title: Self-Organization of Blood Pressure Regulation: Experimental Evidence.
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.
authors.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.
authors.forename: Jacques-Olivier
authors.initials: JO
authors.lastname: Fortrat
authors.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.
authors.forename: Thibaud
authors.initials: T
authors.lastname: Levrard
authors.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.
authors.forename: Sandrine
authors.initials: S
authors.lastname: Courcinous
authors.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.
authors.forename: Jacques
authors.initials: J
authors.lastname: Victor
keywords: Blood pressure control; autonomic nervous system; baroreflex; heart rate variability; non-linear dynamics; self-organized criticality