1. Pre-shock cardiopulmonary resuscitation might benefit the survival of out-of-hospital cardiac patients with ventricular fibrillation / ventricular tachycardia in a post-hoc analysis of a prehospital trial conducted in Europe (L.Wik,2002). However, it's effectiveness in the Asian countries, where most firstly recorded rhythm in out-of-hospital cardiac arrests patients were asystole/pulseless electric activity rather than ventricular fibrillation / ventricular tachycardia, were not explored yet.
2. This trial was designed to exam if pre-shock cardiopulmonary resuscitation by emergency medical technicians improves the outcome of all out-of-hospital cardiac arrest patients in an Asian metropolitan city.

1. Different from data from the Western countries, non-shockable rhythm (Asystole/pulseless electric activity) was responsible for most out-of-hospital cardiac arrest patients(80%~90%) in metropolitan Taipei.
2. Response time in Taipei emergency medical service was longer than 5 minutes.
3. Bystander cardiopulmonary resuscitation rate were relatively low in Taipei.
4. Cardiopulmonary resuscitation is the only known method to save out-of-hospital cardiac arrest patients with asystole/pulseless electric activity. For those suffered from ventricular fibrillation/ ventricular tachycardia,previous studies revealed pre-shock cardiopulmonary resuscitation may have the potential to improve the outcome.
5. Study hypothesis: Compared with current standard resuscitative sequence (basic life support protocol in Guideline 2005), longer pre-shock cardiopulmonary resuscitation provided to all out-of-hospital cardiac arrest patients in Taipei may improve the outcome of them.

Inclusion Criteria:

• Patients with out-of-hospital cardiac arrest

Exclusion Criteria:

• Trauma
• Age < 18y/o
• Airway obstruction
• Submersion
• Sign of obvious death
• existing do not resuscitate (DNAR) order
• family refusal
• preceding CPR by BLS teams for longer than 2 minutes.