Class note on ECG for Diploma Critical Care

Electrocardiography

Electrocardiography is the process of recording the electrical activity of the heart by  electrodes placed on the skin. These electrodes detect the tiny electrical changes on the skin that arise from the heart’s electrophysiological activity during each heartbeat.

The graph of voltage versus time thus printed by the ECG machine is called electrocardiogram

In a conventional 12 lead ECG, ten electrodes are connected to the patient.

The overall magnitude of the heart's electrical potential is then measured from twelve different angles ("leads") and is recorded over a period of time (usually 10 seconds).

Electrodes and leads:

An electrode is the conductive pad in contact with the body that makes an electrical circuit with the electrocardiograph.

A lead is the source of measurement of a vector.  [A vector is a geometric object that has magnitude (or length) and direction and can be added to other vectors according to vector algebra]

Leads are of two types:

1.       Bipolar leads: they limb leads and are used for comparison between two electrodes.

2.       Unipolar leads: they are Precordial leads and compared to a common lead (commonly the Wilson's central terminal)

The common lead, Wilson's central terminal V_W, is produced by averaging the measurements from the electrodes RA, LA, and LL to give an average potential across the body:

 

Leads are arranged in three sets:

1.       3 limb leads and 3 augmented limbs are arranged like spokes of a wheel in the coronal plane (vertical). They view the heart from a vertical plane.

2.       6 precordial leads that lie on the perpendicular transverse plane (horizontal). They view the heart from a horizontal plane.

Precordium is the region of the thorax immediately in front of the heart.

Limb leads: Leads I, II and III are called the limb leads. The electrodes that form these signals are located on the limbs—one on each arm and one on the left leg. The limb leads form the points of what is known as Einthoven's triangle.

Augmented limb leads: Leads aVR, aVL, and aVF are the augmented limb leads. They are derived from the same three electrodes as leads I, II, and III, but they use Goldberger's central terminal as their negative pole which is a combination of inputs from other two limb electrodes.

Precordial leads: The precordial leads lie in the transverse (horizontal) plane, perpendicular to the other six leads. The six precordial electrodes act as the positive poles for the six corresponding precordial leads: (V₁, V₂, V₃, V₄, V₅ and V₆). Wilson's central terminal is used as the negative pole.

The 12 leads in a 12-lead ECG are listed below: 

LEAD			VIEW OF HEART
Lead I			Lateral
Lead II			Inferior
Lead III			Inferior
aVR			None
aVL			Lateral
aVF			Inferior
V1			Septal
V2			Septal
V3			Anterior
V4			Anterior
V5			Lateral
V6			Lateral

Electrode name	Electrode placement
RA	On the right arm, avoiding thick muscle.
LA	On the left arm, avoiding thick muscle.
RL	On the right leg, lateral calf muscle.
LL	On the left leg, lateral calf muscle.
V1	In the fourth intercostal space (between ribs 4 and 5) just to the right of the sternum (breastbone).
V2	In the fourth intercostal space (between ribs 4 and 5) just to the left of the sternum.
V3	Between leads V2 and V4.
V4	5th Intercostal space at the midclavicular line
V5	Anterior axillary line at the same level as V4
V6	Midaxillary line at the same level as V4 and V5

Artefacts on ECG:

An ECG tracing is affected by patient’s motion. Some rhythmic motions (such as shivering or tremors) can create the illusion of arrhythmia. Artefacts are distorted signals caused by secondary internal or external sources, such as muscle movement or interference from an electrical device.

Accurately separating the ECG artefacts from the true ECG signal can have a significant impact on patient’s diagnosis, treatment, outcome of therapy and legal liabilities.

Reducing Artefacts while measuring an ECG:

Below is a list of guidelines that will help reduce artefacts when performing ECG’s.

Patient Positioning

• Place the patient in a supine or semi-Fowler’s position. If the patient cannot tolerate being flat, you can do the ECG in a more upright position.
• Instruct the patient to place their arms down by their side and to relax their shoulders.
• Make sure the patient’s legs are uncrossed.
• Move any electrical devices, such as cell phones, away from the patient as they may interfere with the machine.

Skin Preparation

• Dry the skin if it’s moist or diaphoretic.
• Shave any hair that interferes with electrode placement. This will ensure a better electrode contact with the skin.
• Rub an alcohol prep pad or benzoin tincture on the skin to remove any oils and help with electrode adhesion.

Electrode Application

• Check the electrodes to make sure the gel is still moist.
• Do not place the electrodes over bones.
• Do not place the electrodes over areas where there is a lot of muscle movement.

Electrocardiogram grid

ECG's are normally printed on a grid. The horizontal axis represents time and the vertical axis represents voltage. The standard values on this grid are shown in the image to the right:

• A small box is 1 mm x 1 mm big and represents 0.1 mV x 0.04 seconds.
• A large box is 5 mm x 5mm big and represents 0.5 mV x 0.2 seconds wide.

The "large" box is represented by a heavier line weight than the small boxes.

An Introduction to Critical Care Technology

Who is a Critical Care Technologist?

Critical care technologists (CCTs) are professionals who specialise in medical physics and clinical engineering. They are an integral part of the Critical Care team and make sure that the equipments and technology needed to support organ function and maintain life are working and being used properly.

Critical care technicians often arrive on the scene to assist during health emergencies. These professionals can treat a variety of injuries or physical ailments, as well as transport patients to a hospital for extended treatment.

Job Description and Duties

Critical care technician’s are trained to provide high-quality out-of-hospital care to patients in emergency situations. They may encounter various situations like cardiac arrest, respiratory distress, choking, fractures, childbirth, road traffic accidents etc. When entering an accident scene, a critical care technician quickly assesses the problems and begins implementing medical aid. Their primary duty is to provide medical care and get patients to a medical facility where they can receive extended treatment. Critical care technicians also work in medical facilities where they assist the critical care team. Additional job duties are based on the amount of training and experience of the technician. For example, critical care technicians with paramedic training can perform procedures like endotracheal intubations, as well as use complex equipment like electrocardiograms.

According to the U.S. Bureau of Labor Statistics (BLS), emergency medical workers, including critical care technicians, can work over 40 hours a week and sometimes at odd or irregular hours (www.bls.gov).

Critical care technicians can also be exposed to harmful diseases, violence from patients, stress, and injuries. Some of the work may involve handling of hazardous chemicals and substances. So, protective overalls, gloves, glasses, mask etc may have to be worn according to the demand of the situation.

A critical care technician works alongside doctors, nurses and other medical staff like physiotherapists, dietitians and pharmacists. So he/she should be able to work in a team. There is possibility of frequent contact with very sick patients and distressed relatives, so the work can be stressful and emotionally challenging at times.​​​

Routine work usually includes the following duties:

• setting up equipment, connecting it to patients and monitoring the machinery as it is being used
• carrying out regular maintenance checks and cleaning of intensive care equipment and bedside technical support
• decontaminating machinery when it needs to be sent for repair
• working with other healthcare professionals during life threatening events, trained at providing CPR

Some of the equipments commonly used include (but are not limited to):

• Blood analysers (ABG machine)
• Dialysis machines
• Mechanical Ventilators
• Defibrillators
• Multichannel monitors – both invasive and non-invasive monitoring devices
• Infusion pumps
• 12 lead ECG
• Portable X-ray
• USG
• Glucometers
• Computer

​

Qualities

To become a critical care technologist, you will need:

• an interest in technology, science and medicine
• the ability to work accurately, precisely
• good problem solving and decision making skills
• the ability to empathise with patients, and put them at ease
• good communication skills
• the ability to cope with distressing situations
• Physical strength
• Ability to work under stress

Training and development

Skills and knowledge should be kept up-to-date through the career by continuing professional development activities (CPD).

Opportunities

Job opportunities may be found within larger Govt. hospitals as well as in private set-ups like ICU, Dialysis unit etc.

With experience, one may be able to progress in his/her career from CCT to Lead CCT. Alternatively, one can move into a specialist field of critical care such as the liver and transplant work, cardiology, neurophysiology, burns, premature baby units, and respiratory physiology.

Pros and Cons of a Critical Care Technician

Pros of Being a Critical Care Technician

Faster-than-average job growth (expected 23% growth between 2012 and 2022)*

Satisfaction of helping others*

May be responsible for saving lives*

Does not require years of formal training*

Cons of Being a Critical Care Technician

May be required to work nights or weekends*

Must pass licensure exam to work*

Work may be physically strenuous and stressful*

May be exposed to contagious diseases*

Sources:*U.S. Bureau of Labor Statistics

Job Prospects 

Current statistics from Indian perspective was not available during write-up of the article. The U.S. Bureau of Labor Statistics (BLS) predicted that EMTs may see an employment growth of 33% from 2010-2020. Predicted contributory factors include an increase in the number of natural disasters, car accidents and violence. With an increase in life expectancy there has been a steady increase in the elderly population. This has led to an increase in the incidence of age-related health emergencies, which also puts these workers in demand.