A person who suddenly collapses may not look like they are in a medical emergency at first. They may make snoring, gasping, or irregular breathing sounds that cause bystanders to wait. Recognizing cardiac arrest means knowing that those sounds are not normal breathing – and responding before that hesitation costs critical time.
Cardiac arrest is a sudden loss of effective heart function. Blood stops moving to the brain and other vital organs, and the person becomes unresponsive within seconds. Every minute without CPR and defibrillation lowers the chance of survival. The goal is not to diagnose the exact cause of the collapse. The goal is to recognize the emergency, call 911, start CPR, and use an AED as soon as one is available.
Recognizing Cardiac Arrest: The Two Signs That Matter
For an adult or teen who has collapsed, look for two things: they are unresponsive, and they are not breathing normally.
First, make sure the scene is safe for you to enter. Tap the person firmly on the shoulders and speak loudly: “Are you okay?” If there is no response, check their breathing for no more than 10 seconds. Watch the chest and listen for normal breaths.
A person in cardiac arrest may take occasional gasps, make gurgling noises, or appear to struggle for air. This is called agonal breathing. It can be alarming, and it is often mistaken for a sign that the person is still okay. It is not normal breathing and should be treated as cardiac arrest when the person is unresponsive.
For untrained bystanders, the decision point is simple: if an adult or teen is unresponsive and not breathing normally, call 911 and begin CPR. Do not spend valuable time trying to find a pulse. Pulse checks can be difficult even for trained responders, especially in a stressful situation.
What Cardiac Arrest Can Look Like in Real Life
Movies often portray cardiac arrest as a dramatic clutching of the chest followed by an immediate collapse. Sometimes that happens, but many emergencies are less obvious.
A person may suddenly slump over at a desk, fall while exercising, collapse in a store, or stop responding while sitting on a couch. Their skin may become pale, gray, or bluish. Their eyes may remain open. They may have brief jerking movements shortly after collapsing, which can look like a seizure. Those movements do not rule out cardiac arrest.
Cardiac arrest can happen to people with known heart disease, but it can also happen without warning. It affects older adults, younger athletes, new parents, coworkers, visitors, and people who have never had a diagnosed heart condition. That is why anyone can benefit from learning how to respond.
Agonal Gasps Are Not Normal Breathing
Agonal gasps are one of the most common reasons bystanders delay CPR. They may sound like snoring, snorting, moaning, or a single forceful inhale every few seconds. The chest may move slightly, but there is no effective breathing.
If the person does not wake up and those breaths are irregular or absent, act immediately. Place the 911 call on speakerphone if possible, so the dispatcher can guide you while you begin care. Dispatchers are trained to help callers identify cardiac arrest and provide CPR instructions.
A Seizure-Like Movement Can Also Be a Warning Sign
Some people have brief twitching or convulsive movements when blood flow to the brain suddenly stops. If you see a person collapse and have seizure-like activity, protect them from injury and watch closely. Once the movements stop, check responsiveness and breathing.
If they are unresponsive and not breathing normally, begin CPR. Do not assume they are recovering simply because the jerking has stopped.
Cardiac Arrest, Heart Attack, Fainting, and Choking Are Different
These emergencies can overlap, but the immediate response depends on what you see.
A heart attack is a blockage of blood flow to part of the heart muscle. A person having a heart attack is often awake and may report chest pressure, shortness of breath, nausea, sweating, or pain that spreads to the arm, back, jaw, or shoulder. Call 911 for these symptoms. A heart attack can lead to cardiac arrest, but it is not the same event.
Fainting usually involves a brief loss of consciousness with a return to normal breathing. The person may wake up quickly, although they still need medical evaluation depending on the situation. Cardiac arrest, by contrast, involves unresponsiveness and no normal breathing.
With severe choking, a conscious person may be unable to speak, cough, or breathe. Provide choking care right away. If they become unresponsive, lower them carefully to the floor, call 911, and begin CPR. Each time you open the airway for breaths, look for a visible object. Remove it only if you can clearly see it. Do not perform blind finger sweeps.
An overdose can also cause a person to become unresponsive and breathe slowly, irregularly, or not at all. If opioid overdose is suspected and naloxone is available, use it according to the device instructions. But if the person is not breathing normally, CPR and an immediate 911 call come first. Naloxone does not replace CPR for cardiac arrest.
What to Do the Moment You Suspect Cardiac Arrest
Once you identify an unresponsive person who is not breathing normally, move with purpose. Send someone to call 911 and retrieve the nearest AED. If you are alone, call 911 yourself on speakerphone before starting CPR, unless the person is an infant or child and you are the only rescuer. In that situation, provide about two minutes of CPR before leaving to call for help if you do not have a phone available.
For an adult or teen, place the heel of one hand in the center of the chest, place your other hand on top, and keep your arms straight. Push hard and fast at a rate of 100 to 120 compressions per minute. Let the chest return fully upward after every compression. Aim for a depth of at least 2 inches while avoiding excessive depth.
If you are not trained in rescue breaths or do not feel able to give them, provide hands-only CPR continuously until help arrives or an AED is ready. If you are trained, give 30 compressions followed by two breaths, then continue that cycle. High-quality chest compressions are the priority.
When the AED arrives, turn it on and follow its voice prompts. Expose the chest, dry it if it is wet, and apply the pads exactly as illustrated. The AED will analyze the heart rhythm and tell you whether a shock is advised. Make sure no one is touching the person during analysis and when a shock is delivered. Resume CPR as soon as the device tells you to do so.
AEDs are designed for public use. You do not need to interpret the rhythm or decide whether a shock is needed. The device makes that decision. Using an AED quickly is one of the strongest actions a bystander can take to improve the person’s chance of survival.
Common Hesitations That Cost Time
People often worry about doing CPR incorrectly, hurting the person, or feeling embarrassed if they misread the situation. Those feelings are understandable, but an unresponsive person who is not breathing normally needs immediate action.
Chest compressions can cause rib injuries, particularly in older adults. That is a real possibility, but it is not a reason to withhold care. A broken rib can heal. Untreated cardiac arrest cannot wait.
You also do not need to wait for a family member, security officer, manager, or medically trained person to take charge. Call 911, start compressions, and ask specific people for help: “You in the blue shirt, get the AED.” Clear direction turns a crowd into a response team.
Training Turns Recognition Into Confident Action
Reading the signs is a strong first step, but cardiac arrest is not the moment to figure out hand placement, compression depth, or AED pads for the first time. Hands-on training gives you the chance to practice the sequence, ask questions, and build muscle memory before an emergency happens.
This matters for healthcare professionals maintaining BLS credentials, parents and caregivers, school staff, fitness teams, and workplace responders. It also matters for any employee who may be the first person near a coworker, customer, or visitor when they collapse. A workplace AED program is most effective when people know where the device is and feel prepared to use it.
East Coast Safety Consulting provides practical CPR, AED, First Aid, and BLS instruction built around the decisions people must make under pressure. Certification is valuable, but the lasting value is being able to recognize an emergency and take the first life-saving steps without freezing.
The next time you see someone collapse, remember the question that guides the entire response: Are they responsive, and are they breathing normally? If the answer is no, call 911, start CPR, and get the AED. A prepared bystander can give someone the chance to make it home.
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