In medicine, resuscitation is the process by which medical personnel attempt to keep a person alive.
The first rule of resuscitation are the ABCs:
Airway check the patient's airway to see if there is any obstruction and clear it if there is any visible.
Breathing check to see if the patient is breathing or not
Circulation check to see if the patient has any pulse or not
If necessary, start CPR in order to get air into the patient's lungs and to get the patient's blood circulating.
Remember: "Air goes in and out, Blood goes round and round. Any deviation from this is not good"