Application of the Variance Delay Fuzzy Approximate Entropy for Autonomic Nervous System Fluctuation Analysis in Obstructive Sleep Apnea Patients

Figures

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  Figure 1. The flow chart of heart rate variability (HRV) analysis in this study.

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  Figure 2. The typical 5-min RR intervals for a segment of normal subject and a segment of obstructive sleep apnea (OSA) subject. The red lines are obtained by calculating the variance of the signal at five points.

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  Figure 3. One hundred-point segments are randomly selected from 1000 simulated (a) MIX (0.1), (b) MIX (0.5), and (c) MIX (0.9) signals; red lines are obtained by calculating the variance of the signal at 5 points; when N increases from 200 to 1000 at each increase of 50 (r = 0.20), there is a change of (d) fuzzy approximate entropy (fApEn) and (f) variance delay (VD)_fApEn; when r increases from 0.1 to 1 at each increase of 0.05, there is a change of (e) fApEn and (g) VD_fApEn.

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  Figure 4. Comparison of the (a) low frequency (LF)/high frequency (HF) ratio, (b) nonlinear index fApEn, (c) VD_fApEn for the normal, mild/moderate OSA, and severe OSA groups.

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  Figure 5. (a) The comparison of VD_fApEn and fApEn for each OSA patient screening; blue/red dot: normal/OSA recording correctly detected; red/blue+: the fApEn has misclassified the OSA/normal recording; red/blue; ×x: the VD_fApEn has misclassified the OSA/normal recording; red *: both indicators misclassify the OSA recording; (b) The comparison of VD_fApEn and LF/HF ratio for each OSA patient screening; blue/red dot: normal/OSA recording correctly detected; red/blue+: the LF/HF has misclassified the OSA/normal recording; red/blue ×: the VD_fApEn misclassified the OSA/normal recording; red *: both indicators misclassify the OSA recording; N:normal subject; OSA: OSA patient.

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  Figure 6. (a) Relationship between VD_fApEn and different RRs scales for three groups; (b) analysis of relationship between OSA screening accuracy and different scales. The black line is the control group; red line is the mild-moderate OSA group; the blue line is the severe OSA group. *: significant difference exist between N and M (p < 0.05); ◊: significant difference exist between N and S (p < 0.05); Δ: significant difference exist between M and S (p < 0.05).