An impedance threshold device did not improve carotid blood flow in a porcine model of prolonged cardiac arrest

BACKGROUND: An impedance threshold device (ITD) was developed to increase venous return to the heart and therefore increase cardiac output and organ blood flow during cardiopulmonary rescue (CPR). Basic CPR aims to maintain coronary and cerebral blood flow at the minimum level necessary for survival. The present study compared the effects of an ITD on cerebral blood flow assessed as blood flow in both carotid arteries to the blood flow of a control group during prolonged CPR. METHODS: Fourteen anaesthetized pigs were monitored during 60 min of CPR after induced ventricular fibrillation. The primary outcome was blood flow in both carotid arteries, and the secondary outcomes were blood pressure, acid–base parameters, plasma potassium, and plasma lactate. The pigs were randomized to mechanical compressions and ventilation with an ITD added to the ventilation or to a control group treated only with mechanical compressions and ventilation. The time course for the parameters was tested using analysis of variance. RESULTS: The cumulative carotid blood flow in the ITD group decreased from 64 to 42 ml/min, and it decreased from 69 to 51 ml/min in the control group during 60 min of CPR. The difference was not significant. The secondary outcome measures were also not significantly different. CONCLUSIONS: This study did not show any beneficial effect of an ITD on carotid blood flow.