The Ultimate BLS Field Guide

Basic Life Support (BLS) is a set of emergency medical skills used to keep someone alive when they are in cardiac arrest, not breathing normally, or choking.

It focuses on maintaining circulation, oxygenation, and airway function until advanced medical help arrives.

BLS typically includes:

• High-quality CPR (chest compressions ± rescue breaths)
• Use of an AED (Automated External Defibrillator)
• Basic airway management
• Response to choking emergencies
• Coordinated team-based resuscitation (especially in clinical settings)

In simple terms, BLS is the first critical level of care that helps sustain life in a medical emergency before advanced treatment begins.

CPR (Cardiopulmonary Resuscitation) and BLS (Basic Life Support) are related, but they are not the same.

CPR (Cardiopulmonary Resuscitation)

CPR is a single emergency technique used when someone’s heart or breathing stops.

It focuses on:

• Chest compressions to circulate blood
• Rescue breaths (if trained)
• Maintaining oxygen delivery to the brain and heart

CPR is one skill within emergency response.

BLS (Basic Life Support)

BLS is a broader emergency care system that includes CPR plus additional life-saving actions.

It includes:

• CPR (core component)
• AED use (defibrillation)
• Choking management
• Airway and breathing support
• Team-based emergency response (especially in hospitals)

BLS = CPR + additional emergency interventions

Cardiac arrest is a sudden and life-threatening condition in which the heart stops pumping blood effectively, causing a complete loss of oxygen supply to the brain and vital organs. The person collapses, becomes unconscious, and will die within minutes without immediate treatment such as CPR and defibrillation. It is important to differentiate it from a heart attack, which is caused by a blockage in blood flow to the heart muscle, whereas cardiac arrest is a sudden failure of the heart’s electrical and pumping system.

The most important sign of cardiac arrest is unresponsiveness, meaning the person does not wake up or respond to voice, touch, or shaking. At the same time, breathing is either absent or abnormal. This can be summarized as key recognition features:

• Unresponsive (does not wake up)
• No normal breathing or only gasping (agonal breathing)
• No pulse within 10 seconds (if trained to check)
• Sudden collapse in many cases

Agonal breathing is a critical warning sign. It may look like weak, irregular gasps or snorting sounds, but it is not effective breathing and should always be treated as cardiac arrest. If a rescuer is trained, they may also check for a carotid pulse, but if there is any doubt, CPR should be started immediately without delay.

To recognize cardiac arrest quickly and correctly, a structured approach should be followed:

• Check scene safety
• Check responsiveness (tap and shout)
• Call emergency services and get an AED
• Check breathing for no more than 10 seconds
• Check pulse only if trained
• If unresponsive + not breathing normally → start CPR immediately

In summary, cardiac arrest is identified mainly by unresponsiveness and abnormal or absent breathing. The key rule is simple: if a person is unresponsive and not breathing normally, assume cardiac arrest and begin CPR immediately, because early action significantly increases survival chances.

Hands-only CPR is a simplified form of cardiopulmonary resuscitation used for adults who suddenly collapse and are not breathing normally. It is designed for untrained or unwilling rescuers to act quickly without the delay of checking pulses or giving rescue breaths. The main goal is to keep blood circulating to the brain and heart until emergency help and an AED arrive.

In adults, cardiac arrest is most often sudden, and immediate chest compressions are the most important action. Hands-only CPR focuses on high-quality, continuous compressions that manually pump blood through the body. It is especially effective in the first few minutes after collapse.

The steps for hands-only CPR are:

• Check scene safety and ensure there is no danger
• Check responsiveness by tapping the person and shouting
• Call emergency services immediately or ask someone to call
• Get an AED if available
• Place the heel of one hand on the center of the chest (lower half of the breastbone)
• Place the other hand on top and interlock fingers
• Push hard and fast at a rate of 100–120 compressions per minute
• Compress at a depth of about 5–6 cm (2–2.4 inches)
• Allow full chest recoil after each compression
• Continue without stopping until help arrives or an AED is ready

The most important points in hands-only CPR are speed, depth, and minimal interruptions. Stopping compressions reduces blood flow to the brain, so the goal is to keep pushing continuously.

The CAB approach is the recommended sequence for adult CPR and stands for Compressions, Airway, and Breathing. This method emphasizes starting chest compressions immediately because maintaining blood circulation is the highest priority during cardiac arrest. Early compressions help deliver oxygen-rich blood to the brain and heart until advanced care arrives.

CAB Steps

• C – Compressions
  • Place the heel of one hand on the center of the chest and the other hand on top.
  • Perform chest compressions at a rate of 100–120 compressions per minute.
  • Compress the chest to a depth of 5–6 cm (2–2.4 inches).
  • Allow complete chest recoil after each compression.
  • Give 30 compressions before opening the airway.
• A – Airway
  • Open the airway using the head tilt–chin lift technique.
  • Check for any visible obstruction in the mouth.
  • Ensure the airway is open before giving breaths.
• B – Breathing
  • Give 2 rescue breaths.
  • Each breath should last about 1 second and produce visible chest rise.
  • Avoid excessive ventilation.

CPR Cycle

• Perform 30 compressions followed by 2 breaths (30:2 ratio).
• Continue CPR cycles until:
  • An AED becomes available,
  • The person shows signs of life,
  • Emergency responders take over, or
  • You are unable to continue.

Key Points

• Start with compressions first; do not delay CPR.
• Minimize interruptions during compressions.
• Maintain a compression rate of 100–120/min.
• Ensure adequate depth and full chest recoil.
• Use an AED as soon as it becomes available.

An Automated External Defibrillator (AED) is a portable device that analyzes the heart’s rhythm and delivers an electrical shock when needed to help restore a normal heartbeat. Early use of an AED, combined with high-quality CPR, significantly increases the chances of survival in cardiac arrest.

When an AED becomes available, it should be used as soon as possible while minimizing interruptions in chest compressions. The device provides voice and visual prompts that guide the rescuer through each step.

Steps for AED Use

• Turn on the AED immediately.
• Expose the person’s chest.
• Dry the chest if it is wet and remove any medication patches.
• Attach the AED pads to the bare chest:
  • One pad on the upper right chest, below the collarbone.
  • One pad on the lower left side of the chest, below the armpit.
• Ensure that no one is touching the patient.
• Allow the AED to analyze the heart rhythm.
• If the AED advises a shock:
  • Loudly state “Clear!”
  • Make sure everyone is away from the patient.
  • Press the shock button if required.
• Immediately resume CPR after the shock.
• If no shock is advised, resume CPR immediately.
• Continue following the AED prompts until emergency responders arrive or the person shows signs of life.

Important Points

• Use the AED as soon as it is available.
• Do not touch the patient while the AED is analyzing the rhythm or delivering a shock.
• Resume chest compressions immediately after a shock or a “no shock advised” message.
• Minimize interruptions in CPR.
• Follow all voice prompts provided by the AED.

CPR for children and infants is performed when they are unresponsive, not breathing normally, and have no pulse or signs of circulation. While the basic principles are similar to adult CPR, the compression depth, hand placement, and techniques are modified according to the child’s size and age. A child is defined as a person from 1 year of age until puberty, while an infant is a baby less than 1 year old.

Before starting CPR, ensure the scene is safe, check responsiveness, and assess breathing and pulse for no more than 10 seconds. If the child or infant is unresponsive and not breathing normally, begin CPR immediately and activate emergency medical services.

Child CPR (1 Year to Puberty)

• Check responsiveness and breathing.
• Call for help and get an AED if available.
• Place one or two hands on the center of the chest.
• Perform chest compressions at a rate of 100–120 compressions per minute.
• Compress the chest to a depth of about 5 cm (2 inches) or one-third of the chest depth.
• Use a compression-to-ventilation ratio of:
  • 30:2 for a single rescuer
  • 15:2 for two rescuers
• Allow full chest recoil after each compression.
• Continue CPR until help arrives or the child shows signs of life.

Infant CPR (Less Than 1 Year)

• Check responsiveness by tapping the sole of the foot.
• Check breathing and pulse for no more than 10 seconds.
• Use two fingers in the center of the chest, just below the nipple line, for a single rescuer.
• Use the two-thumb encircling hands technique when two rescuers are present.
• Perform compressions at a rate of 100–120 compressions per minute.
• Compress to a depth of about 4 cm (1.5 inches) or one-third of the chest depth.
• Use a compression-to-ventilation ratio of:
  • 30:2 for a single rescuer
  • 15:2 for two rescuers
• Give gentle rescue breaths that produce a visible chest rise.

Key Differences from Adult CPR

• Compression depth is shallower.
• One or two hands are used by children instead of two hands for most adults.
• Two fingers or two thumbs are used for infants.
• Pediatric AED pads should be used when available.
• Respiratory problems are a more common cause of cardiac arrest in children and infants.

Rescue breathing alone is provided when a person has a pulse but is not breathing or is only gasping. Its purpose is to deliver oxygen to the lungs while the heart continues to circulate blood.

When to Provide Rescue Breathing without Chest Compressions

Use rescue breathing alone if the person:

• Is unresponsive
• Has a pulse
• Is not breathing or is only gasping

If there is no pulse, begin CPR immediately instead.

Adults

1. Open the airway using the head-tilt, chin-lift technique.
2. Pinch the nose closed.
3. Give 1 rescue breath every 6 seconds (10 breaths per minute).
4. Each breath should last about 1 second and produce a visible chest rise.
5. Recheck the pulse every 2 minutes.

Children

1. Open the airway using the head-tilt, chin-lift technique.
2. Give 1 rescue breath every 2–3 seconds (20–30 breaths per minute).
3. Each breath should last about 1 second with a visible chest rise.
4. Recheck the pulse every 2 minutes.

Infants

1. Place the infant’s head in a neutral position and open the airway.
2. Cover both the mouth and nose with your mouth.
3. Give 1 gentle breath every 2–3 seconds (20–30 breaths per minute).
4. Each breath should be just enough to make the chest rise.
5. Recheck the pulse every 2 minutes.

Important Tips

• Give only enough air to make the chest rise.
• Avoid excessive ventilation, as too much air can reduce blood flow and increase the risk of stomach inflation.
• If the chest does not rise, reposition the airway and try again.
• If the person loses their pulse at any time, begin CPR immediately.

While every emergency is different, knowing how to respond to special situations can improve outcomes and help you succeed on the BLS exam. Stay calm, follow the BLS sequence, and prioritize high-quality CPR whenever indicated.

Drowning

Drowning victims often suffer from a lack of oxygen, making early rescue breathing and CPR especially important.

What to Do:

1. Remove the person from the water only if it is safe.
2. Call 911 or activate the emergency response system.
3. Check for responsiveness, breathing, and pulse.
4. Begin CPR immediately if there is no pulse or the person is not breathing normally.
5. After resuscitation begins, keep the person warm to help prevent hypothermia until emergency personnel arrive.

Suspected Opioid Overdose

An opioid overdose can cause severe breathing problems or cardiac arrest. Rapid intervention can save a life.

What to Do:

1. Call 911 immediately.
2. Administer Naloxone (Narcan) if available and you are trained to use it.
3. If the person has a pulse but is not breathing, provide rescue breaths.
4. If there is no pulse, begin CPR immediately.
5. Continue care until emergency medical services arrive.

Shock Management

Shock occurs when the body’s organs do not receive enough blood and oxygen. Early recognition and supportive care are essential.

What to Do:

1. Lay the person flat on their back unless they have difficulty breathing or a suspected head, neck, or spinal injury.
2. Keep the person warm and still.
3. Do not give food or drinks.
4. Monitor breathing, pulse, and responsiveness until help arrives.

Trauma Emergencies

Trauma patients may have serious injuries that require additional precautions while providing lifesaving care.

What to Do:

1. Ensure the scene is safe before approaching.
2. Stabilize the head and neck if a spinal injury is suspected.
3. Control severe bleeding with direct pressure.
4. Continuously monitor the person’s airway, breathing, and circulation (ABCs).
5. Begin CPR if the person becomes pulseless.

Effective teamwork is essential during a BLS emergency. When multiple rescuers work together efficiently, CPR quality improves, interruptions are reduced, and patient outcomes are enhanced. Successful team dynamics depend on clear communication, defined responsibilities, and coordinated actions.

Leadership

A team leader should take charge of the situation, assign tasks, monitor performance, and ensure that all interventions are carried out correctly. Strong leadership helps maintain organization and prevents confusion during emergencies.

Key Responsibilities:

• Take charge of the response
• Assign tasks to team members
• Monitor CPR quality and progress
• Make decisions and provide direction

Communication

Clear and effective communication ensures that all team members understand their roles and the patient’s condition. Information should be shared using concise and direct statements.

Key Points:

• Share clear and accurate information
• Confirm instructions are understood
• Report changes in patient status
• Use closed-loop communication when possible

Role Assignment

Each team member should have a specific responsibility to improve efficiency and reduce delays in care.

Examples of Roles:

• Chest compressor
• Airway manager
• AED operator
• Team leader
• Medication provider (if applicable)

Coordination

Team members must work together smoothly and anticipate each other’s actions. Good coordination minimizes interruptions in CPR and allows critical tasks to be completed quickly.

Key Points:

• Work together efficiently
• Coordinate CPR, ventilation, and AED use
• Minimize delays and interruptions
• Support other team members when needed

Adaptability

Emergency situations can change rapidly. Team members must be prepared to adjust their actions based on the patient’s condition and available resources.

Key Points:

• Adapt to changing circumstances
• Be ready to switch roles when needed
• Respond quickly to new information
• Maintain flexibility during the emergency

The BLS certification exam evaluates your understanding of CPR, AED use, rescue breathing, and emergency response procedures. To successfully pass the course, students must demonstrate knowledge of both theoretical concepts and practical skills. Being familiar with the exam structure and key requirements can help improve confidence and performance.

Exam Facts

• 25 Questions
  • The exam typically consists of 25 multiple-choice questions covering BLS concepts, CPR techniques, AED use, and emergency response procedures.
• Passing Score
  • A minimum score of 84% or higher is required to pass the written examination.
• Certification Validity
  • BLS certification is generally valid for 2 years before renewal is required.
• Course Duration
  • Most BLS courses take approximately 4–5 hours to complete, including both instruction and skills assessment