Respiratory patterns and baroreflex function in heart failure

Figures

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  Figure 1. Breath-by-breath respiratory series. From the respiratory volume sampled at 200 Hz (continuous black line) we extracted 5 breath-by-breath series: the end-inspiratory (EI, green dashed line) and end-expiratory (EE, purple dashed line) volumes; the inspiratory (I, blue arrow) and expiratory (E, red arrow) volumes; and the breathing interval (BI, black arrow). For a given breath b, the EI volume is the maximum respiratory volume within the breath; the EE volume is the minimum respiratory volume between the EI volumes of breaths b and b + 1; I volume is the difference between the EI volume of the breath b and the EE volume of the breath b − 1 while the E volume is the difference between the EI and EE volumes of the same breath b; finally, BI is the time interval between consecutive EI volumes.

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  Figure 2. Power spectra during free, fast-paced, and slow-paced breathing. Power spectra in heart failure (HF) patients and controls (CNT) are shown as geometric mean ± geometric sem separately for R–R intervals (RRI), systolic blood pressure (SBP), and respiration (RSP). Panels below each couple of CNT and HF spectra show the Student T statistics between groups at each frequency, with horizontal dashed lines indicating the 0.05 and 0.01 significance thresholds: this means that T-values above the dashed lines point out differences between HF and CNT groups significant at the corresponding significance threshold. Frequency bands defining the very-low frequency power (VLFp), low-frequency power (LFp) and high-frequency power (HFp) are shown. Note the lower SBP and RRI powers around 0.1 Hz and the greater VLFp of RSP for the HF group during free breathing.

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  Figure 3. Power spectra of breath-by-breath respiratory series during free breathing. Geometric mean ± geometric sem in HF patients and controls (CNT). The panels below each spectrum show the Student T statistics between groups at each frequency: the horizontal dashed lines are the 0.05 and 0.01 significance thresholds. From left to right: spectra of end-expiratory (EE), end-inspiratory (EI), inspiratory (I), and expiratory (E) volumes, and of breathing intervals.

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  Figure 4. SBP–RRI coherency spectra during free, fast-paced, and slow-paced breathing. Coherency spectra as mean ± sem. Below each spectrum, the Student T between groups is shown at each frequency with horizontal dashed lines indicating the 0.05 and 0.01 significance thresholds. Left panels compare heart failure (HF) patients and controls (CNT): T-values above the dashed lines point out significant differences between groups. Central panels compare original and surrogate coherency spectra in the HF group while right panels compare original and surrogate coherency spectra in the CNT group: T-values above the dashed lines point out coherences significantly greater than 0. Note that the highest coherency occurs at frequencies around the 10-s rhythm and the lowest coherency at frequencies corresponding to fluctuations of about 25 s.

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  Figure 5. RSP–SBP coherency spectra during free, fast-paced, and slow-paced breathing. Spectra as mean ± sem, with Student T between groups. Left panels compare heart failure (HF) patients and controls (CNT): T-values above the dashed lines point out significant differences between groups. Central panels compare original and surrogate coherency spectra in the HF group while right panels compare original and surrogate coherency spectra in the CNT group: T-values above the dashed lines point out coherences significantly greater than 0. During free breathing, note the significantly greater respiratory-blood pressure coupling around 25 s in the CNT group, and that only in the CNT group, and not in HF patients, the RSP–SBP coherency around 25 s is significantly greater than 0.

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  Figure 6. RSP–RRI coherency spectra during free, fast-paced, and slow-paced breathing. Spectra as mean ± sem, with Student T between groups. Left panels compare heart failure (HF) patients and controls (CNT): T-values above the dashed lines point out significant differences between groups. Central panels compare original and surrogate coherency spectra in the HF group while right panels compare original and surrogate coherency spectra in the CNT group: T-values above the dashed lines point out coherences significantly greater than 0.