The purpose of this study is to find out if a Doppler ultrasound patch placed on the neck can accurately and quickly detect when a cardiac arrest patient's heart starts beating again (return of spontaneous circulation, or ROSC) during resuscitation in the emergency department. The study compares the ultrasound readings to data from an arterial line, which is considered the most reliable way to check for a pulse. The main question the study is trying to answer is whether using Doppler ultrasound is better than the traditional method of feeling for a pulse, which can be unreliable, especially in stressful situations. Secondarily, this study aims to assess blood flow through the carotid artery from chest compressions during resuscitative events to determine overall effectiveness. This research hopes to show that Doppler ultrasound can help medical teams recognize when a patient's heart has restarted more accurately and quickly, leading to better care during cardiac arrest.