More lives can be saved if rescuers reduce the time between chest compressions and delivering a shock to people suffering cardiac arrest, suggests a new study of Canadian and U.S. patients.
Researchers examined the files of 815 patients at five sites who had an out-of-hospital cardiac arrest and were treated by paramedics or firefighters between December 2005 and June 2007. Bystander and home use of defibrillators was not included.
''The longer that pre-shock pause, or the pause between completing CPR and delivering a shock - the longer that is, the lower the chances are of survival to discharge,'' said lead author Dr. Sheldon Cheskes of St. Michael's Hospital in Toronto.
''So I think certainly we felt that has significant ramifications for particularly professional providers who are doing cardiac arrest resuscitation on a regular basis, such as paramedics, firefighters.''
Cheskes said if the pre-shock pause is over 20 seconds, chances of surviving to reach a hospital, be treated and discharged are 53 per cent less than if the pause is less than 10 seconds.
The study was published Monday in Circulation: Journal of the American Heart Association, and used data from the Resuscitation Outcomes Consortium - clinical centres that carry out research on cardiac arrest and traumatic injuries.
Cheskes recommended that less than 10 seconds should elapse from the time of CPR to shock using a defibrillator.
His EMS team is aiming for less than five seconds between completing cardiopulmonary resuscitation and a decision to shock using a defibrillator, he said.
Changes to defibrillator software are also being urged.
When defibrillators are in automatic mode, the time frame can be about 18 seconds from when someone finishes CPR, the defibrillator analyzes a rhythm, determines if it's shockable and charges up and tells the provider to deliver a shock, Cheskes explained.
In manual mode, he said the median pre-shock pause is 10 seconds.
Trained providers should work in manual mode as opposed to automatic to shorten the pre-shock pause time, he said.
Cheskes said bystanders who see someone having a cardiac arrest should perform cardiopulmonary resuscitation because without it, chances of patient survival decrease significantly.
''But once a bystander uses an automatic defibrillator, which is what most of the pad defibrillators are, that's where we want the defibrillator manufacturers to improve that analysis and charging phase, so it doesn't take so long to deliver a shock, whether you're a firefighter, paramedic, or just a lay person using a pad defibrillator,'' he said.
''It shouldn't take 18 seconds - that's the point we have for the defibrillator manufacturers.''
The Heart and Stroke Foundation of Canada and the Canadian Institutes of Health Research are among the main funders of the resuscitation consortium.
Dr. Jean Rouleau, scientific director of the Institute of Circulatory and Respiratory Health, said in a statement that when the findings of the resuscitation study are translated into practice, ''they will have the potential to save countless lives in Canada and throughout the world.''
BY ANNE-MARIE TOBIN / The Canadian Press