title: Phase synchronization of hemodynamic variables at rest and after deep breathing measured during the course of pregnancy.
abstract: BACKGROUND
  The autonomic nervous system plays a central role in the functioning of systems critical for the homeostasis maintenance. However, its role in the cardiovascular adaptation to pregnancy-related demands is poorly understood. We explored the maternal cardiovascular systems throughout pregnancy to quantify pregnancy-related autonomic nervous system adaptations.
  
  
  METHODS
  Continuous monitoring of heart rate (R-R interval; derived from the 3-lead electrocardiography), blood pressure, and thoracic impedance was carried out in thirty-six women at six time-points throughout pregnancy. In order to quantify in addition to the longitudinal effects on baseline levels throughout gestation the immediate adaptive heart rate and blood pressure changes at each time point, a simple reflex test, deep breathing, was applied. Consequently, heart rate variability and blood pressure variability in the low (LF) and high (HF) frequency range, respiration and baroreceptor sensitivity were analyzed in resting conditions and after deep breathing. The adjustment of the rhythms of the R-R interval, blood pressure and respiration partitioned for the sympathetic and the parasympathetic branch of the autonomic nervous system were quantified by the phase synchronization index γ, which has been adopted from the analysis of weakly coupled chaotic oscillators.
  
  
  RESULTS
  Heart rate and LF/HF ratio increased throughout pregnancy and these effects were accompanied by a continuous loss of baroreceptor sensitivity. The increases in heart rate and LF/HF ratio levels were associated with an increasing decline in the ability to flexibly respond to additional demands (i.e., diminished adaptive responses to deep breathing). The phase synchronization index γ showed that the observed effects could be explained by a decreased coupling of respiration and the cardiovascular system (HF components of heart rate and blood pressure).
  
  
  CONCLUSIONS
  The findings suggest that during the course of pregnancy the individual systems become increasingly independent to meet the increasing demands placed on the maternal cardiovascular and respiratory system.
authors.affiliation: Department of Obstetrics and Gynecology, Medical University of Graz, Graz, Austria.
authors.forename: Manfred Georg
authors.initials: MG
authors.lastname: Moertl
authors.forename: Helmut Karl
authors.initials: HK
authors.lastname: Lackner
authors.forename: Ilona
authors.initials: I
authors.lastname: Papousek
authors.forename: Andreas
authors.initials: A
authors.lastname: Roessler
authors.forename: Helmut
authors.initials: H
authors.lastname: Hinghofer-Szalkay
authors.forename: Uwe
authors.initials: U
authors.lastname: Lang
authors.forename: Vassiliki
authors.initials: V
authors.lastname: Kolovetsiou-Kreiner
authors.forename: Dietmar
authors.initials: D
authors.lastname: Schlembach
mesh_terms: D001341:Autonomic Nervous System / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics; D006801:Humans; D011247:Pregnancy; D012119:Respiration; D012146:Rest / Q000502:physiology*