Compressions come first in the deliberate C-A-B sequence, followed by Airway and then Breathing. Check the scene and the person’s responsiveness, call 911, and push hard and fast on the center of the chest at 100 to 120 compressions per minute, with the depth set between 2 and 2.4 inches for adults. Trained rescuers add two rescue breaths after every thirty compressions; untrained bystanders stay on continuous chest compressions until an AED arrives or EMS takes over.
This walkthrough breaks down each phase of CPR for anyone who might face a sudden cardiac emergency, from spotting the warning signs to using an AED on scene.
Recognizing a Cardiac Emergency Before Anything Else
A cardiac emergency rarely looks like a movie scene. The person does not gasp dramatically or clutch their chest first. Often they simply collapse, stop responding, and breathe in shallow gasps or not at all. A few quick checks in the first ten seconds tell you whether to start CPR or stand down.
Confirm the Scene Is Safe
Look around before you kneel. Traffic, downed power lines, a slippery floor, or an unstable crowd can turn a rescuer into a second victim. Move the person only if the spot is unsafe or you cannot reach them where they lie. Your safety comes first, because a second collapsed person helps no one.
Check Responsiveness and Breathing
Tap the shoulder firmly and shout, “Are you okay?” A person who does not move, blink, or speak is unresponsive. Then look at the chest and face for normal breathing. Occasional gasps or no breathing at all both point to cardiac arrest. Agonal breathing, those irregular, snoring-like gasps, is not real breathing and should trigger CPR right away.
- Confirm scene safety before approaching the person, watching for traffic, fire, or structural hazards.
- Tap and shout at the shoulder, then watch the face and chest for any response.
- Check for breathing for no more than ten seconds, treating gasps as a sign of arrest.
- Call 911 immediately and ask a bystander to bring the nearest AED.
Once you have called 911, do not hang up until the dispatcher tells you to. Many 911 centers can coach you through CPR in real time, count your compressions, and tell you when the AED is ready.
Once you have dialed 911 and started counting, the next decision is how to sequence compressions, airway, and breathing.
The C-A-B Framework That Guides Every CPR Sequence
Older CPR courses taught A-B-C: airway, then breathing, then compressions. The American Heart Association switched the order to C-A-B in 2010 because compressions buy the brain time, and every second of delay in starting them costs blood flow. Knowing this order helps you resist the urge to hunt for a pulse before you begin pushing.
Why Compressions Lead the Sequence
When the heart stops, oxygen already in the blood can keep the brain alive for a short window. Each compression squeezes the heart between the breastbone and the spine, pushing that oxygenated blood out to the brain and organs. Starting compressions first keeps that window open while you sort out breathing.
Airway and Breathing Come After Thirty Compressions
Once thirty compressions are done, trained rescuers open the airway with a head-tilt chin-lift and give two rescue breaths. Untrained bystanders stay on compressions, because the rate and depth matter more than the breaths in the first few minutes of an adult cardiac arrest.
That priority order is exactly why getting your hands on the chest correctly comes first.
Use the head-tilt chin-lift maneuver unless you suspect a head or neck injury, in which case a jaw thrust is safer. A pocket mask or face shield with a one-way valve protects you during rescue breaths and is worth carrying in any first aid kit.
Delivering Chest Compressions With Correct Form
Good compressions are deep, fast, and uninterrupted. They are also tiring, and form often slips after a minute, which is one reason switching rescuers every two minutes improves survival. The American Heart Association calls for a rate of 100 to 120 compressions per minute and a depth of at least 2 inches (5 cm) but no more than 2.4 inches (6 cm) for adults.
Hand Position and Body Mechanics
Place the heel of one hand on the center of the chest, right on the lower half of the breastbone, and stack the other hand on top with fingers interlaced. Lock your elbows, drop your shoulders so they sit directly above your hands, and use your upper body weight to press straight down. Bending at the elbows wastes energy and reduces depth.
Depth, Rate, and Full Recoil
Push hard enough to compress the chest at least 2 inches, then let the chest come all the way back up before the next push. Leaning on the chest between compressions keeps it partially compressed and cuts blood flow. A simple trick: count “one-and-two-and-three” out loud, which lands at about 100 beats per minute, or mentally pace yourself to the beat of the disco song “Stayin’ Alive.”
- Hand placement: heel of one hand on the lower breastbone, other hand on top, fingers kept off the ribs.
- Posture: shoulders over hands, elbows locked, push straight down using body weight.
- Rate: 100 to 120 compressions per minute, a tempo close to a fast pop song.
- Depth: at least 2 inches, no more than 2.4 inches for adults.
- Recoil: let the chest fully return to its starting position between every push.
Adding Rescue Breaths Versus Hands-Only CPR
Whether to add breaths depends on training, the cause of arrest, and the victim. Trained rescuers follow a 30:2 ratio of compressions to breaths. Bystanders with no training stay on chest compressions, because the AHA and Red Cross agree that any CPR beats no CPR, and hands-only is easier to remember under stress.
| Situation | Recommended Approach | Why It Works |
|---|---|---|
| Trained adult rescuer on an adult | 30 compressions, then 2 rescue breaths, repeat | Maintains circulation and refreshes blood oxygen in a witnessed adult arrest |
| Untrained bystander, any adult | Hands-Only CPR, continuous compressions | Keeps blood moving without pausing for breaths, easier to remember |
| Child or infant | 30:2 if one rescuer, 15:2 if two trained rescuers | Children often arrest from respiratory causes, so breaths matter more |
| Drowning, drug overdose, or known respiratory cause | 30:2 with rescue breaths from the start | Oxygen was used up or blocked, so the blood needs a fresh supply |
When giving breaths, tilt the head back with one hand on the forehead and two fingers under the chin. Each rescue breath lasts about one second and should make the chest rise visibly. If the chest does not rise, reposition the head and try again, because the airway is likely still blocked.
Carry a pocket mask or face shield with a one-way valve if you might ever give rescue breaths. A one-way valve stops backflow from the victim to the rescuer and is a small, cheap layer of protection for a bystander who hesitates because of infection worries.
Integrating an AED Into the CPR Sequence
An automated external defibrillator is the only device that can restart a heart in ventricular fibrillation, the most common arrest rhythm in adults. Modern AEDs talk you through every step with voice prompts, so even a person who has never seen one can use it correctly. The trick is to keep compressing while someone else fetches it.
Pad Placement and Voice Prompts
Turn the AED on as soon as it arrives. Bare the chest and place one pad on the upper right side of the chest, just below the collarbone, and the other on the lower left side, a few inches below the armpit. The pad diagram shows the exact spots. If the chest is wet, wipe it dry; if there is a medication patch, peel it off and wipe the skin before applying the pad.
When to Pause Compressions
The AED will tell you when to stop moving so it can analyze the heart rhythm. Clear everyone away, including yourself, and make sure no one is touching the person. If the device advises a shock, push the flashing button when prompted, then resume compressions immediately. Most AEDs run a two-minute cycle of analysis, shock if needed, then prompt you to continue CPR.
After the AED analyzes and shocks, the rhythm of rescue work still depends on avoiding a handful of common errors.
- Power on the AED as soon as it arrives and follow the spoken prompts without hesitation.
- Apply pads to a bare, dry chest in the positions shown on the pad diagram.
- Stay clear during analysis and shock, and announce “Everyone clear” out loud.
- Resume compressions the moment the shock is delivered or the AED says “no shock advised.”
Knowing When to Stop and Common Mistakes to Avoid
CPR keeps a person alive, it does not restart the heart on its own. Knowing when to keep going, when to stop, and what to avoid is just as important as knowing the steps. The single biggest mistake is doing nothing at all because you are unsure.
When to Keep Going or Stop
Continue CPR until one of four things happens: EMS arrives and takes over, an AED advises a pause, you are too exhausted to push hard and fast, or the person shows obvious signs of life like breathing, moving, or opening their eyes. Do not stop just because the person looks unresponsive, because flat color and fixed pupils are normal during CPR and can change quickly once circulation returns.
Mistakes That Lower Survival Odds
Leaning on the chest between compressions cuts blood flow. Checking the pulse over and over burns time and usually produces a false reading under stress. Interrupting compressions for more than ten seconds drains pressure from the heart. And the most common error of all is waiting for help before starting, when every minute without CPR drops survival by roughly 7 to 10 percent.
- Don’t lean on the chest: let it fully recoil after every compression to refill the heart.
- Don’t keep checking the pulse: trained rescuers limit pulse checks to ten seconds, lay rescuers skip them.
- Don’t stop for more than ten seconds: pause only for AED analysis, shocks, or rescue breaths.
- Don’t wait for EMS to start: hands-only CPR doubles or triples survival odds in adult cardiac arrest.
A written guide only carries you so far. A certified Basic Life Support course from the American Heart Association, the Red Cross, or a local EMS agency puts you on a manikin with a metronome and an AED trainer, which is the only way to build the muscle memory that survives panic. Aim to refresh your skills every two years, or sooner if your certification lapsed.
The Bottom Line
CPR is a simple, high-impact skill: check the scene, call 911, push hard and fast on the center of the chest at 100 to 120 compressions per minute, add two breaths after every thirty if you are trained, and use an AED the moment it arrives. The order exists because circulation buys time, and time buys the brain. Hands-only CPR is enough for an untrained bystander, and any CPR is better than none.
FAQ
What are the steps used when performing CPR?
Check the scene and the person’s responsiveness, call 911, and start chest compressions at a rate of 100 to 120 per minute and a depth of at least 2 inches on an adult. Trained rescuers add two rescue breaths after every thirty compressions and use an AED as soon as one is available.
How many chest compressions per minute should be given during CPR?
Aim for 100 to 120 compressions per minute for adults, children, and infants. A simple way to pace yourself is to push to the beat of a song with about that tempo, since the rate matters as much as the depth for moving blood.
Do you perform CPR before or after calling 911?
Call 911 first, or have a bystander call while you check the person. If you are alone with an adult, call before starting CPR; if you are alone with a child or infant, do two minutes of CPR first, then call. The dispatcher can talk you through the steps in real time either way.
What is the correct hand placement for CPR chest compressions?
Place the heel of one hand on the lower half of the breastbone, right in the center of the chest, and stack the other hand on top with fingers interlaced. Keep your shoulders directly above your hands and lock your elbows so you can use your body weight to push.
When should you stop performing CPR?
Stop when EMS takes over, an AED prompts you to pause, you are physically unable to continue, or the person shows clear signs of life like breathing, movement, or eye opening. Do not stop just because the person looks pale or unresponsive, because those signs can reverse quickly with good compressions.
