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Cardiopulmonary resuscitation (CPR)

Author: Alexandra Juhász

Sudden cardiac arrest can happen to anyone at any time. It can affect all age groups, including healthy young and older adults.

Quick and proper treatment is crucial in a sudden cardiac arrest; if not, it will cause sudden death within a few minutes. A minute without help decreases the success of reanimation by 7–10%.

Reanimation

Reanimation (cardiopulmonary resuscitation – CPR) is an emergency procedure that combines chest compressions, often with artificial ventilation, to preserve intact brain function until further measures are taken to restore spontaneous blood circulation and breathing in a person who is in cardiac arrest.

It includes recognising critically ill patients and the actions taken to prevent fatal heart conditions.

First, in 1960, an electrical engineer and his medical colleagues presented closed-chest cardiac massage to clinical medicine practitioners. Until then, only ventilation techniques, with or without instruments, were used and developed, simply because the physiology of breathing and circulation, and their relationship, had not yet been discovered.

Scientists were aware of the fact that the cause of death was cardiac arrest, but their only hope of restoring circulation was artificial respiration.

During thoracic and cardiac surgeries, it was discovered that the heart's pumping function can be artificially stimulated. In cases of cardiac arrest, internal or open cardiac massage has been successfully used several times during surgeries, and with experience gained from this technique, external cardiac massage has also been successfully performed.

Peter Safar, a pioneer of critical care medicine and a three-time nominee for the Nobel Prize in Physiology or Medicine, is widely recognised as the father of cardiopulmonary resuscitation (CPR).

There are two types of life support: advanced (ALS) and basic (BLS). BLS is the basic procedure that anyone can start, even without a device.

The main goal of BLS is to immediately recognise sudden cardiac arrest, activate the emergency response system (chain of survival), and support the patient's circulation and respiration.

Advanced Life Support (ALS), also known as Advanced Cardiac Life Support (ACLS), is a set of life-saving protocols and skills that extend beyond Basic Life Support (BLS) but are based on it. Healthcare professionals perform ALS.

The steps of the ALS and the decisions are made by a team leader, who proceeds with the course of action based on reading the patient’s ECG. The procedure involves using manual defibrillator, airway management devices and administering specific medication.

Cardiac arrest causes poor and ineffective tissue perfusion. Anaerobic metabolism ensues, resulting in the production of lactic acid. This creates a “gap” metabolic acidosis, and in certain tissues, irreversible cell damage occurs.

In cardiac arrest, blood in the arteries drains into the veins, placing a more significant load on the right ventricle. After the pressure becomes equal in both ventricles, the interventricular septum deviates to the left, decreasing the cavity of the left ventricle.

If circulation started spontaneously in this case, the stroke volume of the left ventricle and the perfusion of the coronary arteries would be extremely low.

Continuous chest compression may be performed with or without rescue breathing. The theory is that CPR mimics the heart's pumping action, maintaining the supply of oxygen and nutrients to essential organs such as the brain.

The external cardiac massage model suggests that chest compressions directly compress the heart between the depressed sternum and the thoracic spine.

This ejects blood into the systemic and pulmonary circulations, while the cardiac valves limit backward flow during decompression. Continuous chest compressions generate a small but critical amount of blood flow to the coronary arteries. Interrupting chest compressions prevents blood from reaching vital organs.

The return of spontaneous circulation (ROSC) is the resumption of sustained perfusing cardiac activity, accompanied by significant respiratory effort, after cardiac arrest. (Signs of ROSC include breathing, coughing, or movement and a palpable pulse or a measurable blood pressure.)

Most common causes of cardiac arrest are ventricular fibrillation and pulseless ventricular tachycardia.

Ventricular fibrillation (rhythm strip)

Ventricular tachycardia (rhythm strip)

These are the two types of electrical heart activity that are likely to be corrected by delivering energy. If so, this is known as a shockable rhythm.

Two types of non-shockable heart rhythms exist: pulseless electrical activity (PEA) and asystole. Therefore, defibrillation is not a viable treatment for these heart rhythms.

The semi-automatic and fully automatic external defibrillator (AED) automatically analyse the patient's heart rhythm to determine if a shock is needed.

DNAR (do not attempt resuscitation) orders apply in any care facility, in or out of the hospital, within the constraints of applicable law. In the event a patient suffers a cardiopulmonary arrest when there is no DNAR order in the medical record, resuscitation must be attempted.

A DNAR is a written decision not to perform CPR in case of cardiac arrest. It is made and recorded by a senior healthcare team member, such as a general practitioner or oncologist.
DNAR orders are often placed late in the disease process, e.g., in cancer care in the terminal phase of the illness.
When irreversible signs of death, such as rigor mortis, dependent lividity, decapitation, decomposition, incineration, and other apparent lethal injuries, are present, CPR should not start.

Chain of Survival

The Chain of Survival, a concept introduced two decades ago to visually and simply emphasize the critical and time-sensitive steps required to improve survival following cardiac arrest.

Early recognition &
call for help

Early CPR &
defibrillation

Advanced & post
resuscitation care

Survival & recovery

Prevent
cardiac arrest

Preserve brain &
restart the heart

Optimise brain &
heart function

Restore quality
of life

To reflect recent scientific progress, the four links of the chain have been updated for 2025 and now include enhanced guidance for dispatchers, first responders, and long-term survivor support.

Elements of the Chain of Survival

The initial ring prioritises prevention and the rapid identification of medical crises to ensure that professional help is summoned without delay.
The second ring combines early chest compressions with defibrillation. These vital actions maintain blood flow and aim to restore heart and brain activity as quickly as possible.
The third ring involves specialised medical intervention by professionals to stabilise the patient and preserve neurological and cardiac health.
The final ring addresses the long-term recovery journey, emphasising the need for comprehensive support for survivors and their families to ensure the best possible quality of life.

Steps of BLS

The main goal of BLS is to provide care to patients with life-threatening conditions until advanced life support can be delivered.

1.) SAFETY

Assess scene safety

Look for clear and less obvious hazards to caregivers, patients, and bystanders. Continually assess the scene for danger properly before responding to an emergency, and mitigate these if possible. Focus on the evident hazards (e.g., fire, smoke, fallen power line, biohazards, chemicals), dangers that are hidden (e.g., a needle under a casualty) or hazards which may develop (e.g., a change in the weather, movement of a vehicle or a structure, a fire which is out of control). In the event of a road accident, ensure the ignition switches of all vehicles involved are turned off.

2.) RESPONSE

Check for any response from the patient

Gently shake the patient's shoulders and loudly ask, "Can you hear me?” or “Are you alright?”
Then, give some basic commands, such as “Tell me your name!” “Open your eyes!” or” Squeeze my hand!”
Check if the patient can respond to you and follow simple commands.

3.) CALL FOR HELP AND CHECK THE PATIENT'S AIRWAY

If the patient is unresponsive and unconscious, immediately call the emergency services on 112. If you are alone and do not have a mobile phone, shout for help. If you have a phone, dial the emergency number, activate the speaker, and begin the assessment while following the dispatcher's instructions.

First, ensure the patient’s mouth and throat are clear by removing any visible blockages, such as vomit, blood, or food. To open the airway, place one hand on the patient’s forehead and your fingertips under the chin, then gently tilt the head back and lift the chin.
Assess breathing for no more than 10 seconds using the "look, listen, and feel" method: place your ear over the patient’s mouth while watching for chest movement.
Do not mistake agonal breathing or gasping (irregular breaths caused by oxygen deprivation) for normal breathing. It occurs in about half of cardiac arrest cases and may sound like infrequent snorting or snoring (around 5–6 breaths per minute), but it does not provide effective oxygenation.
If breathing is absent or abnormal (such as gasping), treat the situation as cardiac arrest and act immediately. As a lay rescuer, do not check for a pulse; begin chest compressions without delay.

Look, listen, and feel for any evidence of breath sounds,
and feel for air blowing against your cheek for no more than 10 seconds.

4.) START CARDIOPULMONARY RESUSCITATION (CPR)

If the patient is not breathing, start CPR without delay

Ask bystanders for assistance and ensure 112 has been notified. Lay rescuers are not expected to check for a pulse; unresponsiveness and lack of normal breathing are sufficient indicators to begin chest compressions.

When speaking to the emergency operator, provide the following details clearly:

Your exact location.
Confirm that CPR is currently in progress.
Ask if there is an AED in the vicinity.
Briefly describe the situation.

It is crucial to stay as calm as possible and describe the emergency succinctly. Keep the line open and strictly follow all instructions provided by the dispatcher until professional medical help arrives.

Proper technique for chest compressions

Place the person on their back on a firm, flat surface.
Kneel next to the person's shoulders.
Place the heel of your hand in the centre of the chest on the lower half of the sternum.
Place the heel of your other hand on the top of the first hand and interlock your fingers.
Keep your arms straight.

Position yourself vertically above the victim's chest and press down on the sternum at least 5 cm (but not more than 6 cm).

After each compression, release all the pressure on the chest without losing contact between your hands and the sternum. Allow the chest to recoil completely; do not lean on it.

Repeat at a rate of 100–120 compressions per minute.
Each compression and release should take an equal amount of time.

Combine rescue breathing with chest compressions:

After 30 chest compressions, reopen the airway with head tilt and chin lift.
Pinch the soft part of the nose closed using the index finger and thumb.
Allow the victim's mouth to open, but maintain a chin lift.

Take a normal breath and place your lips around the victim's mouth, ensuring a tight seal.
Blow steadily into the mouth whilst watching for the chest to rise, taking about 1 second as in normal breathing.
Maintaining head tilt and chin lift, take your mouth away from the victim and watch for the chest to fall as air comes out.
Take another normal breath and blow into the victim's mouth once more to achieve a total of two rescue breaths.
Do not interrupt compressions by more than 10 seconds to deliver the two breaths, even if one or both are ineffective.
Then return your hands to the correct position on the sternum without delay and give an additional 30 chest compressions.
Continue with chest compressions and rescue breaths in a ratio of 30:2.

Available evidence from randomised controlled trials suggests that compression-only CPR is superior to standard CPR, at least when performed by untrained bystanders.

WHEN AED IS AVAILABLE

Steps to use an AED:

1. Assess the scene

Switch on the AED and follow the instructions for placing the pads on the victim's bare chest. Minimise pauses in chest compressions, if possible.

The CPR area should be dry. Also, thoroughly dry the victim’s bare chest, upper stomach, armpits, the sides of their ribcage, and neck with a towel or dry clothing.

2. Switch on the device

3. Once the patient’s chest is completely dry, apply the AED pads to the skin and continue performing CPR.

4. Before pressing the shock button (for semi-automatic models) or before the device delivers a shock automatically (for fully automatic models), shout “stand clear” to make sure that no one is touching the patient’s body.

5. After 2 minutes, the AED will say, “Stop CPR, analysing.”

The AED is now analysing the victim to see whether a shockable rhythm is present and instructs you again to either ”Shock advised” or “No Shock advised.”

6. Follow the instructions on the AED and perform CPR until the patient responds, you cannot continue, or a health care professional arrives and takes over care or directs cessation.

Ventricular tachycardia (VT) and ventricular fibrillation (VF) are the most common causes of sudden cardiac death.

Early defibrillation is the primary determinant of the success of resuscitative attempts. The latest Adult Basic Life Support (BLS) guidelines support the inclusion of the use of the automated or semi-automated external defibrillator (AED) as part of BLS.

These devices can measure core parameters, such as compression depth and rate, in real time, helping the rescuer adjust the technique if necessary. AEDs use voice prompts and visual indicators to guide the rescuer through a resuscitation sequence that may include defibrillation and/or CPR.

Basic Life Support (BLS)

Kardiovaskulárny systém

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