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Cardiac arrest is one of the most common reasons for a person to collapse and become unresponsive for no other obvious reason, such as due to a car accident. Providing CPR (if necessary) while waiting for the arrival of paramedics can double or even triple a person’s chance of survival in the event of cardiac arrest. Find out if anyone in the immediate vicinity is CPR certified. If the person isn’t breathing or has stopped breathing, then the first step is to check his airway. Place one hand on his forehead and the other underneath his jaw. With the forehead hand, slide his head backward and tilt his jaw with the other. Watch for any signs of his chest beginning to rise and fall. Place your ear over his mouth and feel for any breath on your face.  If you can easily see something in his airway when you look into his mouth, then try to remove it, but only if the object is loose. If the object is clearly lodged, then do not try to remove it from his throat since you may inadvertently push the object farther down his airway.  The reason we check the airway first is that if there is a blockage (or an obstruction, such as often happens in choking victims), and if we can easily remove it, our problem is solved. However, if there is not, check for a pulse and, if there is no pulse (or if you cannot find one and are in doubt), immediately begin chest compressions. Head-tilt chin-lifts should not be done on skull, spine, neck injuries. Instead, use the jaw-thrust method, in which you kneel above the person's head and place your hands on either side of his head. Place your middle and index finger along his jaw bone and gently push it upward so that the jaw is jutting forward, as though he has an underbite. Current CPR standards place the emphasis on chest compressions with a ratio of thirty compressions for every two rescue breaths. Begin chest compressions by:  Placing the heel of your hand on the person’s breastbone directly between his nipples Placing the heel of your opposite hand over the top of the first Positioning your body mass directly over your positioned hands Compressing hard and fast downward approximately two inches into his chest Allowing his chest to rise completely Repeating to a count of thirty At this point, add in the two rescue breaths if you are trained in CPR. If you are not, continue with compressions and ignore the breaths as they are much less important. You can stop performing CPR as soon as the person shows signs of breathing on his own. Watch for the rise and fall of the person’s chest and place your ear near his mouth to check if he’s breathing on his own. If the person continues to show no signs of consciousness or breathing on his own, then keep performing CPR at a rate of two rescue breaths to every thirty chest compressions until emergency responders arrive.

Summary:
Ask if anyone around knows CPR. Check the person’s airway. Perform chest compressions. Check for signs of breathing again (reassess the person for breathing approximately every two minutes). Continue CPR until paramedics arrive.