Decreased Autonomic Responses to Obstructive Sleep Events in Future Victims of Sudden Infant Death Syndrome

Abstract

To evaluate changes in autonomic nervous system controls in response to obstructive events in future victims of sudden infant death syndrome (SIDS), we studied the polysomnographic sleep recordings of 18 future SIDS infants and those of 36 matched control infants. A heart rate autoregressive power spectral analysis was performed preceding and after the obstructive apneas. The low-frequency to high-frequency power ratio was computed to evaluate sympathovagal balance. Future SIDS victims had significantly more obstructive apneas (p = 0.001) and mixed apneas (p = 0.005) than control infants. Obstructive events occurred mainly during rapid eye movement sleep in the two populations (84.5% in future SIDS victims and 95.8% in control infants; p = NS). Comparing heart rate power spectral analysis before and after obstructive apneas in rapid eye movement sleep, high-frequency power values were significantly lower and low-frequency to high-frequency power ratios higher in future SIDS victims than in control infants. Compared with preapnea values, low-frequency to high-frequency power ratios significantly decreased after obstructive apneas in control infants (p < 0.001) but not in the future SIDS victims. When the obstructive apneas were divided according to duration, the findings were seen mainly for long apneas. In conclusion, future SIDS victims were characterized by different autonomic status and responses to obstructive apneas during sleep. These findings could be relevant to mechanisms implicated in some cases of SIDS.

Síndrome de muerte súbita del lactante: prevalencia y cambios en los últimos años en Chile

“…La triple teoría postula que la MS se debe a: una vulnerabilidad innata, edad y noxa exógena. Dentro de los factores descritos como parte de esta vulnerabilidad innata están la alteración en el despertar ante ciertos estímulos como la hipoxemia e hipercarbia 17 . El deficiente control del despertar estaría menos desarrollado en algunos sujetos más susceptibles, en especial en niño(a)s nacidos de pretérmino 18 .…”

“…Una de las teorías más aceptadas se basa en la "triple teoría" 5 postulada por Wegdwood ya en 1972 6 y ratificada en estudios posteriores por Kahn y cols 7,8 , la cual explica este fenómeno basado en tres factores: 1) riesgo innato del individuo; 2) edad de riesgo y 3) condición predisponente. Recientemente, se ha postulado como mecanismo principal involucrado en la MS una alteración en el umbral del despertar 9 . Durante años la MS ha sido objetivo de múl-tiples estudios que han permitido mejorar el conocimiento y de sus factores relacionados.…”

Precursors of cardiorespiratory events in infants detected by home memory monitor

“…The studies using the CHIME memory monitor and extensive database 1,[5][6][7][8] are unique in comparison to other studies [9][10][11][12][13] because the CHIME monitor provides data for substantially longer periods of time preceding events, and for periods when there are no events. Across a broader range of postmenstrual and postnatal ages, the CHIME data base includes not only a substantial number of events exceeding the threshold for a CE but also a subset of more severe or extreme events (EE) of potentially greater clinical significance (Table 1A).…”

“…5 Although it is not possible to compare directly these results to other studies, it is nevertheless important to consider the extent to which our results may be consistent with prior studies or may enhance our knowledge regarding apnea and bradycardia-related events in at-risk-for-SIDS groups, As recently reviewed, numerous studies have been conducted in infants born premature, SIDS-sibs, and ALTE infants, and have included comparisons with healthy full term infants. [9][10][11][12][13][14][15] These earlier studies indicate evidence of impaired autonomic regulation of cardiorespiratory systems, including increased frequency of mixed and central apneas and respiratory pauses, periodic breathing, differences in resting respiratory or heart rate, and altered heart rate variability or decreases in sustained heart rate changes to respiratory events. Although our threshold criteria for defining a bradycardia event were more stringent than what is typically used to trigger a monitor alarm for bradycardia, heart rate decelerations or more brief bradycardias associated with shorter periods of apnea were not ignored since they were included in the analyses of each recorded event.…”

Potential Asphyxia and Brainstem Abnormalities in Sudden and Unexpected Death in Infants

“…3,11,12 The association of unsafe sleep environmentswith SIDS raises the possibility that normal infants die of asphyxia and that eliminating these dangerous sleeping conditionswill in turn eradicate all SIDS deaths. Yet there is mounting evidence that at least some infants who die of SIDS are not "normal" before death but rather have underlying vulnerabilities, 5,[13][14][15][16][17][18][19][20][21][22][23][24][25][26] including genetic susceptibilities, 27 that put them at risk.…”