Metrics of mechanical chest compression device use in out-of-hospital cardiac arrest

Objective: The quality of cardiopulmonary resuscitation (CPR) affects outcomes from cardiac arrest, yet manual CPR is difficult to administer. Although mechanical CPR (mCPR) devices offer high quality CPR, only limited data describe their deployment, their interaction with standard manual CPR (sCPR), and the consequent effects on chest compression continuity and patient outcomes. We sought to describe the interaction between sCPR and mCPR and the impact of the sCPR-mCPR transition upon outcomes in adult out-of-hospital cardiac arrest (OHCA). Methods: We analyzed all adult ventricular fibrillation OHCA treated by the Anchorage Fire Department (AFD) during calendar year 2016. AFD protocols include the immediate initiation of sCPR upon rescuer arrival and transition to mCPR, guided by patient status. We compared CPR timing, performance, and outcomes between those receiving sCPR only and those receiving sCPR transitioning to mCPR (sCPR + mCPR). Results: All 19 sCPR-only patients achieved return of spontaneous circulation (ROSC) after a median of 3.3 (interquartile range 2.2–5.1) minutes. Among 30 patients remaining pulseless after sCPR (median 6.9 [5.3–11.0] minutes), transition to mCPR occurred with a median chest compression interruption of 7 (5–13) seconds. Twenty-one of 30 sCPR + mCPR patients achieved ROSC after a median of 11.2 (5.7–23.8) additional minutes of mCPR. Survival differed between groups: sCPR only 14/19 (74%) versus sCPR + mCPR 13/30 (43%), P = 0.045. Conclusion: In this series, transition to mCPR occurred in patients unresponsive to initial sCPR with only brief interruptions in chest compressions. Assessment of mCPR must consider the interactions with sCPR.