Twelve investigations were considered, of which 7 were included in the meta-analysis.
For all trials combined in the meta-analysis, defibrillation by BLS personnel significantly reduced the risk of mortality; p=0.0003. The overall RR was 0.915 (95% CI: 0.876, 0.955), a reduction in the risk of mortality for BLS using defibrillation relative to BLS teams without access to this treatment of 8.5%.
For single-tier systems, where only BLS personnel arrived at the scene of a cardiac arrest (n=281), the RR was 0.864 (95% CI: 0.764, 0.919), a risk reduction of 16%. For two-tier systems, where BLS personnel were succeeded on the scene by advanced cardiac life support providers (n=1,546), the RR was 0.937 (95% CI: 0.890, 0.987), a risk reduction of 6.3%.