Cardiopulmonary resuscitation (CPR) is a lifesaving technique used when someone's breathing or heartbeat has stopped. It involves maintaining an open airway, providing rescue breaths, and performing chest compressions to pump oxygenated blood to the brain and heart until emergency medical treatment can restore normal function. The basic steps of CPR are to check for response, call for help, provide 30 chest compressions and 2 rescue breaths, and continue CPR until advanced medical help arrives. Complications can include injuries to the chest, heart, or other internal organs.