5Acquisition & Transmission Read the clipper manufacture’s recommendations. This is one model designed for medical applications and may be used near oxygen. In addition the head is disposable, avoiding de-contamination issues.
6Acquisition & Transmission Skin PreparationHelps obtain a strong signalSkin oils reduce adhesion of electrode and hinder penetration of electrode gelDead, dried skin cells do not conduct wellWhen measured from the patient’s skin, the heart’s electrical signal is extremely small, about to volts.That’s as small as one-ten thousandth of a volt. Compare this with energy from a nine volt battery.Good skin prep will make the ECG signal as strong as possible, and make the artifact signals as small as possible.
7Acquisition & Transmission Rubbing skin with a gauzepad can reduce skin oiland remove some of dead skin cellsSimply rubbing the skin with a gauze pad can have a noticeable effect on ECG clarity by:• Reducing skin oil• Removing part of the stratum corneum
8Acquisition & Transmission Other causes of artifactPatient movementCable movementVehicle movementElectromagnetic Interference (EMI)Once the skin has been prepped and the electrodes applied, there are still other sources of artifact to consider.
9Acquisition & Transmission Patient MovementMake patient as comfortable as possibleSupine preferredLook for subtle movementtoe tapping, shiveringLook for muscle tensionhand grasping rail, head raised to “watch”It is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact.When possible, the patient should be in the supine position for a 12-lead ECG.Sometimes this is not feasible, practical or desirable.If ECG is not recording in supine position, simply note this on ECG.
10Acquisition & Transmission Cable MovementEnough “slack” in cables to avoid tugging on the electrodesMany cables have clip that can attach to patient’s clothes or bed sheetIt is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact.When possible, the patient should be in the supine position for a 12-lead ECG.Sometimes this is not feasible, practical or desirable.If ECG is not recording in supine position, simply note this on ECG.
11Acquisition & Transmission Electromagnetic Interference (EMI)Can interfere with electronic equipment60 cycle interference is a type of EMILook for nearby cell phones, radios or electrical devicesNo contact between cables & power cordsTurn off or move away from AC devicesUse shielded cables; inspect for cracksIt is important to place the patient in a position of comfort. The reduction in muscle tension will help to prevent artifact.When possible, the patient should be in the supine position for a 12-lead ECG.Sometimes this is not feasible, practical or desirable.If ECG is not recording in supine position, simply note this on ECG.
12Traditional Placement Limb Lead PlacementTraditional PlacementAvoid placing on the trunk!!!Limb leads should be placed on the limbs. The traditional placement is near the ankles and wrists.Acceptable Placement
13Chest Lead Placement V1: fourth intercostal space to right of sternum V2: fourth intercostal space to left of sternumV3: directly between leads V2 and V4V4: fifth intercostal space at left midclavicular lineV5: level with V4 at left anterior axillary lineV6: level with V5 at left midaxillary lineV1 fourth intercostal space to the right of the sternumV2 fourth intercostal space to the left of the sternumV3 directly between leads V2 and V4V4 fifth intercostal space at left midclavicular lineV5 level with lead V4 at left anterior axillary lineV6 level with lead V5 at left midaxillary line
14Chest Lead PlacementHere is what lead placement looks like on a patient.
15Acquisition & Transmission Things to look forLittle or no artifactSteady baseline
16Acquisition & Transmission Note how the baseline straightened out by simply repositioning the patient cables and clipping them onto the sheet.What technique(s) would you consider in order to resolve the muscle artifact?
1712-Lead Validation Lead I – Global Negativity? R Wave Progression? P, QRS and T Wave inverted?R Wave Progression?R Wave size increases in V leadsTransition Zone?R Wave should be predominately positive in V3 and V4
1812-Lead Validation Limb leads P wave, QRS, and T wave upside down in Lead IGlobal negativityUpper limb leads switched12-leads should be validated for correct lead placement. First, look at Lead I. The P, QRS, and T waves are typically upright. If the P, QRS, and T waves are all inverted, this is a sign of global negativity and the RA and LA leads are switched.
1912-Lead Validation R wave progression normalpoor12-Lead ValidationR wave progressionR waves progress in size from V1 to V4If poor progression, check lead placement on electrodesR wave progression is the way to validate a 12-lead for precordial leads. The insert on your left (viewing) has normal R wave progression where the one on your right has poor progression. If this is seen, check to see that Leads V1–V6 are snapped on the right location. In this example on the right, Leads V2 and V4 have been switched.Poor R wave progression can be caused by pathology as well. It is important that the acute care provider double check the lead placement before disconnecting the V leads following the 12-lead acquisition.