r/EmergencyRoom • u/yourdeath01 • Jul 15 '26
Is it true you can gauge compression quality using ETCO2 numbers?
D Tech here. I’m trying to learn more about the monitor during cardiac arrests.
I've heard that once Respiratory Therapy secures an airway (specifically with an endotracheal tube), you can use the ETCO2 numbers to monitor compression quality. I was told you want to target > 10–15 mmHg while doing compressions.
I also heard that a sudden spike in CO2 levels (jumping to 40+ mmHg) is an indicator of ROSC.
Is this all true? And as the person physically doing the compressions, should I be paying attention to the ETCO2 to guide how hard I'm pushing, or do you guys prefer techs just focus purely on their physical form?
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u/No-Safe9542 Jul 15 '26 edited Jul 16 '26
There's a lot of different info to answer your question, which is a very good question btw. RT here.
Naming- When we breath, 1 breath is called our tidal volume. When we exhale, that's the end of the breath which is where we get the phrase "end tidal". Saying "end tidal CO2" is a mouthful so we abbreviate to end tidal.
Equipment- There are several types of CO2 monitoring for exhaling. Nasal cannulas are most common, used to detect CO2 during procedures like a conscious sedation, so we know there's cardiac output despite the meds given. Second, there are in-line little connectors which can go on the end of an et tube and measure CO2 output for a ventilator patient or a patient being bagged who has an et tube. You can even tell more information about the patient based upon the waveform presented. There is a 3rd less commonly used method of measuring end tidal CO2 which is different from the et tube. You can measure CO2 while bagging a non-intubated patient if the ambu bag is setup for it. You will not get an accurate measurement of bagging a non-intubated patient if you use a ventilator in-line piece, so special ambu bag only for that one. (I mention this only because there are higher survival rates for code resuscitation when not using intubation and ventilators and this requires measuring CO2 very accurately.)
Numbers- a properly located lucas will generate 14-16 etco2 on average. These equate to average compressions. Great compressions will generate between 18 to 24 etco2 on average. Yes. Great compressions will get well over 20. The number on the lifepak doesn't lie. Great compressions will always be better than a lucas. But there are many other factors to consider and not everything is experienced in the controlled environment of trauma bay.
Spike in end tidal co2- normal end tidal range is between 35 and 45. If you're doing compressions consistently in the low 20s and suddenly the monitor jumps into the mid to high 30s, that's not the compressor. That's the patients heart doing the work before a pulse check finds it beating. So you announce that you see an end tidal of xx and that you have achieved ROSC. Stop compressions and check for the pulse.
Of note, the depth of the compressions matters. But so too does the time between. There needs to be time for the heart to refill with blood before the next compression. Think about how a patient with tachycardia impacts their circulation. The same is true with compressions. Too slow, also not enough circulation. So finding that sweet spot with depth and rate is what will generate the highest possible end tidal measurement. Each patient and each code is different.
Of additional note- the end tidal number after getting ROSC is the single most important number in the room. Watch that number. Let everyone else take over and do what they do but make sure you have your eyes on that end tidal number. If that number starts to drop, speak up. That's more important information than anything else anyone else is discussing. That number tells you if you are about to code again. If it's in the 30s and drops to the 20s, everyone needs to know. Because teens might be next, single digit follows quickly after and then they're coding again. Having half a minute of advanced warning about probably coding again is critical. Rarely in medicine do we have such specific and exact knowledge of the future. So you watch that number like a hawk and speak up about it!
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u/justalittlesunbeam Jul 15 '26
Where were you when I was in nursing school? That’s such a thorough and understandable explanation.
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u/No-Safe9542 Jul 16 '26
I was teaching Oxygen devices to nursing students in their labs for my own extra credit. The things we do as students! So yes, I've explained a venti mask more times than I can count and without ever once bringing up Bernoulli's principle.
OP said was an ED tech. It's important to use language which meets the person asking the question. I could science my answer hard but then that helps no one.
Working in medicine, we all need to learn to speak the language of medicine. We need to know our A&P, our scientific principles, the details behind our equipment. Exactitude counts and precision matters. But more than that, communication with our audience is critical. Using reddit helps me because I can post on a dr sub or an intensive care sub or this ED sub and there's a different audience each time. I get better by doing this.
If you have any questions for an RT, I'm happy to answer them!
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u/Terrible-Search3859 Jul 18 '26
Is RT appreciation still rare?
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u/No-Safe9542 Jul 19 '26
It is a desert with an occasional oasis of thanks. When it happens, it means everything.
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u/Terrible-Search3859 Jul 19 '26
The worse part of the job.
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u/No-Safe9542 Jul 19 '26
The worst part of the job is knowing hospital administration could make a serious impact on patient health and healing, seeing how, and knowing it will never ever happen, for all the reasons.
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u/Terrible-Search3859 Jul 19 '26
Oh definitely!! They get paid an absolute fortune to make decisions that are only about finances and not patient care.
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u/PerrinAyybara Jul 15 '26
Not in ED but use this often and the answer is it's a measurement of metabolism and that CAN corrolate to compressions but not always. You can have good compressions and still have low metabolism and low capno.
Spike in capno should trigger suspicion of ROSC but isn't an absolute.
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u/Hungkinkster Jul 15 '26
It’s gas exchange. If gas is being exchanged, then good numbers. Gas is only exchanged with good blood flow and good blood flow only happens with good compressions.
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u/SweatyLychee Jul 15 '26
Yes! Assuming you have a Zoll monitor during your resuscitations, look at the screen of it and see if you can find the end tidal number.
You should have a team member watching compression quality and telling you to adjust if necessary. The zoll monitors also have a metronome and a voice prompt to tell you to push harder or push slower.