Does the number of rescuers affect the survival rate from out-of-hospital cardiac arrests? Two or more rescuers are not always better than one.

REVIEW: An increased number of rescuers may improve the survival rate from out-of-hospital cardiac arrests (OHCAs). The majority of OHCAs occur at home and are handled by family members. MATERIALS AND METHODS: Data from 5078 OHCAs that were witnessed by citizens and unwitnessed by citizens or emergency medical technicians from January 2004 to March 2010 were prospectively collected. The number of rescuers was identified in 4338 OHCAs and was classified into two (single rescuer (N=2468) and multiple rescuers (N=1870)) or three (single rescuer, two rescuers (N=887) and three or more rescuers (N=983)) groups. The backgrounds, characteristics and outcomes of OHCAs were compared between the two groups and among the three groups. RESULTS: When all OHCAs were collectively analysed, an increased number of rescuers was associated with better outcomes (one-year survival and one-year survival with favourable neurological outcomes were 3.1% and 1.9% for single rescuers, 4.1% and 2.0% for two rescuers, and 6.0% and 4.6% for three or more rescuers, respectively (p=0.0006 and p<0.0001)). A multiple logistic regression analysis showed that the presence of multiple rescuers is an independent factor that is associated with one-year survival (odds ratio (95% confidence interval): 1.539 (1.088-2.183)). When only OHCAs that occurred at home were analysed (N=2902), the OHCAs that were handled by multiple rescuers were associated with higher incidences of bystander CPR but were not associated with better outcomes. CONCLUSIONS: In summary, an increased number of rescuers improves the outcomes of OHCAs. However, this beneficial effect is absent in OHCAs that occur at home.

Direct observation of grain growth from molten silicon formed by micro-thermal-plasma-jet irradiation.

Phase transformation of amorphous-silicon during millisecond annealing using micro-thermal-plasma-jet irradiation was directly observed using a high-speed camera with microsecond time resolution. An oval-shaped molten-silicon region adjacent to the solid phase crystallization region was clearly observed, followed by lateral large grain growth perpendicular to a liquid-solid interface. Furthermore, leading wave crystallization (LWC), which showed intermittent explosive crystallization, was discovered in front of the moving molten region. The growth mechanism of LWC has been investigated on the basis of numerical simulation implementing explosive movement of a thin liquid layer driven by released latent heat diffusion in a lateral direction.