A blinded, randomized controlled evaluation of an impedance threshold device during cardiopulmonary resuscitation in swine.

BACKGROUND

An impedance threshold device (ITD) has been designed to enhance circulation during CPR. A recent study suggests that the ITD does not improve hemodynamics and that it may actually worsen outcomes. We sought to independently assess the effect of the ITD on coronary perfusion pressure (CPP) and passive ventilation (PaCO(2) and PaO(2)) during standard CPR (S-CPR), and its impact on the return of spontaneous circulation (ROSC) and short-term survival in a blinded fashion.

METHODS

Thirty male swine were instrumented under anesthesia. Ventricular fibrillation (VF) was electrically induced. CPP was continuously recorded. After 8 min of untreated VF, baseline characteristics were documented and S-CPR initiated. After 3 cycles of S-CPR, an ABG was drawn and drugs were given. Following 6 additional cycles of S-CPR, an ABG was drawn and the first rescue shock was delivered. Group comparisons were assessed using descriptive statistics. Proportions with 95% confidence intervals were calculated for outcomes.

RESULTS

Baseline characteristics between the two groups were the same. The mean CPP in the ITD group was 51.2 mmHg [95% CI: 37.7, 64.7] compared to 50.2 mmHg [95% CI: 37.0, 63.4] in the sham group. The PaCO(2) and PaO(2) were 68 Torr [95% CI: 55.7, 79.5] and 103 Torr [95% CI: 76, 129] in the ITD group and 59 Torr [95% CI: 49.1, 68.5] and 137 Torr [95% CI: 83, 191] in the sham group. The rate of ROSC was 14/15 in both groups and 13 animals in each groups survived.

CONCLUSIONS

In this independent blinded study, use of the active ITD had no significant impact on CPP, passive ventilation, or outcomes compared to the sham device.