Sudden Infant Death Syndrome: Abnormalities in Short Term Fluctuations in Heart Rate and Respiratory Activity

Abstract

SummaryIn order to test the hypothesis that a defect in cardiorespiratory regulation contributes to death of infants from sudden infant death syndrome (SIDS), we analyzed the power spectra of heart rate and respiratory activity during 256-sec epochs of quiet sleep. Data were obtained from pneumogram recordings performed for 12 h at night on eight infants who subsequently died from SIDS and 22 age-matched control infants. We computed the heart rate and respiratory power spectra from a single epoch on each infant using an algorithm developed for an 8085 microprocessor system dedicated to this investieation. There was no statistically sienificant difference betweenvSID~ and controls based on mean-respiratory and heart rates. Spectral analysis revealed enhancement in general has rested on the analysis of naturally occurring fluctuations in system variables (4). These fluctuations contain information concerning the spontaneously changing load on the system as well as the system's response. A useful first step in the quantitative analysis of the control system is the spectral analysis of the system variables. Prior work (1, 7, 9, 11) has emphasized the importance and relevance of the analysis of fluctuations in heart rate to assess autonomic functions. We present here the results of spectral analysis of 256-sec-long segments ofthe instantaneous heart and respiratory waveform in 22 control infants and eight infants who died of SIDS. MATERIALS AND METHODSof low frequency power in the 0.02 to 0.1 Hz band in the heart rate power spectrum in the SIDS group compared to control ( p Infants who died of SIDS diagnosed after an autopsy failed to < 0.002) and dispersion in respiratory frequency as determined identify the cause of death were evaluated because they all had by the respiratory band width ( p < 0.0000~). These data suggest at least one nocturnal recording of ECG and respiration at home. that a predisposition to SIDS manifests itself in an abnormal The indications for conducting the recording were near-SIDS pattern of fluctuations in heart rate and respiratory activity.(2), choking spells (2), and death from SIDS in one sibling (1) or two siblinns (2). One of the latter also exmrienced a near--. , SIDS event. Thus, three had not experiencedmnear-SIDS; in two Abbreviations of these, GER was identified on barium swallow. Although she SIDS, sudden infant death syndrome had no choking spells, GER was also identified in a sibling with ECG, electrocardiogram near-SIDS (patient 7, Table 1). The shortest interval between a EEG, electroencephalogram spell and the nocturnal recording was 5 days (the first recording GER, gastroesophageal reflux in patient 7). Near-SIDS was defined as sleep onset apnea asso-HR, heart rate ciated with limpness and cyanosis or pallor responding only to vigorous stimulation or resuscitation. Identifiable causes of pathologic apnea were ruled out by complete blood count, ECG, The purpose of this investigation was to test the hypothesis EEG, chest x-ray, serum Na' , K' , C1-, HC03-, and Ca2+, and sugg...

Mice Lacking Brain-Derived Neurotrophic Factor Exhibit Visceral Sensory Neuron Losses Distinct from Mice Lacking NT4 and Display a Severe Developmental Deficit in Control of Breathing

“…For example, increased incidence of periodic breathing and apnea (Steinschneider, 1972;Guilleminault et al, 1979;Kelly et al, 1986), impaired regulation of alveolar ventilation (Shannon and Kelly, 1977), abnormal fluctuations in heart rate and respiratory patterns (Gordon et al, 1984;Schechtman et al, 1988Schechtman et al, , 1990Schechtman et al, , 1992, and abnormal development of vagal nerve fibers (Becker et al, 1993) have all been implicated as factors contributing to the Sudden Infant Death Syndrome. Impaired hypoxic ventilatory responsiveness may also contribute to some forms of congenital chronic hypoventilation syndrome (Marcus et al, 1991;Weese-Mayer et al, 1992;Ogawa et al, 1993).…”

Analysis of Heart Rate and Respiratory Patterns in Sudden Infant Death Syndrome Victims and Control Infants

“…We also compared the control and SIDS groups in the present general population study with those groups in the previous spectral analysis study (2) of a referred infant population. Using the two measures (respiratory bandwidth and low frequency HR oscillations), we found no statistical difference in the two control groups, but did find a significant difference between the two SIDS groups (Fig.…”

“…We wished to compare the results of the analysis described herein with the results of the analysis obtained from infants at high risk of SIDS (2). For this comparison to be made, it was necessary to show that the data from the two studies were compatible.…”

“…The value of the low frequency power in the HR power spectrum and the value of the respiratory bandwidth were identified for each segment so chosen. These two parameters distinguished SIDS from controls in a retrospective study (2). In order to avoid introducing bias, we selected from all the segments analyzed that segment with the lowest power in the low frequency band in the HR power spectrum.…”

Analysis of respiratory rate and the respiratory cycle in infants and children using an optical sensor

“…the fiindamental frequency) gives a measure of dispersion in respiratory frequency around the mean RR (Gordon et al, 1984).…”