Actions Taken by Bystanders During Sudden Cardiac Arrest: Analysis of Emergency Medical Service Documentation in Poland.

: Sudden cardiac arrest (SCA) is a severe medical condition involving the cessation of the heart's mechanical activity. Following the chain of survival, which includes early recognition and calling for help, early initiation of cardiopulmonary resuscitation (CPR), early defibrillation, and post-resuscitation care, offers the greatest chances of saving a person who has experienced SCA. The aim of this study was to analyze cases of out-of-hospital cardiac arrest (OHCA) and assess the actions taken by bystanders. : The input for analysis consisted of 49,649 dispatch records from the emergency medical team (EMT) at the Voivodeship Emergency Medical Station in Bialystok in 2018-2019. : Among the patients where bystanders performed CPR, the return of spontaneous circulation (ROSC) occurred in 30.53% of cases, whereas in the cases where the bystander did not perform CPR, ROSC occurred in 2.35% of cases. When cardiac arrest rhythm was ventricular fibrillation (VF) or pulseless ventricular tachycardia (pVT), ROSC occurred in 58.62% of cases, while there was asystole or pulseless electrical activity (PEA) present, ROSC occurred in 26.56% of cases. In patients who experienced OHCA in a VF/pVT rhythm and who underwent intubation, ROSC occurred in 58.73% of cases, whereas in patients who underwent alternative procedures for airway management, ROSC occurred in 83.33% of cases. : The most significant factor influencing the occurrence of ROSC in patients is CPR initiation by bystanders. The presence of a rhythm that requires defibrillation increases the likelihood of achieving ROSC in the patient. Alternative methods for airway management appear to be more beneficial in VF/pVT rhythms.