Basic cardiac life support (BCLS) is a set of emergency skills used to keep someone alive when their heart stops beating or they stop breathing. It covers chest compressions (CPR), rescue breathing, use of an automated external defibrillator (AED), and relief of choking. BCLS and BLS (basic life support) are the same thing. The American Red Cross notes that the two certifications differ only in name, with some organizations preferring “BCLS” and others using “BLS.”
While BCLS training is designed for healthcare professionals and first responders, anyone can learn these techniques. The goal is straightforward: maintain blood flow to the brain and heart until advanced medical help arrives.
The Chain of Survival
Every cardiac arrest response follows a sequence the American Heart Association calls the Chain of Survival. In 2025, the AHA consolidated this into a single chain for all patients, whether adult or child, in or out of the hospital. The links are:
- Prevention and preparedness: Avoiding the arrest in the first place is the best possible outcome.
- Recognition and emergency activation: Recognizing that someone is in cardiac arrest and calling 911 immediately.
- High-quality CPR: Starting chest compressions quickly, with the right rate and depth.
- Defibrillation: Using an AED as soon as one is available.
- Advanced resuscitation: Paramedics and hospital teams take over with medications, advanced airway tools, and other interventions.
- Post-cardiac arrest care: Hospital-level treatment including temperature management and heart evaluation.
- Recovery: Long-term physical, cognitive, and emotional support that continues well beyond hospital discharge.
BCLS covers the middle of this chain: recognition, CPR, and defibrillation. These are the steps bystanders and first responders control, and they have an outsized impact on whether someone survives.
How CPR Works
CPR is the core skill in BCLS. When someone’s heart stops, blood is no longer circulating oxygen to the brain. Within minutes, brain cells begin to die. Chest compressions act as a manual pump, forcing blood through the body until the heart can be restarted.
For adults, the AHA specifies a compression rate of 100 to 120 per minute, roughly the tempo of the song “Stayin’ Alive.” Each compression should push the chest down at least 2 inches (5 centimeters). Between compressions, you need to let the chest fully rise back up. This recoil creates a suction effect that refills the heart with blood, so leaning on the chest between pushes reduces effectiveness significantly.
One of the most important metrics is something called chest compression fraction: the percentage of time during a resuscitation attempt that compressions are actually being delivered. The target is above 80%. That means pauses for breathing, rhythm checks, or switching rescuers should be as brief as possible. Interruptions of even a few seconds cause blood pressure to drop, and it takes several compressions to build it back up.
Hands-Only CPR vs. CPR With Breaths
When a teenager or adult suddenly collapses from cardiac arrest, their blood still contains enough oxygen to support vital organs for the first several minutes. This is why hands-only CPR (compressions without rescue breaths) is just as effective as traditional CPR in those early minutes. If you’re an untrained bystander, pushing hard and fast on the center of the chest is the single most important thing you can do.
Rescue breaths become critical in certain situations, though. Infants, children, drowning victims, people who overdose on drugs, and anyone whose cardiac arrest stems from a breathing problem all need ventilation along with compressions. In these cases, the arrest is often caused by a lack of oxygen rather than a heart rhythm problem, so compressions alone won’t address the root issue. The standard ratio for a single rescuer is 30 compressions followed by 2 breaths. When two trained rescuers are working on a child or infant, a ratio of 15 compressions to 2 breaths is commonly used.
CPR for Infants and Children
The basic principles are the same for younger patients, but the technique changes. For infants, you use two fingers or two thumbs on the breastbone rather than the heel of your hand. For children, one hand may be enough depending on their size. Compression depth should be at least one-third the depth of the chest, which translates to about 1.5 inches for infants and 2 inches for children.
Breathing support matters more in pediatric arrests. Large observational studies have shown that children who receive both compressions and ventilation have better outcomes than those who receive compressions alone. This holds true whether rescuers use a 30:2 or 15:2 ratio.
Using an AED
An automated external defibrillator analyzes the heart’s rhythm and delivers an electric shock if it detects a pattern that can be corrected by defibrillation. AEDs are designed for use by anyone, not just medical professionals. They provide voice prompts that walk you through each step.
The process is simple. Turn the device on, then remove clothing from the person’s chest and wipe it dry if needed. Place one adhesive pad on the upper right side of the chest and the other on the lower left side, a few inches below the armpit. If the pads are large enough that they might touch (on a small person or child), place one in the center of the chest and the other on the back between the shoulder blades.
Once the pads are attached, the AED will analyze the heart rhythm. Before it does, make sure no one is touching the person and say “clear” loudly. The device will tell you whether a shock is advised. If it is, confirm again that no one is touching the person, say “clear,” and press the shock button. Immediately resume CPR afterward. The AED will prompt you to stop again in about two minutes for another rhythm check.
Speed matters enormously here. For every minute defibrillation is delayed, the chance of survival drops. This is why public-access AEDs in airports, gyms, and office buildings exist. The sooner one is applied, the better the odds.
Choking Relief
BCLS also covers airway obstruction, specifically what to do when someone is conscious but unable to breathe, cough, or speak because something is lodged in their throat.
For adults and children, the approach combines back blows and abdominal thrusts. First, stand to the side and slightly behind the person (or kneel behind a child). Place one arm across their chest for support, bend them forward at the waist, and deliver five firm strikes between the shoulder blades with the heel of your hand. If the object doesn’t come out, switch to abdominal thrusts: wrap your arms around their waist, place your fist just above the navel, grasp it with your other hand, and press inward and upward with a quick thrust. Alternate between five back blows and five abdominal thrusts until the airway is clear.
For children, the same technique applies but with gentler, more controlled force to avoid injuring internal organs. For infants, abdominal thrusts are not used at all. Instead, the technique combines back blows with chest thrusts delivered using two fingers on the breastbone.
The Recovery Position
If someone is unconscious but still breathing normally and has a pulse, they don’t need CPR. What they do need is protection from choking on saliva or vomit. The recovery position places them on their side with their airway angled downward so fluids drain out of the mouth rather than into the lungs. You maintain this position and monitor their breathing until emergency services arrive.
Getting BCLS Certified
BCLS certification courses are offered by organizations including the American Heart Association and the American Red Cross. They typically take a few hours and combine classroom instruction with hands-on practice using mannequins and training AEDs. Certification is valid for two years, after which you take a renewal course to stay current with any guideline changes.
Healthcare employers generally require BCLS certification. But the skills are equally valuable for parents, teachers, coaches, and anyone who wants to be prepared. Cardiac arrest can happen anywhere, and bystander CPR roughly doubles or triples the chance of survival when performed before paramedics arrive.