Continuous Chest Compressions vs. 30:2. Does It Matter? Depends On the Quality!

seattle fire engine 2 resus

Seattle Fire Department Engine 2. The rescuer on the left has just placed a metronome on the ground.

I will eventually get around to composing a more thoughtful blog post about my experiences at the Resuscitation Academy but in the interim I wanted to share something about the ventilation strategy in King County, Washington.

There isn’t much controversy in the fact that ventilations are probably unnecessary in the first 4 minutes of sudden cardiac arrest. The idea is that the arterial system is full of fresh, oxygenated blood at the time of collapse. However, after that time period has elapsed things get a bit murky and this is where there are differences of opinion.

instrumented manikin

Instrumented manikin at the Resuscitation Academy.

There is a high rate of bystander CPR in King County (about 1/2 the time dispatcher-directed) so bystanders are performing continuous chest compressions for 4-6 minutes prior to the arrival of EMS. I think we can all agree this is a good thing. However, you can also argue (and Peter Kudenchuk, M.D. does) that ventilations are not so easily omitted when 4-6 minutes of continuous chest compressions have already taken place.

Once EMS arrives at the scene, expertly performed chest compressions (rate, depth, and recoil) are initiated. They train with instrumented manikins in King County, and one thing we discovered is that every single one of us “leaned”. The smallest amount of leaning on the chest destroys recoil, preventing the negative pressure gradient responsible for blood return to the heart.

(See also: The Science of CPR by Peter Kudenchuk, M.D.)

As a side note (not to stray too far off topic) the communication is excellent in the Medic One system, so problems with rate, depth, and recoil are corrected quickly because a fellow rescuer will point out the problem. It’s a part of their culture and professionalism that everyone observes what is happening.

There are slight differences between King County EMS and Seattle Fire but they are not too caught up in whether or not you shock as soon as possible or at the 2-minute mark once you have reached the patient’s side. However, the emphasis is on chest compressions and defibrillation. For example, if there were only 2 rescuers on scene, chest compressions and the first shock would take priority over using the BVM.

Once more help arrives, or assuming there is a third person, a BVM is deployed. As we have previously discussed, King County EMS uses a 30:2 strategy initially, while Seattle fire performs “BLS Continuous” where they ventilate at a 10:1 ratio without interrupting chest compressions.

(See also: Trial of Continuous or Interrupted Chest Compressions During CPR)

This is where I want to point something out that is critical to understand. They are only bagging with 300-400 ml of volume! That is a very small bag squeeze. Without the instrumented manikin I wouldn’t have believed it was adequate. In the absence of chest compressions it causes a noticeable chest rise, and that’s all they interested in — just enough for air exchange and to prevent atelectasis.

Resuscitation Academy logo with stylized heart, the tree of life or knowledge, 10 branches for 10 steps to improve resuscitation, and 4 stars for the chain-of-survival (prior to 2010). Two stars are larger because they are more important (CPR and defibrillation)

Resuscitation Academy logo with heart, the tree of life (or knowledge) with 10 branches for 10 steps to improve survival, and 4 stars for each link in the chain-of-survival (prior to 2010). Two stars are larger because they are more important (CPR and defibrillation)

There is no doubt that we have been over-bagging in my system, and I can see why cardiocerebral resuscitation confers a benefit in systems that bag overzealously with 30:2 or delay for too long to deliver the breaths.

In the Medic One system, when 30:2 is used, the rescuer on chest compressions is “divorced” from the person on airway. They deliver 30 perfect chest compressions, pause for 2 seconds, and then deliver another 30 chest compressions. They don’t “wait” for the person on the airway.

As you can imagine it takes training, and re-training, to achieve this level of performance. But that’s sort of the point. They have been perfecting their craft since the Apollo program and each iterative change has been made thoughtfully and using the best available evidence (mostly derived from their own measurements).

Still, they readily concede that resuscitation is, and perhaps will always be, an unsolved puzzle. So whatever you do, don’t just be good at it; be absolutely phenomenal at it. If you are successful in cultivating a culture of excellence and continuous quality improvement your EMS system will get where it needs to go.

Further reading

Ten Steps for Improving Survival from Sudden Cardiac Arrest


Nichol G, Leroux B, Wang H et al. Trial of Continuous or Interrupted Chest Compressions during CPR. New England Journal of Medicine. 2015;373(23):2203-2214. doi:10.1056/nejmoa1509139.

Kleinman M, Brennan E, Goldberger Z et al. Part 5: Adult Basic Life Support and Cardiopulmonary Resuscitation Quality. Circulation. 2015;132(18 suppl 2):S414-S435. doi:10.1161/cir.0000000000000259.

Ewy G. Cardiocerebral Resuscitation: The New Cardiopulmonary Resuscitation. Circulation. 2005;111(16):2134-2142. doi:10.1161/01.cir.0000162503.57657.fa.

See also

How to Master BVM Ventilation at ACLS Medical Training


  • Seini Pepe Gudsell says:

    Great stuff!! Keep it coming please. Thanks

  • Clay Odell says:

    Good infromation, but the title is a bit misleading. The NEJM article cited showed no difference whether doing continuous or interrupted (30:2) compressions. The study was designed to ensure high quality CPR in both arms of the study.

    A more accurate title would be: Continuous Chest Compressions vs. 30:2 – Does it Matter? No, but Quality CPR is Essential.

    Thank you for the article.

    • Tom Bouthillet says:

      Hi, Clay. The point, at least from my perspective, is that poorly performed 30:2 is probably not as good as continuous chest compressions (whether you include 10:1 upstroke ventilations or not). It’s really easy to get this wrong, either by squeezing the bag too hard or delaying too long to give breaths. So I think it does matter. Thanks for the comment! Tom

  • Tony Sirgedas says:

    In King County we are still switching back and forth from CC and 30:2. Currently the department I work for (which has one of the highest number of CPR cases in KC) is at 30:2 after doing our 6 months of CC. Personally I don’t think one is better over another, that it comes down to quality compressions,minimizing pauses in those compressions, and on our calls being very diligent at swapping out the rescuer doing compressions every 2 minutes (fatigue leads to inconsistant compression depth, rate, and the “lean”).

  • Andy says:

    Great article. I have long wondered if by teaching CC we are teaching to not delay compressions for interventions, and that rescuers are taking this teaching and applying it to 30:2. We need to study the difference in the two ways, but I think your spot on that the compressor needs to be the best possible and best form.
    On the ventilation side I make a conscious acknowledgement not to over ventilate and not to over bag.

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