Fig. 3.

Percentage of significant coherence, $P(s)$, derived from the in-phase $\mathrm{MAP}\to {\mathrm{S}}_{\mathrm{ct}}{\mathrm{O}}_2$ coherence (i.e., $\mathrm{\Delta }\phi \in 0\pm \pi /4$). In this graph, the $x$-axis represents the wavelet scale, $s$, which is in inverse proportion to Fourier frequency. The $y$-axis represents the percentage of time during which the $\mathrm{MAP}\to {\mathrm{S}}_{\mathrm{ct}}{\mathrm{O}}_2$ coherence was statistically significant over the background noise ($p<0.05$). Therefore, $P(s)$ represented the scale/frequency characteristics of the $\mathrm{MAP}\to {\mathrm{S}}_{\mathrm{ct}}{\mathrm{O}}_2$ coherence. For ECMO patients, predominant in-phase $\mathrm{MAP}\to {\mathrm{S}}_{\mathrm{ct}}{\mathrm{O}}_2$ coherence was seen in a wavelet scale range of 8 to 32 min (the shaded area), which corresponded to a frequency range of 0.0005 to 0.002 Hz. This range was selected to calculate the autoregulation index.