What to Do During Cardiac Arrest: A Step-by-Step Guide

When someone collapses and stops responding, knowing what to do during cardiac arrest in the first few minutes can determine whether they survive. Cardiac arrest happens when the heart suddenly stops pumping, which is different from a heart attack, where blood flow to the heart is blocked but the heart is still beating. This guide walks through the exact sequence taught in CPR and BLS courses, no prior training required, though hands-on certification builds the muscle memory to act without hesitation.

Step 1: Check the Scene and the Person

Before you touch anyone, look around. Is there oncoming traffic, live electrical wires, deep water, or fire nearby? If the scene is not safe for you, it is not safe for the person you want to help, and you cannot assist anyone if you become a second casualty. Take a few seconds to scan the environment before moving in.

Once you have confirmed it is safe to approach, kneel next to the person and check for responsiveness. Tap both shoulders firmly and shout, "Are you okay?" Use a loud, clear voice, since some people respond to sound before touch. If there is no response, no movement, and no sound, treat this as an emergency.

Next, check breathing. Look at the chest and abdomen for 5 to 10 seconds. You are looking for normal, regular breathing. If the person is not breathing at all, or if they are only gasping, that counts as not breathing. This gasping pattern is called agonal breathing, and it is a common and often confusing symptom of cardiac arrest. It can look like snoring, gulping, or occasional labored gasps, and bystanders sometimes mistake it for a sign that someone is still okay. It is not. Agonal breathing along with unresponsiveness means you need to move to the next step immediately.

This entire assessment, scene safety, responsiveness, and breathing, should take well under 30 seconds. Speed matters here, because every minute without intervention lowers the odds of a good outcome. Do not spend time trying to find a pulse unless you have current training and confidence in that skill. For a bystander, unresponsiveness plus absent or abnormal breathing is enough to act.

Step 2: Call 911 and Get an AED

If you are alone with the person, call 911 yourself before starting anything else, and put the phone on speaker so your hands stay free. If other people are nearby, do not shout a general "someone call 911" into the crowd. Diffuse responsibility means everyone assumes someone else is handling it, and calls get delayed or missed entirely. Instead, point at a specific person and say directly, "You, in the red shirt, call 911 now." Assign the task to one individual so there is no ambiguity.

At the same time, send a second bystander to look for an automated external defibrillator, commonly known as an AED. These devices are increasingly common in workplaces, gyms, schools, airports, and public buildings, often mounted in a marked cabinet near an entrance or hallway. If you know the location of a nearby AED already, say so specifically: "Get the AED by the front desk." A clear instruction gets results faster than a vague request.

Keep the phone on speaker once you reach a 911 dispatcher. Dispatchers are trained to walk callers through CPR step by step, including compression rate and hand placement, and they can keep you informed about how far away emergency medical services are. Do not hang up until told to, and do not let the search for an AED delay the start of chest compressions. The two tasks, calling for help and beginning compressions, should happen within moments of each other, not one after the other in sequence. If you are truly alone with no phone access nearby, current guidance for adults is to call first, then begin CPR, since early defibrillation and paramedic response are critical to survival.

Step 3: Start Chest Compressions Immediately

Once you have confirmed the person is unresponsive and not breathing normally, and help is being contacted, begin chest compressions right away. Do not wait for an AED or for EMS to arrive first. Every minute that passes without compressions or defibrillation reduces the chance of a good outcome, so starting fast matters more than starting perfectly.

Position yourself beside the person, kneeling at chest level. Place the heel of one hand on the center of the chest, roughly between the nipples, and place your other hand on top, interlacing your fingers. Lock your elbows and position your shoulders directly over your hands so you can use your body weight rather than just your arms.

Push hard and fast. The target rate is 100 to 120 compressions per minute, which happens to match the tempo of the Bee Gees song "Stayin' Alive," a rhythm many CPR instructors use as a mental cue. For an average adult, compress at least 2 inches deep, and let the chest fully recoil, or rise back up, between each compression. Partial recoil reduces blood flow back into the heart between compressions and lowers the effectiveness of your efforts.

A few things trip up first-time rescuers:

Pushing too shallow out of fear of hurting the person. Broken ribs are a known and acceptable risk; a properly performed compression is sometimes forceful enough to cause one, and it is far preferable to the alternative.

Leaning on the chest between compressions instead of allowing full recoil.

Stopping for too long to check on the person, reposition, or catch your breath. Interruptions longer than a few seconds meaningfully reduce blood flow to the brain and heart.

Compressions are physically tiring, and quality drops noticeably after about two minutes, even for fit rescuers. If another trained person is present, switch every two minutes, trying to keep the pause during the switch as short as possible. If you are alone, keep going as best you can until help arrives or the AED prompts you to stop for analysis.

Step 4: Use the AED as Soon as It Arrives

When the AED shows up, turn it on immediately. Modern AEDs are designed for use by untrained bystanders and will talk you through every step out loud. You do not need prior experience to operate one correctly. Follow the voice prompts exactly, and do not let fear of "doing it wrong" slow you down. The device analyzes the heart's rhythm and will only advise a shock if one is actually needed; it cannot shock a rhythm that does not call for it.

The AED will instruct you to attach two adhesive pads to the person's bare chest. Skin needs to be dry, so quickly wipe away sweat or water if necessary, and if the chest has heavy hair, some AED kits include a razor for a quick shave to help the pads adhere. Pad placement is usually illustrated directly on the pad: one goes on the upper right side of the chest, below the collarbone, and the other on the lower left side, below the armpit. Press each pad down firmly so it makes full contact with the skin.

Once the pads are placed, the AED will say "analyzing" and ask everyone to stand clear. This is important: no one should be touching the person during analysis, including you, since movement can interfere with the reading. If a shock is advised, the device will say so and instruct everyone to stay clear again before you press the flashing shock button.

Immediately after the shock is delivered, or if no shock is advised, resume chest compressions right away without pausing to check for a pulse or breathing. The AED will prompt you to continue CPR and will automatically re-analyze the rhythm after a set interval, typically about two minutes. Keep following its prompts until EMS personnel arrive and take over care.

Step 5: Add Rescue Breaths if Trained

If you have current CPR training, you can add rescue breaths to your compressions rather than performing compressions alone. The standard ratio taught in AHA and Red Cross courses is 30 compressions followed by 2 rescue breaths, repeated in cycles. To deliver a breath, tilt the person's head back slightly, lift the chin to open the airway, pinch the nose shut, and seal your mouth completely over theirs before giving a breath lasting about one second.

Watch for visible chest rise with each breath. That rise is your confirmation that the airway is open and the breath is getting into the lungs. If the chest does not rise, reposition the head and try again, but do not spend more than a few seconds troubleshooting before returning to compressions. Compressions matter more than breaths in the early minutes of cardiac arrest, so never let breathing attempts eat into compression time.

If you are an untrained bystander, current AHA guidance is clear: stick to hands-only CPR. Continuous chest compressions without pauses for breathing are simpler to perform correctly under stress, and they still provide meaningful benefit by keeping blood circulating to the brain and heart. Attempting rescue breaths without training often leads to wasted time, an improperly sealed airway, or unnecessary interruptions in compressions, all of which can do more harm than good. There is no shame in sticking to compressions only. It is the recommended approach for the general public, and it saves lives every year.

This is also one of the clearest arguments for getting certified in advance. A hands-on CPR or BLS course teaches you to perform rescue breaths correctly and confidently, so in a real emergency you are not guessing at technique while someone's life is on the line.

Step 6: Continue Until Help Takes Over

Keep working the cycle, either continuous hands-only compressions or 30:2 compressions and breaths if you are trained, until one of two things happens: EMS personnel arrive and take over, or the person begins showing clear signs of life, such as normal breathing, movement, or opening their eyes. Do not stop to reassess repeatedly; brief checks only interrupt blood flow without adding useful information in most cases.

If you have a second rescuer, continue trading off every two minutes, ideally timing the switch with the AED's rhythm analysis so you are not interrupting compressions separately from the device's built-in pause. A quick, practiced handoff, hands off, new rescuer's hands on, within a few seconds, keeps compression quality high throughout the emergency.

As paramedics arrive, be ready to hand off key information quickly. This includes:

The approximate time the person collapsed or was found unresponsive

How many shocks the AED delivered, if any

Any known medical history, medications, or allergies, if you or someone nearby knows the person

Whether the person was witnessed collapsing or found already down

This information helps EMS providers make fast decisions about ongoing treatment and transport. Once they take over compressions and airway management, your direct role in the physical response ends, though you may be asked to stay nearby to answer additional questions.

Step 7: Debrief and Consider Getting Certified

Responding to a cardiac arrest is intense, and it is normal to feel shaken, replay the event in your head, or struggle to sleep in the days afterward, regardless of the outcome. Many workplaces, EMS agencies, and fire departments offer critical incident stress debriefing for bystanders and responders involved in emergencies like this. If your employer offers an employee assistance program, that is also a reasonable place to process what happened. Do not dismiss the emotional weight of what you just did.

If this was your first time performing CPR outside of training, or your first time ever, consider it a strong signal to get formally certified. Reading through steps in the moment, or half remembering a video you saw once, is a poor substitute for hands-on practice with an instructor correcting your hand placement, depth, and rhythm in real time. Courses in CPR, BLS, and First Aid build the kind of muscle memory that lets you act immediately under pressure instead of hesitating while trying to recall what to do.

If an AED was used during the event, it needs attention before it goes back into service. Check the battery level and replace it if it is low or expired, and inspect the pads, since they are single-use and need to be replaced after every deployment. Many AED units display a status indicator showing whether the device is ready for use; confirm it shows a ready or green status before returning it to its cabinet. A device with dead pads or a drained battery is not going to help the next person who needs it.

Turning Preparedness Into Practiced Skill

Acting fast and following this sequence, checking, calling, compressing, and shocking, gives someone in cardiac arrest their best chance at survival. Reading through the steps once is a start, but real confidence comes from practicing them under an instructor's guidance until the actions feel automatic rather than something you have to think through in the moment.

Taylored Instruction offers CPR, BLS, First Aid, and Lifeguard certification courses through both the American Red Cross and the American Heart Association, along with AED sales and maintenance support so your workplace or home is genuinely ready for an emergency. Don't wait until an emergency happens, get the life-saving certification you need today. Register for a CPR, First Aid, or Lifeguarding class and gain the confidence and skills to respond when it matters most.