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Increased amplitude modulation of continuous respiration precedes sudden infant death syndrome -detection by spectral
T Rantonen1, J Jalonen, J Grönlund
1Department of Paediatrics, University of Turku, Finland. tiiran@utu.fi
Insights
Infants at risk of sudden infant death syndrome (SIDS) exhibit more slow oscillatory breathing due to immature autonomic nervous system control. Spectral analysis of respiratory activity can detect these patterns, even in seemingly regular breathing, aiding in SIDS risk assessment.
Area of Science:
- Cardiorespiratory physiology
- Infant health and development
- Autonomic nervous system function
Background:
- Sudden infant death syndrome (SIDS) is linked to immature autonomic nervous system control.
- This immaturity may lead to attenuated respiratory control and increased slow oscillatory breathing in at-risk infants.
Purpose of the Study:
- To investigate respiratory activity (RAV) and heart rate variability (HRV) patterns in infants who later experienced SIDS.
- To determine if spectral analysis can differentiate SIDS infants from controls based on cardiorespiratory control parameters.
Main Methods:
- Prospective analysis of Medilog recordings from 16 SIDS infants and 22 matched controls.
- Visual selection of regular breathing segments (120s duration) for Fast-Fourier transformation and spectral analysis.
- Examination of RAV and HRV in low (LF) and high (HF) frequency bands, calculating LF/HF ratios and oscillation amounts.
Main Results:
- The SIDS group showed significantly greater LF/HF ratios in respiratory activity spectral analysis compared to controls.
- A significantly higher amount of slow oscillation was detected in the respiratory signal of SIDS victims.
- No significant intergroup differences were found in HRV parameters or cross-spectral parameters.
Conclusions:
- The respiratory control system appears less stable in SIDS victims, leading to increased slow oscillatory breathing.
- Spectral analysis of respiratory activity is a valuable tool for detecting subtle respiratory control abnormalities in infants at risk for SIDS, even during regular breathing.
Abstract:
The immaturity of the control of the autonomic nervous system has been suggested as one of the key factors in the pathophysiology of sudden infant death syndrome (SIDS). Therefore, the attenuated control of respiration may also cause more slow oscillatory breathing among infants at risk of SIDS. In this study, patterns of respiratory activity (RAV) and heart rate variability (HRV) were examined in Medilog-records prospectively obtained from 22 tape recordings made on 16 babies subsequently suffering from SIDS and from 22 matched control babies. A total of 248 signal segments, 120 s in duration, representing the state of regular breathing were visually selected for further analysis. The digitised signal sets were detrended, Fast-Fourier-transformed and autospectra as well as cross-spectra for the HRV and HRV were computed. The RAV and HRV were examined at two spectral bands: (1) a low frequency (LF) band 0.03-0.17 Hz (1.8-10 cycles/min) and (2) a high frequency (HF) band 0.3-1.3 Hz (18-90 cycles/min). Different parameters of each band were tested in the spectral analysis of cardiorespiratory control. The LF/HF-ratio of the spectral peak area of the respiratory activity and the LF/HF-ratio of the spectral band area of the respiratory activity were greater in the SIDS group when compared to the controls. No significant intergroup differences were found in the parameters of HRV, or the cross-spectral parameters. Interestingly, the technique appeared helpful in displaying that the victims of SIDS had a significantly greater amount of slow oscillation in the continuous respiratory signal (1.05+/-1.89 vs. 0.41+/-0.57, P=0.02). In the victims of SIDS the respiratory control system seems to be less stable and cause more slow oscillatory breathing and this can be detected using spectral analysis of respiratory activity even during breathing that visually seems to be regular.