A cardiac arrest happens when the heart suddenly stops pumping blood around the body. Someone who is suffering from a cardiac arrest will suddenly lose consciousness and will stop breathing or stop breathing normally.
Find out more about how to identify if someone is having a cardiac arrest and needs CPR.
Remember: do not put your own safety at risk. Be aware of your surroundings and make sure you are in a safe environment before helping another person.
Once you have identified that a person is having a cardiac arrest, call for help, call 999 and start CPR immediately. Learn how to perform CPR with our guide.
Visit our CPR landing page for all you need to know abut CPR.