CPR basics come down to three decisions: call for help, push hard and fast in the centre of the chest, and use an AED as soon as one arrives. For an untrained bystander, compressions alone are the recommended approach, and doing them imperfectly is far better than doing nothing.
When should I start CPR?
Start when someone is unresponsive and not breathing normally. Those are the only two checks
required, and both take seconds. Shout and shake the shoulders for responsiveness; look at the chest
for no more than ten seconds for normal breathing.
The trap is agonal gasping: irregular, noisy, gulping breaths that occur in the first minutes of
cardiac arrest. They look like breathing to an untrained observer and they are not effective
breathing. Bystanders regularly withhold CPR because of them, which is one of the most costly errors
in the whole sequence.
Call emergency services first, or have someone else call while you begin. On a phone, put it on
speaker and keep your hands free, because the dispatcher will talk you through compressions and their
instructions measurably improve outcomes. Standards are set out by the American Heart Association CPR and ECC guidelines.
How do I do CPR chest compressions?
Place the heel of one hand in the centre of the chest on the lower half of the breastbone, the
other hand on top, fingers interlocked. Keep your arms straight and your shoulders directly above your
hands, so the force comes from your body weight rather than your arms.
Push hard and fast: roughly two to two and a half inches deep in an adult, at a rate of one hundred to
one hundred and twenty compressions per minute. Let the chest recoil completely between compressions,
because incomplete recoil prevents the heart refilling and is a very common error in real events.
Minimize interruptions. Every pause reduces the pressure that has been built up, and pressure takes
several compressions to re-establish. If two people are present, swap roughly every two minutes,
because compression quality falls off measurably with fatigue and the person doing it is usually the
last to notice.
What does an AED do, and why should I use it?
An automated external defibrillator analyzes the heart rhythm and delivers a shock only if the
rhythm is one a shock can correct. It will not shock someone who does not need it, and this is the
single most important thing for a bystander to understand, because fear of causing harm is what keeps
these devices on walls during cardiac arrests.
Operating one requires no training. You turn it on and it speaks instructions: where to place the
pads, when to stand clear, when to resume compressions. Follow the voice. Modern units are designed
specifically to be usable by someone who has never seen one before.
Time matters enormously. Survival falls with every minute that passes before defibrillation, which
is why sending a second person for the nearest AED at the same moment you start compressions is worth
far more than a perfect compression technique achieved alone.
Why hands only is the right default
For untrained bystanders responding to an adult collapse, compressions without rescue breaths
are recommended. There is oxygen already in the blood in the first minutes, and circulating it is the
priority. Removing the breathing element also removes the hesitation that stops people acting at all,
which is the larger problem in practice.
The exceptions are drowning, children, and cases where the arrest was caused by a breathing
problem. In those, rescue breaths matter more because the arrest is oxygen driven from the outset. That
is precisely why lifeguards and pool staff train the full sequence rather than the bystander version.
If you want the full method with breaths and an AED component, that is a certification course
rather than an article. Ours, and the credential they lead to, are described on the
CPR and First Aid Instruction page.
Key takeaways
- Start if the person is unresponsive and not breathing normally; those are the only checks needed.
- Agonal gasping looks like breathing and is not, and mistaking it is a costly and common error.
- Call emergency services on speaker so the dispatcher can coach you with your hands free.
- Send someone for an AED at the same time you start compressions, not afterwards.
- Push two to two and a half inches deep at one hundred to one hundred and twenty per minute.
- Allow full chest recoil between compressions, or the heart cannot refill.
- Swap rescuers every two minutes; quality drops with fatigue before the rescuer notices.
- An AED only shocks a rhythm that needs it, requires no training, and speaks its instructions.
- Hands only CPR is the right default for untrained bystanders responding to an adult collapse.
- Drowning and children are the exceptions where rescue breaths genuinely matter.
The bystander sequence
| Step | Action | Detail that matters |
|---|---|---|
| 1. Check | Unresponsive and not breathing normally | Agonal gasping is not breathing; do not be fooled by it |
| 2. Call | Emergency services, speaker on | The dispatcher will coach you and that improves outcomes |
| 3. Send | Someone for the nearest AED | Do this at the same time, not afterwards |
| 4. Compress | 5 to 6cm deep, 100 to 120 per minute | Full recoil, minimal interruption |
| 5. Defibrillate | Turn the AED on, follow the voice | It only shocks a rhythm that needs it |
| 6. Continue | Until help arrives or the person recovers | Swap every 2 minutes if someone else is present |
Want to book a class?
Call (718) 954-5567. Lifeguard and instructor classes are held at 37 Mineola Ave, Roslyn, NY 11576.
Frequently asked questions
Can I hurt someone by doing CPR wrong?
Rib fractures happen and are an accepted consequence of adequate compressions. The alternative to imperfect CPR in a cardiac arrest is not a better outcome; it is no circulation at all.
What if they are actually breathing?
Someone breathing normally will respond to being disturbed. If you genuinely cannot tell within ten seconds, treat it as an arrest and begin. Under-treating is the far more common and more costly error.
Do I need to do rescue breaths?
Not as an untrained bystander with an adult collapse; compressions alone are recommended. Drowning, children and breathing-caused arrests are the exceptions, which is why aquatic staff train the full sequence.
How do I know the right compression rate?
One hundred to one hundred and twenty per minute, which is roughly two per second. Many people use a familiar song with that tempo, and dispatchers will count with you over the phone.
Is an AED safe for me to use?
Yes. It analyzes the rhythm and will not deliver a shock unless one is indicated, and it gives spoken instructions throughout. No training is required to operate one correctly.
How long do I keep going?
Until emergency services take over, the person shows clear signs of life, or you are physically unable to continue. Swapping with another rescuer every two minutes keeps quality up.
Are CPR basics different for children?
Yes. Compressions are shallower, technique differs by size, and rescue breaths matter considerably more because paediatric arrests are more often caused by a breathing problem than a cardiac one.
Should I take a certification course?
If you supervise water, work with children or have any duty of care, yes. A single session covers the full sequence, and nobody learns this usefully in the moment they need it.
