Ventilation and ventilatory pattern during sleep in aborted sudden infant death syndrome

To assess ventilatory control during sleep in infants at risk for the sudden infant death syndrome (SIDS), we made serial measurements of resting tidal volume (Vt), respiratory cycle time (Ttot), and the ventilatory changes resulting from inhalation of 2% CO2 in aborted SIDS infants in rapid eye movement and quiet sleep and compared them to a group of normal infants during the first 4 months of life. Ventilation was measured by the barometric method, and sleep was staged using electroencephalogram, electrooculogram, and electromyogram and behavioral criteria. Although resting instantaneous minute ventilation (Vt/Ttot) was virtually the same in both groups of infants, Vt tended to be smaller (by up to 50% in the first 2 months) and Ttot tended to be shorter in aborted SIDS than in normal infants in both rapid eye movement and quiet sleep. The increase in the mean Vt/Ttot with 2% CO2 is greater by about 5 to 20% in aborted SIDS than in normal infants at 3 and 4 months of age in both sleep states. These findings, together with our previous findings that aborted SIDS infants have an increase in heart rate and a shortening of the QT interval, provide indirect evidence that infants at high risk for SIDS may have increased sympathoadrenal activity.     

Effect of sleep state on the QT interval in normal infants.

Twenty QT intervals selected at random from the middle periods of rapid eye movement (REM) and quiet sleep were measured in 12 normal infants studied at 2 weeks and 1, 2, 3, and 4 months of life. A digitizing system, consisting of a precision rotational potentiometer mounted on a pair of calipers and an A/D converter, was used for measurements. An accuracy of +/- 2 msec was achieved by high resolution of the digitized signal and calibration of each QT measurement with an accurately generated time code. Sleep staging was done visually using an electroencephalogram (EEG), an electrooculogram (EOG), a submental electromyogram (EMG), and behavioral criteria. Our results show that the QT index (QTc = QT/square rootRR) was significantly greater during quiet sleep (mean = 0.439) than during REM sleep (mean = 0.433) (P less than 0.01) and that this difference existed at all ages studied.     

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.     

Functional residual capacity and sleep states in the premature newborn

Functional residual capacity (FRC) variations in relation to sleep state changes were studied in 11 premature infants with birth weights of 1.68 +/- 0.48 kg and gestational ages of 32.7 +/- 2.2 weeks (mean +/- SD). Helium dilution was used to measure FRC, and sleep states were identified using neurophysiologic criteria. No significant difference in FRC could be demonstrated between data collected during active sleep (AS) and quiet sleep. However a relationship was shown between AS and paradoxical breathing (p less than 0.02) and between AS and irregular breathing (p less than 0.05). Several factors are discussed which might explain the discrepancy between the present data in premature infants and the previously published data in term infants. (1) Neurophysiologic identification of sleep states does not include breathing pattern whereas behavioral identification does. It is therefore possible that lung volume changes are related to breathing pattern changes and not to sleep state changes per se. (2) Maturational changes may occur among the mechanisms which control FRC, leading to a progressive stabilisation of FRC, the variation of which could become related to sleep state changes.     

Behaviour and physiological responses during prone and supine sleep in early infancy

AIMS: To study the effect of prone and supine sleep on infant behaviour, peripheral skin temperature, and cardiorespiratory parameters to aid understanding of why prone sleeping is associated with an increased risk of sudden infant death syndrome. METHODS: Of 33 enrolled infants, 32 were studied at 2.5 and 28 at 5 months of age. A computer aided multichannel system was used for polysomnographic recordings. Behaviour was charted separately. RESULTS: Prone REM (active) sleep was associated with lower frequencies of short arousals, body movements and sighs, and a shorter duration of apnoeas than supine REM sleep at both ages. At 2.5 months there were less frequent episodes of periodic breathing during prone sleep in non-REM (quiet) and REM sleep. Heart rate and peripheral skin temperature were higher in the prone position during both sleep states at both ages. CONCLUSIONS: The observation of decreased variation in behaviour and respiratory pattern, increased heart rate, and increased peripheral skin temperature during prone compared with supine sleep may indicate that young infants are less able to maintain adequate respiratory and metabolic homoeostasis during prone sleep.     

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.     

Heart rate variation in normal infants and victims of the sudden infant death syndrome

Infants who later succumb to the sudden infant death syndrome (SIDS) exhibit lower overall heart rate variability during waking than do other infants. This study attempts to determine which type or types of heart rate variation are reduced in SIDS victims. Long-term recordings of heart rate and respiration were obtained from normal infants and infants who later died of SIDS, and heart rate variation in three frequency bands was examined: respiratory sinus arrhythmia (periods 0.9-3.0 s), 'mid-frequency' (periods 4.0-7.5 s) and 'low-frequency' (periods 12-30 s). All three types of heart rate variation were diminished in SIDS victims under 1 month of age during waking and rapid eye movement (REM) sleep compared with controls. Partitioning heart rate effects showed that in waking, and to a lesser extent in REM sleep, the reduction in all types of heart rate variation exceeded that which would have been predicted based on higher heart rates in SIDS victims. No heart rate-independent reduction in any type of heart rate variation was observed in quiet sleep. This state-dependent reduction in three types of heart rate variation could indicate an abnormality of autonomic control mechanisms during waking and REM sleep in infants who later succumb to SIDS.     

Do lung volumes change with sleep state in the neonate?

We have studied 12 healthy full-term babies, mean age 3.2 days, using physiological criteria — EEG, electro-oculogram, electromyogram, respiratory regularity and visible movement — to assess sleep state, and a respiratory jacket to record changes in functional residual capacity (FRC). A total of 593 min of sleep data were analysed. Of the recordings, 39% were scored as quiet sleep, 40% as active and 21% as indeterminate sleep. The mean maximum variation in FRC overall was 29 ml (SD±15.4 ml). Examination of these figures showed that FRC variations during sleep state changes were smaller than those seen within a defined sleep state. We conclude that changes in sleep state are not associated with variations in FRC.Abbreviations EMG electromyogram - EOG electro-oculogram - FRC functional residual capacity     

Behaviour and physiological responses during prone and supine sleep in early infancy

Accepted 23 December 1996
AIMS—To study the effect of prone and supine sleep on infant behaviour, peripheral skin temperature, and cardiorespiratory parameters to aid understanding of why prone sleeping is associated with an increased risk of sudden infant death syndrome.
METHODS—Of 33 enrolled infants, 32 were studied at 2.5 and 28 at 5 months of age. A computer aided multichannel system was used for polysomnographic recordings. Behaviour was charted separately.
RESULTS—Prone REM (active) sleep was associated with lower frequencies of short arousals, body movements and sighs, and a shorter duration of apnoeas than supine REM sleep at both ages. At 2.5months there were less frequent episodes of periodic breathing during prone sleep in non-REM (quiet) and REM sleep. Heart rate and peripheral skin temperature were higher in the prone position during both sleep states at both ages.
CONCLUSIONS—The observation of decreased variation in behaviour and respiratory pattern, increased heart rate, and increased peripheral skin temperature during prone compared with supine sleep may indicate that young infants are less able to maintain adequate respiratory and metabolic homoeostasis during prone sleep.

     

Sleep organization and energy expenditure of breast-fed and formula-fed infants.

Sleep organization of infants may be influenced by differences in nutrient intakes from human milk and formula. Because sleep/awake and sleep stage patterns affect energy expenditure, we hypothesized that differences in sleep organization between breast-fed and formula-fed infants might account in part for differences in energy expenditure between feeding groups. Sleep stages and cycling of 4-mo-old breast-fed (n = 10) formula-fed (n = 10) infants were studied with simultaneous measurements of energy expenditure. EEG, electrooculogram, body movement by triaxial accelerometry, heart rate, and oxygen saturation were monitored during an overnight sleep session. Sleep stages, nonrapid eye movement (NREM), and rapid eye movement (REM) were determined. Behavioral observations were recorded by video tape and by a technologist. Oxygen consumption and carbon dioxide production were measured with an indirect calorimeter. Total number and duration of sleep cycles, REM latency, number of NREM and REM epochs, and duration of NREM epochs did not differ between feeding groups. Sleep latency was shorter (p < 0.05) and duration of REM epochs longer (p < 0.01) in the formula-fed group. Formula-fed infants spent a higher percentage of sleep time in REM compared with the breast-fed infants (42 versus 34%) (p < 0.003). Conversely, breast-fed infants spent a higher percentage of sleep time in NREM sleep and their heart rates during sleep were lower (114 versus 126 bpm; p < 0.01). Energy expenditure during REM sleep was 13.0 +/- 4.4% higher than during NREM sleep (p < 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)     

The sleep state characteristics of apnea during infancy.

The sleep state characteristics of infant sleep apnea were studied in 36 twins examined by polygraphy at 40, 44, and 52 weeks after conception. The definition of sleep apnea is dependent upon the length of apnea, sleep state, and post-conceptional age. None of the infants had apnea longer than 20 seconds and apnea of 10 seconds or longer was uncommon. The attack rates for apneas 2 to 4.9 seconds long were highest in REM and lowest in qliet sleep. The attack rates for apneas 5 to 9.9 seconds long were equal in REM and indeterminate and lowest in quiet sleep. The percentage of infants with apnea of 10 seconds or longer at 40 weeks was highest in REM (27%) and indeterminate sleep (42%) and lowest in quiet sleep (12%). At 52 weeks, apnea 10 seconds or longer during REM decreased to 0%. The effect of maturation on apnea varies with sleep state. Over the period from 40 to 52 weeks, quiet sleep apnea was unchanged and indeterminate sleep apnea decreased only between 40 and 44 weeks. Although REM apnea 2 to 4.9 seconds long was unchanged, REM apnea 5 to 9.9 seconds long decreased between 40 and 44 weeks, and REM apnea of 10 seconds or longer decreased from 27% at 40 weeks to 0% at 52 weeks. This suggests that semi-independent apnea turn-on and turn-off mechanism operate during REM sleep. A correlation between brief apneas and the longer apneas was seen only during REM sleep. For all sleep states, there was no correlation between the levels of apnea of 5 seconds or longer at 40, 44, and 52 weeks.     

Cardiac and respiratory responses to esophageal dilatation during REM sleep in human infants

Forty-one preterm and fullterm infants (26.5-40.5 weeks gestational age and 31.5-50 weeks postconceptional age) free from neurologic and cardiopulmonary disease at the time of testing underwent a standardized esophageal dilatation test (EDT) during polygraphically controlled REM sleep. RR interval and total duration of the respiratory cycle (TTOT) were measured (1) during the 60 s preceding the EDT, i.e. mean control RR and mean control TTOT; (2) during EDT. Percent RR (%RR) was defined as the longest RR interval in milliseconds during EDT divided by mean control RR in milliseconds multiplied by 100, and percent TTOT (%TTOT) as the longest TTOT in seconds during EDT divided by mean control TTOT in seconds multiplied by 100. EDT provoked prolongation of both RR interval and TTOT. %RR decreased significantly with advancing gestational age (p less than 0.003), and %TTOT with advancing postconceptional age (p less than 0.003), indicating that both cardiac and respiratory responses to an EDT challenge are blunted with maturation.     

Relation of sleep state to hypoxemic episodes in ventilated extremely-low-birth-weight infants

OBJECTIVE: To determine whether hypoxemic episodes in ventilated extremely-low-birth-weight infants correlate with specific behavioral states.Study design: Three-hour video-electroencephalography-polysomnography was performed on 13 ventilated extremely-low-birth-weight infants with mean postconceptional age of 28.3 weeks. The electroencephalogram was scored for discontinuity. Rapid eye movements, body, head, and limb movements were scored from synchronized video. Sleep states were defined from electroencephalography, rapid eye movements, and movement criteria. Nonparametric statistics were used to test for differences in the proportion of time hypoxemic (oxygen saturation 相似文献   

Control of breathing in the central alveolar hypoventilation syndrome with and without a phrenic pacemaker

Primary central alveolar hypoventilation (CAHV) is a rare disorder described in newborns, children, and adults. We report a 2 9/12 year old child with CAHV of unknown etiology. The evaluation of her ventilatory control system showed abnormalities awake and in the different sleep states. Hypoventilation was found to be more severe during non-REM sleep than during REM sleep and awake state. She had central apnea, an irregular respiratory rhythm in the non-REM sleep too, and diminished ventilatory response to inhaled 5%-6% CO2 in both REM and non-REM sleep. Her ventilation decreased when she was breathing 50% and 100% oxygen. During breathing 15% oxygen she did not arouse in spite a transcutaneous pO2 of 10 mmHg. She was first treated with mechanical ventilation during sleep and has now received bilateral simultaneous phrenic pacemaker support during quiet sleep for about one year. With the phrenic pacemaker she has normal minute volume and transcutaneous blood gases during sleep. During a respiratory infection she needed again mechanical ventilation via her tracheostoma 24 hours a day for one week. This case of a CAHV demonstrates a dysfunction of the central and partially also of the peripheral chemoreceptors. The abnormalities of the ventilation were demonstrable not only in the non-REM sleep but also in the REM sleep and awake state.     

Regular and irregular human fetal respiratory movement

Fetal respiratory movements (FRM) were studied using abdominal strain gauges (tocodynamometers). The patterns of the FRM were evaluated during both active and quiet fetal time periods, which were determined by the fetal heart rate (FHR) and fetal body movement (FM). The FRM were classified into Regular and Irregular patterns based on neonatal respiratory criteria for sleep-state studies in the term infant. Evaluation of the breath-to-breath intervals (BBI) showed statistically significant respiratory differences during active and quiet fetal time periods. Irregular fetal respiratory movement patterns were noted during fetal active periods. It would appear that the correlation of regular fetal respiratory movement with fetal quiet periods in the term fetus adds additional evidence that a quiet sleep state may exist in the term fetus.     

A developmental study on types and frequency distribution of short apneas (3 to 15 seconds) in term and preterm infants

We measured the frequency distribution and the ventilatory correlates of the various types of apneas 3 to 15 s long during sleep in eight term infants (birth weight 3.65 +/- 0.16 kg; gestational age 39.5 +/- 0.3 wk) and eight preterm infants (birth weight 2.07 +/- 0.18 kg; gestational age 34.3 +/- 0.4 wk). Each infant was studied on five to seven occasions from birth to 56 wk of postconceptual age using a modified flow-through system. Sixty-six paired epochs of quiet sleep (1163 min) and rapid eye movement sleep (829 min) were analyzed in term infants and 85 paired epochs of quiet sleep (1553 min) and rapid eye movement sleep (1328 min) in preterm infants. Of the 783 apneas recorded in term infants 82% were central, 1.5% obstructive, 0.5% mixed, and 16% were of the breath-holding type; the corresponding figures for the 4086 apneas recorded in preterm infants were 93, 0.5, 1.0, and 5.5%. This distribution was similar in the two sleep states but term infants had a higher percentage of breath-holding apneas than preterm infants (p less than 0.01). In preterm infants the rate of central apneas decreased with postnatal age (p less than 0.01); in term infants the rate did not change significantly. The duration of apneas showed a modal distribution for central apneas at about 8 s for both groups during the 1st month of life (p less than 0.05). The findings suggest: 1) apneas in the newborn and early infancy are primarily central and are more frequent in preterm than in term infants.(ABSTRACT TRUNCATED AT 250 WORDS)     

SCSB method compared to EEG-based polygraphy in sleep state scoring of newborn infants

Knowledge of the sleep state is important in physiological studies since many physiological variables show different properties in different sleep states. The recently developed static charge sensitive bed (SCSB) method allows long-term recordings of body movements, respiration and ballistocardiogram without electrodes attached to the subject. The recordings are easy to carry out and they do not disturb the subject in any way. The recorded variables are basic characteristics of different sleep states. SCSB-recordings and electroencephalography (EEG) based polygraphy as well as blind sleep state scoring were carried out in 8 newborn infants. The positive correlation between SCSB-scoring and EEG-based polygraphy scored by two clinical neurophysiologists was 68.1 and 64.1%. Only in 2% of all epochs was active sleep scored as quiet sleep or vice versa. The results indicate the usefulness of the SCSB method in sleep state scoring of newborn infants.     

SCSB Method Compared to EEG-Based Polygraphy in Sleep State Scoring of Newborn Infants

Abstract. Knowledge of the sleep state is important in physiological studies since many physiological variables show different properties in different sleep states. The recently developed static charge sensitive bed (SCSB) method allows long-term recordings of body movements, respiration and ballistocardiogram without electrodes attached to the subject. The recordings are easy to carry out and they do not disturb the subject in any way. The recorded variables are basic characteristics of different sleep states. SCSB-recordings and electroencephalography (EEG) based polygraphy as well as blind sleep state scoring were carried out in 8 newborn infants. The positive correlation between SCSB-scoring and EEG-based polygraphy scored by two clinical neurophysiologists was 68.1 and 64.1%. Only in 2 % of all epochs was active sleep scored as quiet sleep or vice versa. The results indicate the usefulness of the SCSB method in sleep state scoring of newborn infants.     

Central hypoventilation during quiet sleep in two infants.

Expired ventilation (VE), tidal volume (VT), frequency (f), and alveolar PCO2 (PACO2) were examined in six normal infants at 41 to 52 weeks post-conceptional age and in two infants who were apneic at birth. Their response to breathing 5% carbon dioxide in air and to 100% oxygen in quiet sleep were compared to those in rapid eye movement (REM) sleep. VE in normal infants was 259 ml/kg/min in REM and 200.2 ml/kg/min in quiet sleep with the difference being due to decreased carbon dioxide production and to decreased dead space. VE increased 34.4 ml/kg/min/mm Hg of PCO2 elevation with 5% carbon dioxide breathing during REM and was not significantly different during quiet sleep. During oxygen breathing VE fell by 32.7% at 30 seconds before increasing again. In the affected infants, VE and PACO2 during REM at 1 and 4 months were normal. At 1 month, during quiet sleep, each infant became apneic and PACO2 rose 9 and 8 mm Hg/min respectively. At this time mechanical ventilation was begun. At 4 months, during quiet sleep, VE was 0.064 and 0.063 ml/kg/min at PACO2 of 66 mm Hg in each infant. The change was due entirely to a decrease in VT to 2.3 and 2.5 ml/kg. At this time 5% carbon dioxide breathing given during normal ventilation in REM produced an abrupt fall in VT to 2.0 and 2.2 ml/kg with no change in frequency. Oxygen breathing during REM at one month had no effect but at 4 months produced apnea requiring mechanical ventilation after one minute. The findings suggest that the ventilatory response to carbon dioxide is (1) important in initiation of extrauterine ventilation and (2) in sustaining ventilation particularly in quiet sleep. It is not necessary in sustaining ventilation awake or in REM sleep and it represents a balance between the stimulatory and depressant effects of carbon dioxide on the central nervous system.     

Spectral analysis assessment of respiratory sinus arrhythmia in normal infants and infants who subsequently died of sudden infant death syndrome

Reduced heart rate variability has been found in infants who later succumb to the sudden infant death syndrome (SIDS). To determine whether respiratory sinus arrhythmia, a major component of heart rate variability, is also reduced in SIDS victims, nighttime portions of eighteen 24-h recordings of ECG and respiration from infants who later died of SIDS and 52 recordings from control infants were assessed using spectral analysis. Two aspects of respiratory sinus arrhythmia were examined: "extent" (the absolute heart rate variation at the respiratory frequency) and "coherence" (the degree to which heart rate follows respiration regardless of the absolute amount of variation). Respiratory parameters were used to classify each 1-min epoch as quiet sleep, rapid eye movement sleep, waking, or indeterminate state. Median extent and coherence values across the night were then computed for each sleep-waking state. Two-way (group X state) repeated measures analysis of variance tests were then used to compare respiratory sinus arrhythmia values for 13 SIDS victims and 13 control infants matched by postnatal age, birth weight, sex, and gestational age. Extent of respiratory sinus arrhythmia was significantly lower in the SIDS victims across all sleep-waking states, a finding that persisted after adjusting for heart rate. Coherence values did not differ significantly. These results suggest that even before the time of maximal risk for the syndrome, SIDS victims, as a group, differ from controls in the extent to which cardiac and respiratory activity couple, and this difference is independent of basal heart rate.