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Self-Organization of Blood Pressure Regulation: Experimental Evidence.

Fortrat JO, Levrard T, Courcinous S, Victor J - Front Physiol (2016)

Bottom Line: We checked that this angle was significantly different between Tilt-Up and Tilt-Down to demonstrate hysteresis.We observed a significant non-equilibrium phase transition in nine healthy volunteers out of 11 with significant hysteresis (48.1 ± 7.5° and 21.8 ± 3.9° during Tilt-Up and Tilt-Down, respectively, p < 0.05).It provides new insights into blood pressure regulation and its related disorders.

View Article: PubMed Central - PubMed

Affiliation: CaDyWec Associated Lab, Faculté de Médecine d'Angers, UMR Centre National De La Recherche Scientifique 6214 Institut national de la santé et de la recherche médicale 1083 (Biologie Neurovasculaire et Mitochondriale Intégrée) Angers, France.

ABSTRACT
Blood pressure regulation is a prime example of homeostatic regulation. However, some characteristics of the cardiovascular system better match a non-linear self-organized system than a homeostatic one. To determine whether blood pressure regulation is self-organized, we repeated the seminal demonstration of self-organized control of movement, but applied it to the cardiovascular system. We looked for two distinctive features peculiar to self-organization: non-equilibrium phase transitions and hysteresis in their occurrence when the system is challenged. We challenged the cardiovascular system by means of slow, 20-min Tilt-Up and Tilt-Down tilt table tests in random order. We continuously determined the phase between oscillations at the breathing frequency of Total Peripheral Resistances and Heart Rate Variability by means of cross-spectral analysis. We looked for a significant phase drift during these procedures, which signed a non-equilibrium phase transition. We determined at which head-up tilt angle it occurred. We checked that this angle was significantly different between Tilt-Up and Tilt-Down to demonstrate hysteresis. We observed a significant non-equilibrium phase transition in nine healthy volunteers out of 11 with significant hysteresis (48.1 ± 7.5° and 21.8 ± 3.9° during Tilt-Up and Tilt-Down, respectively, p < 0.05). Our study shows experimental evidence of self-organized short-term blood pressure regulation. It provides new insights into blood pressure regulation and its related disorders.

No MeSH data available.


Examples of phase diagrams obtained in healthy subjects during slow changes of position from supine to the 70° head-up position (Tilt-Up) and from the 70° head-up position to supine (Tilt-Down). These diagrams show the phase relationship between oscillations of the RR-interval and of the Total Peripheral Resistances at the breathing frequency. (A) Example of a diagram showing a non-equilibrium phase transition during both changes of position with a hysteresis between Tilt-Up and Tilt-Down (6 subjects out of 11). This graph resembles the theoretical graph shown in Figure 1B. (B) Example of a diagram showing a non-equilibrium phase transition during Tilt-Down but not during Tilt-Up (2 subjects out of 11). (C) Example of a diagram showing no phase transition during both Tilt-Up and Tilt-Down (2 subjects out of 11). The maximum y values are not the same on the different panels.
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Figure 5: Examples of phase diagrams obtained in healthy subjects during slow changes of position from supine to the 70° head-up position (Tilt-Up) and from the 70° head-up position to supine (Tilt-Down). These diagrams show the phase relationship between oscillations of the RR-interval and of the Total Peripheral Resistances at the breathing frequency. (A) Example of a diagram showing a non-equilibrium phase transition during both changes of position with a hysteresis between Tilt-Up and Tilt-Down (6 subjects out of 11). This graph resembles the theoretical graph shown in Figure 1B. (B) Example of a diagram showing a non-equilibrium phase transition during Tilt-Down but not during Tilt-Up (2 subjects out of 11). (C) Example of a diagram showing no phase transition during both Tilt-Up and Tilt-Down (2 subjects out of 11). The maximum y values are not the same on the different panels.

Mentions: The duration of the Tilt-Up procedure was 21′23″ ± 1′12″ and that of the Tilt-Down procedure was 20′47″ ± 1′10″. We excluded a subject from the analysis because of occurrence of ectopic beats during monitoring. Figure 3 shows the RR-interval and Total Peripheral Resistance time series of one of the subjects during Tilt-Up. RR-interval variability (or Heart Rate Variability) is obvious in this Figure, as is Total Peripheral Resistances variability. Figure 2 also shows this variability in the time domain (two lower left panels) and in the frequency domain (two lower right panels). Figure 3 also shows systolic blood pressure during the procedure. This subject maintained his systolic blood pressure well during the position change thanks to a decrease in the RR-interval (increase in heart rate) and an increase in Total Peripheral Resistances as usually described for cardiovascular adaptation to the head-up position (parasympathetic withdrawal and sympathetic activation; Rowell, 1993). Table 1 shows that the whole group followed such an adaptation to head-up position. Diastolic blood pressure increase is also expected during a change of position from supine to 70° head-up (Table 1; Rowell, 1993). This increase reflects overall vasoconstriction (Rowell, 1993). Breathing frequency did not change during the procedures (Table 1). Table 2 shows the changes of the phase between respiratory oscillations of the RR-intervals and Total Peripheral Resistances during position changes. Coherence between these two variables was good at the breathing frequency (0.58 ± 0.06 and 0.68 ± 0.03 during Tilt-Up and Tilt-Down, respectively). Nine subjects (out of 11) presented non-equilibrium phase transitions (Figure 4). Of these nine subjects, only six presented the typical hysteresis pattern of self-organized criticality with a non-equilibrium phase transition during both Tilt-Up and Tilt-Down (Figure 5A). The three remaining subjects among these nine presented a non-equilibrium phase transition during only one procedure out of the two indicating an extreme hysteresis that occurred outside the x-scale in one of the procedures (Figure 5B). Lastly, only two subjects did not show any phase behavior suggesting self-organization (Figure 5C). Statistical analysis of the nine subjects with non-equilibrium phase transitions identified a significant hysteresis between Tilt-Up and Tilt-Down, as demonstrated by the occurrence of phase transition at a significantly different head-up tilt angle depending upon whether in the Tilt-Up or Tilt-Down procedure (Figure 6). Moreover, when we look at the whole group of subjects, the phase between the respiratory oscillations of the RR-intervals and Total Peripheral Resistances in the supine position was slightly but significantly different between the Tilt-Up and Tilt-Down procedures, also indicating hysteresis (Table 2).


Self-Organization of Blood Pressure Regulation: Experimental Evidence.

Fortrat JO, Levrard T, Courcinous S, Victor J - Front Physiol (2016)

Examples of phase diagrams obtained in healthy subjects during slow changes of position from supine to the 70° head-up position (Tilt-Up) and from the 70° head-up position to supine (Tilt-Down). These diagrams show the phase relationship between oscillations of the RR-interval and of the Total Peripheral Resistances at the breathing frequency. (A) Example of a diagram showing a non-equilibrium phase transition during both changes of position with a hysteresis between Tilt-Up and Tilt-Down (6 subjects out of 11). This graph resembles the theoretical graph shown in Figure 1B. (B) Example of a diagram showing a non-equilibrium phase transition during Tilt-Down but not during Tilt-Up (2 subjects out of 11). (C) Example of a diagram showing no phase transition during both Tilt-Up and Tilt-Down (2 subjects out of 11). The maximum y values are not the same on the different panels.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4814514&req=5

Figure 5: Examples of phase diagrams obtained in healthy subjects during slow changes of position from supine to the 70° head-up position (Tilt-Up) and from the 70° head-up position to supine (Tilt-Down). These diagrams show the phase relationship between oscillations of the RR-interval and of the Total Peripheral Resistances at the breathing frequency. (A) Example of a diagram showing a non-equilibrium phase transition during both changes of position with a hysteresis between Tilt-Up and Tilt-Down (6 subjects out of 11). This graph resembles the theoretical graph shown in Figure 1B. (B) Example of a diagram showing a non-equilibrium phase transition during Tilt-Down but not during Tilt-Up (2 subjects out of 11). (C) Example of a diagram showing no phase transition during both Tilt-Up and Tilt-Down (2 subjects out of 11). The maximum y values are not the same on the different panels.
Mentions: The duration of the Tilt-Up procedure was 21′23″ ± 1′12″ and that of the Tilt-Down procedure was 20′47″ ± 1′10″. We excluded a subject from the analysis because of occurrence of ectopic beats during monitoring. Figure 3 shows the RR-interval and Total Peripheral Resistance time series of one of the subjects during Tilt-Up. RR-interval variability (or Heart Rate Variability) is obvious in this Figure, as is Total Peripheral Resistances variability. Figure 2 also shows this variability in the time domain (two lower left panels) and in the frequency domain (two lower right panels). Figure 3 also shows systolic blood pressure during the procedure. This subject maintained his systolic blood pressure well during the position change thanks to a decrease in the RR-interval (increase in heart rate) and an increase in Total Peripheral Resistances as usually described for cardiovascular adaptation to the head-up position (parasympathetic withdrawal and sympathetic activation; Rowell, 1993). Table 1 shows that the whole group followed such an adaptation to head-up position. Diastolic blood pressure increase is also expected during a change of position from supine to 70° head-up (Table 1; Rowell, 1993). This increase reflects overall vasoconstriction (Rowell, 1993). Breathing frequency did not change during the procedures (Table 1). Table 2 shows the changes of the phase between respiratory oscillations of the RR-intervals and Total Peripheral Resistances during position changes. Coherence between these two variables was good at the breathing frequency (0.58 ± 0.06 and 0.68 ± 0.03 during Tilt-Up and Tilt-Down, respectively). Nine subjects (out of 11) presented non-equilibrium phase transitions (Figure 4). Of these nine subjects, only six presented the typical hysteresis pattern of self-organized criticality with a non-equilibrium phase transition during both Tilt-Up and Tilt-Down (Figure 5A). The three remaining subjects among these nine presented a non-equilibrium phase transition during only one procedure out of the two indicating an extreme hysteresis that occurred outside the x-scale in one of the procedures (Figure 5B). Lastly, only two subjects did not show any phase behavior suggesting self-organization (Figure 5C). Statistical analysis of the nine subjects with non-equilibrium phase transitions identified a significant hysteresis between Tilt-Up and Tilt-Down, as demonstrated by the occurrence of phase transition at a significantly different head-up tilt angle depending upon whether in the Tilt-Up or Tilt-Down procedure (Figure 6). Moreover, when we look at the whole group of subjects, the phase between the respiratory oscillations of the RR-intervals and Total Peripheral Resistances in the supine position was slightly but significantly different between the Tilt-Up and Tilt-Down procedures, also indicating hysteresis (Table 2).

Bottom Line: We checked that this angle was significantly different between Tilt-Up and Tilt-Down to demonstrate hysteresis.We observed a significant non-equilibrium phase transition in nine healthy volunteers out of 11 with significant hysteresis (48.1 ± 7.5° and 21.8 ± 3.9° during Tilt-Up and Tilt-Down, respectively, p < 0.05).It provides new insights into blood pressure regulation and its related disorders.

View Article: PubMed Central - PubMed

Affiliation: CaDyWec Associated Lab, Faculté de Médecine d'Angers, UMR Centre National De La Recherche Scientifique 6214 Institut national de la santé et de la recherche médicale 1083 (Biologie Neurovasculaire et Mitochondriale Intégrée) Angers, France.

ABSTRACT
Blood pressure regulation is a prime example of homeostatic regulation. However, some characteristics of the cardiovascular system better match a non-linear self-organized system than a homeostatic one. To determine whether blood pressure regulation is self-organized, we repeated the seminal demonstration of self-organized control of movement, but applied it to the cardiovascular system. We looked for two distinctive features peculiar to self-organization: non-equilibrium phase transitions and hysteresis in their occurrence when the system is challenged. We challenged the cardiovascular system by means of slow, 20-min Tilt-Up and Tilt-Down tilt table tests in random order. We continuously determined the phase between oscillations at the breathing frequency of Total Peripheral Resistances and Heart Rate Variability by means of cross-spectral analysis. We looked for a significant phase drift during these procedures, which signed a non-equilibrium phase transition. We determined at which head-up tilt angle it occurred. We checked that this angle was significantly different between Tilt-Up and Tilt-Down to demonstrate hysteresis. We observed a significant non-equilibrium phase transition in nine healthy volunteers out of 11 with significant hysteresis (48.1 ± 7.5° and 21.8 ± 3.9° during Tilt-Up and Tilt-Down, respectively, p < 0.05). Our study shows experimental evidence of self-organized short-term blood pressure regulation. It provides new insights into blood pressure regulation and its related disorders.

No MeSH data available.