Today marks national Restart a Heart Day, aiming to raise awareness of cardiac arrests.
The annual worldwide campaign, which is run by the Resuscitation Council, also hopes to increase the number of people equipped with CPR skills.
Restart a Heart Day is now in its sixth year, and sees a range of different organisations coming together to promote public awareness.
In the UK, there are more than 30,000 cardiac arrests suffered away from hospitals each year, with the survival rate less than one in 10.
Prompt CPR in these situations can increase the likelihood of survival by two or three times.
The news that 500,000 people have been equipped with CPR has been widely celebrated.
Scottish Ambulance Service medical director Dr Jim Ward said: “This is wonderful news and it is thanks to the commitment of many organisations across Scotland working in partnership, and particularly to those members of the public who have come forward in huge numbers to be trained in CPR.
“Fast action is critical to save the life of a person in cardiac arrest, and without prompt CPR, the chances of surviving cardiac arrest are very low.”
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To mark the importance of knowing about cardiac arrests and what to do, volunteer teams such as the Westhill First Responders often help teach members of the public, schools and groups basic skills to help.
If someone is unconscious and not breathing, those tasked with starting CPR should shout for help, before putting their ear to a person’s mouth to check if they are breathing.
Emergency services should be called and operators will talk people through the process.
From there, 30 chest compressions should be given, followed by two rescue breaths.
Westhill First Responders group co-ordinator Liam Neil advised that people should look for the centre between the chin and belly button, level with the nipples as a place to begin compressions and their arm should be locked.
Donald Montgomery, community resilience co-ordinator at the Scottish Ambulance Service, said: “The quicker we get someone on the chest the better.
“The control staff are all trained in CPR and will talk you through it.
“We go into schools free of charge and show the pupils CPR.
“We want to teach them to call 999 from a young age but also deliver the skills to the older kids.”
Anyone interested in learning CPR skills from the first responders should contact the Scottish Ambulance Service.