The heart is a large muscle with four internal chambers, responsible for circulating blood throughout the body. The blood carries oxygen to the tissues and carries away waste products from the organs. Most of the waste products are filtered out of the blood by the liver and kidneys, but the carbon dioxide in the blood must be expelled by the lungs.
Blood enters the heart from the superior vena cava, a large vein that collects blood from the other veins of the body in much the same way a large river catches water from numerous smaller tributaries and dumps it into the ocean. The chamber of the heart that receives the blood is called the right atrium. The blood is pushed through a one-way valve known as the right atrioventricular valve into the right ventricle. When the heart muscle contracts, the blood is pumped through the pulmonary artery to the lungs, where the carbon dioxide is removed and the blood is enriched with oxygen. The blood leaves the lungs through the pulmonary vein and enters the left atrium, then flows through the left atrioventricular valve into the left ventricle. Contraction of the heart muscle sends the blood out through the aorta to the body.
Any disease or injury that causes damage to the heart or lungs means that the pump described above stops working efficiently. When disease affects the heart, the changes may be so gradual you might not notice that your dog is ill until the damage is quite severe. One day your dog's heart may simply stop beating, but at that point you would likely not have much success with CPR
However, when an injury to the heart comes on suddenly, CPR will keep your dog alive until professional help can be obtained. Some of the situations which may require CPR and / or artificial respiration include:
When the dog's heart stops beating, he or she will soon stop breathing. And conversely, when the dog stops breathing, the heart will soon stop beating, so it doesn't really matter which happens first. You will know your dog needs CPR if you find the animal unconscious and are unable to arouse him or her.
The steps of CPR and artificial respiration can be remember with the letters ABC. A stands for airway, B for breathing, and C for circulation.
First, check to see if the dog is breathing has an open airway. Place your hand on the chest to see if it is moving, and place your cheek near the dog's nose and mouth to see if there is air movement. With the dog lying on his or her side, stretch the neck out to open the airway, then try to force your breath into the dog's lungs.
The dog's mouth must be held closed, and you will be breathing into the dog's nostrils. Cup your hands around the dog's muzzle, pressing only hard enough to keep the mouth closed. Blow air into the nostrils using four quick breaths. For small dogs, use short, shallow breaths. For larger dogs, use longer, deeper breaths.
If the air goes in, you will see the dog's chest rise. If it doesn't, try repositioning the neck to make sure the airway is open and give two more rescue breaths. If the air still does not go in, there may be an obstruction in the airway. Very carefully, open the dog's mouth and look inside to see if you can see an obvious obstruction. Try to manually pull out the obstruction if possible.
If you can't manually remove the obstruction, or if you cannot see any obstruction, you will attempt the Heimlich maneuver. Turn the dog upside down, placing his or her back against your chest. Make a fist with one hand and place the thumb side of the hand just below the rib cage of the dog. Cover your fist with your other hand and give five hard, sharp upward thrusts into the dog's abdomen.
***Warning*** Even an unconscious dog can bite in a reflexive movement, so use extreme caution while working around the dog's mouth.
Do not proceed with CPR until you have established a clear airway. It does no good to get the blood circulating through the body if there is no oxygen in it. Continue trying to clear obstructions until you are sure air is moving into the lungs when you give the rescue breaths. Your proof will be the rise and fall of the dog's chest. Continue giving two rescue breaths every three to six seconds until the dog begins breathing on his or her own.
Once you are certain that air is entering the lungs, in between rescue breaths you will check to see if you also need to be doing cardiac massage. Feel the inside of the dog's thigh, just above the knee to check for a pulse. If you cannot feel one there, place your hand over the dog's chest where the elbow touches the middle of the chest. If you cannot feel a heartbeat, you will need to begin cardiac massage.
If there are two people present, one will do the cardiac massage and one will do the rescue breathing. If you are the only one who knows how to do CPR, you will alternate between the two tasks.
To determine where to place your hands, count down from the top rib to the third rib. Your dog should be lying on his or her right side, so you will be working on the left side of the chest. For small dogs, use one hand or even just your thumb slightly below the third rib. For large dogs, place one hand between the third and sixth ribs and cover it with the other hand. Push down fifteen times over the course of ten seconds.
After each set of fifteen compressions, either you or the other person should give one rescue breath. Then squeeze the dog's lower abdomen between your hands to help the blood to circulate back to the heart. Continue this pattern of fifteen compressions, one rescue breath, and one abdominal squeeze until the dog regains consciousness or until you can no longer continue due to physical exhaustion. If someone is present to drive you to the emergency clinic or veterinary office, continue CPR while you are in transit.
Once your dog has started breathing on his or her own, contact your veterinarian or emergency clinic right away. Your dog will need immediate professional car to resolve the underlying problem that created the need for CPR.
There are a couple of things to keep in mind about CPR. First and foremost is the fact that if a dog needs CPR, he or she is already technically dead. Anything you can do to try to help the dog will be better than the alternative.
There is the potential for you to break the dog's ribs and / or puncture a lung while you are doing CPR, which is another reason you will need to take the dog for medical follow-up.
Never practice CPR techniques on a dog who is not in trouble. Using CPR on a dog who is breathing and has a heartbeat can be fatal. Check with your local chapter of the Red Cross or with your local kennel club to see if they give pet first aid classes. If so, these classes may include CPR practice on a mannequin dog.
There are no readily available statistics on the success rate of canine CPR, but in humans CPR done outside of a hospital has a success rate of only about 7%. Don't be upset with yourself if your efforts aren't successful. Remember that you tried your best, but that your dog was beyond saving.
Video from Pets America demonstrating proper CPR technique