CPR Versus Defibrillation - Which Comes First?

A colleague suddenly collapses in the staff room. They are unresponsive and not breathing normally. In that moment, CPR versus defibrillation is not a choice between two competing treatments. Both are time-critical parts of the response to a suspected cardiac arrest, and knowing how they work together can help a workplace team act with greater confidence.

The immediate priorities are to call 999 or 112, start chest compressions and send someone for the AED if one is available. An automated external defibrillator, or AED, will guide the user through the next steps. You do not need to diagnose the person’s heart rhythm yourself.

CPR versus defibrillation: the essential difference

CPR, or cardiopulmonary resuscitation, uses chest compressions and rescue breaths to keep a limited supply of oxygenated blood moving around the body. It does not usually restart the heart. Its purpose is to support the brain and vital organs while emergency services are on their way and while a defibrillator is being brought to the casualty.

Defibrillation is the delivery of a controlled electrical shock to the heart through adhesive pads placed on the chest. The shock may allow a heart in a shockable rhythm to reset and resume a more effective rhythm. An AED analyses the heart rhythm before giving any advice, then tells the responder whether a shock is needed.

That distinction matters. CPR is needed in every suspected cardiac arrest where the person is unresponsive and not breathing normally. Defibrillation is only appropriate when the AED identifies a shockable rhythm. If the machine says, “No shock advised”, continue CPR immediately and follow its prompts.

Why time matters so much

During cardiac arrest, the heart is no longer pumping blood effectively. Without rapid action, the chance of survival falls with every minute. High-quality CPR buys valuable time by maintaining some circulation. Early defibrillation can be decisive when the person has a rhythm that responds to a shock.

This is why workplace response plans should not treat an AED as a substitute for first aid training, or CPR as a reason to wait for equipment. The strongest response is coordinated: one person calls for an ambulance, another starts compressions, and someone else retrieves the AED and directs emergency services to the correct entrance.

In a small workplace, one person may need to do several of these things in sequence. Call emergency services on speakerphone if possible, start CPR promptly, then use the AED as soon as it arrives. The operator can provide support while help is on its way.

What should happen first?

If you find an adult who is unresponsive and not breathing normally, first make sure it is safe to approach. Check for a response, open the airway and assess breathing for no more than 10 seconds. Occasional gasps, known as agonal breathing, are not normal breathing and should be treated as a sign of cardiac arrest.

Call 999 or 112, or ask another person to do so. Begin chest compressions in the centre of the chest, pressing hard and fast at a rate of 100 to 120 compressions a minute. If you are trained, willing and able, give 30 compressions followed by two rescue breaths. If you are not able to give breaths, continuous chest compressions are far better than doing nothing.

Use the AED the moment it arrives. Turn it on and follow the spoken or visual instructions. Expose the chest, dry it if it is wet, and attach the pads as shown in the diagrams. The device will analyse the rhythm and advise whether a shock is required.

When the AED is analysing or delivering a shock, make sure nobody is touching the casualty. As soon as it tells you to resume CPR, start again straight away. Try to keep pauses in chest compressions as short as possible. The AED may reanalyse at intervals, so continue to follow every prompt until the ambulance crew takes over, the person shows clear signs of life, or you are physically unable to continue.

Do not wait to find out whether a shock is needed

A common concern is whether CPR should stop while an AED is being located. It should not. Start CPR immediately and continue while the defibrillator is fetched. If there are other people present, this can happen at the same time.

It is also understandable to worry about using an AED incorrectly. Modern public-access and workplace devices are designed for use by people with limited experience. They assess the rhythm themselves and will not advise a shock unless it is appropriate. Training still makes a significant difference because it helps responders remain calm, position pads correctly and reduce unnecessary delays.

When an AED may not give a shock

Not every cardiac arrest is caused by a rhythm that can be corrected with defibrillation. Some rhythms are not shockable. In these cases, the AED will say that no shock is advised. This does not mean the person is beyond help, nor does it mean the device has failed.

Continue CPR with as few interruptions as possible. Good chest compressions and early emergency care remain essential. The AED will keep monitoring and may later identify a rhythm where a shock is appropriate.

This is one reason the phrase “CPR versus defibrillation” can be misleading. The responder does not need to decide which treatment is medically correct. The AED makes the shock decision; the responder provides CPR and follows the device’s instructions.

Practical considerations in the workplace

An AED is most useful when staff can get to it quickly. It should be clearly signed, accessible during all operating hours and included in induction information, first aid arrangements and emergency drills. A locked cabinet, an inaccessible reception area or uncertainty over who holds the key can cost precious time.

Organisations should also nominate people to check the device regularly. This includes confirming that the status indicator is normal, pads and batteries are within date, the rescue kit is present, and any cabinet alarm is working. Different AED models have different maintenance requirements, so the manufacturer’s instructions should be followed.

Consider the situations likely to arise on your site. A school may need to account for sports areas and visitors. A care setting may require clear escalation arrangements for residents, relatives and staff. A warehouse, office or community venue may need a plan for directing ambulance crews through security gates or to a remote building.

For children, use paediatric pads or a paediatric setting where the AED provides one, usually for children under eight years old or weighing less than 25 kg. If these are unavailable, do not delay defibrillation to search for them. Use the AED available and follow its instructions. Staff in education, childcare and activity settings should receive training relevant to the ages and risks they support.

Training turns equipment into a response plan

Buying an AED is a positive step, but it is only one part of readiness. Staff need the confidence to recognise cardiac arrest, call for help, begin effective CPR and use the device without avoidable hesitation. They should also understand how to work as a team, manage bystanders and hand over useful information to ambulance crews.

Practical AED and basic life support training gives people the opportunity to handle the equipment, practise pad placement and rehearse the sequence under realistic pressure. Annual refreshers are particularly valuable because skills that are rarely used can fade, even among experienced first aiders.

Employers should review their first aid needs assessment when staffing, premises, activities or risk levels change. The number and location of AEDs, the availability of trained responders and the arrangements for lone workers may all need to be reconsidered. MI Team Training can deliver on-site training that allows teams to practise the response in the context of their own workplace.

The most helpful question is not whether CPR or defibrillation matters more. It is whether your people could bring both together quickly, safely and without waiting for someone else to take the lead.