Cardiopulmonary Resonance Function and Indices—A Quantitative Measurement for Respiratory Sinus Arrhythmia

Figures

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  Figure 1. Illustration of Cardiopulmonary Resonance Function (CRF) and Cardiopulmonary Resonance Indices (CRI). (A) the power spectral curves of RR interval series and respiration series, as well as the corresponding cardiopulmonary resonance function, G(f). (B) the schematic diagram of CRA and CRW. CRA is taken from the maximum point of G(f) (CRF); CRW, the bandwidth of CRF as indicated by the bi-directional arrow line.

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  Figure 2. The wearable hardware device used to collect ECG and respiration signals.

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  Figure 3. G(f) (CRF) and corresponding HRV, R-HRV, and NR-HRV in frequency domain.

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  Figure 4. A typical power spectral density curves of respiratory, HRV and corresponding cardiopulmonary resonance function CRF in the frequency domain of a subject for 4 cases of breathing at resting state. From the top: free breathing, paced breathing at frequency of 0.33, 0.26, and 0.12 Hz. It can be seen that paced breathing increases the strength of RSA, and that as the frequency of paced breathing coming down toward, the cardiopulmonary resonance phenomenon becomes stronger, which is very well-captured by the cardiopulmonary resonance function. It can also seen that as the paced breathing frequency approaches 0.1 Hz, around which there is an optimal resonance state for the subject, where HRV_HF is small. That is to say that CRI do represent level of parasympathetic nervus activity at various cases, while HRV do not.

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  Figure 5. DTB-SVM model for classifying the sleep stages. First, a classifier is used to separate the awake phase and the sleep phase, and then within the sleep phase, the REM phase and the NREM phase are separated, and finally the light sleep and deep sleep are separated by the last classifier.

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  Figure 6. G(f) (CRF), CPC, power spectral density of HRV and respiration. By definition, cardiopulmonary resonance function CRF, reflects the strength of RSA, with the peak near the mean of the respiration rate, while CPC is the correlation between HRV and respiration with respect to their power spectrum, having multiple peaks. As the name indicated, CRF well capture the resonance nature of cardiopulmonary system.

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  Figure 7. G(f) (CRF) and CPC in light sleep (top) and deep sleep (bottom).