RescueDoppler is an innovative, hands-free Doppler system designed for continuous monitoring of blood flow in the carotid artery, distinguishing between the presence and absence of a pulse. It is non-invasive, user-independent, and does not require specialized ultrasound expertise. The primary goal of this study is to assess the feasibility and clinical utility of RescueDoppler for monitoring carotid artery blood flow in patients experiencing sudden cardiac arrest.

The multi-center study will be performed both pre-hospital and in-hospital.

When treating sudden cardiac arrest (SCA), manual pulse checks are currently the standard method to detect blood flow, but this approach has significant limitations. It's neither quick nor consistently reliable (Germanoska et al. 2018, Eberle et al. 1996). Studies show that 45% of healthcare workers struggle to accurately detect a central pulse during cardiac arrest (Moule 2000, Nakagawa et al. 2010). If blood flow has already been restored, continuing chest compressions could cause more harm than good. This highlights the need for an easy-to-use tool to assess blood flow during cardiopulmonary resuscitation (CPR).

Cardiac arrest is responsible for 7-8 million deaths per year and ranks as the third leading cause of death in industrialized countries. Despite advances in resuscitation techniques and post-resuscitation care, the survival rate following cardiac arrest remains low-around 10% or less. Survival rates drop sharply with every minute that passes without advanced cardiac life support (OECD 2017). Successful resuscitation after cardiac arrest requires restoring the heart's normal electrical activity and ensuring adequate blood flow to vital organs. Currently, only the heart's electrical activity (via electrocardiogram [ECG]) is monitored during resuscitation, with no information available on blood flow.

CPR involves chest compressions and artificial ventilation to maintain circulation and oxygenation. In cases of shockable rhythms, a defibrillator delivers an electrical shock to the heart. Automated external defibrillators (AEDs) are capable of diagnosing life-threatening arrhythmias, enabling even untrained bystanders to use them effectively. However, while defibrillators can detect, treat, and confirm the return of normal heart rhythm, they don't provide feedback on whether blood flow has been successfully restored (return of spontaneous circulation [ROSC]). A quicker ROSC is linked to better long-term survival outcomes.

Non-shockable rhythms, such as pulseless electrical activity (PEA) and asystole, are increasingly common. Research shows that up to 60% of patients with suspected PEA and 10-35% of those with suspected asystole still have mechanical heart activity (Deakin 2000, Gaspari et al. 2016). In these cases, using cardiac ultrasound has changed patient management in 78% of cases and has been linked to increased survival. European Resuscitation Council guidelines recommend limiting interruptions during CPR to 10 seconds to check for a pulse (Perkins et al. 2021). However, cardiac ultrasound cannot be performed during chest compressions, which limits its usefulness (Zengin et al. 2018).

Doppler ultrasound measurements of carotid artery blood flow offer a promising alternative for guiding CPR without interrupting resuscitation. The RescueDoppler system, a newly developed ultrasound Doppler tool, continuously monitors blood flow in the carotid artery during CPR.

The RescueDoppler device uses a small ultrasound probe that is quickly attached over the carotid artery using an innovative patch. This probe continuously monitors blood flow to the brain, alerting first responders if chest compressions are ineffective or if the patient has achieved ROSC (when the heart starts beating again).

RescueDoppler probe is placed on the left side of the neck during cardiac arrest to monitor blood flow from the carotid artery during CPR. The medical team won't see the signals during this phase.

The multi-centre study will involve 300 patients experiencing in-hospital or pre-hospital cardiac arrests. Five hospitals in Norway will participate in the in-hospital portion, with recruitment expected to take one year. The pre-hospital study will include two hospitals in Norway, also with a one-year recruitment period. The goal is to gather crucial medical and physiological data on blood circulation during cardiac arrest, beyond initial feasibility.

Inclusion Criteria:

Male or female, aged 18 years or older. Subjects experiencing a sudden cardiac arrest, either pre-hospital or in-hospital. Sudden cardiac arrest is defined as the abrupt loss of heart function, breathing, and consciousness.

Exclusion Criteria:

Subjects where resuscitation is not continued after the initial application of RescueDoppler or resuscitation efforts are halted due to a do-not-resuscitate order.

Subjects deemed unable to comply with the study requirements as determined by the Investigator.

Subjects with extensive trauma injuries that prevent proper attachment of the RescueDoppler patch.

ECG and carotid blood flow velocity will be shared if required.

Starting 6 months after the publication of results and ending 2 years later.

A data sharing agreement must be signed and submitted to the steering committee, which includes the Principal Investigator (PI) and Site Investigators (SI) from all participating hospitals in the study.