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

Abstract

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.

Figure 1. Description of Impedance Threshold Device

The ITD (Figure 1a) is designed to be inserted easily between a facemask or advanced airway (e.g., ET tube, Combitube, or LMA) and a manual resuscitation bag (Figure 1b). In addition to an advanced airway, the ITD can be attached to any pediatric or adult facemask (Figure 1c) taking care to provide a continuously tight seal around the nose and mouth during compressions and ventilations (Figure 1d). As such, the device can be easily used by rescuers trained at both basic and advanced life support levels and moved quickly from any facemask once the patient is intubated. The ITD contains ventilation timing assist lights, which flash at 10/minute at 1 second/flash to help promote the proper ventilation rate and duration for the patient with an advanced airway. For this trial, ITDs will be specially manufactured in an opaque color so that active (functional) and sham (non-functional placebo) devices will appear externally identical.

Figure 1. Description of Impedance Threshold Device

The ITD (Figure 1a) is designed to be inserted easily between a facemask or advanced airway (e.g., ET tube, Combitube, or LMA) and a manual resuscitation bag (Figure 1b). In addition to an advanced airway, the ITD can be attached to any pediatric or adult facemask (Figure 1c) taking care to provide a continuously tight seal around the nose and mouth during compressions and ventilations (Figure 1d). As such, the device can be easily used by rescuers trained at both basic and advanced life support levels and moved quickly from any facemask once the patient is intubated. The ITD contains ventilation timing assist lights, which flash at 10/minute at 1 second/flash to help promote the proper ventilation rate and duration for the patient with an advanced airway. For this trial, ITDs will be specially manufactured in an opaque color so that active (functional) and sham (non-functional placebo) devices will appear externally identical.

Figure 2. Outcomes for Patients Presenting with PEA

ROSC=Return of Spontaneous Circulation; 1 Hr=1-Hour Survival; ICU=ICU Admission Rate; 24 Hr=24 Hour Survival

Figure 3. Femoral Arterial Blood Pressure in Humans During CPR with ITD Use