Abstract 9: The Effect of CPR Quality: A Potential Confounder of CPR Clinical Trials

Abstract

Background: The Resuscitation Outcomes Consortium (ROC)-PRIMED clinical trial evaluated an active inspiratory impedance threshold device (ITD) during standard CPR (intended to improve CPR hemodynamics) on survival to hospital discharge with favorable neurological outcome (modified Rankin Score [mRS] ≤3) in adults with out-of-hospital cardiac arrest and found no benefit. CPR quality varied widely in the trial. We hypothesized the quality of CPR provided would have a significant interaction with the intervention. Methods: We used the NIH public access ROC-PRIMED database. A large proportion of patients had CPR quality parameters (compression rate, depth and fraction) collected. “Quality CPR” was considered delivered if simultaneous provision of the following occurred: a compression rate of 80-120, depth of 4-6 cm and fraction of >50%, consistent with American Heart Association guidelines at the time of the study. We assessed for interaction between each individual parameter of “quality CPR” and their combinations with the active and sham ITD for survival with mRS≤3. Interaction was considered to be significant when p<0.1. Results: Overall, a total of 848 and 827 patients in the active and sham ITD groups had documented “quality CPR” performed. Including all presenting rhythms, use of an active ITD increased survival to hospital discharge with MRS ≤3 compared to sham (61/848 [7.2%] versus 34/827 [4.1%], respectively; p=0.006, OR: 1.8, 95% CI: 1.17, 2.78). There was significant interaction between the active and sham ITD and compression rate, depth and fraction as well as their combinations. (Table 1) Conclusion: When “quality CPR” was delivered, the active ITD improved survival with mRS≤3 by an absolute 3.1%. CPR quality parameters showed significant interaction with the active and sham ITD. The quality of CPR delivered is a potential confounder of CPR clinical trials and should be appropriately controlled.