With few exceptions, asymptomatic premature infants do not exhibit significant delays in sleep architecture compared with term infants at comparable postmenstrual age. The preterm infant with an early gestational age and morbidity exhibited delayed sleep architecture.

ExtractThis study examined spontaneous heart rate ( H R ) and variability as a function of age and sleep state in eight normal full term infants from birth to 6 months of age. Heart rates recorded during sleep were lower and less regular a t 1 week (quiet sleep (QS) mean rate = 128, interquartile range = 6.4 beatslmin; rapid eye movement (REM) = 134.5, 11.6) than at 1 month ( Q S = 138.6, 3.4; REM 139.6.4.2). Rate decreased sharply from 1 to 3 months ( Q S = 118; REM 123.8) and decreased only slightly thereafter (6-month Q S = 113.5; REM 118.9). Variability decreased rapidly in REM from 2 to 4 months (from 11.4 to 9.1) and less quickly from 4 to 6 months (from 9.1 to 8.2), while Q S variability decreased at 1 month (from 6.4 to 5.7) and became stable from that point (6.0 at 6 months). Waking heart rate and variability were both relatively low at 1 week (163, 11.2 beatslmin) and increased from that age to 1 month (167.4, 14.3). Rate decreased rapidly in waking at 3 months (152 beatslmin) and more slowly thereafter (152 beatslmin at 4 months, 149 beatslmin a t 6 months), whereas variability remained elevated until after 3 months, becoming stable a t a lower level during later infancy (3 months = 14.8,6 months 11.7). Lowest values of rate and variability were found in Q S and the highest values were found in waking a t all ages, except at 1 week. Heart rates during REM closely approximated those in QS, whereas variability values more closely resembled those of waking. SpeculationIt would appear that, in the normal infant, there are at least three relatively discrete stages in the ontogenetic sequence of cardiac rate and variability characteristics: a newborn period, early infancy ( 1-3 months), and later infancy. Since regulation of cardiac activity is greatly modified by sleep and waking behavior, the measurement of heart rate and variability must consider state as a factor in such regulation. Moreover, since states undergo both qualitative and quantitative changes during the first 6 months of age, the nature of cardiac regulation during this period may be a function of state maturation.Normative heart rate data from the newborn period have been reported by several research groups (2,(11)(12)(13)(14)(15)(16)(17)(18). However, data from older infants have largely been collected incidentally in the form of baseline levels during studies focused upon heart rate stimulus-response characteristics. Thus, Lipton et al. (10) provided individual H R levels before and after stimulation of infants at 2.5 and 5 months, from which a normative range and variability index could only be inferred. Lewis et al. (8) and Campos and Brackbill (3) also presented cardiac data for infants between 2 and 8 weeks and 2 and 4 weeks with sample baseline rates. In addition, Lewis et al. (9) followed resting heart rate and variability from the prenatal period through the first year of life. The sequential development of cardiac regulation postnatally, except for these latter studies, is relatively unexplored.Few studies, either of newborns or o...

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SummaryThis study examined spontaneous respiratory rate and variability as a function of age and sleep state in eight normal fullterm infants. Each infant was admitted at 5 0 0 PM to the sleep laboratory for 12-hr monitoring sessions during the first week of life and at 1, 2, 3, 4, and 6 months of age. Both sleep and cardiopulmonary variables were recorded. A Beckman pCO, monitor sampled expired gas through a miniature cannula taped under the infant's nostrils. Peaks and troughs of breaths were measured by a computer peak sensing program. Median respiratory rates and interquartile ranges of breath intervals for each minute were determined. Each minute was coded as quiet sleep (QS), active sleep (AS), waking (AW), and indeterminate state (IN). Respiratory rates and variability were highest during the first week of life. They declined during the next 2 months and began to level out at 3 months of age (Table 3).The state-relationship was not homogeneous at all ages. Respiratory rates and variability during wakefulness were always higher than those during sleep states. The strongest relation between respiration and sleep states was found between birth and 3 months of age. QS values were uniformly low, and those of AS and IN minutes were intermediate between AW and QS. SpeculationRespiration rates and variability decreased linearly between birth and three months of age. The differences between the developmental course of respiratory rates and variability between 1 and 3 months reported here and cardiac rates and variability previously reported in the same infants suggest a difference in the central nervous system modulation of these systems.Early studies of respiration in infants are characterized by a lack of systematic attention to sleep states (3,4,15) (18) were among the first to establish conclusively the significant state modulation of respiratory rate and variability in infants up to 8 days of age. During the QS state, Prechtl et al. (18) reported breathing rates between 34 and 40/min, whereas during AS, the range increased to 42-60/min. Breath to breath variability was found to be less during QS than during AS. These studies are restricted to the newborn period.Another variable found to influence baseline respiratory rates is the feeding or prandial cycle. Ashton and Connolly (2) found higher breathing rates during the time period immediately after feeding as compared to the remainder of the interfeeding time in all sleep states. Again, these studies were restricted to newborn infants. The lack of systematic studies in older infants has precluded assessment of the theoretical and clinical significance of early developmental respiratory patterns. A long term continuous monitoring paradigm is particularly suited for evaluation of the relative effects of state and feeding, as well as the emergence of a circadian modulation. Such normative data are essential for subsequent identification of abnormal breathing patterns.The present report is the second in a series of papers which will describe polygraphic measureme...