Quantification of compensatory processes of postnatal hypoxia in newborn piglets applying short-term nonlinear dynamics analysis

Abstract

BackgroundNewborn 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.MethodsIn 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.ResultsThe 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.ConclusionsIn 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.

Autonomic regulation during quiet and active sleep states in very preterm neonates

“…Due to higher respiratory frequencies (>0.6 Hz), which only occur at very young ages, the direction is less pronounced or even abolished. In an animal study on newborn piglets significant differences for cardiorespiratory coupling was revealed by indices from JSD due to hypoxia following reoxygenation (Reulecke et al, 2011 ; Schulz et al, 2011 ). Hypoxia initially led to greater HR complexity and to stronger cardiovascular and respiratory coupling, maintaining life in the newborn piglets.…”

Short-term vs. long-term heart rate variability in ischemic cardiomyopathy risk stratification

“…By means of stationary NN interval time segments, a possible bias on our final results will be excluded or at least minimized. In accordance with Schulz et al (Schulz et al, 2011 ), we therefore extracted and used only 30 min NN time segments for daytime and nighttime hours, thereby fulfilling the pre-selection criterion for most stationary segments.…”

Yoga in school sports improves functioning of autonomic nervous system in young adults: A non-randomized controlled pilot study

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