Resuscitation Outcomes Consortium (ROC) PRIMED cardiac arrest trial methods part 1: rationale and methodology for the impedance threshold device (ITD) protocol.

Aim: The primary aim of this study is to compare survival to hospital discharge with a modified Rankin score (MRS)< or =3 between standard cardiopulmonary resuscitation (CPR) plus an active impedance threshold device (ITD) versus standard CPR plus a sham ITD in patients with out-of-hospital cardiac arrest. Secondary aims are to compare functional status and depression at discharge and at 3 and 6 months post-discharge in survivors.

Design: Prospective, double-blind, randomized, controlled, clinical trial.

Population: Patients with non-traumatic out-of-hospital cardiac arrest treated by emergency medical services (EMS) providers.

Setting: EMS systems participating in the Resuscitation Outcomes Consortium.

Sample Size: Based on a one-sided significance level of 0.025, power=0.90, a survival with MRS< or =3 to discharge rate of 5.33% with standard CPR and sham ITD, and two interim analyses, a maximum of 14,742 evaluable patients are needed to detect a 6.69% survival with MRS< or =3 to discharge with standard CPR and active ITD (1.36% absolute survival difference).

Conclusion: If the ITD demonstrates the hypothesized improvement in survival, it is estimated that 2700 deaths from cardiac arrest per year would be averted in North America alone.