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. Author manuscript; available in PMC: 2016 Jul 22.
Published in final edited form as: Anesth Analg. 2015 Jul;121(1):198–205. doi: 10.1213/ANE.0000000000000790

Figure 2.

Figure 2

The mean coherence between intracranial pressure (ICP)/total hemoglobin index (THI) and transcranial Doppler (TCD)/regional cerebral tissue hemoglobin oxygen saturation (rSo2), a measure of similarity of the oscillations between these modalities. Therefore, this relationship forms the foundations for applying a pressure reactivity index (PRx) style analysis using near-infrared spectroscopy. A particular spectral feature is seen in each of the comparisons with increased coherence <0.1 Hz. However, the mean coherence is not strong. The significance threshold has been calculated from Monte Carlo modeling, shown as a dashed line. Below a frequency of 0.008 Hz, coherence in both comparisons is nonsignificant. The frequency across the x-axis is nonlinear because it reflects the nonlinear frequency scales of wavelets.