Sleep Respiratory Instability in Term Neonates under Hyperthermic Conditions: Age, Sex, Type of Feeding, and Rapid Eye Movements

Abstract

SummaryThe purpose of this study was to examine the influence of neonatal age, sex, type of feeding, and rapid eye movements on the occurrence of apneic pauses during sleep in a hyperthermic environment. One hundred and twenty fullterm infants (equally divided by sex and type of feeding) were observed during a complete nap within the first and approximately fourth wk of life. Each sleep session was characterized by twenty-one measures including the longest apneic pause, mean apnea duration, relative frequency of apnea, apnea periodicity, respiratory rate, and relative frequency of REM epochs. The relative frequency of REM epochs decreased with age and was greater in formula-fed (versus breast-fed) infants.The longest apneic pauses were greater in the first wk of life and in breast-fed infants. In addition, the average Longest Duration: REM"" was '-' greater,"", than ...... the,""" average...... Longest Duration:NREM. Of potential importance was the demonstration that this latter effect was greater in the first wk than in the fourth wk of life. Breast-fed infants and females had larger apnea Mean Duration scores. The relative frequency of apneic pauses (~2 sec in duration), periodicity, and the relative amount of apnea were greater in the fourth-wk study and in breast-fed infants. The relative frequency of apneic pauses~6 sec in duration (Apnea6%) and the A6/D% measure were greater in breast-fed infants. Numerous interactions were observed between age, sex, and type of feeding. Respiratory rate decreased with age and was greater during NREM epochs and in formula-fed infants.served at home on an apnea monitor, were interpreted as consistent with the sleep apnea-SIDS hypothesis; however, difficulty in controlling environmental variables and the numerous problems associated with the use of commercially available apnea monitors in the home (such as the frequency of false alarms as well as its potential psychologic effects on family members) limit its potential as a routine research technique for assessing the influence of SIDS-related variables on the occurrence of prolonged apnea.The current study makes use of the observation that infants who have prolonged sleep apnea, in contrast to controls, also demonstrate more frequent and longer apneic pauses during a complete nap when observed in a controlled hyperthermic environment (13). In the latter study, this testing approach was employed because of the underlying hypothesis that respiratory instability was most apt to occur when infants were exposed either to an environmental or endogenous stress. The choice of a hyperthermic environment was based on the observation that prolonged apnea tended to occur when the ambient temperature was elevated (7). The primary purpose of this study was to examine the affects of neonatal age, sex, type of feeding, and rapid eye movements on the occurrence of apneic pauses during sleep. Because the occurrence of apneic pauses may be a reflection of a more generalized ability to control respiratory activity, it also seemed appropriate to...

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