CPR and Defibrillation: What the Evidence Actually Says
Survival from cardiac arrest depends almost entirely on what bystanders do in the first minutes.
Key takeaways
- Compression depth, adult: 5-6cm
- Rate: 100-120 per minute
- Most useful single change: Call 999 first and put the phone on speaker.
- Commonest mistake: Delaying compressions to check for a pulse.
- See a doctor if any of the signs under "When to speak to a doctor" below apply to you.
What it is
Keeping blood moving until a defibrillator or ambulance arrives. It sits within Emergency Care. What follows are the published numbers, not the ones that get passed around.
The numbers, in one place
| Measure | Figure |
|---|---|
| Compression depth, adult | 5-6cm |
| Rate | 100-120 per minute |
| If untrained | hands-only, continuous compressions |
| Defibrillators | safe for untrained use; they will not shock unless needed |
| Agonal gasping | is not normal breathing; start CPR |
What helps
What follows is the practical part: the things guidance actually asks of you.
- Call 999 first and put the phone on speaker
- Push hard and fast in the centre of the chest
- Send someone for a defibrillator while you continue
What to avoid
The common mistakes, including the ones that sound sensible.
- Delaying compressions to check for a pulse
- Stopping because you are unsure you are doing it right
Where to go next
- Your Questions About CPR and Defibrillation, Answered
- CPR and Defibrillation: Just the Figures
- CPR and Defibrillation — the reference entry
- Choking: What the Evidence Actually Says
- Severe Bleeding: What the Evidence Actually Says
When to speak to a doctor
Call 999 immediately for anyone unresponsive and not breathing normally, and start CPR straight away. This is a summary, not training — a practical first aid course is what builds the skill, and it is the single most useful thing most people can learn.
Where this comes from
- Resuscitation Council UK — adult basic life support
- British Heart Foundation — CPR
How this page was put together
Every figure, recommendation and warning above is taken from the guidance named in Where this comes from. Nothing on this page is inferred, summarised or generalised beyond what those bodies publish: where they give a number, it is their number, and where they are silent, so are we. Pages are rebuilt whenever the underlying record changes. Sign-off by a named clinician, where it has happened, is shown at the top of the page along with the date.
Medical disclaimer
This article is general information, not medical advice. It cannot account for your own history, medication or circumstances. Always speak to a GP, pharmacist or another qualified health professional before making changes that affect your treatment, and never delay seeking medical advice because of something you have read here. In an emergency, call 999.
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