On Consistency of Cross-Approximate Entropy in Cardiovascular and Artificial Environments

Figure 2

Illustrative example of inconsistent results: a threshold-length () plane for XApEn estimated from SBP and PI signals of rats at baseline (black lines and circles) and stress (red lines and circles). Gray regions: estimated XApEn is higher at baseline than at stress. White regions: XApEn is higher at stress than at baseline. Circles: threshold for which XApEn reaches its maximal value; for a particular , the empty circle denotes the lower of two maximal XApEn values. Embedded plot shows a complete threshold profile for . Results are obtained from borderline hypertensive rats exposed to shaker stress.