Chest Compressions Are Critical in CPR!

 The chance of surviving a cardiac arrest outside a hospital was found to be twice as high when bystanders performed continuous chest compressions without mouth-to-mouth breathing than when bystanders performed standard CPR. These are the latest findings reported by the Resuscitation Research Group at the University of Arizona Sarver Heart Center and the SHARE Program (Save Hearts in Arizona Research and Education) at the Arizona Department of Health Services. ​
According to the study, only 5 percent of cardiac arrest victims survived if nobody performed CPR. In those receiving standard CPR (alternating between 30 compressions and 2 breaths), survival was marginally higher at 6 percent. In contrast, 11 percent survived if bystanders kept pumping on their chest and did not stop for mouth-to-mouth breaths until emergency medical services arrived. 
http://deptmedicine.arizona.edu/node/548​