Realtime detection of spontaneous circulation in humans during cardiopulmonary resuscitation using a continuous hands-free carotid Doppler: a pilot study

Background: The resuscitation society calls for precision-guided cardiopulmonary resuscitation (CPR), as current methods are inaccurate and time-consuming. RescueDoppler, a novel hands-free Doppler ultrasound system, continuously measures carotid blood flow during CPR. This pilot study assessed its performance, safety, and ability to detect chest compression-generated blood flow, spontaneous circulation, and return of spontaneous circulation (ROSC). Method: We investigated RescueDoppler in adult cardiac arrest patients at two centres, in-hospital (IHCA) and out-of-hospital (OHCA). The cardiac arrest team placed the RescueDoppler probe over the left common carotid artery with a self-adhesive patch, collecting blinded data during CPR. Data were later interpreted and time-synchronized with defibrillator data using custom MATLAB® software. Results: RescueDoppler was used in 26 IHCA and 36 OHCA patients from October 2023 to September 2024. Carotid blood flow curves were analyzed in 36 patients and synchronized with defibrillator data in 30. The RescueDoppler identified blood flow velocities generated by chest compressions and detected spontaneous circulation during rhythm checks. ROSC was defined by the presence of systolic and diastolic blood flow. No adverse events were reported but there were 22 device deficiencies mostly related to the self-adhesive patch and connecting cable. The system is user-friendly and requires minimal training. Conclusion: Real-time detection of blood flow in the carotid artery with hands-free Doppler ultrasound during CPR is safe and feasible, although the fastening patch and host unit need optimization. The RescueDoppler system detects spontaneous circulation and ROSC during rhythm checks and ongoing chest compressions. Further research is required to confirm clinical relevance.