The Analysis of Ilan¡¦s Out-of-Hospital Cardiac Arrest (OHCA) Patients Abstract The study uses Ilan¡¦s out-of-hospital cardiac arrest (OHCA) patients as the research object to understand the variable backgrounds of OHCA patients how they are affected by first aid factors between the period of pre-hospital and post-hospital admission. The study also discusses whether there is a correlation between first aid factors and first aid prognosis among those OHCA patients during pre-hospital and post-hospital admission periods. The study is retrospective and based on the Utstein style format. It collects 284 out-of-hospital cardiac arrest (OHCA) patient cases with trauma and non-trauma (282 effective samples) in an example of a regional teaching hospital in Ilan from 2007 to 2009. It uses descriptive statistics, independent sample t test, and Chi-Square test as the statistical analysis to obtain the following conclusions: 1. There are 282 effective sample patients in the study. There are 57 patients ( 20.2 %) who were return of spontaneous circulation (ROSC) after cardiac arrest approximately 14.77 minutes on average. There are 33 patients (11.7 % ) who survived to be hospitalized for 15.36 days on average, and there are 6 patients ( 2.1 % ) who were discharged from the hospital. 2. Internal medicine disease is the major causative factor of out-of-hospital cardiac arrest. Among those internal medicine disease cases, the history showed hypertension, diabetes mellitus, and heart diseases are the main causes of out-of-hospital cardiac arrest. Patients who are older than 65 years old are the main age groups, accounting for 67.7% of these cases. 3. The pre-hospital admission factors which affect the prognosis after the Emergency Department (ED) are the place of the accident, whether there are witnesses, scene process time , total reaction time , whether automatic external defibrillation was used, and whether people at the scene used CPR. 4. The post-hospital admission factors which affect the prognosis after the ED are initial cardiac rhythm, body temperature, pupil size , dose of epinephrine, whether defibrillation was used, the time of applying emergency first-aid, and medical expense. 5. The percentages of return of spontaneous circulation and survival rates in the study are lower than those of past studies of Taipei City and National Taiwan University Hospital. The possible factors are probably related to differences between rural and urban areas in the quality of emergency medical service systems (EMSS), and healthcare training. 6. From now on, in addition to improving the first-aid continuous monitoring system, we should also enhance EMT related training, and actively educate people to understand and learn CPR, so that comprehensive first-aid systems are available everywhere to effectively increase the success rate of first-aid. Keywords¡GOut-of-hospital cardiac arrest (OHCA), Cardiopulmonary resuscitation