How Do You Know Someone Is in Cardiac Arrest?

The hardest part of helping someone who has collapsed isn't the technique. It's the few seconds beforehand, when you're trying to decide whether this is really happening — whether they're unconscious or just fainted, whether that sound they're making counts as breathing, whether you'd look ridiculous if you were wrong.

The good news is that the test got smaller. It used to have more steps in it. What's left is two things you can genuinely check.

The whole test, start to finish

Look at the chest for no more than 10 seconds — that's it, there's no third check.

Ten seconds is a limit rather than a target. You're not trying to become certain; you're trying to rule out normal breathing, and if you haven't seen it by then, you won't see it by staring longer. The most common mistake at this moment is watching for a full minute and hoping the question answers itself.

Gasping isn't breathing

This is the single most useful thing on the page, and it catches almost everybody.

In the first minutes after a heart stops, people often keep making breathing sounds. It can be gasping, gurgling, snoring, or a slow irregular catch every few seconds. It looks like breathing to someone standing over them, and it's the reason bystanders wait. It isn't breathing. It has a name — agonal breathing — and if you hear it, that's a reason to start rather than a reason to pause.

Normal breathing is regular, quiet and moves the chest visibly and repeatedly. Anything slow, noisy, irregular or occasional isn't that, and you should treat it as not breathing.

Nobody checks a pulse anymore

If you were taught to feel for a pulse at the neck, that instruction has gone — and it's worth knowing why, because "we stopped doing it" isn't the same as "it doesn't matter."

Finding a pulse on a person who may not have one is genuinely difficult. Studies of it are unflattering to everybody, including trained rescuers, who are wrong often enough that the check can't be relied on. And it costs time — while a hand is on a neck, nobody is pushing on a chest, and compressions are the only thing keeping blood moving.

So the test was cut down to things a frightened person can actually determine. That's a simplification in your favor rather than a lowering of standards. What changed and when has the rest of the guideline updates if you learned this a while ago.

Tapping and shouting, properly

Responsiveness sounds obvious and gets done too gently. Take hold of the shoulders, shake firmly, and shout close to them — "are you okay?" — loudly enough that you'd wake somebody who was genuinely asleep.

A groan, a hand moving, eyes opening: that's a response, and this isn't cardiac arrest. Nothing at all is what you're looking for. Be firmer than feels polite; the alternative is deciding somebody is unresponsive when they were only being tapped softly.

Being wrong in either direction

This is the fear underneath the hesitation, so it's worth answering directly: the two ways of being wrong aren't the same size.

If you start CPR on someone who didn't need it, you'll find out quickly. They'll move, make a noise, or push your hands away, and you stop. It's embarrassing and it's survivable, and the injuries people worry about are far less common than the worry is.

If you wait to be sure about someone who was in cardiac arrest, those are the minutes that decided it. Nothing you do afterward buys them back.

That's the whole argument for acting on an imperfect signal. You aren't being asked to diagnose anything — you're being asked to notice two things and start, and the system is built so that being wrong in the cautious direction costs almost nothing.

Then the lesson you need next

Once both things are true, this page has done its job and hands you to another one.

• An adult or teenager: the full sequence, or compressions only if you'd rather not give breaths.

• A child: CPR on a child — a few things change.

• A baby under one: CPR on an infant.

• Somebody has found a defibrillator: turn it on and follow it.

Put it into practice

Training scenario:

Four days ago you were on a train platform when a man in his sixties sat down on a bench and then slumped sideways. You went over. He didn't answer you, but he was making a sound — a slow, rasping catch every few seconds, almost like snoring. You decided he was breathing, so you stayed with him and waited for the paramedics, who arrived about seven minutes later and started chest compressions immediately. You have been thinking about it since.

Walking it through:

The sound was agonal breathing, and the paramedics recognized it in about a second because they have heard it before. That's the only advantage they had over you at that moment — not equipment, not training in compressions, just having heard that noise and knowing what it means.

The two-part test would have given you the same answer: he didn't respond, and the sound he was making wasn't normal breathing. Two things, both of which you could see and hear from where you were standing.

And the useful thing to take from it isn't guilt. You stayed with a stranger who had collapsed, which is more than most people do, and you were caught by the single most convincing false signal in all of first aid. What you have now is the thing you didn't have then — you know what that sound is. The next time you hear it you won't wait, and that's what this page was for.