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How to identify and treat cardiac arrest

Cardiac arrest is easily identified. If someone is unconscious and not breathing, or they are not breathing normally (known as agonal breathing - gasping, laboured breathing), then they are most likely suffering a cardiac arrest. If they are breathing normally, but appear to be unconscious (they're unresponsive), call 999 and put them in the recovery position until help arrives or instructed otherwise by medical staff (for example in the case of the patient being sick).

Every second counts in cases of cardiac arrest, so it’s important to identify it quickly. If you see someone who has collapsed and appears to be unconscious, gently shake them and shout at them to see if they are responsive. As first aiders we can't be 100% sure someone is unconscious, so we refer to them as unresponsive if there is no response. Next, check their breathing. If they are not breathing, or if their breathing is not normal, contact emergency services and begin CPR immediately. You should check their breathing by looking for regular chest movements, listening for breathing, and feeling for breath on your cheek. Don’t confuse gasps for normal breathing. Do not spend more than 10 seconds doing this, and if you’re unsure whether their breathing is normal, act as if it isn’t.


It’s important to commence CPR as fast as possible, but you should also always contact emergency services for cardiac arrest. If there are other people nearby, tell them to call for an ambulance immediately, and ask someone if they can find and retrieve a publically available automated external defibrillator (AED). Then commence CPR immediately. If you’re alone, call for an ambulance first, then commence CPR as soon as possible. CPR is a series of chest compressions followed by rescue breaths. If you feel unable to give rescue breaths, for example in cases such as during the pandemic to maintain social distancing as much as possible, then you can deliver hands-only CPR. If there is a first aid kit to hand, it may contain face-shields to allow you to give rescue breaths without making contact with the casualty.

The main goal of CPR is to pump the heart and keep a partially oxygenated supply of blood to the brain and vital organs, to prevent irreversible tissue death or brain damage before defibrillation is commenced or emergency services arrive. Without quick, effective CPR, the chances of death or disability for those that do survive are very high. It may be frightening to attempt CPR as there is a chance you may break a patient's rib or cause some internal damage, however whatever damage you may cause the patient, it is far better to try to help them than the alternative outcome.

Using a defibrillator

Defibrillation involves the use of an AED, which shocks the casualty with the aim of restoring their normal heart rhythm, allowing oxygen to flow through their body again. AEDs are available in some public places, such as train stations and shopping centres, and some workplaces.

An AED is designed to be easy to use, including by untrained people. The AED issues clear voice instructions and will assess the casualty’s heart rhythm to see if they should be shocked. An AED will not shock someone who does not need it, and cannot cause harm. As it’s impossible to tell if a casualty’s heart condition is shockable or non-shockable, an AED should always be used when someone has suffered cardiac arrest. Some AEDs work completely automatically, others may require a person to press a button to issue a shock. If someone does not need a shock, or if their condition is non-shockable, then the AED will not shock them.

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