What to Do While Waiting for an Ambulance During Sudden Cardiac Arrest

Learn what to do during sudden cardiac arrest while waiting for an ambulance. Call 999, start CPR and use a defibrillator if available.

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Sudden cardiac arrest (SCA) can strike without warning, and every second is vital. Acting quickly while waiting for an ambulance can make the difference between life and death. In the UK, survival rates for cardiac arrest outside of hospital remain low, but fast action from bystanders significantly improves the chance of survival. This guide explains what you should do while you wait for emergency services.

Recognise Sudden Cardiac Arrest

The first step is to identify when someone is in cardiac arrest. Look for these signs:

  • The person is unresponsive and does not wake when you shake them or call out.

  • They are not breathing normally or may only be gasping.

  • Their skin may look pale or bluish.

If you see these symptoms, call 999 immediately and request an ambulance.

Call for Help Straight Away

Dial 999 and explain the situation clearly. The call handler will stay on the line and give you instructions until help arrives. They will guide you through CPR and how to use a defibrillator if one is available.

If others are present, ask one person to phone for help and another to fetch a defibrillator. Many workplaces, gyms, schools and community centres now have one on site.

Start CPR Immediately

While waiting for an ambulance, start CPR without delay. This keeps oxygen flowing to the brain and other vital organs.

  1. Place the heel of one hand in the centre of the chest and put your other hand on top.

  2. Keep your arms straight and push down hard and fast at 100 to 120 compressions per minute.

  3. Allow the chest to fully rise between compressions.

If you are trained, you can give two rescue breaths after every 30 compressions. If not, continue with hands-only CPR. It is highly effective and far better than doing nothing.

Use a Defibrillator if Available

An automated external defibrillator (AED) is designed so that anyone can use it, even without medical training.

  • Switch the AED on and follow the voice prompts.

  • Expose the chest and attach the pads as shown in the diagrams.

  • The AED will analyse the heart rhythm and tell you if a shock is required.

  • If a shock is advised, make sure no one is touching the casualty and press the button.

Once the shock is given, resume CPR immediately and continue to follow the AED’s instructions. These devices are very safe and will never deliver a shock unless it is needed.

Keep Going Until Help Arrives

Do not stop CPR until one of the following happens:

  • The person begins to show signs of life such as breathing normally or moving.

  • A paramedic or trained professional takes over.

  • You are too exhausted to continue.

If others are nearby, take turns every two minutes to maintain strong and effective compressions.

Stay Calm and Organised

Cardiac arrest is a frightening experience, but staying calm helps you focus on the steps that matter most. Give clear instructions to others and, if possible, ask someone to wait outside to guide the ambulance crew quickly to the scene.

Why Quick Action Matters

Every minute without CPR and defibrillation reduces the chance of survival by about 10 percent. By calling 999 immediately, starting CPR and using a defibrillator, you can double or even triple the chance of survival. Quick action also reduces the risk of long-term brain damage.

Be Prepared for the Future

Sudden cardiac arrest can happen anywhere, at any time. Having a defibrillator close by is one of the best ways to protect your community. Explore our full range of life-saving defibrillators and make sure your workplace, school or organisation is prepared.

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