Basic Life Support

Basic life support (BLS) is the level of resuscitation care that can be provided without advanced equipment or drugs: recognising cardiac arrest, calling for help, performing chest compressions and rescue breaths, and using an automated external defibrillator. It is the foundation of the chain of survival and can be delivered by trained lay rescuers as well as healthcare professionals.

Definition

Basic life support is the maintenance of airway patency and the support of breathing and circulation, without the use of equipment other than a protective device or an automated external defibrillator, until more advanced care is available.

Scope

This topic covers the recognition of cardiac arrest, the components of high-quality CPR (compression rate, depth, recoil, and minimal interruptions), rescue ventilation, and the role of public-access defibrillation, as summarised in current consensus guidelines. It is a reference overview of the concepts, not a procedural certification or a source of dosing or device instructions.

Key concepts

• Recognition of cardiac arrest
• Chest compressions (rate, depth, full recoil)
• Compression-to-ventilation ratio
• Minimising interruptions in compressions
• Automated external defibrillator (AED)
• Public-access defibrillation
• Bystander and hands-only CPR

Mechanisms

BLS supports oxygen delivery while the heart is not generating effective output. Chest compressions raise intrathoracic and direct cardiac pressures to drive forward blood flow toward the brain and coronary circulation, and rescue breaths or passive oxygenation replenish arterial oxygen content. Guidelines emphasise that compressions should be deep enough and fast enough to generate perfusion, allow complete chest recoil between compressions, and be interrupted as little as possible, because perfusion pressure falls quickly when compressions pause. Early use of an automated external defibrillator allows lay rescuers to deliver a shock for shockable rhythms without rhythm interpretation.

Clinical relevance

BLS is the part of resuscitation most likely to be performed by bystanders, and bystander CPR and early defibrillation are consistently associated with improved survival in guideline syntheses. This entry explains the rationale behind those concepts for educational reference and is not a substitute for hands-on certified training or in-the-moment clinical judgement.

Epidemiology

Most cardiac arrests outside hospital occur in settings where the first responder is a bystander, so rates of bystander CPR and public-access defibrillator use are key system-level determinants of survival described in resuscitation guidelines.

History

The technique combining closed-chest compression, rescue ventilation, and defibrillation emerged in the late 1950s and 1960s, building on Kouwenhoven and colleagues' demonstration that the circulation could be supported by external chest compression. Subsequent decades saw the simplification of lay-rescuer instruction, the promotion of compression-only (hands-only) CPR to encourage bystander action, and the spread of automated external defibrillators into public spaces, all reflected in successive international guideline updates.

Debates

Compression-only versus standard CPR for lay rescuers

Whether untrained or telephone-assisted bystanders should be guided toward compression-only CPR to maximise willingness to act and minimise interruptions, or toward conventional CPR with rescue breaths, remains a guideline judgement that balances simplicity against the needs of certain arrest causes.

Key figures

• William Kouwenhoven
• Peter Safar
• Theresa Olasveengen
• Gavin Perkins

Seminal works

• kouwenhoven-1960
• olasveengen-2021
• panchal-2020

Frequently asked questions

What distinguishes basic life support from advanced life support?

Basic life support uses no advanced equipment or drugs — compressions, ventilation, and an automated external defibrillator — while advanced life support adds airway management, vascular access, medications, and rhythm-specific interventions delivered by trained clinical teams.

Why do guidelines stress minimising interruptions in chest compressions?

Perfusion pressure generated by compressions falls rapidly whenever compressions stop, so frequent or prolonged pauses reduce the blood flow reaching the brain and heart during resuscitation.