Increased amplitude modulation of continuous respiration precedes sudden infant death syndrome - Detection by spectral estimation of respirogram

The immaturity of the control of the autonomic nervous system has been sugg ested as one of the key factors in the pathophysiology of sudden infant dea th syndrome (SIDS). Therefore, the attenuated control of respiration may al so cause more slow oscillatory breathing among infants at risk of SIDS, In this study, patterns of respiratory activity (RAV) and heart rate variabili ty (HRV) were examined in Medilog-records prospectively obtained from 22 ta pe recordings made on 16 babies subsequently suffering from SIDS and from 2 2 matched control babies. A total of 248 signal segments, 120 s in duration , representing the state of regular breathing were visually selected for fu rther analysis. The digitised signal sets were detrended, Fast-Fourier-tran sformed and autospectra as well as cross-spectra for the HRV and HRV were c omputed. The RAV and HRV were examined at two spectral bands: (1) a low fre quency (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/H F-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 i n the SIDS group when compared to the controls. No significant intergroup d ifferences were found in the parameters of HRV, or the cross-spectral param eters. 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 bf SIDS the respiratory control system seems to be less stab le and cause more slow oscillatory breathing and this can be detected using spectral analysis of respiratory activity even during breathing that visua lly seems to be regular. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.