Autonomic responses to sighs in healthy infants and in victims of sudden infant death.
OBJECTIVE
Sigh, defined as an isolated breath with an increased tidal volume, can be associated with abrupt changes in heart rate (HR) or blood oxygenation. Sigh may be followed by a central apnea. As impairment of autonomic control was postulated in future SIDS victims, we hypothesized that their autonomic responses to sighs were different from those of healthy control infants.


METHODS
Sighs followed by central apnea were studied in the sleep recordings of 18 infants who eventually died of SIDS and of 18 control infants. The infants of the two groups were matched for sex, gestational age, postnatal age, weight at birth and sleep position during sleep recording. HR autoregressive power spectral analysis was performed on RR intervals preceding and following sighs.


RESULTS
In all infants, most sighs followed by an apnea were found in NREM sleep. Compared to the control infants, the future SIDS victims were characterized by a greater sympathovagal balance and a lower parasympathetic tonus before the sighs. Following the sighs, no more differences were found in NREM sleep.


CONCLUSIONS
Based on the present findings, it can be postulated that sighs contribute to reset autonomic tonus during NREM sleep.
Franco
Patricia
P
Pediatric Sleep Unit, Hôpital Erasme, Brussels, Belgium. patricia.franco@skynet.be
Verheulpen
Denis
D
Valente
Filomena
F
Kelmanson
Igor
I
de Broca
Alain
A
Scaillet
Sonia
S
Groswasser
José
J
Kahn
André
A
D004569:Electroencephalography; D005260:Female; D006339:Heart Rate / Q000502:physiology*; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D010100:Oxygen / Q000097:blood; D017286:Polysomnography; D012119:Respiration; D012720:Severity of Illness Index; D012891:Sleep Apnea Syndromes / Q000175:diagnosis / Q000453:epidemiology / Q000503:physiopathology; D012895:Sleep, REM / Q000502:physiology; D013398:Sudden Infant Death / Q000453:epidemiology*; D014630:Vagus Nerve / Q000503:physiopathology*
D010100:Oxygen