Factors aff ecting ECG trace quality

Factors aff ecting ECG trace quality

Monitor Skin

Environment

Electrode

Cables & lead wires

� CMRR (Common Mode Rejection Ratio) used to separate ECG from other signals

� Filters

� Bandwidth (frequency response)

� Amplifi er noise

� Ground loops

� Saturation distortion (e.g. defi brillation recovery)

� Input impedance

� Diff erential input (required to generate ECG tracing)

� Impedance

� Diaphoresis

� Dryness

� Oiliness

� EMG, respiration and other biopotentials (physiological electrical signals)

� Skin preparation techniques

� Obesity

� Skin stretch

� Motion artifact

� Adhesion

� Conductor

� Gel

� Backing

� Size

� Design

� Motion

� Shelf life

� Application technique

� Electrical/mechanical properties

� Location on the body

� Electrical fi eld (60 Hz)

� Humidity

� Temperature

� Static electricity

� Magnetic fi eld

� Radiofrequency

� Vicinity of other machines

(nebulizers, fans, power cords, etc.)

� Mechanical/electrical properties of materials

� Shielded cable and shielded lead wires

� Open lead wires (avoid loops)

� Triboelectric eff ect (generated by cable movement)

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ECG electrode placement

Artifacts SkinImpedance

MuscleMovement

ElectricalContinuity Electrodes Cabling Interference Equipment

No Base Line2

Check allconnections/

performcontinuity check

4Check for dry-out

3Check for

proper cable

1Check lead switchand ECG machine

set-up

Base Line Wander 3Abrade skin

1Stop patientmovement

2Check groundconnections

4Use same type of

electrode at all sites

6Check for

proper cable

5Check for static

build-up

AC Noise3

Abrade skin6

May be untreatable

involuntary muscletremor

1Check groundconnections

5Check for dry-out

7May need fully

shielded cable andlead wires

2Keep cable away

from AC cord

4Turn off

fl uorescentlights and/or other

equipment

Intermittent Signal 1Check for loose

connections

2Check for loose

electrode or dry-out

4Perform continuity

check

3Check for static

build-up

Motion Artifact2

Abrade skin1

Move electrodes off muscle mass

3Check for loose

connections

4Check for loose

electrode or dry-out

7Perform continuity

check

5Turn off

fl uorescentlights and/or other

equipment

6Check for proper

EKG machine set-up

Low Amplitude3

Abrade skin1

Check allconnections

4Check for dry-out

5Turn off radio,

TV and/or other equipment

2Check gain

settings

Troubleshooting ECG tracesTroubleshoot each artifact in order, starting with 1

3-Lead PlacementMonitoring Electrodes

5-Lead PlacementMonitoring Electrodes

RA LA

LLRL

V2V2

Monitoring ElectrodesMonitoring Electrodes12-Lead Placement

Resting Electrodes

RA

LLRL

V1 V2

V3V5 V6

V2V2LA

V4

RALA

LLRA: Second intercostal space lateral right sideLA: Second intercostal space lateral left sideLL: Lower left lateral chest or left legRL: Lower right lateral chest or right legV2: Fourth intercostal space to the left of

the sternum

RA: Second intercostal space lateral right sideLA: Second intercostal space lateral left sideLL: Lower left lateral chest or left leg

RA: Second intercostal space lateral right sideLA: Second intercostal space lateral left sideLL: Lower left lateral chest or left legRL: Lower right lateral chest or right legV1: Fourth intercostal space to the right of the sternum

V2: Fourth intercostal space to the left of the sternumV3: Between V2 and V4V4: Fifth intercostal space along the mid-clavicular lineV5: Fifth intercostal space between V4 and V6V6: Fifth intercostal space along the mid-axillary line