[Purpose] Our hospital is the only emergency and critical care center in the region serving a population of 420,000. The number of emergency transports is 7,000-7,500 annually, and the number of cardiopulmonary arrest cases is 250-300. Early intervention is necessary to return of spontaneous circulation in patients with cardiopulmonary arrest. Herein, we analyzed the transition of treatment interventions by emergency medical service paramedics annually and examined pre-hospital interventions for return of spontaneous circulation before arriving at the hospital. [Methods] We included 2,010 adults with out-of-hospital cardiopulmonary arrest between 2011 and 2018. We conducted an annual review on the following aspects: number of cases per year, rate of return of spontaneous circulation before arrival at hospital, rate of bystander witness, rate of bystander cardiopulmonary resuscitation, rate of cardioversion by paramedics, rate of securing venous access by paramedics, rate of adrenaline administration by paramedics, and rate of advanced airway management by paramedics. [Results] The number of cases remained approximately 250, and the rate of return of spontaneous circulation before arrival at the hospital increased. As for treatment by a paramedic, the cardioversion rate remained unchanged at 10-15%, and the venous access rate and adrenaline administration rate increased. There was no change in the rate of advanced airway management, and it remained at approximately 10%. [Conclusion] To return of spontaneous circulation before arriving at the hospital, it was considered for the paramedic to perform venous access and administer adrenaline.