What are the differences and basic principles between Basic Life Support (BLS) and Advanced Cardiovascular Life Support (ACLS)?

BLS vs ACLS: Key Differences and Basic Principles

Basic Life Support (BLS) is the foundation of resuscitation that can be performed by anyone without specialized equipment, while Advanced Cardiovascular Life Support (ACLS) builds upon BLS by adding specialized equipment, medications, and advanced interventions requiring healthcare provider training. 1, 2

Core Differences Between BLS and ACLS

Basic Life Support (BLS)

BLS focuses on immediate recognition and support of ventilation and circulation without specialized equipment beyond barrier devices and automated external defibrillators (AEDs). 2, 3 The primary objective is to provide oxygen to the heart and brain to sustain tissue viability until advanced treatment can restore spontaneous circulation. 2

BLS can be performed by:

• Lay rescuers (bystanders) 4, 1
• Healthcare providers 4
• Emergency medical technicians 5

Advanced Cardiovascular Life Support (ACLS)

ACLS includes specialized equipment for airway management, early defibrillation with manual defibrillators, pharmacologic therapy, and rhythm interpretation requiring advanced training. 2, 3 This level of care is provided exclusively by healthcare professionals with specific ACLS certification. 3, 5

ACLS adds:

• Advanced airway devices (endotracheal intubation, supraglottic airways) 6, 3
• Intravenous/intraosseous medication administration 6, 3
• Manual rhythm interpretation and defibrillation 6, 5
• Pharmacologic interventions (epinephrine, antiarrhythmics, etc.) 6, 3

Basic Principles of BLS

The CAB Sequence (Compressions-Airway-Breathing)

The American Heart Association changed the sequence from ABC to CAB to minimize delay to first compression. 4, 1 This represents a fundamental shift prioritizing immediate chest compressions over airway positioning and rescue breaths. 4, 1

Recognition and Activation

• Immediately recognize cardiac arrest: Check for unresponsiveness and absence of normal breathing (or only gasping) 4, 1
• Remove "Look, Listen, and Feel": This step was eliminated to reduce time delays 4, 1
• Activate emergency response immediately: Use mobile phones to call for help without leaving the victim's side 4
• Healthcare providers should check pulse: Limit pulse check to no more than 10 seconds to avoid delaying compressions 1, 6
• Lay rescuers should NOT check pulse: They should begin compressions immediately after recognizing unresponsiveness and absent/abnormal breathing 1

High-Quality Chest Compressions

Compressions are the most critical component of BLS. 4, 1 The American Heart Association emphasizes specific metrics:

• Depth: At least 2 inches (5 cm) for adults 4, 1, 6
• Rate: 100-120 compressions per minute 1, 6
• Complete chest recoil: Allow full recoil between compressions 4, 1, 6
• Minimize interruptions: Keep pauses under 10 seconds 4, 6
• Avoid excessive ventilation: Over-ventilation is harmful 4, 1

Compression-to-Ventilation Ratio

• Single rescuer (all ages except newborns): 30 compressions to 2 breaths 4, 1
• Two healthcare provider rescuers (pediatric): 15 compressions to 2 breaths 4
• After advanced airway placement: Continuous compressions with 1 breath every 6 seconds (10 breaths/min) 6

Hands-Only CPR for Lay Rescuers

The American Heart Association encourages hands-only (compression-only) CPR for untrained lay rescuers. 4, 1 This is easier to perform and can be guided by dispatchers over the telephone. 4, 1 However, trained lay rescuers should provide conventional CPR with both compressions and ventilations. 4

Early Defibrillation

Rapid defibrillation is a powerful predictor of successful resuscitation. 1 AEDs should be retrieved if nearby and easily accessible. 1 For witnessed sudden collapse, getting an AED takes priority after activating emergency services. 4

Basic Principles of ACLS

Rhythm-Based Management

ACLS treatment is determined by the cardiac arrest rhythm identified on the monitor. 6

For VF/pulseless VT (shockable rhythms):

• Deliver one shock immediately when defibrillator available 6
• Use 120-200J for biphasic or 360J for monophasic defibrillators 6
• Resume CPR immediately for 2 minutes before rhythm reassessment 6
• Administer epinephrine 1mg IV/IO every 3-5 minutes 6
• Consider antiarrhythmics (amiodarone or lidocaine) after 2-3 failed shocks 6, 3

For asystole/PEA (non-shockable rhythms):

• Continue high-quality CPR 6
• Administer epinephrine 1mg IV/IO every 3-5 minutes 6
• Consider and treat reversible causes 6

Advanced Airway Management

• Consider advanced airway without interrupting compressions 6
• Confirm placement with waveform capnography 6
• After placement, provide continuous compressions with 1 breath every 6 seconds 6
• Monitor PETCO₂ (target >10 mmHg) to assess CPR quality 6

Pharmacologic Therapy

Epinephrine and oxygen are the mainstay of drug therapy during CPR. 3

• Epinephrine: 1mg IV/IO every 3-5 minutes for all cardiac arrest rhythms 6, 3
• Amiodarone: First-line antiarrhythmic for refractory VF/pVT 6, 3
• Lidocaine: Alternative antiarrhythmic if amiodarone unavailable 6, 3
• Magnesium: Useful for refractory pulseless VT/VF, especially torsades de pointes 3
• Atropine: No longer routinely recommended for cardiac arrest 3
• Bicarbonate and calcium: Not routinely recommended 3

Team-Based Approach

ACLS requires a simultaneous, choreographed approach by an integrated team. 4, 1 Multiple tasks (compressions, airway management, rhythm detection, medication administration) are performed concurrently by different team members. 4

Common Pitfalls to Avoid

In BLS:

• Delaying chest compressions: Start compressions immediately; don't waste time with prolonged assessment 4, 1
• Inadequate compression depth or rate: Use feedback devices when available 4, 1
• Excessive ventilation: Give only enough volume to achieve visible chest rise 4
• Prolonged pulse checks: Healthcare providers should limit to 10 seconds maximum 1, 6
• Interrupting compressions: Minimize all pauses, especially during rhythm checks and defibrillation 4, 6

In ACLS:

• Prioritizing intubation over compressions: Advanced airway should not interrupt high-quality CPR 6
• Failing to confirm airway placement: Always use waveform capnography 6
• Using ETCO₂ alone to terminate resuscitation: This is not recommended 6
• Excessive ventilation after advanced airway: Stick to 1 breath every 6 seconds 6
• Prolonged rhythm analysis: Keep interruptions under 10 seconds 6

The Chain of Survival Integration

Both BLS and ACLS are links in the Chain of Survival, with BLS being the foundation. 4, 2 Survival can approach 50% in witnessed VF arrests when all links are optimally implemented, but falls to 5-10% in many settings where the chain is weak. 4 This underscores that promptly and optimally performed BLS is the most critical factor—ACLS cannot compensate for poor-quality BLS. 2