A Trial of an Impedance Threshold Device in Out-of-Hospital Cardiac Arrest

Study Questions:

What is the effect of standard cardiopulmonary resuscitation (CPR) with the use of an active impedance threshold device (ITD), as compared with standard CPR with the use of a sham ITD on rates of hospital discharge with satisfactory function for adults with out-of-hospital cardiac arrest (OHCA)?


The investigators compared the use of an active ITD with that of a sham ITD in patients with OHCA who underwent standard CPR at 10 sites in the United States and Canada. Patients, investigators, study coordinators, and all care providers were unaware of the treatment assignments. The primary outcome was survival to hospital discharge with satisfactory function (i.e., a score of ≤3 on the modified Rankin scale, which ranges from 0 to 6, with higher scores indicating greater disability). Between-group differences in the rates of survival to discharge with satisfactory functional status, adjusted for baseline characteristics, were estimated with the use of a multiple linear regression model with bootstrap standard errors to allow for the binary nature of the outcome.


Of 8,718 patients included in the analysis, 4,345 were randomly assigned to treatment with a sham ITD and 4,373 to treatment with an active device. A total of 260 patients (6.0%) in the sham-ITD group and 254 patients (5.8%) in the active-ITD group met the primary outcome (risk difference adjusted for sequential monitoring, −0.1 percentage points; 95% confidence interval, −1.1 to 0.8; p = 0.71). There were also no significant differences in the secondary outcomes, including rates of return of spontaneous circulation on arrival at the emergency department, survival to hospital admission, and survival to hospital discharge.


The authors concluded that use of the ITD did not significantly improve survival with satisfactory function among patients with OHCA receiving standard CPR.


This large effectiveness trial did not confirm a survival advantage with the use of an active ITD during standard CPR in patients with nontraumatic OHCA. Based on this routine, use of an ITD during resuscitation is not recommended. Additional studies that incorporate the measurement of chest recoil, hemodynamic data, intrathoracic pressure, and ventilation rate during ITD may help provide insight on potential benefits of ITD for OHCA.

Clinical Topics: Arrhythmias and Clinical EP, Implantable Devices, SCD/Ventricular Arrhythmias

Keywords: Out-of-Hospital Cardiac Arrest, Electric Impedance, Cardiopulmonary Resuscitation, Canada, Emergency Service, Hospital, Heart Arrest, Confidence Intervals, Hemodynamics, United States

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