Choking occurs when a foreign object lodges in the throat or windpipe, blocking the flow of air. In adults, a piece of food often is the culprit. Young children often swallow small objects. Because choking cuts off oxygen to the brain, give first aid as quickly as possible.

The universal sign for choking is hands clutched to the throat. If the person doesn't give the signal, look for these indications:

• Inability to talk
• Difficulty breathing or noisy breathing
• Squeaky sounds when trying to breathe
• Cough, which may either be weak or forceful
• Skin, lips and nails turning blue or dusky
• Skin that is flushed, then turns pale or bluish in color
• Loss of consciousness

If the person is able to cough forcefully, the person should keep coughing. If the person is choking and can't talk, cry or laugh forcefully, the American Red Cross recommends a "five-and-five" approach to delivering first aid:

• Give 5 back blows. Stand to the side and just behind a choking adult. For a child, kneel down behind. Place one arm across the person's chest for support. Bend the person over at the waist so that the upper body is parallel with the ground. Deliver five separate back blows between the person's shoulder blades with the heel of your hand.
• Give 5 abdominal thrusts. Perform five abdominal thrusts (also known as the Heimlich maneuver).
• Alternate between 5 blows and 5 thrusts until the blockage is dislodged.

The American Heart Association doesn't teach the back blow technique, only the abdominal thrust procedures. It's OK not to use back blows if you haven't learned the technique. Both approaches are acceptable.

To perform abdominal thrusts (Heimlich maneuver) on someone else:

• Stand behind the person. Place one foot slightly in front of the other for balance. Wrap your arms around the waist. Tip the person forward slightly. If a child is choking, kneel down behind the child.
• Make a fist with one hand. Position it slightly above the person's navel.
• Grasp the fist with the other hand. Press hard into the abdomen with a quick, upward thrust — as if trying to lift the person up.
• Perform between six and 10 abdominal thrusts until the blockage is dislodged.

If you're the only rescuer, perform back blows and abdominal thrusts before calling 911 or your local emergency number for help. If another person is available, have that person call for help while you perform first aid.

If the person becomes unconscious, perform standard cardiopulmonary resuscitation (CPR) with chest compressions and rescue breaths.

To perform abdominal thrusts (Heimlich maneuver) on yourself:

First, if you're alone and choking, call 911 or your local emergency number immediately. Then, although you'll be unable to effectively deliver back blows to yourself, you can still perform abdominal thrusts to dislodge the item.

• Place a fist slightly above your navel.
• Grasp your fist with the other hand and bend over a hard surface — a countertop or chair will do.
• Shove your fist inward and upward.

To clear the airway of a pregnant woman or obese person:

• Position your hands a little bit higher than with a normal Heimlich maneuver, at the base of the breastbone, just above the joining of the lowest ribs.
• Proceed as with the Heimlich maneuver, pressing hard into the chest, with a quick thrust.
• Repeat until the food or other blockage is dislodged. If the person becomes unconscious, follow the next steps.

To clear the airway of an unconscious person:

• Lower the person on his or her back onto the floor, arms to the side.
• Clear the airway. If a blockage is visible at the back of the throat or high in the throat, reach a finger into the mouth and sweep out the cause of the blockage. Don't try a finger sweep if you can't see the object. Be careful not to push the food or object deeper into the airway, which can happen easily in young children.
• Begin CPR if the object remains lodged and the person doesn't respond after you take the above measures. The chest compressions used in CPR may dislodge the object. Remember to recheck the mouth periodically.

To clear the airway of a choking infant younger than age 1:

• Assume a seated position and hold the infant facedown on your forearm, which is resting on your thigh. Support the infant's head and neck with your hand, and place the head lower than the trunk.
• Thump the infant gently but firmly five times on the middle of the back using the heel of your hand. The combination of gravity and the back blows should release the blocking object. Keep your fingers pointed up to avoid hitting the infant in the back of the head.
• Turn the infant faceup on your forearm, resting on your thigh with the head lower than the trunk if the infant still isn't breathing. Using two fingers placed at the center of the infant's breastbone, give five quick chest compressions. Press down about 1 1/2 inches, and let the chest rise again in between each compression.
• Repeat the back blows and chest thrusts if breathing doesn't resume. Call for emergency medical help.
• Begin infant CPR if one of these techniques opens the airway but the infant doesn't resume breathing.

If the child is older than age 1 and conscious, give abdominal thrusts only. Be careful not to use too much force to avoid damaging ribs or internal organs.

To prepare yourself for these situations, learn the Heimlich maneuver and CPR in a certified first-aid training course.