High quality chest compressions are the cornerstone of effective cardiopulmonary resuscitation (CPR). There is no available method of real time noninvasive hemodynamic measurement and feedback to inform rescuers of the efficacy of compressions. Ultrasound-based measures of blood flow may provide immediate, noninvasive hemodynamic information. Our objective was to determine the feasibility and safety of using ultrasound to measure blood flow on patients with cardiac arrest.