Figure 4

Two plots illustrating the problem with the analysis performed in the article by Eftestol et al. (a) The original plot from Eftestol et al.'s [16] article where each case was assigned to one of three subgroups ('high', 'medium' and 'low') according to their initial value of probability of return of spontaneous circulation (P _ROSC). The time axis refers to time into intervals without compressions. The median P _ROSC in each group is represented with a solid line and the various broken lines represent the 25th and 75th percentiles for each group. The median of the 'high' group differs from the median of the 'medium' group only for the first 5 seconds, and the median of the 'low' group appears to be increasing towards the end. (b) This plot was generated with the same analysis as (a), but here the cases were assigned to the three subgroups according to their P _ROSC value at 10 seconds. From the difference between plots (a) and (b), it is evident that the short time random variations in the P _ROSC estimates greatly affect the results of this form of analysis.