Effect of maturation on heart rate response to ocular compression test during rapid eye movement sleep in human infants.

Thirty-three premature and full-term infants (31.5-50 wk postconceptional age) free from neurologic and cardiopulmonary disease at time of testing, underwent a standardized ocular compression test during polygraphically controlled rapid eye movement sleep. RR intervals were measured on the ECG before and during ocular compression. RR interval changes during ocular compression were compared to the preceding 60-s mean RR interval in each infant. Results were analyzed relative to gestational age, postnatal age, and postconceptional age. Baseline heart rate during REM sleep decreased with postconceptional age. During ocular compression, there was a significant negative correlation between the longest RR interval or the "latency" variable with postconceptional age. Latency is defined as the time, in milliseconds, from beginning of eyelid pressure to the first measurable RR increase compared to mean control RR + 1 SD. Our results indicate that during rapid eye movement sleep, "baseline heart rate" decreases with maturation, an effect supposedly related to increased vagal activity, whereas the heart rate response on ocular pressure stimulus, a vagally mediated reflex, is significantly influenced and blunted with maturation.