Basic Life Support (BLS)

BLS is the foundation of emergency resuscitation — the set of life-saving interventions that can be initiated without advanced equipment or medications.

What BLS Includes

BLS encompasses:

Scene safety assessment and activation of EMS (911)
High-quality CPR (cardiopulmonary resuscitation)
Airway management (head-tilt/chin-lift, basic oral/nasal airways, bag-mask ventilation)
Defibrillation with an automated external defibrillator (AED)
Choking/foreign-body airway obstruction (FBAO) management
Hemorrhage control, fracture/spine immobilization (in EMS BLS systems)

BLS is performed by emergency medical responders (EMRs), EMTs, trained healthcare providers, and trained lay bystanders.

Adult BLS Sequence (C-A-B) — 2025 AHA Guidelines

The current standard follows the Compressions → Airway → Breathing sequence (C-A-B), prioritizing chest compressions over ventilation:

Step	Action
1. Scene safety	Ensure the scene is safe
2. Assess responsiveness	Shout, tap shoulders
3. Activate EMS	Call 911; get AED
4. Check breathing & pulse	Simultaneously, ≤10 seconds
5. Begin chest compressions	Start immediately if no normal breathing or no pulse
6. Airway	Head-tilt/chin-lift (jaw thrust if trauma suspected)
7. Rescue breaths	2 breaths after every 30 compressions (30:2 ratio)
8. AED	Attach and follow prompts as soon as available; minimize interruptions

High-Quality CPR Parameters

Parameter	Target
Compression rate	100–120/min
Compression depth (adult)	≥2 inches (5 cm), not >2.4 inches (6 cm)
Hand placement	Heel of hand on lower half of sternum
Chest recoil	Full — allow complete recoil between compressions
Interruptions	Minimize; pause <10 seconds for rhythm check
Compression-to-breath ratio	30:2 (single or 2-rescuer adult BLS)
Ventilation duration	~1 second per breath; visible chest rise

2025 AHA Updates (Key Changes)

The 2025 AHA BLS Guidelines represent the most comprehensive revision in years:

C-A-B reinforced: Compressions-first approach is solidified across all adult algorithms
Naloxone integration: Opioid antagonist (naloxone) is now explicitly incorporated into BLS for respiratory/cardiac arrest suspected to be opioid-related
Choking standardized: Adults and conscious children → 5 back blows + 5 abdominal thrusts, repeated until airway cleared or victim becomes unresponsive
Compression-only CPR: Acceptable for untrained bystanders or those unwilling to give rescue breaths
System-level emphasis: Outcomes depend on the full Chain of Survival — bystander CPR, AED access, EMS dispatch, and hospital post-arrest care
Simplified algorithms: Reduced special-case branching to allow faster decisions under stress

AED Use

Power on the AED
Attach pads: Upper right chest (infraclavicular) + lower left lateral chest (apex)
Analyze rhythm — stand clear
Deliver shock if advised, then immediately resume CPR
Repeat every 2 minutes until ALS arrives or ROSC

Pediatric BLS Highlights

Age groups: newborn (≤1 month), infant (1 month–1 year), child (1 year to puberty)
Infants/children: 15:2 compression-to-breath ratio with 2 rescuers; 30:2 with lone rescuer
Infant FBAO: 5 back blows + 5 chest thrusts (NOT abdominal thrusts — risk of organ injury)
Compression depth: ~1.5 inches for infants, ~2 inches for children

BLS vs. ALS

BLS	ALS (Advanced Life Support)
No/minimal medications	IV/IO access, drug administration
Basic airway (BVM, OPA/NPA)	Advanced airway (intubation, supraglottic)
AED	Manual defibrillation, cardiac monitoring, 12-lead ECG
EMR/EMT level	AEMT/Paramedic level

Sources: Goldman-Cecil Medicine; Tintinalli's Emergency Medicine; Rosen's Emergency Medicine; 2025 AHA BLS Guidelines (PMID: 41122888)

Is there a specific aspect of BLS you want to focus on — adult CPR, pediatric, AED use, choking management, or something else?

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