Responses to partial nasal obstruction in sleeping infants

Partial nasal obstruction was performed during a morning of quiet sleep (QS: non-REM) and active sleep (AS: REM) at ages 1 week, 2 weeks, 1, 2, 3, 4 and 6 months on 12 normal infants, 15 subsequent siblings of victims of the Sudden Infant Death Syndrome (SIDS) and 12 infants admitted for investigation of infant apnoea ('near-miss' SIDS). In all three groups the numbers failing to arouse after 240 s (FTA-240) in QS were significantly greater than those in AS. After 2 months of age all groups showed a decrease in the number FTA-240 in AS, whereas in QS the number did not change significantly. Subsequent siblings of SIDS had a significantly higher number FTA-240 in QS than controls. There was no significant difference in FTA-240 in QS between controls and infant apnoeas, although there was a trend for this to be higher in subsequent siblings of SIDS than infant apnoeas.
It was concluded that arousal from AS is more marked than from QS, that after 2 months of age the ability to arouse from AS increases, and that in relation to SIDS, QS is the sleep state in which the infant is less able to arouse. Furthermore, subsequent siblings of SIDS differ from normal infants in their ability to arouse from QS.     

Responses to partial nasal obstruction in sleeping infants

Partial nasal obstruction was performed during a morning of quiet sleep (QS: non-REM) and active sleep (AS: REM) at ages 1 week, 2 weeks, 1, 2, 3, 4 and 6 months on 12 normal infants, 15 subsequent siblings of victims of the Sudden Infant Death Syndrome (SIDS) and 12 infants admitted for investigation of infant apnoea ('near-miss' SIDS). In all three groups the numbers failing to arouse after 240 s (FTA-240) in QS were significantly greater than those in AS. After 2 months of age all groups showed a decrease in the number FTA-240 in AS, whereas in QS the number did not change significantly. Subsequent siblings of SIDS had a significantly higher number FTA-240 in QS than controls. There was no significant difference in FTA-240 in QS between controls and infant apnoeas, although there was a trend for this to be higher in subsequent siblings of SIDS than infant apnoeas. It was concluded that arousal from AS is more marked than from QS, that after 2 months of age the ability to arouse from AS increases, and that in relation to SIDS, QS is the sleep state in which the infant is less able to arouse. Furthermore, subsequent siblings of SIDS differ from normal infants in their ability to arouse from QS.     

Model of normal prepubertal growth

Overheating may cause terminal apnoea and cot death. Rectal temperature and breathing patterns were examined in normal infants at home during the first 6 months of life. Twenty one infants had continuous overnight rectal temperature and breathing recordings for 429 nights (mean 20.4 nights, range 7-30) spaced over the first six months of life. Periods when breathing was 'regular' were directly marked on single night records. Sleep state was determined from respiratory variables. 'Regular' breathing was a reliable marker of 'quiet' sleep (specificity 93%). The duration of 'quiet' sleep increased from 6 to 22 minutes from two weeks to three months of age and then remained static, as did the proportion of sleep spent in the quiet phase (9% to 34%). Rectal temperature fell during 66% of quiet sleep and usually rose during rapid eye movement (REM) sleep. The drop in rectal temperature was maximal at the start of quiet sleep, whereas the maximum rise during REM sleep was reached after 10 to 15 minutes. Oscillations in rectal temperature are associated with changes in sleep and breathing state. The maturation of rectal temperature patterns during the first six months of life are closely related to a maturation of sleep state and breathing patterns.     

Polygraphic studies of normal infants during the first six months of life. I. Heart rate and variability as a function of state.

This study examined spontaneous heart rate (HR) 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 at 1 week (quiet sleep (QS) mean rate= 128, interquartile range = 6.4 beats/min; rapid eye movement (REM) = 134.5, 11.6) than at 1 month (QS = 138.6, 3.4; REM 139.6, 4.2). Rate decreased sharply from 1 to 3 months (QS = 118; REM 123.8) and decreased only slightly therafter (6-month QS = 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 QS 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 beats/min) and increased from that age to 1 month (167.4, 14.3). Rate decreased rapidly in waking at 3 months (152 beats/min) and more slowly therafter (152 beats/min at 4 months, 149 beats/min at 6 months), whereas variability remained elevated until after 3 months, becoming stable at a lower level during later infancy (3 months = 14.8,6 months 11.7). Lowest values of rate and variability were found in QS and the highest values were found in waking at all ages, except at 1 week. Heart rates during REM closely approximated those in QS, whereas variability values more closely resembled those of waking.     

Breathing,sleep state,and rectal temperature oscillations.

Overheating may cause terminal apnoea and cot death. Rectal temperature and breathing patterns were examined in normal infants at home during the first 6 months of life. Twenty one infants had continuous overnight rectal temperature and breathing recordings for 429 nights (mean 20.4 nights, range 7-30) spaced over the first six months of life. Periods when breathing was ''regular'' were directly marked on single night records. Sleep state was determined from respiratory variables. ''Regular'' breathing was a reliable marker of ''quiet'' sleep (specificity 93%). The duration of ''quiet'' sleep increased from 6 to 22 minutes from two weeks to three months of age and then remained static, as did the proportion of sleep spent in the quiet phase (9% to 34%). Rectal temperature fell during 66% of quiet sleep and usually rose during rapid eye movement (REM) sleep. The drop in rectal temperature was maximal at the start of quiet sleep, whereas the maximum rise during REM sleep was reached after 10 to 15 minutes. Oscillations in rectal temperature are associated with changes in sleep and breathing state. The maturation of rectal temperature patterns during the first six months of life are closely related to a maturation of sleep state and breathing patterns.     

Metabolic rate and O2 consumption in newborns during different states of vigilance.

In 135 asymptomatic newborn infants, 1--53 days of age, body weight 1,820--4,120 g, indirect calometry was performed. According to the state of wakefulness the infants showed during the testing procedure, they were divided into four groups of vigilance (V1--V4). Metabolic rate and oxygen consumption showed similar results between groups V1, V2 and V3 (deep sleep; REM sleep; wakefulness with no muscular activity). V4 infants (with muscular activity) had a higher metabolic rate and O2 consumption. Correlation between metabolic rate and body surface area is similar in V2 and V3 but shows a steeper slope in the V1 group. It is speculated that central regulatory mechanisms may account for this difference.     

Spontaneous awakenings in preterm and term infants assessed throughout 24-h video-recordings

The study aimed to evaluate the development of awakenings during preterm and term age in 12 low-risk infants observed between 33 and 40 weeks of post-conceptional age. Waking was been detected through the analysis of body motility. Gross generalized body movements with prolonged startles, marked stretching and writhing was considered as waking, whereas vigorous, forceful abrupt body movements with high frequency tremor sometimes superimposed upon movements were considered as corresponding to crying. Total number of awakenings in the 24 h does not show significant changes with age, whereas the mean duration increases significantly, which is accounted for mainly by those awakenings starting with crying, in particular, during the day. These data suggest a developmental gap between the ability to sustain the waking state, which already starts to increase before term age, and the ability to maintain prolonged sleep episodes, which has been shown to develop later. Furthermore, the developmental difference between awakenings starting with crying and awakenings starting with wakefulness suggests that two kinds of awakenings might be modulated by different factors.     

Heart rate responses to non-arousing trigeminal stimulation in infants: effects of sleep position, sleep state and postnatal age

AIMS: The aim of this study was to examine the effects of maternal smoking, sleeping position, sleep state and postnatal age on heart rate changes following non-arousing trigeminal stimulation in infants. SUBJECTS: We studied healthy term infants, 13 of whom were born to mothers who did not smoke and 11 to mothers who smoked during pregnancy. Each infant was studied using daytime polysomnography on 3 occasions: (a) 2-3 weeks, (b) 2-3 months and (c) 5-6 months after birth. Nasal air-jet stimulation was presented in both active sleep (AS) and quiet sleep (QS) when infants slept both prone and supine. RESULTS: We found no difference between infants of smoking and non-smoking mothers in any of the parameters measured. Minimum HR (MinHR) following non-arousing trigeminal stimulation was significantly lower in the supine compared to the prone sleeping position at 2-3 weeks and 2-3 months of age (p<0.05) in AS, and at all 3 ages in QS (p<0.01). MinHR was significantly lower in QS compared to AS at 2-3 months when infants slept prone and at 5-6 months when sleeping supine (p<0.01). In QS, MinHR became lower with increasing postnatal age in both sleep positions (p<0.01). In AS, there was no maturational effect. The normalized bradycardia (DeltaHR%) was significantly greater in AS than in QS at 2-3 weeks of age (p<0.05) when infants slept supine. CONCLUSION: Our study has shown that there was a decrease in heart rate (MinHR) following trigeminal stimulation in infants up to 6 months of age and this was affected by sleep position and sleep state, being larger in the supine sleeping position and the QS state.     

Infants with colic have a normal sleep structure at 2 and 7 months of age

OBJECTIVE: To compare nighttime sleep structure between infants with colic and a control group. STUDY DESIGN: Sleep and cry times of 15 infants with colic and 16 infants in a control group were recorded with the use of a daily diary at the ages of 5 weeks and 6 months. The diary was kept at home for a 1-week period. Overnight polygraphic sleep recordings in a sleep laboratory were performed when the infants were 2 months of age and were repeated for 11 infants with colic and 14 infants in a control group at 7 months of age. RESULTS: Daily sleep time was shorter in infants with colic compared with the control group at 5 weeks of age (P =.001). Polygraphic data showed a similar sleep structure between the study groups at 2 and 7 months of age. Infants with colic had somewhat more obstructive apneas during rapid eye movement sleep at the age of 2 months (P =.04), and they had fewer awakenings at the age of 7 months than the control group (P =.003). CONCLUSION: Infants with colic had normal sleep polygraphic finding at 2 and 7 months of age including sleep structure, movements, and breathing. Despite the shorter reported daily sleep times, the polygraphic data did not suggest infantile colic to be associated with a sleep disorder.     

Sleep states development in the first year of life assessed through 24-h recordings

Sleep measures have been evaluated in 13 normal infants aged between 2 weeks and 11 months 3 weeks, with 24 h polygraphic records. Values over the whole 24 h period show that quiet sleep (QS) increases with age while paradoxical sleep (PS) and ambiguous sleep (AmbS) decrease; however, when the 24 h period is split into two periods (day-time, night-time) it can be seen that QS increases only during the night-time while PS and AmbS decrease only during the day-time. The QS in older subjects becomes mainly located at the beginning of the night-time period, when particularly long phases take place. The distribution during the night-time of PS (in terms of the amount and of the mean duration of the phases) does not change with age.     

Lack of temporal relation between acid reflux in the proximal oesophagus and cardiorespiratory events in sleeping infants

We studied sleeping infants in order to investigate whether a temporal relation exists between acid reflux extending to the proximal portion of the oesophagus and cardiorespiratory events. One hundred infants with occasional regurgitations were studied: 50 infants admitted after an apparently life-threatening event (ALTE) that occurred during sleep and that remained unexplained despite medical investigation, and 50 asymptomatic infants (non-ALTE). The infants had a median age of 8 weeks (range 4-26 weeks); 54 were boys. In each child a pH probe was placed in the proximal portion of the thoracic oesophagus, under radiological control. Polygraphic monitoring of state of alertness, cardiorespiratory activity, and proximal oesophageal pH changes was conducted continuously during 1 night. The data were analysed blind. In 80 infants a total of 186 decreases in oesophageal pH below 4 units were seen; 37% occurred during wakefulness, and 40% during rapid eye movement (REM) sleep. A total of 7029 central and 61 obstructive apnoeas were monitored, mainly during REM sleep. Within 5 min before, and 5 min after the drops in pH, there was no difference in the number, or the duration of bradycardia, central, mixed, or obstructive apnoea. The infants with an ALTE could not be differentiated from the non-ALTE infants for any of the variables studied. It is concluded that spontaneous acid refluxes extending to the proximal portion of the oesophagus during sleep are usually not temporally related with the development of apnoeas or bradycardias.     

Effects of maternal tobacco smoking,sleeping position,and sleep state on arousal in healthy term infants

OBJECTIVES: To investigate whether a history of maternal tobacco smoking affected the maturation of arousal responses and whether sleeping position and infant age alters these relations. DESIGN: Healthy term infants (13 born to mothers who did not smoke and 11 to mothers who smoked during pregnancy) were studied using daytime polysomnography on three occasions: (a) two to three weeks after birth, (b) two to three months after birth, and (c) five to six months after birth. Multiple measurements of arousal threshold in response to air jet stimulation were made in both active sleep (AS) and quiet sleep (QS) when infants slept both prone and supine. RESULTS: Maternal smoking significantly elevated arousal threshold in QS when infants slept supine at 2-3 months of age (p<0.05). Infants of smoking mothers also had fewer spontaneous arousals from QS at 2-3 months in both prone (p<0.05) and supine (p<0.001) sleeping positions. In infants of non-smoking mothers, arousal thresholds were elevated in the prone position in AS at 2-3 months (p<0.01) and QS at 2-3 weeks (p<0.05) and 2-3 months (p<0.001). CONCLUSIONS: Maternal tobacco smoking significantly impairs both stimulus induced and spontaneous arousal from QS when infants sleep in the supine position, at the age when the incidence of sudden infant death syndrome is highest.     

Respiratory frequency during sleep in siblings of sudden infant death syndrome victims. A comparison with control, normal infants

The present study was carried out on 76 polygraphic recordings performed on 38 siblings of sudden infant death syndrome victims and on 38 control (2 days to 18 weeks old) infants. Each sibling corresponded to a control infant according to gender, gestational age at birth and postnatal age criteria. We found that in siblings as in controls, respiratory frequency (RF) was higher in active sleep (AS) compared to quiet sleep (QS) state (P less than 0.05 for 11-18 week siblings, p less than 0.01 for the other groups). During the transitional sleep (TS), RF was on an intermediate level (AS greater than TS greater than QS). There were no significant differences between RF of siblings compared to controls, except that RF during QS in 6-10 week control infants was higher than in siblings of the same age (P less than 0.05). We found a wide variability between RF of different individuals within all the age groups of siblings and of controls (P less than 0.001). However, a high correlation was usually noted between RF found in different sleep states: some infants (siblings or controls) breathed more rapidly and others more slowly in all states studied. In siblings, as previously described in other groups of normal infants, RF seems to be an individual characteristic. In addition, the present work shows that according to RF criterion, healthy siblings are similar to normal infants.     

Motility and arousal in near miss sudden infant death syndrome

Developmental sleep patterns were compared in infants at known risk for "near-miss" sudden infant death syndrome and age-matched normal infants. Near-miss SIDS infants had significant differences suggestive of a temporary developmental delay. They retained rapid eye movement (REM) sleep at neonatal proportions, and stage 2 non-REM sleep appeared later. They also had a significantly increased apnea index. Twenty-four-hour recordings of sleep and respiratory patterns in near-miss SIDS infants from 3 weeks through 6 months of age showed a significant reduction in number of body movements in REM, non-REM, and total sleep time and in percentage of movement time at 3 weeks through 3 months of age. These findings can be used to address the role of arousal threshold in infants at risk for SIDS.     

Insomnia and cow's milk allergy in infants

A group of eight infants (six boys and two girls, 7 to 46 weeks of age) is reported, in whom a causal relationship between cow's milk allergy and chronic sleeplessness was suspected. They were referred because of waking and crying episodes that had occurred since the early days of life during sleep hours. During an average night, they slept about 4.5 hours and woke their parents about five times. They cried a lot during the day and were described as fussy. Two infants had been treated with phenothiazine without improvement. No cause for chronic insomnia was found during a standard medical and psychologic workup. An all-night polygraphic recording confirmed the disrupted sleep pattern of these infants, as compared with that of normal infants, and excluded further causes of arousals. Due to a clinical suspicion of atopy, the infants were further subjected to a series of allergy tests. IgE levels were shown to be elevated in each child, and radioallergosorbent tests were positive for cow's milk protein. The infants were than fed exclusively with a hydrolyzed milk protein mixture for 4 weeks. Sleep normalized within 2 weeks in every infant: night sleep increased to a median of 10 hours, and the awakenings only occurred occasionally. In four infants less than 6 months of age, cow's milk was reintroduced in the diet, and within 1 week all four became severely sleepless. Cow's milk was again excluded from the diet and the babies' sleep behaviors were again normalized. It is concluded that, when no evident cause for sleeplessness can be found in an infant, the possibility of milk allergy should be given serious consideration.     

Comparison of evoked arousability in breast and formula fed infants

Background: Currently, there is no consistent evidence that breast feeding reduces the risk for sudden infant death syndrome (SIDS). Arousal from sleep is believed to be an important survival mechanism that may be impaired in victims of SIDS. Previously it has been shown that arousability is impaired by the major risk factors for SIDS such as prone sleeping and maternal smoking. Aims: To establish whether arousability was altered by method of feeding, and whether breast fed infants would have lower arousal thresholds. Methods: Forty three healthy term infants were studied using daytime polysomnography on three occasions: 2–4 weeks post-term, 2–3 months post-term, and 5–6 months post-term. Multiple measurements of arousal threshold (cm H₂O) in response to nasal air jet stimulation applied alternately to the nares were made in both active sleep (AS) and quiet sleep (QS) while infants slept supine. Arousal thresholds and sleep period lengths were compared between formula fed and breast fed infants at each age. Results: Arousal thresholds were not different between breast fed and formula fed infants in QS. However, in AS breast fed infants were significantly more arousable than formula fed infants at 2–3 months of age. There was no difference between groups of infants when sleep period length was compared at any study. Conclusions: Breast fed infants are more easily aroused from AS at 2–3 months of age than formula fed infants. This age coincides with the peak incidence of SIDS.     

Comparison of evoked arousability in breast and formula fed infants.

BACKGROUND: Currently, there is no consistent evidence that breast feeding reduces the risk for sudden infant death syndrome (SIDS). Arousal from sleep is believed to be an important survival mechanism that may be impaired in victims of SIDS. Previously it has been shown that arousability is impaired by the major risk factors for SIDS such as prone sleeping and maternal smoking. AIMS: To establish whether arousability was altered by method of feeding, and whether breast fed infants would have lower arousal thresholds. METHODS: Forty three healthy term infants were studied using daytime polysomnography on three occasions: 2-4 weeks post-term, 2-3 months post-term, and 5-6 months post-term. Multiple measurements of arousal threshold (cm H(2)O) in response to nasal air jet stimulation applied alternately to the nares were made in both active sleep (AS) and quiet sleep (QS) while infants slept supine. Arousal thresholds and sleep period lengths were compared between formula fed and breast fed infants at each age. RESULTS: Arousal thresholds were not different between breast fed and formula fed infants in QS. However, in AS breast fed infants were significantly more arousable than formula fed infants at 2-3 months of age. There was no difference between groups of infants when sleep period length was compared at any study. CONCLUSIONS: Breast fed infants are more easily aroused from AS at 2-3 months of age than formula fed infants. This age coincides with the peak incidence of SIDS.     

Infant sleep apnea profile: preterm vs. term infants

By means of polygraphic sleep recording, the sleep apnea profile with respect to the number and duration of inactive, obstructive and mixed apneic episodes as well as periodic breathing has been investigated in infants born preterm at 40, 52 and 64 weeks conceptional age and compared to that of term infants. At 40 weeks preterm infants showed significantly more apnea and periodic breathing compared to term infants. The difference was essentially due to obstructive and mixed apnea in non-REM sleep.There was a sharp decrease in all apneic variables—inactive, obstructive and mixed apnea as well as of periodic breathing—at 52 weeks conceptional age in infants that were previously preterm. Both groups exhibited a rather identical sleep apnea profile at 64 weeks. Two prospectively studied infants in the preterm group later became SIDS victims. One of them might have been identified as being at risk on the basis of his apnea profile compared to the normative data now available.Abbreviations REM rapid eye movements     

Effects of sleep position,sleep state and age on heart rate responses following provoked arousal in term infants

Previous studies have suggested that autonomic dysfunction may be involved in Sudden Infant Death Syndrome (SIDS). The major risk factors for SIDS are the prone sleeping position and maternal smoking. Our aim was to examine the effects of sleeping position and maternal smoking on the postnatal maturation of autonomic function by examining heart rate responses following arousal in healthy term infants. Twenty-four infants (11 born to mothers who smoked during pregnancy and 13 to mother who did not smoke) were studied using daytime polysomnography and multiple measurements of arousal threshold (cm H(2)O) in response to air-jet stimulation applied alternately to the nares were made in both active sleep (AS) and quiet sleep (QS).We demonstrated no difference between smoking and non-smoking groups of infants in any of our measurements, and thus combined data from the groups. Baseline (BHR) was elevated in the prone compared to the supine position in quiet sleep (QS) at 2-3 weeks (p<0.001) and 5-6 months (p<0.001), and in active sleep (AS) at 2-3 and 5-6 months (p<0.05). BHR was significantly elevated in AS compared to QS in the supine position at all ages (p<0.01) and in the prone position at 2-3 (p<0.001) and 5-6 months (p<0.05). Increases in heart rate (deltaHR%) following arousal were significantly greater in the supine compared to the prone position in QS at 2-3 weeks (p<0.05) and in AS at both 2-3 (p<0.01) and 5-6 months (p<0.05). DeltaHR% was significantly greater in AS compared to QS in both supine (p<0.05) and prone (p<0.001) positions at 2-3 weeks and in the supine position at 2-3 months (p<0.001). We conclude that sleep state, sleep position and postnatal age affect the cardiac responses following arousal from sleep in healthy term infants. Impairment of heart rate control in the prone position may be important in understanding the increased risk for SIDS in this position.     

Phenothiazine-induced sleep apneas in normal infants

A relationship between sudden infant death syndrome and the use of phenothiazine-containing medications is suspected. In order to investigate the influence of phenothiazines upon cardiorespiratory and sleep characteristics, four normal infants (mean age 15.8 weeks) had polygraphic recordings made for one night. The recordings were repeated three nights later, after the daily administration of a usual therapeutic dose of a standard phenothiazine syrup (promethazine, 1 mg/kg of body weight per day). The infants were monitored for six days after the first treatment. Findings from the first polygraphic recordings were normal for each infant. The second recordings disclosed an increase in sleep time, a reduction in the number and duration of awakenings, an increase in non-rapid eye movement (NREM) III sleep state, and a reduction in body movements. During the second night, each infant showed an increase in the number of central apneas, and each infant also had several episodes of obstructive apneas (median duration four seconds). It is concluded that promethazine depresses the arousal and respiratory mechanisms in normal infants during sleep. This observation reinforces the opinion that CNS depressants should be avoided in infants less than 1 year of age; CNS depressants could result in sudden death in apnea-prone infants.