Improvements to the "chain of survival" increased survival and decreased residual neurological damage in out-of-hospital cardiac arrest patients in Japan, researchers report in Circulation: Journal of the American Heart Association.

Researchers considered 8,782 bystander-witnessed cardiac arrests from May 1998 to December 2006 in Osaka, Japan. During this time period, Japanese citizens received training in cardiopulmonary resuscitation (CPR), dispatcher instruction in CPR was introduced and procedures were changed to allow emergency service personnel to deliver shocks with a defibrillator without online physician oversight and to intubate patients in the field.

As a result, the researchers said:

• One-month survival of witnessed cardiac arrests rose from 5 percent to 12 percent, an improvement over past reports in which out-of-hospital cardiac arrest survival doesn't exceed 5 percent in most communities and only 3 percent in urban areas.
• The median time from collapse to CPR decreased from 9 to 7 minutes due to citizen training.
• Bystander-initiated CPR increased from 19 percent to 36 percent.
• The neurologically intact one-month survival after witnessed ventricular fibrillation (VF) arrest increased from 6 percent to 17 percent.
• The median time from collapse to calling emergency services decreased from 4 to 2 minutes.
• The median time from collapse to first shock dropped from 19 to 9 minutes.
• Median time to intubation remained at 25 minutes, but only took 15 minutes when specially trained paramedics were available.

"This study proves that improvement in the 'chain of survival' results in increased survival from out-of-hospital cardiac arrest in the real world," said Taku Iwami, M.D., lead author of the study and an assistant professor at Kyoto University Health Service. "The improvement is mainly due to the improvement in the first three links of the chain, but there was some incremental benefit in the fourth link of advanced life support."

The links in the chain of survival are:

1. Early recognition of the emergency and activation of the emergency medical services "phone 9-1-1".
2. Early bystander CPR.
3. Early delivery of a shock with a defibrillator
4. Early advanced life support followed by post resuscitation care delivered by healthcare providers.

For each minute of delay in starting CPR, the chance of neurologically intact survival decreased 11 percent, researchers said. For each minute of delay in shock for ventricular fibrillation, researchers found a 16 percent decrease in survival. For every minute of delay to intubation, survival decreased 4 percent.

In Osaka (population, 8.8 million), about 120,000 citizens per year participated in conventional CPR training. There were no programs to train in compression-only CPR during this study period.

Only 24 patients received shocks administered by bystanders during this period, but the researchers expect this to increase with further spread of AEDs and training of the general public.

"We need to increase the number of automated external defibrillators in public places as well as train people in not only CPR but in use of AEDs," Iwami said. "In many areas of the world, there are serious delays in the use of CPR and AEDs. We hope this study encourages other EMS systems to start or continue their efforts to improve based on objective data."

The Japanese Ministry of Education, Science, Sports, and Culture and The Japanese Ministry of Health, Labor and Welfare funded the study.

Co-authors are: Graham Nichol, M.D., M.P.H.; Atsushi Hiraide, M.D., Ph.D.; Yasuyuki Hayaski, M.D., Ph.D.; Tatsuya Nishiuchi, M.D.; Kentaro Kajino, M.D., Ph.D.; Hiroshi Morita, M.D., Ph.D.; Hidekazu Yukioka, M.D., Ph.D.; Hisashi Ikeuchi, M.D., Ph.D.; Hisashi Sugimoto, M.D., Ph.D.; Hiroshi Nonogi, M.D., Ph.D.; and Takashi Kawamura, M.D., Ph.D. Individual author disclosures are available on the manuscript.