The success rate of CPR varies greatly and depends mainly on the time from the patient's cardiac arrest to the start of resuscitation and the professionalism of the CPR technique. If cardiac resuscitation is performed promptly and professionally, the success rate is generally greater than 90%. But if resuscitation is not timely, the success rate may be 0.

If a professional doctor provides effective cardiopulmonary resuscitation within 1 minute of the patient's cardiac arrest, the success rate is basically over 90%. If cardiopulmonary resuscitation is performed within 4 minutes of the patient's cardiac arrest, the success rate is about 60%. For cardiopulmonary resuscitation performed within 6 minutes of cardiac arrest, the success rate is approximately 40%. However, if CPR is performed after 6 minutes of cardiac arrest, the success rate may drop to 20%. If the interval from cardiac arrest to the start of resuscitation exceeds 10 minutes, the success rate may be almost zero.

In addition, patient factors may also affect the success rate of cardiopulmonary resuscitation. For example, obesity, neck stiffness, chest wall deformation, severe craniocerebral diseases, shock, etc. may affect the effectiveness of cardiopulmonary resuscitation.

The latest research has found that compared with traditional static chest compressions, dynamic chest compressions can provide better blood perfusion and oxygen delivery, significantly improving the efficiency and success rate of cardiopulmonary resuscitation. At the same time, appropriate chest compression frequency and depth are also crucial to the effectiveness of cardiopulmonary resuscitation.

Please note that while CPR is an emergency measure, it is not a substitute for professional medical attention. Therefore, when someone is found to have suffered a cardiac arrest, the emergency number should be called as soon as possible and cardiopulmonary resuscitation should be performed under the guidance of professionals to maximize the patient's survival rate.