When someone collapses from sudden cardiac arrest, the person nearby often sees something that looks reassuring: the chest still moving, an occasional noisy gasp, something that resembles breath. That impression is one of the most dangerous moments in the whole emergency, because what they are usually looking at is agonal breathing — a reflex the brainstem produces when the heart has stopped and the body is starved of oxygen, not a sign that the person is recovering or breathing adequately.
What Agonal Breathing Actually Is
Agonal breathing describes irregular, gasping breaths that can appear in the first minutes after the heart stops pumping effectively. It is not conscious or voluntary; it is a brainstem reflex firing while the brain and other organs are being deprived of oxygenated blood. The gasps are typically slow, often noisy, and can sound like snoring, gurgling, moaning, or snorting. Crucially, they do not move enough air to keep someone alive — agonal breathing is not effective breathing, even though the chest may still visibly rise and fall.
Research on out-of-hospital cardiac arrest suggests agonal breathing is common, appearing in roughly four to six out of every ten cases in the first minutes after collapse. That makes it far more than a rare edge case: recognising it correctly is a routine, everyday part of what separates a fast bystander response from a delayed one.
Why Bystanders and 999 Callers Get It Wrong
The confusion is understandable. Someone taught that “breathing means they’re okay” sees movement and noise and reasonably assumes the person is still breathing normally. But normal breathing is quiet, regular, and effective. Agonal breathing is irregular, effortful-sounding, and gets slower and further apart as time passes — a pattern that is easy to miss under the stress of an emergency, especially from someone with no first-aid training.
This misreading has a measurable cost. Bystander hesitation caused by mistaking agonal breathing for normal breathing is a recognised factor in delayed CPR, and in some studies a meaningful share of cardiac arrest patients did not receive any CPR at all specifically because of the presence of this kind of abnormal breathing. The problem is not limited to bystanders standing over the person: when a 999 call handler cannot get an accurate description of the breathing over the phone, it becomes harder for them to issue the clear dispatcher-assisted CPR instructions that are often what gets compressions started before an ambulance arrives.
Agonal Breathing vs Normal Breathing
| Feature | Normal Breathing | Agonal Breathing |
|---|---|---|
| Rhythm | Regular, even | Irregular, gasping, gaps between breaths |
| Sound | Quiet | Often noisy — snoring, gurgling, moaning, snorting |
| Trend over time | Stable | Usually slows and becomes less frequent |
| What it means | Person is breathing effectively | Heart has likely stopped — treat as cardiac arrest |
| What to do | Monitor, place in recovery position if unresponsive | Call 999 immediately and start CPR |
What UK Guidance Says To Do
Resuscitation Council UK guidance is direct on this point: slow, noisy, gasping breaths and other abnormal patterns described as agonal gasping or panting must be recognised as a sign of cardiac arrest, not a sign of life. If a person is unresponsive and not breathing normally, cardiac arrest should be assumed and CPR started immediately — and if there is any doubt at all, the advice is the same: assume cardiac arrest and begin CPR rather than wait to be certain. Training materials increasingly use recordings of real agonal gasps specifically so that lay rescuers can recognise the sound rather than be reassured by it. When calling 999, describing what is heard as “gasping” or “agonal” — rather than saying the person “is breathing” — helps the call handler give the right instructions faster.
London Ambulance Service guidance follows the same logic: check for normal breathing for no more than about ten seconds, and understand that in the first few minutes after a cardiac arrest, a casualty can make odd, usually slow and sometimes noisy gasping breaths. If someone is unresponsive, gasping in this way, and showing no other signs of life, the advice is to treat it as cardiac arrest — call 999 and start chest compressions without waiting.
Why This Matters for London’s Bystander Response
This review exists to track how the recommendations in the Mayor of London’s 2014 “Better Health for London” report, chaired by Professor Lord Ara Darzi, play out in practice across the capital’s health system. Rapid bystander response to cardiac arrest sits squarely inside that agenda: it is a community-level intervention that costs nothing to deploy but depends entirely on ordinary people recognising an emergency correctly in the first seconds. A community first responder scheme, a public-access defibrillator, or a well-trained call handler cannot compensate for someone standing over a collapsed person and deciding, wrongly, that gasping means the situation is under control.
The evidence is consistent on the other side of that decision too: people who show agonal breathing after cardiac arrest and then receive prompt CPR and defibrillation have a meaningfully better chance of survival than those who do not. The gasping itself is not the danger — the danger is what it gets mistaken for.
What To Do If You Hear It
- Don’t wait to be sure. If someone is unresponsive and their breathing looks or sounds irregular, gasping, snoring, or gurgling, treat it as cardiac arrest.
- Call 999 immediately and describe the breathing accurately — say “gasping” or “abnormal,” not “breathing.”
- Start chest compressions straight away rather than waiting for the call handler to confirm cardiac arrest.
- Follow the call handler’s instructions — they can talk you through compressions and tell you if a nearby defibrillator is available.
- Keep going until emergency help arrives, a defibrillator is attached, or the person clearly recovers normal breathing.
Agonal breathing is one of the clearest examples of how a small piece of correct knowledge changes an outcome. It is not a sign that help can wait — it is often the clearest sign that a person urgently needs CPR, and recognising it for what it is remains one of the most decisive things a bystander can get right.