Fewer than one in 10 people who suffer a cardiac arrest outside of hospital survive, a leading charity has warned.
Hundreds of lives are also being needlessly lost because members of the public are too afraid to intervene.
Jayne Murray from the British Heart Foundation said: "Knowing simple CPR skills is vital to ensure that every person has the best chance of survival."
In Northern Ireland, an estimated 1,400 out of hospital cardiac arrests occur every year.
But bystanders lack the confidence and skills to help.
A survey commissioned by the British Heart Foundation found that 59% of people feared making the situation worse while just 18% could identify the signs of a cardiac arrest.
Ms Murray added: "It is a huge concern that so few people have the skills and confidence to perform CPR and this is undoubtedly costing lives."
The chance of survival is slashed by 10% for every minute without CPR or defibrillation.
After 10 minutes without appropriate help, there is, at best, only a 2% chance of making it.
In many cases where people do take action, bystanders had to be prompted by emergency service operators to act, delaying vital CPR and further reducing the chances of survival.
To coincide with European Restart a Heart Day, the British Heart Foundation has launched a new campaign to have life-saving CPR skills taught in all secondary schools.
The charity also wants the Department of Health to prioritise the funding for the delivery of the community resuscitation strategy which was launched last summer.
Ms Murray said: " By funding and implementing this resuscitation strategy, families will not needlessly lose loved ones and lives will be saved."