If your pet has stopped breathing, check to see if the throat and mouth are clear of foreign objects. Be careful about placing your fingers inside the mouth! An unresponsive cat may bite on instinct.
If the airway is blocked, do the following: Lay your pet down on his side.
Gently tilt the head slightly back to extend the neck and head, but be very careful: Do not overextend the neck in cases of neck trauma!
Pull the tongue out of your pet's mouth.
Carefully use your fingers to sweep for any foreign material or vomit from the mouth.
If necessary, perform the Heimlich maneuver. For detailed information on the procedure, please see the article Heimlich for Your Cat
If your cat is breathing, allow him to assume the position most comfortable for him. If not, make sure the airway is open and begin rescue breathing. Again, remember that even an unresponsive cat may bite on instinct.
Make sure the neck is straight without overextending.
Close the mouth and lips by placing your hand around the lips and holding the muzzle closed.
Place your mouth over the cat's mouth and nose. Your mouth will form a seal.
Exhale forcefully. Give four or five breaths quickly.
Check to see if breathing has resumed normally. If breathing hasn't begun or is shallow, begin rescue breathing again.
Give 20 to 30 breaths per minute.
Now check for a heartbeat. If no heartbeat is detected, begin cardiac compressions with rescue breathing.
Cardiopulmonary Resuscitation (CPR).
Here is another video demonstrating CPR. Click on the arrow to play
For most animals, chest compressions are best done with the animal lying on his side on a hard surface.
Make sure your pet is on a hard surface. The sidewalk or ground should work. If the animal is on a soft area, chest compressions will not be as effective.
Place your palm or fingertips over the ribs at the point where the raised elbow meets the chest.
Kneel down next to the animal with the chest near you.
Compress the chest about 1 inch at a rate of twice per second. (Small animals have higher heart rates than people so compressions need to be more rapid.)
Begin 5 compressions for each breath. After 1 minute, stop and check for a heartbeat. Continue if the beat has not resumed.
Perform CPR until you have reached a veterinary hospital. After 20 minutes, however, the chances of reviving an animal are extremely unlikely.