2.1 Adult BLS Sequence: Safety, Recognition, Activation, CPR
Key Takeaways
- Start with scene safety and responsiveness before committing to patient care.
- For an adult in cardiac arrest, a lone responder activates the emergency response system first, then begins CPR.
- Check breathing and pulse quickly; do not let pulse checks delay compressions.
- BLS is the foundation of ACLS because every advanced action depends on perfusion generated by CPR.
2.1 Adult BLS Sequence: Safety, Recognition, Activation, CPR
Adult BLS begins with a simple sequence: ensure safety, assess responsiveness, activate help, check breathing and pulse, start compressions, and use the AED as soon as it arrives.
Current official baseline
The adult BLS guidance covers recognition of cardiac arrest, emergency response activation, high-quality CPR, AED use, adult foreign-body airway obstruction, and opioid antagonist integration. Use the official AHA 2025 Adult Basic Life Support Guidelines page when your course materials or training-center instructions differ from third-party summaries: AHA 2025 Adult Basic Life Support Guidelines.
What you need to know
| Decision point | What to do |
|---|---|
| Scene safety | Do not become a second patient. Look for electrical hazards, traffic, violence, water, chemicals, or unstable surfaces. |
| Responsiveness | Tap and shout. If the patient does not respond and is not breathing normally, activate the response system and get an AED. |
| Pulse and breathing | Agonal gasps are not normal breathing. If no definite pulse is found quickly, start compressions. |
| ACLS link | Even in a monitored hospital arrest, the first lifesaving treatment is still high-quality CPR while the defibrillator and team arrive. |
How this shows up on BLS/ACLS questions
BLS and ACLS items usually test priority. Read the patient state first: age, pulse status, breathing status, rhythm, stability, and number of rescuers. Then choose the action that protects perfusion, oxygenation, defibrillation timing, or the correct algorithm branch. If an answer sounds advanced but delays CPR, shock delivery, ventilation, or an urgent stability intervention, it is usually a distractor.
Scenario anchor
A visitor collapses in a clinic hallway. You verify the hallway is safe, tap and shout, tell a bystander to call 911 and bring the AED, check breathing/pulse quickly, and begin compressions when there is no normal breathing and no definite pulse.
Common traps
- Spending too long checking for a pulse.
- Opening the airway repeatedly while delaying compressions.
- Leaving the patient without activating help when other rescuers are available.
Study action
Write this section as a one-line rule in your own words, then test it with mixed questions from the BLS/ACLS practice bank. Do not review only the matching topic. Mix it with nearby branches so you can tell when the rule applies and when it does not. For example, compare respiratory arrest with a pulse against pulseless arrest, or compare unstable tachycardia against VF/pVT arrest. The exam rewards that discrimination more than memorizing isolated facts.
During CPR on an adult without an advanced airway, what is the compression-to-ventilation ratio for 2 rescuers?
An AED is attached to a patient in cardiac arrest. The AED analyzes and advises "No Shock." What should the rescuer do NEXT?