Successful resuscitation after cardiac arrest requires restoring normal electrical activity in the heart and adequate blood flow to vital organs. Presently, only information about the heart´s electrical activity (electrocardiogram [ECG]), but not blood flow is available during resuscitation.

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Cardiopulmonary resuscitation (CPR) consists of chest compressions and artificial ventilation to maintain circulatory flow and oxygenation. If the cardiac rhythm is shockable, an electrical current is delivered to the heart by a defibrillator. Automated external defibrillators can diagnose life-threatening cardiac arrhythmias by interpreting the ECG, enabling untrained laypersons or bystanders to use them successfully. Although defibrillators can detect, treat, and give feedback on the reappearance of normal cardiac rhythm, crucial feedback regarding the successful restoration of blood flow (return of spontaneous circulation [ROSC]) is missing. Shorter time to ROSC is associated with better long-term survival.

 

Non-shockable rhythms (pulseless electrical activity [PEA] and asystole) are increasingly encountered. Studies show that as many as 60% of the subjects with suspected PEA and 10-35% of those with suspected asystole had mechanical cardiac activity (Deakin 2000, Gaspariet al. 2016). The use of cardiac ultrasound altered the management in 78% of the cases and was associated with increased survival. The European Resuscitation Council guidelines recommend a maximum of 10 seconds interruption to check the pulse during CPR (Perkins et al. 2021). However, cardiac ultrasound cannot be performed during chest compressions and the use is therefore limited (Zengin et al. 2018).

 

Doppler measurements of blood flow of the carotid artery can be performed without interrupting resuscitation, making it an attractive alternative for haemodynamically guided and personalised treatment. An ultrasound Doppler-system has been developed that continuously measures blood flow in the carotid artery