Assessment of Baroreflex Sensitivity Using Time-Frequency Analysis during Postural Change and Hypercapnia

Figure 3

Exemplary representations of TF coherence (TFCoh), TF phase shift (TFPS), and TFCoh-TFPS binary mask for the same subject as in Figure 2 (postural change in normocapnia stage of the experiment). (a) Exemplary representation of TFCoh between pulse interval variability (PIV) and systolic arterial pressure variability (SAPV) signals. (b) Exemplary representation of TFPS between PIV and SAPV signals. White areas denote parts of the representation where TFCoh is lower than 0.9. (c) Binary mask M based on TFCoh and TFPS representations. Black areas denote parts of the representation which fulfil the following criteria: (1) TFCoh > 0.9 and (2) TFPS < 0. The low (0.04–0.15 Hz) and high (0.15–0.4 Hz) frequency ranges used in baroreflex sensitivity estimation are shown together.

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