Related Experiment Videos
Linear and nonlinear properties of heart rate control in infants at risk
A Patzak1, B Schlüter, W Orlow
1Institut für Physiologie, Universitätsklinikum Charité, Humboldt-Universität zu Berlin, Germany.
Insights
Infants at risk showed altered linear heart rate (HR) control, specifically reduced sympathovagal balance during sleep. However, nonlinear HR control remained similar to healthy infants, indicating preserved complex regulatory mechanisms.
Area of Science:
- Neonatal physiology
- Autonomic nervous system regulation
- Cardiovascular control
Background:
- Infants with bronchopulmonary dysplasia (BPD) may exhibit altered autonomic nervous system (ANS) function.
- Understanding heart rate (HR) control differences is crucial for assessing infant health and development.
Purpose of the Study:
- To compare linear and nonlinear heart rate (HR) control between infants at risk (former preterm with BPD) and healthy controls.
- To investigate potential differences in autonomic regulation during sleep states.
Main Methods:
- Polygraphic recordings during quiet and active sleep in 12 infants with BPD and 18 healthy controls.
- Linear analysis of HR spectra (LF power, HF power, LF/HF ratio).
- Nonlinear analysis using the largest Lyapunov exponent (LLE) of R-R interval time series.
Main Results:
- Infants at risk had significantly lower LF power and LF/HF ratio during quiet sleep, suggesting altered linear sympathovagal balance.
- Nonlinear analysis (LLE) showed no significant differences between groups, indicating similar low-dimensional chaotic behavior of HR control.
- Sleep state-related changes in spectral parameters and LLE were comparable across both groups.
Conclusions:
- Altered linear components of HR control in infants at risk reflect changes in the sympathovagal balance.
- Nonlinear HR control dynamics are preserved in infants with BPD, suggesting intact complex regulatory mechanisms.
- These findings highlight specific alterations in autonomic regulation in infants with BPD.
Abstract:
The aim of this study was to test whether the heart rate (HR) control in infants at risk differs in comparison with healthy infants. Twelve former preterm infants suffering from bronchopulmonary dysplasia and 18 control infants, matched for their postconceptional age, were examined polygraphically during quiet and active sleep. HR, low-frequency (LF) power, high-frequency (HF) power, total power, and the ratio of LF to HF power (LF/HF) of the instantaneous HR spectra were calculated for linear analysis. The largest Lyapunov exponent (LLE) of the R-R interval time series was calculated to determine a nonlinear property of HR. Infants at risk had significantly lower LF power (median: 0.51 x 10(-3) vs. 1.16 x 10(-3) Hz2) and lower LF/HF (median: 1.05 vs. 1.94) during quiet sleep. LLE was positive, revealing low-dimensional chaotic behavior of HR control, and did not differ between both groups (median: quiet sleep, 0.05 bit/s vs. 0.06 bit/s; active sleep, 0.16 bit/s vs. 0.15 bit/s). Sleep state-related changes in spectral parameters and LLE were similar in both groups. In infants at risk, the lower LF/HF during quiet sleep can be interpreted in terms of changes in the rhythmic components of the sympathovagal balance of the autonomic system, which is an expression of linear properties of HR control. Conversely, the lack of differences in LLE between both groups indicates similar nonlinear properties of the control system.