Since 2005 guidelines have made statements on CPR compression depth. Those first recommendations recommended a compression depth of 3,8 to 5 cm. In 2010 the recommended depth was increased to >5 cm. This was based on mostly animal data and, as far as I know, very little human data. Recently the US/Canadian ROC consortium published a study that tries to link compression depth with outcomes.

The Study
The ROC collected data from out of hospital cardiac arrests were defibrillators with accelerometers was used. The accelerometer allows for measuring compression depth. Primary outcome was survival to discharge from hospital. Secondary outcomes were ROSC and 1-day survival.

10 participating sites participated. After exclusion 1.029 patients remained. The results are in the curves to the right

Patients with compression depths of >38 mm had better chances of achieving ROSC, better 1-day survival and better chances of surviving to discharge.

So this study supports the 2005 guidelines recommendation of 3,8 to 5 cm compressions depth and likely the 2010 recommendation of > 5 cm too.

Unfortunately the data also suggests more than half of patients received less than the 2005 recommended compressions depth.

More than 9o% received less than the 2010 recommendation of 5 cm.

They also found a significantly deleterious effect on compression depth when compression depth was faster than the recommended ‘approximately 100 bpm.’  from the 2010 AHA guidelines.

Depth suffers from too high compression rates.


The study is worth a read. It is a quite large study and there more to learn from it.

Stiell IG, Brown SP, Christenson J et al. What is the role of chest compression depth during out-of-hospital cardiac arrest resuscitation? Crit Care Med. 2012 Apr;40(4):1192-1198.

Stiell IG, Brown SP, Christenson
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