Figure 4

The inter-beat-intervals (IBIs) in ms as a function of time (s) in a single patient 120 s prior to escape from the chamber. Variability of IBIs, that is heart rate variability, first increased but then continuously decreased starting 60 s after onset of exposure and almost breaks off during the last 20 s prior to escape. The length of the IBIs also substantially decreased during this period to an average length of 410 ms, corresponding to a heart rate of 146 beats per minute, just prior to escape.