Certification tests your knowledge. A real code tests your recall under stress — and those are two very different things.
These 10 numbers are the ones that show up in every algorithm, every scenario, every debrief. Drill them until they're automatic. Cover the right column. Say each number out loud. Be wrong a few times. That's the only way they get into long-term memory.
"Knowing what to do and being able to do it under pressure are two different skills. One comes from reading. The other comes from repetition."
Chest compression rate
Compressions per minute. Too slow doesn't perfuse. Too fast doesn't refill. Stay in this range.
Compression depth
Roughly 5–6 cm in an adult. Shallow is the far more common error — but deeper is not better past this range.
Maximum interruption
Pulse checks, intubation attempts, pad changes. If it takes longer, coronary perfusion pressure has already collapsed.
CPR cycle length
The interval between rhythm checks, and the interval at which you swap compressors.
Compressions to breaths
Adult, no advanced airway. Once the airway is secured, ratios stop and continuous compressions begin.
Ventilation with an advanced airway
About 10 breaths a minute, delivered without pausing compressions. Hyperventilation actively harms.
Epinephrine, IV/IO
Repeated every 3–5 minutes for the duration of the arrest.
Amiodarone, mg
First and second dose for refractory VF or pulseless VT. Lidocaine is the alternative agent.
ETCO₂ during CPR
Below this, your compressions are not generating meaningful cardiac output. An abrupt jump toward normal suggests ROSC.
Chest compression fraction
The proportion of the code spent actually compressing. Most teams believe theirs is higher than it is.
Why these ten and not fifty
There are far more than ten numbers in the ACLS algorithms. Adenosine doses, cardioversion energies, atropine maximums, bicarbonate calculations — all of them matter, and all of them are on a wall chart you can read when the time comes.
These ten are different because they govern the things you do continuously, from the first minute to the last. There is no moment in a code where you can stop and look up your compression rate. Recall has to be instant, because the demand is constant.
The numbers you can look up are not the numbers that decide outcomes. Compression quality and interruption time are what survival curves are actually built on — and they are the two things no one hands you a card for mid-arrest.
The three that get missed most
Depth. Almost every audit of real resuscitations finds compressions that are too shallow, and the providers delivering them are usually confident they are deep enough. Fatigue makes this worse within about a minute — which is exactly why the two-minute compressor swap exists, and exactly why teams skip it when they feel fine.
Full recoil. Leaning on the chest between compressions prevents the heart from refilling. You can be perfectly on rate and perfectly on depth and still generate very little forward flow because you never let the chest come all the way back. It is invisible without feedback, and it is extremely common.
Ventilation rate. Under stress, bagging speeds up. Excessive ventilation raises intrathoracic pressure, reduces venous return, and lowers the perfusion your compressions are working to create. The instinct to do more is the thing causing harm.
ETCO₂ is the closest thing you have to a real-time report card on all three. A number that will not rise above 10 mmHg is telling you the compressions are not working — before any other measurement in the room will.
How to actually drill them
- Say them out loud, cold Not read — recalled. Silent reading produces recognition, which feels like knowledge and disappears the moment someone is shouting.
- Test in random order If you can only recite them as a list, you have memorised the list, not the numbers. A code will not ask them in order.
- Attach each number to a decision "Two minutes" is not a fact, it is a prompt: rhythm check, pulse check, swap compressor. Numbers stored as decisions survive stress; numbers stored as trivia do not.
- Rehearse under noise Practise with alarms, a timer and someone asking you questions. Quiet recall is not the skill being tested at 3 AM.
- Re-test at one week Spacing is what moves these into durable memory. One pass the night before a recert produces numbers that are gone by the time you need them.
Scenarios that hold you to these numbers instead of asking you to recite them. Compress too slowly and the pressure drops. Interrupt for too long and you watch the cost. The numbers stop being a table and start being consequences.
What every clinician should remember
- These ten govern continuous actions — there is no point in a code where you can pause to look them up
- Depth, full recoil and ventilation rate are the three most commonly missed, and all three degrade with fatigue
- Swap compressors every two minutes even when the current one feels fine — especially then
- ETCO₂ under 10 mmHg means the compressions are not generating output, regardless of how they look
- Drill by recall in random order, not by re-reading; test again a week later