Every second counts when performing CPR: Increase in survival when AED used less than 10 seconds after CPR pause

The number of people who survive rises significantly if the pause is less than 10 seconds.

"If your pre-shock pause is over 20 seconds, the chances of surviving to reach a hospital, be treated and be discharged are 53 per cent less than if the pause is less than 10 seconds." said Dr. Sheldon Cheskes, lead author of the study published June 20 in Circulation: Journal of the American Heart Association.

Looking at the data another way, Cheskes said researchers found an 18 per cent drop in the number of patients surviving to be discharged from hospital for every five second increase in the pause between CPR and providing a shock with a defibrillator.

Cheskes is a collaborative investigator at the Li Ka Shing Knowledge Institute of St. Michael's Hospital as well as medical director for the Sunnybrook Osler Centre for Prehospital Care.

Cheskes said he hoped the findings would encourage paramedics to minimize any interruption in CPR. He'd also like to see manufacturers produce new software to shorten the length of time it takes to analyze a patient's heart rhythm and charge the defibrillator before delivering a shock. He said more paramedics should be trained to use defibrillators on manual mode rather than automatic to also speed up those two steps.

The researchers examined the files of 815 patients who suffered an out-of-hospital cardiac arrested between December 2005 and June 2007. The data was gathered by the Resuscitation Outcomes Consortium (ROC), a group of 11 Canadian and U.S. regional clinical centres including more than 200 EMS/fire agencies that carry out research related to cardiac arrest resuscitation and life-threatening traumatic injury. The Toronto centre, Rescu, is based at St. Michael's.

ROC's main funders include the Heart and Stroke Foundation of Canada and the Canadian Institutes of Health Research.

"Currently in Canada, less than five per cent of people survive an out-of hospital cardiac arrest," said Manuel Arango, director of health policy for the Heart and Stroke Foundation. "New techniques from the Resuscitation Outcomes Consortium have the potential to dramatically increase these odds. To date, ROC research has tripled survival rates in their test communities − revolutionizing how healthcare professionals do CPR in the field."

"The Canadian Institutes of Health Research are proud to support this resuscitation study," said Dr. Jean Rouleau, Scientific Director of the Institute of Circulatory and Respiratory Health. "When these findings are translated into practice, they will have the potential to save countless lives in Canada and throughout the world."

Cheskes said previous smaller studies showed the length of time between CPR and delivering an electric shock affected whether the patient's heart rhythm was restored. This was the first study to show it impacted how many not only made it to the hospital for treatment but also survived and were discharged.

The study found the length of time between delivering a shock and resuming CPR had no significant impact on survival rates.