How to Do CPR: Compression Depth, Rate, and What to Do When Help Is Far Away

Learning how to do CPR comes down to four numbers and one honest admission. The numbers are rate, depth, recoil, and pause length. The admission is that reading them is not the same as having practiced them, and the gap between those two states is real. I will give you the numbers straight, and I will also tell you where a class does something an article cannot.

The reason to know this at all: the American Heart Association states that "immediate CPR can double or triple chances of survival after cardiac arrest." Not a small effect, and it depends entirely on whoever happens to be standing there.

When should you start CPR?

When the person does not respond and is not breathing, or is only gasping. That is the American Red Cross threshold, and it also says to spend no more than 10 seconds checking for responsiveness.

The gasping part is the trap. Agonal gasping is common in the first minutes of cardiac arrest, and it looks and sounds like breathing to someone who has never seen it. It is slow, irregular, snoring or fish-out-of-water breathing, and it is not effective breathing. People stand and watch it happen because it seems like the person is still breathing. If the person is unresponsive and all you see is that, the Red Cross's answer is to call 911 and start.

Two more things to do in those first seconds, in this order: get 911 on the line and put the phone on speaker so the dispatcher can coach you, and send someone specific for an AED. Not "somebody get an AED." Point at a person and give them the job.

How deep should CPR compressions be?

At least 2 inches (5 cm) for an average adult. The American Heart Association gives that as the floor and also sets a ceiling, saying to avoid going deeper than 2.4 inches (6 cm).

Two inches is deeper than almost anyone expects. It is the single most common shortfall in bystander CPR, and the reason is not squeamishness so much as calibration. You cannot feel 2 inches. On a manikin with a depth indicator you find out immediately that what felt like a firm push was about an inch, and that correction sticks. That is the thing a class gives you that an article cannot.

The Red Cross describes the mechanics that make depth achievable: "two hands centered on the chest" with "shoulders directly over hands; elbows locked." You are not pushing with your arms. You are locking your arms and using your upper body weight, hinging from the hips. If your elbows bend, you will be exhausted in 90 seconds and you will not be reaching depth.

How fast should you do CPR compressions?

100 to 120 per minute. Both the AHA and the Red Cross publish that same window, and it works out to roughly two compressions per second.

Under stress people either race well past 120 or drift below 100, and both cost you. Too fast and the chest never refills between compressions. Too slow and you are not moving enough blood. Counting out loud is the simplest fix, and it has a second benefit: it keeps your own breathing regular, which keeps you steadier.

If you want a mental metronome, pick a song you know at around 100 to 110 beats per minute and use it. It is a well-worn trick in CPR classes precisely because it works when your hands are shaking.

Why does letting the chest come back up matter so much?

Because the recoil is the part that refills the heart. Compressions push blood out. The upstroke is when blood returns, and if you rest your weight on the chest between compressions, that return is reduced.

The AHA lists it as a component of high-quality CPR: "avoid leaning on the victim between compressions." It is easy to violate without noticing, especially as you fatigue, because leaning feels like efficiency. Lift your weight fully every single time, even when it is the 200th compression and your shoulders are burning.

Should you do hands-only CPR or add rescue breaths?

If you are untrained, hands-only. The AHA recommends hands-only CPR for bystanders who witness an adult or teen suddenly collapse outside a medical setting, in a home, a workplace, or a park. Its instruction is as short as it sounds: call 911, then "push hard and fast in the center of the chest."

There is a reason the guidance is that simple. Rescue breaths done badly cost time away from compressions, and hesitation about mouth-to-mouth stops people from acting at all. The AHA notes that even sixth graders have been shown able to perform hands-only CPR correctly. If you remember nothing else from this article, remember that you are allowed to help with only your hands.

If you are trained and willing, conventional CPR is cycles of "30 chest compressions and 2 breaths." The Red Cross specifies that each breath should last "about 1 second and makes the chest rise," delivered with the nose pinched. A breath that does not make the chest rise is a breath that did not go in, and forcing more volume is not the fix.

What about an AED, and how long do you keep going?

Get the AED on as early as you can. The Red Cross puts it with an exclamation point: "Use an AED as soon as one is available! Minimize interruptions to chest compressions to less than 10 seconds."

That 10 second rule governs everything. Switching compressors, attaching pads, checking a pulse, all of it lives inside a 10 second budget. Modern AEDs talk you through the process and will not shock a rhythm that should not be shocked, so the machine is not the part you need to be confident about. The part you need to be confident about is not stopping compressions while you wait for it.

As for duration, the Red Cross says to continue until emergency responders take over or the AED advises otherwise. If two or more people are present, plan to swap compressors regularly. Compression quality degrades measurably before the person doing it feels tired, so trade off on a schedule rather than when you feel like it.

What if help is genuinely far away?

Then the honest answer is that the plan has to start before the emergency, because CPR alone is a bridge and not a destination. Chest compressions keep blood moving toward the brain while you wait for a defibrillator and advanced care. If neither is coming for a long time, the odds get hard, and no article should pretend otherwise.

What that means practically, if you spend time far from an ambulance:

• Solve communication before you go. A satellite messenger or a plan for reaching help is worth more than any gear in your pack, because everything downstream depends on help being on its way.

• Know your evacuation time honestly. Not the optimistic number. The real one, including the time it takes to reach you.

• Plan for more than one rescuer. Sustained compressions are a team activity. One person cannot deliver quality CPR for long.

• Take a course that covers remote settings. Wilderness first aid and wilderness first responder courses deal specifically with long transport times, which standard courses do not.

• Find out where the nearest AED is in the places you spend time, including the cabin, the trailhead lot, the gym, and the office.

Prevention deserves more weight than technique in this setting. Knowing cardiac risk factors, not ignoring chest pain on the second day of a trip, and turning back early are not exciting, but they are what actually keeps people alive when the ambulance is three hours out.

What this article cannot do for you

It cannot let you feel 2 inches. It cannot let you discover that your elbows unlock when you get tired, or that your rate creeps to 140 when your heart is pounding. Those are physical calibrations, and you only get them on a manikin with someone watching.

So treat this as the reference you reread, and treat a class as the thing you actually do. A basic CPR and AED course is a few hours and it is widely available. If you want to compare the options, we covered first aid and CPR certification choices separately.

Logan Pierce is the editorial voice of Prepped and Ready, not a medical professional. Everything above is drawn from the published guidance of the American Heart Association and the American Red Cross, linked throughout. In a real emergency, call 911 and follow the dispatcher.

Frequently asked questions about CPR

How deep should CPR compressions be?

At least 2 inches (5 cm) for an average adult, and the American Heart Association also says to avoid going deeper than 2.4 inches (6 cm). Two inches is deeper than most people expect, and shallow compressions are the most common problem with bystander CPR.

How fast should you do CPR compressions?

100 to 120 compressions per minute, per both the American Heart Association and the American Red Cross. That is roughly two per second. Counting out loud or matching a steady beat helps more than trying to judge it by feel.

Should I do hands-only CPR or give rescue breaths?

If you are untrained, the AHA recommends hands-only CPR for an adult or teen who suddenly collapses: call 911, then push hard and fast in the center of the chest. If you are trained and willing, the conventional approach is cycles of 30 compressions and 2 breaths, with each breath lasting about 1 second and making the chest rise.

When should you start CPR?

The Red Cross says to call 911 and begin when the person does not respond and is not breathing or is only gasping. Spend no more than 10 seconds checking for responsiveness. Gasping is not breathing, and treating it as breathing is a costly mistake.

How long should you keep doing CPR?

The Red Cross says to continue until emergency responders take over or the AED advises otherwise. Use an AED as soon as one is available and keep interruptions to chest compressions under 10 seconds. If more than one person is present, swap compressors regularly, because quality drops as you tire long before you feel tired.

Can I hurt someone by doing CPR wrong?

You can cause injury, and that is a real tradeoff that the guidance already accounts for, which is why the AHA sets both a minimum depth of 2 inches and a maximum of 2.4 inches. The alternative to imperfect CPR on someone in cardiac arrest is no CPR, and the AHA's position is that immediate CPR can double or triple the chance of survival. Call 911, follow the dispatcher, and push.

Is CPR different for children and infants?

Yes, in hand placement, depth, and the emphasis on breaths, and that is exactly the kind of detail worth learning in a class rather than from an article. The guidance above is adult and teen guidance. If children are in your life, take a course that covers pediatric CPR specifically, and check the American Red Cross and American Heart Association pages for their current child and infant instructions.

Rate, depth, recoil, pauses. Call, push, and do not stop. And then go take the class, because the version of you that has done this on a manikin is a much more useful person to have in the room.

You never know, but you can always be ready.

Sources: American Heart Association, What Is CPR · American Red Cross, CPR Steps