ACTION PLAN FOR FES 2000 AND BEYOND

U Stanič

Institute Jožef Stefan

Jamova 39, 1000 Ljubljana, Slovenia - SI

ABSTRACT

The FES field during the last 35 years became scientifically, technologically and clinically recognised field of mutual public interest. FES enables locomotion, grasping, ventilation, incontinence, decubitus healing etc. But all these achievements can be understand only as the top of the iceberg of FES real potentials. The FES based therapies offer only the most simple set of functional movements compared to the richness of the natural ones. Sometimes the benefits are too poor and patients reject further use of FES devices during their activities of daily living. The main reason for that lies in the out-of date servomechanistic FES control and lean complexity and sophistication of the FES systems.

The developments in the beginning of 2000 should be devoted to three main directions:

1) Perfection of the present FES approach making the FES systems more efficient and less cumbersome and enable its dissemination to acute phase of illnesses and elderly population;

2) Introduce, by extensive basic research and exploiting results of other disciplines like bio-information, more powerful control principles, based on the immense redundancy of the central nervous system

3) The FES devices of 21^st century will talk to the brain and will execute the patients will or desire for functional activities without any delay and effort.

We hope that we shall still see this achievements that can be made only by the youngest researchers of the coming generations.

INTRODUCTION

In 1993 after the Ljubljana FES Conference, Slovenia, the participants were invited to Portorož, Slovenian tourist resort on Adriatic coast, for the initiative meeting for the establishment IFESS and for active participation at the brainstorming event entitled: "FES for the third millennium "[1]. For the preparation of Sendai IFESS'99 Annual Conference I selected the most important messages from all the active presenters. The thoughts are collected under two directions, first concerning the perfection of the present FES and the second the need for basic research.

Perfection of the present FES approach making the FES systems more efficient and less cumbersome and enable its dissemination to acute phase of illnesses and elderly population

Under the perfection of the present FES the following ideas were contributed.

Vodovnik: -cost/ efficiency ratio of FES systems will be decreased

Pedotti: -use "direct dynamic problem" approach for FES supported SCI walking for the first approximation and then refine it by measuring kinematics and ground reaction forces

Kralj: -multielectrode system for blocking or stimulation of motoric and sensory nerves

Strojnik et al:- implantable orthotic devices with natural and artificial sensory control and

powered by energy cells burning fat tissue

Andrews: -"smart orthotics" as a fusion of robotics and neuroproshetic (FES) technology

Stanič: - advaced FES devices "gait - makers" and "dexterity - makers" to solve the

encumbrance to the level like pacemakers do

Jaeger: - success(commercial) may be expected in new simple FES devices restorating

important function like bladder control, foot-drop, respiration and coughing, or

anal incontinence

Mizrahi: - surface EMG techniques should be incorporated in FES devices to monitor

muscle performance

Ačimović: - extensive technology transfer needed to meet clinical needs

Poumarat: - wheelchairs for SCI subjects that would use biological energy (FES)

Boucher: - merge the efforts of knowledge base, technology, and application reseachers

on global scale to enable the FES breakthrough

Veltink: - asses the real needs and and problems of patients to be compesated by FES

Kawamura: - new FES devices that will sustain the bathing of the patients and new FES

devices for more dexterous movements

Campbell: -give the user economical devices to use 24 hours/day at home-(now)

Davis: - closed-loop programmable implantable FES systems for restoration of upper

and lower extremities function and genito-urinary function.

Extensive basic research and exploiting results of other disciplines like bio-information, more powerful control principles, based on the immense redundancy of the central nervous system

The needs for basic research projects:

Mortimer: - calculate mathematically appropriate stimulus parameters to avoid tissue and

electrode damage and reduce the need for animal experiments and

- available technology to record, process and decode neural signals in real time

- "rewire" denervated muscle by sprouting

Vodovnik: - nerve and spinal cord regeneration

- brain stimulation in order to improve motor function after CVI

Sinkjaer: - develop "natural" systems for FES control by recording sensory activity in

skin, muscle and joint receptors

Solomonov: - generate the knowledge how people move, e.g. biomechanics and

electophysiology of movement for advanced FES devices simulating voluntary

patterns

Kralj: - FES of autonomous nervous systems (blood circulation, excretion, bowel,

kidney, body weight control)

Andrews: - new control to reduce physical and mental effort

Ačimović: - analyse mechanisms of carry-over effect in FES

- FES to prevent abnormal synergies in post-stroke patients during acute stage

Flohic: - FES ASAP after lesion, CVA, CP, SCI

Poumarat: - application of FES to elderly people to assist the activities of daily living

- FES to compensate a sedentary lifestyle

B. Kralj: - FES treatment of female urinary incontinence after 65 years of age

Davis: - FES applied to brain for correction in the functional release of neurohormones for control of weight and diabetic effects, substance abuse, blood pressure, circulation, and gastro-intestinal abnormalities.

During the period from 1993-1999, an extensive research and development (R&D) efforts took place worldwide and enhaced by IFESS activities. In the following paragraph the idea of new generation of FES devices for third millenium are described.

FES DEVICES OF THE 21^ST CENTURY WILL TALK TO BRAIN

The innitial ideas and invention to use electrical stimulation in order to restore the functional movement that appeared in early seventies, was also described as electronic bypass, figure 1. It was supposed that a patient has still his voluntary control over certain muscle. By recording of its EMG activity, the control signal can be derived, that could be used for triggering of the electronic stimulator, generating train of pulses that would contract paralysed muscle and consequently generate the desired functional movement. By this idea the field of functional electrical stimulation (FES) was born.

Fig.1: The electronic bypass - the FES principle (Reswick, Vodovnik, Long, Lippay, Starbuck 1964)

But only few years later, this very simple diagram has become much more complicated, very likely, after the first experiments were performed on experimental subjects, checking the performance of the EMG control in vivo. The researchers faced the crual reality, that there were many usolved technological and basic problems in implementation of this idea. The reaction was brain storming that generated two possible solutions: first, the more practical idea of using switch and position control instead of EMG one and second, that the ideal FES control should mimic the natural neurophysilogy of movement. The result is shown in fig.2, where the voluntary command of the movement, generated in the brain, is the input to the electronic box, together with inputs from proprioceptors signals and visual feedback. In this special purpose computer, then the stimulation sequences are computed in real time and stimulation applied to the target muscles, what finaly generates functional movements, desired by the subject.

Fig.2.: Neural bypass control (Vodovnik 1965, Reswick et al. 1967)

This control approach was called neural bypass control. One can imagine, that this idea was at that time not realisable at all, due to general lack of basic knowledge and poor level of technology as well. This concept has been forgotten for more than 30 years. During this period the first approach gave first practical results for clinical practice, and has later developed in the research field what is presently known as the FES [2].

But carefull analysis of the leading FES specialists opinions, published in the Proceedings of the Ljubljana FES Conference in 1993, reveals the fact, that the intrinsic bottle neck of the further long term development of the FES, lies in the lack of suitable new control of complex functional movements, with less mental effort for the patients. Namely, all the FES systems for lower extremities, one-, two-, and multichannel, surface and implantable, are triggered by heel or hand switches.

Also the most sophisticated upper extremity implantable multichannel FES system is controlled by shoulder position sensor, what seriously limits the dexterity of the movements,

so characteristic for normal subjects. The short term R&D problems, cited above, are well

defined and can be realised in the near future, at the beginning of the third millenium. The concerted efforts of the FES specialists worldwide would speed-up this process.

For the long term solution the way should be found, how the brains and the FES systems will

talk (FESTALK) to each other, what will result in "like normal" FES induced movements. Tremenduous development of computers, microelectronics, sensors and implantable FES technology and new basic knowledge gathered on the generation of voluntary movement,

represent solid basis for the start of this key R&D FES action. Besides, there are several neighbouring new emerging disciplines, like studies of human genom and bio-informatics, that could support the project as well. But it will take a lot of money and big parts of life of this and next generation of FES scientist.

How to do the first step.It is already done by the scientists studying the EEG-based brain-computer interface (BCI). They use electroencephalogram (EEG) recordings during right and left motor imagery to move a cursor to a target on the computer screen [3]. The BCI can provide a new communication channel to replace an impaired motor function, e.g. in patients with amyotrophic lateral sclerosis (ALS) to develop a simple binary response in order to reply to specific questions. The EEG is recorded from electrodes overlying sensory-motor areas during left and right motor imagery. The EEG signals are processed, analysed and classified on-line by a neural network. The classification error was 10% to 40%, what seems not selective enough for the FESTALK control. Another study investigated the potential of the Utah Intracortical Electrode Arrey (UIEA) to provide signals for a BCI [4]. The UIEA records from small populations of neurons which have an average signal-to-noise ratio (SNR) of 6:1.

It was found that the activities of these populations of neurons contain sufficient information to perform control tasks.

In order to develop FESTALK technology we should use this and other research results to generate control signals from the brain, that would have enough selectivity and dynamics to meet the need for dexterious movements of the FES generation of the third millenium.

REFERENCES

[1] FES for the third millenium. Proceedings of "The Ljubljana FES Conference", Ljubljana 1993

[2] U Stanič. History of functional electrical stimulation. INS & IFESS Joint Congress, Luzern 1998.

[3] EM Maynard, CT Nordhausen, RA Normann. The Utah intracortical electrode array: A recording structure for potential brain-computer interfaces. Electroencephalogr Clin Neurophysiol 1997;102:228-39.

[4] DJ McFarland, LM McCane, JR Wolpaw. EEG-based communication and control: Short- term role and feedback. IEEE Trans Rehab Eng 1998;6:7-11.