Transcript suction electrodes

TYPES OF ELECTRODES
BY
Parmar Anjali
Singh Sweta
WHY NEEDED ?
• Normally metal paste is used to applied on skin after
cleaning in form of electrolyte paste or jelly.
• But sometimes this treatment is time consuming &
irritating due to poor quality signal & baseline drift etc.
• During long term monitoring ,the electrode-skin interface
get dries out.Therefore,many reactions in skin takes
place.
• Periodically,jelly replinishment requires,produces
discomforts.
• Types:- Airjet electrode
Capacitive type
PASTELESS ELECTRODE
Electrode
unit
cable
Current sinks
Instrumentation
amplifier
10K
R
can
LED
R
47K
10K
R
shield
shell
gnd
V
+V
gnd
PASTELESS ELECTRODE
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The dia. is of integrated electrode & amplifier arrangement for pasteless
operation.
It was designed in 1979.
Here electrode & amplifier acts as an integrated unit.
Arrangement comprises of metal shell whose function are
(1)places electrode.
(2)has gnd contact.
Shell is made up of pure titanium metal measuring 30*15*7nm.
2 FETs are connected with epoxy glue in middle of shell.Their centres are 10mm
apart.
Cans have diameter of 4.5mm & made of stainless steel.
Rectangular border of shell acts as gnd & remainder of it forms shield against
interfacing radiation.
Source terminal of 2 FETs are connected to different inputs of instrumentation
amplifier.
Amplifier has a high ac input impedence (>100Mohm).
DRAWBACKS
• High electrode resistance & strong sensitivity
to motion.This resistance can be overcome by
high input resistance.
• Skin preparation required to remove motion
artefacts.
• All process are time consuming & so loses
practicability of dry electrodes for routine
clinical use.So,less acceptable to patient.
PRE-GELLED DISPOSABLE ELECTRODE
• Electrode snap contact.
• Sensor has diameter:0.5-1.5
• Ag-Agcl conductor
• Buffer layer
• Diameter of electrode:4.6cm
• Tape of polyethylene is
used
PROPERTIES OF GEL
• Moistness is due to intended shelf life by
including humectant in gel.
• Prevent micro-organism & mould growth.
• Provide low electrolyte skin impedance.
• Causes minimum skin irritation
STANDEREDS
• Direct current offset
voltage.
• Combined offset instabiliy &
internal noise.
• Alternating current
impedance.
• Defibrillation overload
recovery.
• Bias current tolerance.
ADVANTAGES
• Reduces artefacts,drift
• Baseline wandering
provides buffer layer.This
absorbs effects of
movement of electrode in
relationship to skin.
• No risk of infection.
• Small size & so easy to
handle.
• Less time required per ECG
procedure.
SUCTION
ELECTRODES
SUCTION ELECTRODES
 THESE ELECTRODES ARE USED IN
ELECTROCARDIOGRAPHY AS PRECORDIAL
LEADS,AS THEY CAN BE PLACED AT A
PARTICULAR LOCATION AND USED TO TAKE
RECORDING.
 THEY CONSIST OF A HOLLOW METALLIC
CYLINDRICAL ELECTRODE THAT MAKES
CONTACT WITH SKIN AT ITS BASE.
SUCTION ELECTRODE
 AN APPROPRIATE
TERMINAL FOR THE
LEAD WIRE IS
ATTACHED TO THE
METAL CYLINDER,AND A
RUBBER SUCTION BULB
FITS OVER ITS BASE.
 ELECTROLYTE GEL IS
PLACED OVER
CONTACTING SURFACE
OF THE ELECTRODE.
SUCTION ELECTRODE
 THEN THE BULB IS
SQUEEZED,AND THE
ELECTRODE IS THEN
PLACED ON THE CHEST
WALL.
 THE BULB IS RELEASED
AND APPLIES SUCTION
AGAINST THE
SKIN,HOLDING THE
ELECTRODE ASSEMBLY
IN PLACE.
DISADVANTAGES OF SUCTION
ELECTRODE
 THIS ELECTRODE CAN BE USED ONLY FOR A
SHORT PERIODS OF TIME.
 THE SUCTION AND THE PRESSURE OF THE
CONTACT SURFACE AGAINST THE SKIN CAN
CAUSE IRRITATION.
 ALTHOUGH THE ELECTRODE ITSELF IS QUITE
LARGE THE ACTUAL CONTACTING AREA IS
RELATIVELY SMALL.
 THESE ELECTRODES HAVE A HIGHER SOURCE
IMPEDANCE.
FLOATING
ELECTRODES
INTRODUCTION
 LIMB ELECTRODES GENERALLY SUFFER FROM
WHAT IS KNOWN AS MOTION ARTEFACTS DUE
TO THE RELATIVE MOTION AT THE INTERFACE
BETWEEN THE METAL ELECTRODE AND THE
ADJACENT LAYER OF ELECTRODE JELLY.
 THE INTERFACE CAN BE STABILISED BY THE
USE OF FLOATING ELECTRODES IN WHICH THE
METAL ELECTRODE DOES NOT MAKE DIRECT
CONTACT WITH THE SKIN.
 THESE ELECTRODES CAN BE RECHARGED;THAT
IS THE JELLY IN THE ELECTRODES CAN BE
REPLENISHED IF DESIRED.
 CONNECTION WITH THE INSTRUMENT CAN BE
ESTABLISHED WITH SILVER PLATED COPPER
WIRES FIXED IN CONDUCTING DHESIVES.
 THESE ELECTRODES ARE EXTREMELY LIGHT
WEIGHT AND DO NOT MAKE USE OF
ELECTRODE JELLY.
FACIAL ELECTRODES
• PRECORDIAL LIMB PLACEMENT
CLAMP ELECTRODES