Effect of State of Alertness on the Heart Rate Response to Ocular Compression in Human Infants

Abstract

Because the state of alertness exerts a profound influence on autonomic cardiac control, we hypothesized, that the heart rate response to a vagal stimulus, i.e., ocular compression, may differ during different states of alertness. We studied 8 healthy infants with a postconceptional age of 35-41 weeks (mean ± SD 37.9 ± 2.1 weeks). They underwent a standardized ocular compression test during polygraphically controlled wakeful-ness, rapid eye movement (REM) sleep, and non-REM (NREM) sleep. The R-R intervals were measured (1) during the 60 s preceding the ocular compression test, to determine the mean control R-R interval, and (2) during compression. Percent R-R interval was defined as the longest R-R interval in milliseconds during the test divided by the mean control R-R interval and multiplied by 100. The longest R-R interval during the test was significantly greater in REM sleep than in wakefulness (p < 0.05) and in NREM sleep (p < 0.01): 939 ± 360, 623 ± 355, and 538 ± 60 ms, respectively. The percent R-R interval was significantly greater in REM sleep than in NREM sleep (p < 0.01): 236 ± 91 and 129 ± 16, respectively. The time from the longest R-R interval to return to mean control R-R interval, i.e., vagal escape, was significantly shorter in REM sleep than in NREM sleep and in wakefulness (p < 0.01): 843 ± 168,2,131 ± 712, and 2,078 ± 913 ms, respectively. This study indicates that the state of alertness should be defined when performing tests on autonomic reflexes in infants.

Comparison of postnatal development of heart rate responses to trigeminal stimulation in sleeping preterm and term infants

“…No effects of PNA were seen in AS in either term or preterm infants. In contrast to our findings, other studies have reported that the bradycardic reflex decreases with age after birth in both preterm and term infants in responses to ocular compression, oesophageal dilation and trigeminal airstream stimulation to the face during AS and that by term responses were minimal (Ramet et al. , 1988, 1990, 1995).…”

Cardiovascular Consequences of Preterm Birth in the First Year of Life

“…In active sleep no maturation in heart rate responses was observed in either preterm or term infants, however in quiet sleep the magnitude of the heart rate response increased with chronological age in both preterm and term infants (Tuladhar et al, 2005b). These findings are in contrast to other studies which have reported that the bradycardic reflex decreases with age after birth in both preterm and term infants in responses to trigeminal air-stream stimulation to the face, ocular compression and esophageal dilation and during active sleep and that by term responses were minimal (Ramet et al, 1995, Ramet et al, 1988, Ramet et al, 1990. The authors suggested that this bradycardic reflex may be inappropriate and increase the risk of the Sudden Infant Death Syndrome (SIDS) in preterm infants.…”

An old drug for use in the prevention of sudden infant unexpected death due to vagal hypertonia

“…Indeed, by facilitating daily monitoring of RVH-related electrocardiographic changes, the procedure takes into account the circadian rhythm of vagal tone activity, and influence of the state of alertness on autonomic cardiac control. In this respect, RVH appears to be higher during rapid eye movement sleep and early morning hours [19][20][21].…”