BY Parmar Anjali Singh Sweta 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 Current sinks Electrode unit cable Instrumentation amplifier 10K R can LED R 47K 10K R shield gnd shell -V +V gnd

PASTELESS ELECTRODE 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