title: Quantification of compensatory processes of postnatal hypoxia in newborn piglets applying short-term nonlinear dynamics analysis.
abstract: BACKGROUND
  Newborn mammals suffering from moderate hypoxia during or after birth are able to compensate a transitory lack of oxygen by adapting their vital functions. Exposure to hypoxia leads to an increase in the sympathetic tone causing cardio-respiratory response, peripheral vasoconstriction and vasodilatation in privileged organs like the heart and brain. However, there is only limited information available about the time and intensity changes of the underlying complex processes controlled by the autonomic nervous system.
  
  
  METHODS
  In this study an animal model involving seven piglets was used to examine an induced state of circulatory redistribution caused by moderate oxygen deficit. In addition to the main focus on the complex dynamics occurring during sustained normocapnic hypoxia, the development of autonomic regulation after induced reoxygenation had been analysed. For this purpose, we first introduced a new algorithm to prove stationary conditions in short-term time series. Then we investigated a multitude of indices from heart rate and blood pressure variability and from bivariate interactions, also analysing respiration signals, to quantify the complexity of vegetative oscillations influenced by hypoxia.
  
  
  RESULTS
  The results demonstrated that normocapnic hypoxia causes an initial increase in cardiovascular complexity and variability, which decreases during moderate hypoxia lasting one hour (p < 0.004). After reoxygenation, cardiovascular complexity parameters returned to pre-hypoxic values (p < 0.003), however not respiratory-related complexity parameters.
  
  
  CONCLUSIONS
  In conclusion, indices from linear and nonlinear dynamics reflect considerable temporal changes of complexity in autonomous cardio-respiratory regulation due to normocapnic hypoxia shortly after birth. These findings might be suitable for non-invasive clinical monitoring of hypoxia-induced changes of autonomic regulation in newborn humans.
authors.affiliation: Department of Medical Engineering and Biotechnology, University of Applied Sciences, Jena, Germany.
authors.forename: Steffen
authors.initials: S
authors.lastname: Schulz
authors.forename: Sina
authors.initials: S
authors.lastname: Reulecke
authors.forename: Michael
authors.initials: M
authors.lastname: Eiselt
authors.forename: Karin
authors.initials: K
authors.lastname: Schwab
authors.forename: Herbert
authors.initials: H
authors.lastname: Witte
authors.forename: Bernd
authors.initials: B
authors.lastname: Walter
authors.forename: Reinhard
authors.initials: R
authors.lastname: Bauer
authors.forename: Andreas
authors.initials: A
authors.lastname: Voss
mesh_terms: D000465:Algorithms; D000818:Animals; D000831:Animals, Newborn; D001341:Autonomic Nervous System; D001794:Blood Pressure; D001921:Brain / Q000503:physiopathology; D004562:Electrocardiography; D006321:Heart / Q000503:physiopathology; D006339:Heart Rate; D000860:Hypoxia / Q000503:physiopathology*; D023421:Models, Animal; D008954:Models, Biological; D017711:Nonlinear Dynamics; D010100:Oxygen / Q000378:metabolism; D012119:Respiration; D013552:Swine
chemical_list: D010100:Oxygen