Biopotential electrodes (ECG, EEG and EMG recording electrodes)

01

Choose the electrode type and construction

US regulations identify an electrocardiograph electrode as the electrical conductor applied to the body surface to transmit the signal to a processor that produces an electrocardiogram or vectorcardiogram, classed as Class II (special controls) under 21 CFR 870.2360; a cutaneous electrode, applied directly to the skin to record signals such as the electroencephalogram or to apply stimulation, is Class II under 21 CFR 882.1320. [1] [2]

FDA's ECG electrode guidance covers bare electrodes and those with a conductive gel, adhesive system or lead wire, supplied reusable or disposable, sterile or non-sterile, and also electrodes for bioimpedance measurement, which deliver about 2 mA rms at about 60 kHz across the thorax; it excludes defibrillation, cardioversion and pacing electrodes. [3]

Two 510(k) summaries from Leonhard Lang show two constructions: a resting-ECG tab electrode made of PET tape printed with Ag/AgCl ink and a conductive gel, supplied ten to a siliconised PET card; and a snap electrode with a stainless-steel stud and an ABS sensor coated with silver, partly or wholly covered with silver chloride where it meets the gel, offered with liquid or solid-wet gel. Both were tested to ANSI/AAMI EC12:2000 and given a 24-month shelf life. [5] [6]

A Marquette Electronics patent on disposable biopotential electrodes describes a laminated design — a plastic backing, a carbon or graphite conductive layer, a silver/silver chloride layer and an ionically conductive adhesive — with a tab for the lead connection, and explains that slow recovery after defibrillation delays ECG data when it is needed. [7]

For EEG and EMG, FDA's cutaneous-electrode criteria apply to single-use electrodes on intact skin with electroconductive media, and say electrode size, shape and spacing should suit the site and the patient population, such as children or adults. [4]

Give the supplier the signal and use (resting ECG, monitoring, stress test, Holter, EEG, EMG, bioimpedance), patient group, wear time and conditions (sweat, exercise), sensor material, gel type (liquid, solid-wet, hydrogel), adhesive and backing (foam, cloth, PET tape), connector (snap, tab, pre-wired lead), radiolucent or MRI needs, size and shape, packaging count, sterility, shelf life and the regulatory markets.

02

Set the electrical, adhesion, biocompatibility and shelf-life tests

FDA's ECG electrode guidance asks for electrical performance by ANSI/AAMI EC12 or equivalent methods for AC impedance, DC offset voltage, combined offset instability and internal noise, defibrillation overload recovery and bias current tolerance, tested with the labelled gel for bare electrodes. Its cutaneous-electrode criteria list the EC12 limits: AC impedance at 10 Hz of 2 kΩ maximum averaged over 12 electrode pairs and 3 kΩ maximum for any pair; offset voltage 100 mV maximum; combined offset instability and internal noise 150 µV maximum; and bias-current DC offset 100 mV maximum. [3] [4]

For adhesion, the cutaneous criteria use IEC 60601-2-2 tests: in the pull test no more than 5% of the adhesive area should separate in at least 90% of tests, and in the conformability and fluid-tolerance tests no more than 10% should separate at 1 hour after application or within 15 minutes after saline is poured. The ECG guidance adds that electrodes for diaphoretic patients or strenuous exercise should be tested under those conditions. [4] [3]

Skin-contacting gels, adhesives and electrodes should be biocompatible under ISO 10993-1, with cytotoxicity, sensitisation and irritation as the endpoints for intact-skin surface devices. Shelf life should be supported by real-time stability testing — for example at 1, 3, 6, 9 and 12 months in a 12-month study — with accelerated ageing validated by real-time data; the cutaneous criteria require tests 1–5 to be repeated on samples aged to within 30 days of the labelled expiry. Lead wires with a conductive patient connection must meet the 21 CFR 898 performance standard. [3] [4]

Editorial note: these are US regulatory references. For other markets, ask the supplier for the equivalent conformity evidence and test reports to the current edition of ANSI/AAMI EC12 or the standard your market recognises.

03

Find biopotential electrode manufacturers

The companies in the manufacturer list below show this product on their own websites. Confirm the legal seller, factory and scope for your order.

04

Trace the parts of a biopotential electrode

This is a functional reference built from the sources cited; it is not one maker's design.

05

Fill the specification fields with values for your use

An electrode quotation needs values for your signal and users. The table explains each field, gives published values where a reviewed source states them, and says what to obtain from the supplier.

06

Send the signal, use and test data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Use: [ECG resting, monitoring, stress; EEG; EMG; wear time]
Construction: [sensor; gel; adhesive and backing; connector]
Patients: [adult or paediatric; skin conditions]
Tests: [EC12 report; adhesion; ISO 10993; shelf life]
Regulatory: [markets; registrations]
Supply: [size; pack count; quantity; private label]

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