Group, SHARE Study

Background: The 2010 AHA Guidelines state rescuers should perform chest compressions (CCs) of at least 2 inches in depth for adult cardiac arrest patients. Although the pediatric guidelines recommend adjustment of CC depth based upon anteroposterior chest dimension, there is no such recommendation for adults. Purpose: To determine 1) whether prehospital providers intuitively vary CC depth in adults according to patient size and 2) whether implementation of real-time audiovisual CPR feedback (RTAVF) impacts weight/CC depth variation. Methods: CC quality data were prospectively collected prior to (9/08-4/10; Pre-feedback) and after (5/10-12/10; Post-feedback) implementation of an RTAVF system (ZOLL Medical, Chelmsford MA) from 3 EMS agencies. The RTAVF includes a visual display of absolute CC depth and gives audio prompts when depth is outside of the Guideline-recommended range. Among 363 cases of adult, non-traumatic out-of-hospital cardiac arrest (OHCA), body weight was estimated by EMS in 249 patients (study group; 66%). CPR quality data were available for all cases via code review software. Results: 168 Pre-feedback and 81 Post-feedback study group cases (mean 64±16 years, 68% male). Mean estimated body weight was 201 lbs (quartiles 161, 231; range 70-451) and was not different between groups. CC depth increased significantly with RTAVF use (Pre-feedback = 1.77, 95% confidence interval [CI]:1.71-1.83 in.; Post-feedback = 2.10, CI: 2.04-2.15 in.; p<0.001). CC depth did not vary significantly by patient gender or age (p>0.4). Multivariate linear regression (r 2 =0.23, p<0.001 for model) revealed a significant increase in CC depth with estimated weight in both periods (0.07in/50lbs, p<0.001) after controlling for the presence of RTAVF. RTAVF was not an effect-modifier of the relationship between estimated weight and CC depth (p-value for interaction term=0.4). Conclusion: Although not specifically recommended in the 2010 AHA Guidelines for adults, rescuers may instinctively and/or intentionally adjust CC depth according to patient size. In this setting, weight/CC depth adjustments occurred both without and with real-time feedback. Follow-up studies are needed to determine the potential effect of size-adjusted CC depth on patient outcome.