Ch6 P1 Stimulation - Polytechnique Montréal · PDF file2 GBM8320 - Dispositifs...

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GBM8320 Dispositifs Médicaux Intelligents

Electrostimulation Part 1: Basic principle

Mohamad Sawan et al Laboratoire de neurotechnologies Polystim !

!!

http://www.cours.polymtl.ca/gbm8320/[email protected]!

M5418

March 2013

GBM8320 - Dispositifs Médicaux Intelligents 2

Electrostimulation : Outline

•  Introduction!–  Basic principle (Depolarization, hyper polarization, etc..!–  Stimulation types (Magnetic and electrical)!–  Main stimulation parameters (Current, voltage, etc…)!–  Characteristics (Muscular fatigue, accommodation)!

•  Technologies and architectures!–  Stimulator, electrodes, system flexibility, reliability, security, etc.!

•  Main applications!–  Pacemaker, Cochlear implants, Visual implant, DBS!–  Respiration, Vestibular prosthetics,, etc…!–  Urinary bladder dysfunctions!–  Motor neuroprosthetics!


Electrostimulation : Introduction •  Shock of Torpedo fish as treatment for headache and gout. AD 46. •  Frog muscle contracts when brought into contact with a bimetallic

conductor composed of copper and silver, 17th century. •  Invention of the Leyden jar ("stores" static electricity), 1745. •  Electricity came to be used as therapy for all known diseases (paralysis,

angina, foot drop, sciatica, epilepsy, etc...)

Torpedo

fish Leyden jar

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Electrostimulation : Historical background •  Muscular contractions in the legs of frogs by applying a pair of scissors along the

trajectory of the sciatic nerve during an electric storm, Luigi Galvani, 1786.

•  Strong interest in the effects of electricity on the nervous system after Alessandro Volta's invention of the dry cell battery in 1800 and Faraday's induction coil in 1831.

•  High frequency alternating currents transmitted inductively could be used to stimulate biological tissues, 1937.

•  Early equipment was large and bulky until the advent of transistor in the late 1950s.


Electrical Stimulation History : Pacemaker

First Wearable Pacemaker Early implantable cardiac Pacemaker (1960)

http://www.nationalpainfoundation.org/MyTreatment/news_implantabletherapy.asp


Electrostimulation : Introduction

•  Basic principle!–  Neural Membrane, !–  Depolarization, hyper polarization, etc..!

•  Stimulation types!–  Magnetic and electrical!

•  Main stimulation parameters!–  Current, voltage, !–  Mono-phasic, biphasic, stimulus, train of pulses!

•  Characteristics!–  Muscular fatigue, accommodation !

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Electrical stimulation : Principle •  Neural membrane!

Cytoplasm (K+)!

Extracellular (Na+)

VPA = 30 m/sec PA

+ + + + + + - - - - - - - -

STIM

+ + + + + + - - -

-70 mV

Node of Ranvier Myelin Sheath

Axone

(K+)!

(Na+)!

•  When stimulation occurs, an AP starts and moves along the membrane.!

http://www.gregalo.com/action_potential.jpg

GBM8320 - Dispositifs Médicaux Intelligents 8 http://kvhs.nbed.nb.ca/gallant/biology/saltatory_conduction.jpg

Electrical nerve stimulation : Principle

Alberts et al, Garland Publishing: Taylor Francis Group.


Electrostimulation : Background & definitions •  All excitable tissues are electrically

polarized: the cell cytoplasm is negative relative to the extracellular fluid.

•  The potential difference across the cell membrane, the resting membrane potential, is approximately 90 mV.

•  To evoke a response in a muscle or nerve, this resting potential must be lowered to a threshold which initiates an action potential.

•  Current circulates from the active region and by depolarizing the region ahead an action potential is propagated.

-70 mV

40 mV

1 msec

0

•  Depolarization!–  Membrane Threshold!

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Electrostimulation : Background & definitions •  The chronaxie is defined as the

shortest stimulus duration to produce a response with a stimulus strength twice that of the rheobase.

•  The rheobase is the minimum effective stimulus when applied for infinite period (in practice over 100 ms).

•  Nerve fibers have a lower threshold of excitation, and shorter chronaxie than muscle fibers.

•  The chronaxie of the skeletal muscle is up to 200 times that of myelinated nerve fibers.

Imin

Tmin

I (µ-mA)

T (msec)

2Imin

Q = I T Imin = Rheobase Tmin = Chronaxy Q = IminT/(1 - e-T/τ)


A B

C

Amp

PW

1/Freq

Ton Toff

Principle of electrical stimulation : Stimuli •  Current/voltage constant!

–  Stimulus mono- and bi-phasic, train of pulses!–  muscule fatiguing, accommodation!–  Selective stimulation, blocage «anodal», etc..! I

V

I

V


•  Selective stimulation allows improvement in voiding; •  This technique diplexes high and low frequency stimuli to activate

both categories of sacral nerve fibres:

-  HF stimuli for somatic fibres which innervate the sphincter. -  LF stimuli for parasympathetic fibres which innervate the detrusor.

Principle of electrical stimulation : Stimuli

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Electrostimulation : Advanced systems

•  Front-end selection can be used to stimulate only sites of interest.

•  Amplitude and timing information of stimulation currents for multiple sites can be placed on one data lead and decoded using active circuits in vivo.

•  Neural prosthetic systems can stimulate based on in vivo recordings without transferring the data out of the probes.

•  For wireless applications, stimulation data for multiple sites must be modulated onto the carrier, decoded in vivo, and on-chip current generation must be provided.

•  The electrode should be of high quality to prevent large leakage currents into the tissue due to high supply voltages required for neural stimulation.

Case Western Reserve University

GBM8320 - Dispositifs Médicaux Intelligents 14 http://www.nationalpainfoundation.org/MyTreatment/news_implantabletherapy.asp

Renew RF SCS System (ANS Inc.)

Mattrix SCS System (Medtronic Inc.)

Synergy IPG SCS System (Medtronic

Inc.) Versetrel IPG SCS System (Medtronic

Inc.)

Electrical Stimulation History : Pacemaker


Acumed Medical Supplies Adaptive Technology Resource Centre (University of Toronto)

Advanced Neuromodulation Systems (ANS)/ Hi-Tronics Designs, Inc. (HDI) American Imex

Amrex Electrotherapy Equipment (Division of Amrex-Zetron) Austin Medical Equipment Banner Therapy Products BioMedical Life Systems

Chattanooga Group Compex

CONMED Corporation CPR Medical Cyberonics

Delsys Dynatronics DynaWave

Electromedical Products International (EPI) EME Services

Empi Exogen/Smith & Nephew

Hill Laboratories International Medical Electronics

Koalaty Products

Companies

LSI International Magstim MedFaxx

Medtronic (Medtronic Neurological) Medical Services Company (MSC)

NESS Ltd. NeuMed

Neuronetics NeuroTech

Newcare Products Noraxon

Northstar Neuroscience OrthoLogic

Pharmaceutical Innovations, Inc. (PII) Prizm Medical

Quality Health Products (QHP) Rehabilicare

Rich-Mar RS Medical

Sparta Surgical Somatics, LLC

Thought Technology Ltd. Vertis Neuroscience

Williams Healthcare Systems

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Stimulation types : Magnetic •  Coils are 2D 3D mounted to generate precise magnetic field for non invasive

stimulation. •  The advantage of magnetic stimulation over electrical one is that the stimulation

intensity at the level of the nerves can be high. •  Not enough local precision is obtained which avoid this technique to emerge. •  No long term effectiveness data are available. Magnetic stimulation normally

causes no serious discomfort but is probably unsuitable for long-term treatment because technically the stimulation can not be applied for prolonged periods.

Thompson, A physiological effect of an alternating magnetic field. Proc RSL, B82:396-399, 1910. Hsu et al, D., A 3D Différentiel Coil Design for Localized Mag.Stim., IEEE-TBME, Vol. 48, 2001 http://www.biomag.helsinki.fi/tms/


Quizz 1) Cite some examples related to electrical stimulation

a. Shock of Torpedo

b. Layden jar

c. Syringe

d. Pacemaker


Quizz •  Cite some examples related to electrical stimulation

a. Shock of Torpedo

b. Layden jar

c. Syringe

d. Pacemaker

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Quizz 2) Which animal was used to prove the electrical stimulation concept

a. Frog

b. Dog

c. Monkey

d. Cat How?


Quizz 2) Which animal was used to prove the electrical stimulation concept

a. Frog

b. Dog

c. Monkey

d. Cat How? Muscular contractions in the legs of frogs by applying a pair of scissors along the trajectory of the sciatic nerve during an electric storm


Quizz 3) What are the different stimulation types

a. Magnetic

b. Ultra wave

c. Electrical

d. RF

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Quizz 3) What are the different stimulation types

a. Magnetic

b. Ultra wave

c. Electrical

d. RF


Quizz 4) Which sentence is correcte

a. AP starts and stops along the membrane.

b. AP is generated by the membrane.

c. AP starts and moves along the membrane.

d. The membrane stops the AP.


Quizz 4) Which sentence is correct

a. AP starts and stops along the membrane.

b. AP is generated by the membrane.

c. AP starts and moves along the membrane.

d. The membrane stops the AP.

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a. the cell cytoplasm is positive relative to the extracellular fluid.

b. the cell cytoplasm is negative relative to the extracellular fluid.

c. the cell cytoplasm is the same as the extracellular fluid.

d.None



a. the cell cytoplasm is positive relative to the extracellular fluid.

b. the cell cytoplasm is negative relative to the extracellular fluid. c. the cell cytoplasm is the same as the extracellular fluid.

d.None



a. HF stimuli for somatic fibres which innervate the sphincter.

b. LF stimuli for somatic fibres which innervate the sphincter.

c. LF stimuli for somatic fibres which innervate the sphincter.

d. HF stimuli for somatic fibres which innervate the detrusor.

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a. HF stimuli for somatic fibres which innervate the sphincter.

b. LF stimuli for somatic fibres which innervate the sphincter.

c. LF stimuli for somatic fibres which innervate the detrusor.

d. HF stimuli for somatic fibres which innervate the detrusor.

Ch6 P1 Stimulation - Polytechnique Montréal · PDF file2 GBM8320 - Dispositifs...

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