmed stimulation parameters. The implant dimensions are 65 x 17 mm (diameter x height), and it weighs 93 g. The implant has been tested in vitro as well as in vivo.

[Modular PC-based data acquisition and processing system for biological signals]

The data acquisition system described here is designed for biomedical research and permits the recording of up to eight biological signals simultaneously. A personal computer using the Windows 95 operating system is employed for data monitoring, data processing and analysis during experiments. The system has been designed for reliability, economy, flexibility and ease of handling, with the aim of achieving universal application. To avoid interface incompatibility, problems with transfer protocols and the data formats of commercially available products, analog signals are used for further processing. The individual input channels are electrically isolated from one another and the PC to avoid ground loops, and for reasons of safety. An isolated voltage supply is available for pre-amplifiers and bridges. A bandwidth of 0-5 kHz and the maximum sampling rate of 12.5 kHz suffice to pick up higher frequency signals such as EMG and ENG. The modular software and hardware concepts permit the use of almost any desktop or laptop PC as a central processing unit. The PC handless documentation, data acquisition, data analysis and the preparation of publications. If needed, further analytical functions can be added in modular form. Finally, the option of saving data in the ASCII format permits processing of results with such standard software packages as Excel, Access, Matlab and Origin.

Computer aided adjustment of the phrenic pacemaker: automatic functions, documentation, and quality control

Electrical stimulation of the phrenic nerves of patients with complete ventilatory insufficiency with the Vienna respiratory pacemaker has been in clinical use since 1983. During the adjustment of stimulation parameters with this device, the following problems have occurred: for some measurements like the recruitment curve, series of complete inspiration cycles have to be stimulated, which causes the danger of muscle fatigue for unconditioned patients. The documentation is completed predominantly by hand, taking time and increasing the possibility of error. As a first step to solve these problems, we developed a new stimulation and measurement system. It consists of a PC with data acquisition hardware, the necessary sensors, and amplifier circuitry. The implanted stimulator is controlled via the parallel interface. The new system offers some advantages: computer control shortens the time for measurement and documentation, and the stress on the patient and the risk of error is reduced; synchronized measurement makes it possible to use single stimulation pulses instead of bursts and ramps to reduce diaphragm fatigue; digital signal processing improves measurement results and reproducibility; and help functions and self tests are provided, together with a graphical user interface. We used sensors for air flow, diaphragm EMG, and acceleration, on up to 8 channels simultaneously. Combined sample rates of up to 100 kS/s were possible. The system could be adapted for other uses involving functional electrical stimulation with our implantable nerve stimulators. Using this equipment saves a lot of effort, and the adjustment process can be focused on improved stimulation results and better performance for the patient. Current research is studying implementation of automatic functions like acquisition of stimulation thresholds. This could result in a predominantly automated adjustment of the phrenic pacemaker and even in a closed-loop controlled system in the future.

Useful applications and limits of battery powered implants in functional electrical stimulations

Battery powered stimulation implants have been well-known for a long time as heart pacemakers. In the last few years, fully implantable stimulators have been used in the field of functional electrical stimulation (FES) for applications like dynamic cardiomyoplasty and electro-stimulated graciloplasty for fecal incontinence. The error rate of battery powered implants is significantly smaller than that for conventional stimulator systems, and the quality of life for the patients is increased because the need for an external power and control unit is eliminated. The use of battery powered implants is limited by the complexity of the stimulation control strategies and the battery capacity. Therefore, applications like the stimulation of lower extremities for walking, cochlea stimulation, or direct muscle stimulation cannot be supported. The improvement of implantable batteries, microcontrollers, and ultralow power products is ongoing. In the future, battery powered implants will also meet the requirements of complex applications. Systems for restoration of hand and breathing functions after spinal cord injury can be the next field of use for battery powered implants. For these purposes, we developed a battery powered multichannel implant with a sufficient life span for phrenic pacing. The problems during development and the limits of this system are described in this paper.