Introduction: There is an on-going discussion on quality of cardiopulmonary resuscitation (CPR) as related to guideline target values for chest compression depth. Deeper compression depth is generally understood to be more effective. Interestingly, the American Heart Association (AHA) guideline requests a compression depth of "at least 5cm" whereas the European Resuscitation Council (ERC) guideline requests "at least 5 cm, but not to exceed 6 cm". It is unknown which recommendation is more effective to achieve a correct compression depth. This study attempted to determine the difference in chest compression depth by instruction.
Methods: In total, 220 volunteers—110 professional rescuers and 110 lay-rescuers—were randomly assigned to 4 groups in a 1:1 ratio (55 volunteers per group). Participants were randomized to either estimate and compress "at least 5cm" (AHA) or to estimate and compress "at least 5cm, but no more than 6cm" (ERC). Estimation was to be done on a paper (horizontal axis, estimation of end) and chest compressions on a standard resuscitation manikin. Outcome was defined as the percentage of correct estimation of a distance on a horizontal axis and correct compression depth and analysed with a Mann-Whitney-U-Test.
Results: The results differed between professional rescuer and lay rescuer volunteer groups. Professional Rescuers: On a horizontal axis, 20 (36.3%) participants estimated the given distance ">5cm" correctly versus 19 (34.5%) in the "5-6cm" (p=0.84). The mean compression depth estimation on the manikin was 54±10 mm in the ">5cm" group versus 53±9 mm in the "5-6cm" group (p=0.61). In the ">5cm" group 39 (70.9%) professional rescuers estimated compression depth correctly on the manikin versus 36 (65.4%) in the "5-6cm" group (p=0.97). In the "5-6cm" group 16 (29.1%) professional rescuers underestimated, 4 (7.3%) overestimated the given target range. Lay-rescuers: On a horizontal axis, 18 (32.7%) lay-rescuers in the ">5cm" group correctly estimated the given distance versus 20 (36.4%) in the "5-6cm" group (p=0.59). The mean compression depth estimation on the manikin in the ">5cm" group was 52±10 mm versus 49±12 mm in the "5-6cm" group (p=0.09). In the ">5cm" group 39 (70.9%) of the lay-rescuers estimated compression depth correctly on the manikin versus 26 (47.3%) in the "56cm" group (p=0.02). In the "5-6cm" group, 26 (47.3%) lay-rescuers underestimated, 3 (5.4%) overestimated the given target range.
Conclusion: Our study indicates that estimation on a drawn horizontal line is not representative for correct compression depth estimation on a manikin. Furthermore, our study indicates that professional rescuers are aware of correct compression depth regardless of instruction; underestimation of chest compression depth is mainly a problem of lay-rescuers. The main finding is that for lay-rescuers, providing a maximum depth instruction appears to hinder the achievement of correct compression depth.