Sigh-related heart rate changes during sleep in premature and full-term newborns

The functional linkage in the cardio-respiratory system demands precise coordination of their activity. Sighs provide an opportunity to study the interaction and the maturation of the autonomic nervous system. In 4 groups of normal, sleeping newborns (31 to 41 weeks conceptional age [wCA], 2 to 10 days postnatal age) we investigated heart rate changes caused by sighs by means of polygraphy. In full-term (39-41 wCA) and near-term newborns (37-38 wCA) sighs during quiet sleep (QS) were accompanied by heart rate acceleration (p < 0.01) and thereafter by heart rate deceleration (p < 0.01). During active sleep (AS) only heart rate acceleration (p < 0.01) was observable. In prematures (35-36 wCA) acceleration could be observed in QS (p < 0.01) and AS (p < 0.01) but no deceleration in QS. In prematures of 31-34 wCA no changes during AS and QS could be detected. Body movements caused heart rate acceleration but no heart rate deceleration. In conclusion, it can be hypothesized that heart rate acceleration may be caused by reduced vagotonus initiated by augmented lung volume and movements. Sigh-related changes responsible for heart rate deceleration occur solely during quiet sleep. In prematures of 31-34 wCA these reflexes are not developed.