Optimization of Vagal Stimulation Protocol Based on Spontaneous Breathing Rate

Figure 1. Standard Protocol Results (N = 10) - Spectral analysis of autonomic control applied to HRV series of SP. (A) shows the spectral power in absolute values of high frequency band (HFabs) and (B) shows the normalized values of the same component HF. Statistically significant difference compared to blocks: Basal (*) and R10 (#).

Figure 2. Standard Protocol Results (N = 10) - Effect of controlled ventilation maneuvers on the normalized HF component (HFnu) in subjects treated with SP. Solid lines denote transitions with increased HF component with respect to the baseline during the maneuver controlled ventilation. The dotted lines marked decrease in this component during the maneuver. The protocol induced an increase in HFnu on (A) 8 of 10 subjects in R10, (B) 5 of 10 in R15 and (C) 4 of 10 in R20.

Figure 3. Normalized Protocol Results (N = 16): Spectrum examples of Heart Rate Variability (above) and the respiratory signal (below) in spontaneous breathing rate (SBR) ventilatory control situations in the normalized frequency at (A) 100% of the SBR, (B) 70% of the SBR and (C) 50% of the SBR. The underlined area corresponds to higher spectral coherence and demonstrates the shift of the peaks toward the called LF band (0.04-0.15 Hz).

Figure 4. Normalized Protocol Results (N = 16): Parameters for the assessment of autonomic control through spectral analysis applied to the pulse interval series of NP. (A) shows the normalized spectral power of the high frequency HF (HFnu) band, (B) shows the normalized spectral power of the low frequency band LF (LFnu) and (C) shows the relationship between the spectral bands LF/HF. Statistically significant difference compared to blocks: Basal (*) and 100% (#).

Figure 5. Normalized Protocol Results (N = 16): Effect of controlled ventilation maneuver on the normalized HF component (HFnu) in subjects treated with NP. Solid lines denote transitions with increased HF component when compared with baseline. The dotted lines marked decrease in this component. The protocol induced an increase or no change in the HF component (A) on 13 of 16 individuals into the group 100%, (B) in all 16 subjects into the group 80%, (C) in 13 of 16 individuals into the group 70%, (D) in 8 of 16 individuals into the group 60% and (E) in 6 of 16 individuals into the group 50%. The red dots indicate the spectral overlap of the HF band on the LF, blocking the application of such methodology.