Public Access Defibrillation - are we ignoring a vital component in the chain of survival for cardiac arrest? Michael O'Shea reports
Statistics from the Irish Heart Foundation show that in the year 2000 about 40 per cent of all deaths in Ireland were due to cardiovascular disease.
Of this category, half were due to coronary heart disease (heart attack). This equates to 6,000 people, or 16 people per day, dying from a heart attack.
The incidence of heart attacks is higher in the over 65-age group but is by no means exclusive to this group. In fact, Irish men and women have the highest rate of death before the age of 65 from coronary heart disease in the European Union. Currently, about 11 per cent of the population are aged over 65 years. By 2026 it is projected that 18 per cent of the population will be over 65 and therefore the burden of coronary heart disease will have implications for resources and services in both primary care and hospital sector.
Cardiac arrest is the sudden, abrupt loss of heart function. The victim may or may not have diagnosed heart disease. Sudden death occurs within minutes after symptoms appear.
The most common underlying reason for people to die suddenly from cardiac arrest is coronary heart disease. Most cardiac arrests that lead to sudden death occur when the electrical impulses in the heart become chaotic (ventricular fibrillation). Other factors besides heart disease and heart attack can cause cardiac arrest. They include respiratory arrest, electrocution, drowning, choking and trauma.
In more than 70 to 90 per cent of all cardiac arrest cases, ventricular fibrillation is present in the heart. This rhythm causes a quivering of the heart making it "wobble" like jelly rather than pumping effectively. Ventricular fibrillation can be reversed if it's treated within a few minutes with an electric shock to the heart to restore a normal heartbeat. These shocks stun the heart, allowing the heart's natural pacemaker a chance to restore a normal heart rhythm. This process is called defibrillation.
CPR (Cardiopulmonary Resuscitation) alone cannot reverse this abnormal heart rhythm. CPR, which consists of mouth-to-mouth rescue breathing and chest compressions, is only a holding technique, keeping the brain and heart alive until a defibrillator arrives.
A victim's chances of survival are reduced by 7 to 10 per cent with every minute that passes without defibrillation. Few attempts at resuscitation succeed after 10 minutes.
In-hospital survival after cardiac arrest in heart attack patients improved dramatically when the defibrillator and bedside monitoring were developed. Later it also became clear that cardiac arrest could be reversed outside a hospital by properly staffed emergency rescue teams trained to give CPR and to defibrillate. Thus, the problem isn't the ability to reverse cardiac arrest, but reaching the victim in time to do so.
There is now a move to bring one of the most important life-saving techniques into the public domain within minutes of potential cardiac arrest victims. This is the concept of having Public Access Defibrillation (PAD) schemes in places such as shopping centres, golf clubs, airports etc. Public Access Defibrillation involves the use of automated external defibrillators (AEDs) by trained members of the public.
An AED is a computerised device, which will analyse the heart rhythm of a person in cardiac arrest and can recognise a shockable rhythm. The computerised system can then advise the operator whether the rhythm should be shocked. If used within minutes of an arrest, the chances of survival are markedly improved. AED training for lay rescuers teaches the basic adult CPR techniques and how to use an AED.
Statistics from the American Heart Association estimate that more than 95 per cent of cardiac arrest victims die before reaching the hospital. In cities where defibrillation is provided within five to seven minutes, the survival rate from sudden cardiac arrest is as high as 49 per cent.
In one PAD programme initiated by two Chicago airports, 75 per cent survival rates among patients with ventricular fibrillation were reported among 14 patients in the first 10 months of the programme.
In contrast, Irish statistics indicate that only 1 per cent of cardiac arrest victims survive. It is clear that PAD schemes should be getting more encouragement.
Both Blanchardstown Shopping Centre and Dublin Airport already have PAD schemes in place, but we have a long way to go before the penetration of such schemes into the public domain reaches the level required to ensure access to defibrillators by victims of cardiac arrest within five minutes.
Early CPR and rapid defibrillation combined with early advanced care can result in high long-term survival rates for witnessed cardiac arrest.
If bystander CPR was initiated more consistently and if AEDs were more widely available, a significant number of lives could be saved each year.
Death from sudden cardiac arrest is not inevitable. If more people react quickly by calling 999 and performing CPR, more lives can be saved.
Michael O'Shea is an electronic engineering specialist and managing director of Intelligent Health Systems (IHS) Ltd, a healthcare technology, training and consultancy company. He also lectures in DIT.