Cognitive limitations in depth estimation for dispatcher-assisted cardiopulmonary resuscitation: a prospective...

Dispatcher-assisted cardiopulmonary resuscitation (DACPR) protocols often instruct bystanders to perform chest compressions to a target depth of 50-60 mm. However, whether laypersons can accurately perceive and achieve these depth targets remains unclear. This study evaluated laypersons' ability to estimate 50 mm in horizontal length, vertical depth, and chest compression depth.

We conducted a prospective simulation study enrolling adult laypersons without cardiopulmonary resuscitation (CPR) training within two years. Participants were asked to draw a 50 mm line, press a vertical measurement plate to an estimated depth of 50 mm, and perform chest compressions to 50 mm. Tasks were repeated after provision of a 50 mm visual reference. Accuracy was assessed by calculating the mean difference from 50 mm and the proportion of estimations within the acceptable range (45-55 mm).

100 participants were enrolled. Horizontal length was significantly underestimated (mean difference -3.5 ± 16.6 mm, p = 0.036), with 25.0 % (95 % confidence interval [CI], 16.9 %-34.7 %) within the acceptable range. Vertical depth was significantly overestimated (mean difference +4.9 ± 19.4 mm, p = 0.044), with 26.0 % (95 % CI, 17.7 %-35.7 %) within range. Chest compression depth was significantly underestimated both before (44.5 ± 10.7 mm) and after (44.7 ± 11.0 mm) provision of visual reference (both p < 0.001), with no significant improvement after reference exposure (p = 0.548).

Laypersons have significant difficulty estimating 50 mm in length, vertical depth, and applying target chest compression depth. Providing a visual reference did not significantly improve performance.