Infant sleeping position and inspiratory pressures in the upper airways and oesophagus

Inspiratory pressures were measured at three levels in the upper airways and in the oesophagus in different sleeping positions. Thirty one consecutive healthy infants were examined at the age of 1-3 days, 25 of these at 6 weeks, and 23 at 12 weeks. Oxygen saturation, an electrocardiogram, transthoracic impedance, nasal airflow, and inspiratory pressure in the epipharynx, oropharynx, hypopharynx, and in the intrathoracic part of the oesophagus were measured. There was no significant change in the heart rate, oxygen saturation, or respiratory rate in the four sleeping positions. The peak negative inspiratory pressures obtained from the oesophagus (PES) were significantly lower in the supine head straight compared with the supine head turned and the prone positions. At 6 weeks, the only significant difference was between the supine head straight and the prone positions. The PES is less negative at all ages in the supine head straight than in all other sleeping positions, but this does not reach statistical significance.     

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.     

Effect of prone sleeping on circulatory control in infants.

BACKGROUND: The mechanism of death in sudden infant death syndrome (SIDS) remains unclear. Progressive bradycardia is the pre-eminent terminal event, suggesting that circulatory failure might be a crucial factor. Vasomotor tone regulates the circulatory system by controlling blood volume distribution while maintaining venous return and blood pressure. AIM: To examine whether prone sleeping, the most consistently identified risk factor for SIDS, has a measurable influence on vasomotor/circulatory control. METHODS: 44 full term infants (mean age, 7.9 weeks) were studied during an overnight sleep. Recordings were made while the infants were horizontal and asleep in the supine and prone positions, and repeated after a head up tilt to 60 degrees, maintained for 30 minutes, while in both sleep positions. Blood pressure, heart rate, anterior shin, and anterior abdominal wall skin temperatures were measured. RESULTS: Systolic blood pressure was lower, but peripheral skin temperature and heart rate were higher during sleep, while horizontal, in the prone rather than the supine position. After tilting, there was a greater reduction in blood pressure and a greater increase in peripheral skin temperature and heart rate when in the prone position. Anterior abdominal wall skin temperature did not vary in either sleeping positions while horizontal or tilted. CONCLUSION: Prone sleeping has a measurable effect on circulatory control, with a reduction in vasomotor tone resulting in peripheral vasodilatation, a higher peripheral skin temperature, a lower blood pressure, and a higher resting heart rate. Because vasomotor tone is crucially important in circulatory control this could be a factor in increasing the risk of SIDS.     

Sleeping position, oxygen saturation and lung volume in convalescent, prematurely born infants

OBJECTIVE: To determine whether the effects of sleeping position on lung volume and oxygenation are influenced by postmenstrual age (PMA) and oxygen dependency in convalescent prematurely born infants. DESIGN: Prospective study. SETTING: Tertiary neonatal unit. PATIENTS: 41 infants (21 oxygen dependent), median gestational age 28 weeks (range 24-31 weeks) and birth weight 1120 g (range 556-1780 g). INTERVENTION: Infants were studied both supine and prone at two-weekly intervals from 32 weeks' PMA until discharge. Each posture was maintained for 1 h. MAIN OUTCOME MEASURES: Pulse oximeter oxygen saturation (Spo(2)) was monitored continuously, and at the end of each hourly period functional residual capacity (FRC) was measured. RESULTS: Overall, lung volumes were higher in the prone position throughout the study period; there was no significant effect of PMA on lung volumes. Overall, Spo(2) was higher in the prone position (p = 0.02), and the effect was significant in the oxygen-dependent infants (p = 0.03) (mean difference in Spo(2) between prone and supine was 1.02%, 95% CI 0.11% to 1.92%), but not in the non-oxygen-dependent infants. There was no significant influence of PMA on Spo(2). CONCLUSION: In the present study, prone sleeping did not improve oxygenation in prematurely born infants, 32 weeks' PMA or older and with no ongoing respiratory problems. However, the infants were monitored in each position for an hour, thus it is recommended that oxygen saturation should continue to be monitored after 32 weeks' PMA to be certain that longer periods of supine sleeping are not associated with loss of lung volume and hypoxaemia.     

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.     

Prematurity,sleeping position and sudden infant death syndrome

Preterm birth and prone sleeping position significantly increase the risk of sudden infant death syndrome (SIDS). The reduced incidence of SIDS with supine sleeping has been well publicised, yet some prematurely born infants are slept prone at the high-risk age for SIDS. This may reflect inadequate educational targeting of high-risk groups and/or concerns about possible adverse effects of supine sleeping. In addition, parents may receive mixed messages about sleeping positions, as they witness their prematurely born infants being nursed prone on neonatal units, often for many weeks. In the neonatal period, the prone position improves oxygenation, tidal volume and compliance of preterm infants with respiratory distress. The limited data available suggest prone positioning is also beneficial for convalescent, preterm infants. Thus, it is not clear when the advantages of prone sleeping cease. Studies are required to determine when supine sleeping for prematurely born infants can safely be recommended and hence an unambiguous message given to parents.     

Association between sleep position and early motor development

OBJECTIVE: To compare motor performance in infants sleeping in prone versus supine positions. STUDY DESIGN: Healthy 4-month-olds (supine: n = 71, prone: n = 12) and 6-month olds (supine: n = 50, prone: n = 22) were evaluated with the Alberta Infant Motor Scale (AIMS) and Peabody Developmental Motor Scale (PDMS), and parents completed a positioning diary. Infants were reassessed at 15 months. RESULTS: At 4 months, motor scores were lower in the supine group and were less likely to achieve prone extension (P < .05). At 6 months, there were wide discrepancies on the AIMS (supine: 44.5 +/- 21.6, prone: 60.0 +/- 18.8, P = .005) and the gross motor PDMS (supine: 85.7 +/- 7.6, prone: 90.2 +/- 9.5, P = .03). Motor delays were documented in 22% of babies sleeping supine. Prone sleep-positioned infants were more likely to sit and roll. Daily exposure to awake prone positioning was predictive of motor performance in infants sleeping supine. At 15 months, sleep position continued to predict motor performance. CONCLUSIONS: Infants sleeping supine may exhibit early motor lags, associated with less time in prone while awake. This has implications for accurate interpretation of assessment of infants at risk and prevention of inappropriate referrals. Rate of infant motor development appears influenced by extrinsic factors such as positioning practices.     

Acid gastroesophageal reflux in convalescent preterm infants: effect of posture and relationship to apnea

Concerns regarding gastroesophageal reflux (GER) and associated apnea episodes result in some practitioners having convalescent, prematurely born infants sleep in the prone position. We have tested the hypothesis that such infants would not suffer from clinically important acid GER or associated apnea episodes more in the supine compared with the prone position. Lower esophageal pH was measured and videopolysomnographic recordings of nasal airflow, chest and abdominal wall movements, electrocardiographic activity, and oxygen saturation were made on two successive days of 21 premature infants (median gestational age 28 wk) at a median postmenstrual age (PMA) of 36 wk. On each day, the infants were studied prone and supine. The acid reflux index was higher in the supine compared with the prone position (median 3% versus 0%, p = 0.002), but was low in both positions. The number of obstructive apnea episodes per hour was higher in the supine position (p = 0.008). There were, however, no statistically significant correlations between the amount of acid GER and the number of either obstructive or total apnea episodes in either the supine or prone position. Supine compared with prone sleeping neither increases clinically important acid GER nor obstructive apnea episodes associated with acid GER in asymptomatic, convalescent, prematurely born infants.     

Relationship between infant sleep position and motor development in preterm infants.

To determine whether motor development in premature infants varies according to sleep position, we evaluated 213 infants <1750 g birth weight enrolled in the Collaborative Home Infant Monitoring Evaluation (CHIME). At 56 weeks postconceptional age (PCA), sleep position was determined by maternal report, and the Bayley Scales of Infant Development 2nd Edition (BSID-II) were performed. Infants who slept supine were less likely than infants who slept prone to receive credit for maintaining the head elevated to 45 degrees (p = .021), and infants who slept nonprone were less likely than prone sleepers to receive credit for maintaining the head elevated to 90 degrees and lowering with control (p = .001). The Psychomotor and Mental Development Indices at 56 and 92 weeks PCA were not altered by usual sleep position at 56 weeks PCA. In summary, infants sleeping supine are less able to lift the head and lower with control at 56 weeks PCA, but global developmental status was unaffected. Supine sleeping has been associated with decreased risk for sudden infant death syndrome, but compensatory strategies while awake may be needed to avoid delayed acquisition of head control.     

Effects of the supine and prone position on diaphragm thickness in healthy term infants.

BACKGROUND: The physiological basis underlying the decline in the incidence of sudden infant death syndrome (SIDS) associated with changing the sleep position from prone to supine remains unknown. AIMS: To evaluate diaphragm thickness (t(di)) and shortening in healthy term infants in the prone and supine positions in order to determine whether changes in body position would affect diaphragm resting length and the degree of diaphragm shortening during inspiration. METHODS: In 16 healthy term infants, diaphragm thickness at the level of the zone of apposition on the right side was measured using ultrasonography. Heart rate (HR), breathing frequency (f), and transcutaneous oxyhaemoglobin saturation (SaO(2)) were recorded simultaneously during diaphragm imaging with the infants in the supine and prone positions during quiet sleep. RESULTS: At end expiratory (EEV) and at end inspiratory lung volumes (EIV), t(di) increased significantly in the prone position. The change in t(di) during tidal breathing was also greater when the infant was prone. SaO(2), HR, and f were not significantly different at EEV and at EIV in both positions. CONCLUSION: In healthy term infants, placed in the prone position, the diaphragm is significantly thicker and, therefore, shorter, both at EEV and EIV. Diaphragm shortening during tidal breathing is greater when the infant is prone. In the prone position, the decreased diaphragm resting length would impair diaphragm strength, and the additional diaphragm shortening during tidal breathing represents added work performed by the diaphragm. This may compromise an infant's capacity to respond to stressful situations when placed in the prone position and may contribute to the association of SIDS with prone position.     

Arousal from sleep pathways are affected by the prone sleeping position and preterm birth: Preterm birth,prone sleeping and arousal from sleep

Objectives

Preterm infants exhibit depressed arousability from sleep when compared with term infants. As the final cortical element of the arousal process may be the most critical for survival, we hypothesized that the increased vulnerability of preterm infants to the Sudden Infant Death Syndrome (SIDS) could be explained by depressed cortical arousal (CA) responses. We evaluated the effects of preterm birth on stimulus-induced arousal processes in both the prone and supine sleeping positions.

Study design

10 healthy preterm infants were studied with daytime polysomnography, in both supine and prone sleeping positions, at 36 weeks gestational age, 2–4 weeks, 2–3 months and 5–6 months post-term corrected age. Sub-cortical activations and cortical arousals (CA) were expressed as proportions of total arousal responses. Preterm data were compared with data from 13 healthy term infants studied at the same corrected ages.

Results

In preterm infants increased CAs were observed in the prone position at all ages studied. Compared to term infants, preterm infants had significantly fewer CAs in QS when prone at 2–3 months of age and more CAs when prone at 2–4 weeks in AS. There were no differences in either sleep state when infants slept supine.

Conclusions

Prone sleeping promoted CA responses in healthy preterm infants throughout the first six months of post-term age. We have previously suggested that in term infants enhanced CA represents a critical protection against a potentially harmful situation; we speculate that for preterm-born infants the need for this protection is greater than in term infants.     

Arterial oxygen saturation in infants at risk of sudden death: influence of sleeping position

To study the possible influence of sleeping position on arterial oxygen saturation, measured by pulse oximetry (Sp6₂), 7–h overnight recordings of breathing movements and ECG were performed in 43 infants (median age 2.4 months, range 0.2–11 months) at increased risk of sudden infant death syndrome (SIDS). Infants were randomly allocated to start sleeping either in their usual sleeping position or in the opposite position. After 3.5 h, all infants were gently turned over. Thus, each infant served as their own control. Recordings were analysed for sleep time, baseline Sp0₂ (only during regular breathing), and the number and duration of desaturations (a decrease in Sp0₂ to ≤80%). In the prone position, a significantly higher proportion of time was spent asleep (median 79% versus 70%; p < 0.05). Median baseline Sp0₂ was 98.8% (91.7–100%) in the prone and 99.0% (92.0–100%) in the supine position (ns). A total of 191 desaturations were found in 29 recordings; 96 in the prone and 95 in the supine position (ns). One infant subsequently died of SIDS while sleeping in the prone position. He had a relatively high number of desaturations (n = 12) which all occurred in the prone position. These results confirm earlier studies which could not find a significant influence of sleeping position on baseline oxygenation. The occurrence of desaturations in the prone position only in the infant who subsequently died requires further investigation.     

Postural differences in cardiac dynamics during quiet and active sleep in low birthweight infants

To study the effects of body position (supine versus prone) on changes in cardiac inter-beat interval during quiet and active sleep, 6-h continuous electrocardiographic recordings and simultaneous minute-by-minute behavioural activity state assignments were made in 61 healthy, growing, low birthweight infants. The infants weighed 795-1600 g at birth and ranged between 30-38 wk in postconceptual age. Infants were randomly assigned to the supine or prone position for the first 3 h of each study; the position was reversed for the second 3 h. Higher heart rates and lower time and frequency domain measures of inter-beat interval variability were observed in the prone position as compared to the supine position, during both quiet and active sleep. In addition, an analysis of consecutive increases and decreases in the instantaneous heart rate revealed a lower incidence of sustained accelerations or decelerations in the prone position. Although consistent findings concerning inter-beat interval variability and sleeping position were obtained from all analytic techniques, the differences derived from analysis of consecutive inter-beat changes were the most robust. These differences in multiple measures of cardiac rate and rhythm between prone and supine positions suggest that autonomic control of the heart is altered by body position, the net effect on heart rate being increased sympathetic dominance.     

Survey of sleeping position recommendations for prematurely born infants on neonatal intensive care unit discharge

Prematurely born infants are at increased risk of sudden infant death syndrome, particularly if slept prone. Yet, some prematurely born infants are slept prone despite the high risk age for sudden infant death syndrome and this may reflect the advice given by neonatal unit staff. The aim of this study was to determine neonatal units' recommendations regarding sleeping positions for premature infants prior to and after discharge. A questionnaire survey was sent to all 224 neonatal units in the United Kingdom, of which 81% responded. Analysis of their responses demonstrated that 43% of units started to sleep infants supine 1 to 2 weeks prior to discharge, but oxygen-dependent infants were slept non-supine until an older age. Non-supine sleeping was recommended by 40% of units for infants with Pierre Robin syndrome or gastro-oesophageal reflux. All units advised supine sleeping at discharge, but 29% additionally recommended side sleeping and only 58% positively discouraged prone sleeping. Written information was given to parents by 70% of the units, but few provided information which was specifically about prematurely born infants. Conclusion: The worrying lack of consistency in recommending non-prone sleeping emphasises that evidence-based guidelines for the sleeping position of convalescent prematurely born infants are required.     

俯卧位通气对小儿急性肺损伤的疗效

目的评价俯卧位通气对小儿急性肺损伤(ALI)的临床疗效。方法2006年5月-2007年12月苏州大学附属儿童医院儿科重症监护病房收住的17例ALI患儿,在持续镇静下俯卧位通气4h,机械通气模式为压力控制模式(PCmode),以监测呼出潮气量6～8mL/kg反馈调节控制压力,吸气时间0.6～1.0s,呼吸频率28～42次/min,吸入氧体积分数400～1000mL/L,呼气末正压6～16cmH2O(1cmH2O=0.098kPa)。监测0、1、4h及恢复仰卧位通气4h的呼吸循环指标,并进行比较。采用SPSS13.0软件进行统计学分析。结果在实施俯卧位通气1、4h及恢复仰卧位通气4h,氧合指数[pa(O2)/FiO2]和pa(O2)均较实施俯卧位通气前显著升高(Pa<0.05),俯卧位通气4h和恢复仰卧位通气4h时的尿量也有增加(Pa<0.05)。而心率、平均动脉血压、动脉血二氧化碳分压、呼吸系统动态顺应性、呼吸道阻力、呼吸道峰压等比较差异均无统计学意义。结论俯卧位通气可改善ALI患儿的氧合,增加尿量,恢复仰卧位通气后氧合改善,尿量增加仍持续存在。     

The prone sleeping position impairs arousability in term infants

OBJECTIVE: To investigate whether the prone sleeping position impaired arousal from sleep in healthy infants and whether this impairment was related to cardiorespiratory variables, temperature, or age.Study design: Healthy term infants (n = 24) were studied with daytime polysomnography on 3 occasions: 2 to 3 weeks after birth, 2 to 3 months after birth, and 5 to 6 months after birth. 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 and quiet sleep when infants slept both prone and supine. RESULTS: Arousal thresholds were significantly higher in both active sleep and quiet sleep when infants slept prone at 2 to 3 weeks and 2 to 3 months, but not at 5 to 6 months. These increases were independent of any sleep position-related change in either rectal or abdominal skin temperature, respiratory rate, oxygen saturation, or heart rate. CONCLUSIONS: The prone position significantly impairs arousal from both active sleep and quiet sleep in healthy term infants. This impairment in arousability occurred with no clinically significant changes in cardiorespiratory variables or body temperature. Decreased arousability from sleep in the prone position provides an important insight into its role as a risk factor for sudden infant death syndrome.     

Effects of sleep position on infant motor development

BACKGROUND: As a result of the American Academy of Pediatrics' recommendation that healthy infants be placed on their side or back for sleep, the percentage of infants sleeping prone has decreased dramatically. With the increase in supine sleeping, pediatricians have questioned if there are differences in the rate of acquisition of early motor milestones between prone and supine sleeping infants. METHODS: To examine this question, we performed a prospective, practice-based study of healthy term infants. Infants were recruited before the age of 2 months. Parents were asked to record infant sleep position and awake time spent prone until 6 months of age. A developmental log was used to track milestones from birth until the infant was walking. Age of acquisition of eight motor milestones was determined, and the mean ages of milestone attainment of prone and supine sleepers were compared. RESULTS: Three hundred fifty-one infants completed the study. Prone sleepers acquired motor milestones at an earlier age than supine sleepers. There was a significant difference in the age of attainment of rolling prone to supine, tripod sitting, creeping, crawling, and pulling to stand. There was no significant difference in age when infants walked. CONCLUSIONS: The pattern of early motor development is affected by sleep position. Prone sleepers attain several motor milestones earlier than supine sleepers. However, all infants achieved all milestones within the accepted normal age range. Pediatricians can use this information to reassure parents. This difference in milestone attainment is not a reason to abandon the American Academy of Pediatrics' sleep position recommendations.     

Lower body temperature in sleeping supine infants.

Night time rectal temperature recordings were made from 103 infants sleeping in their own home in different sleeping positions. In most cases sleeping position was verified by video monitoring throughout the night. In the period before an adult-like night time body temperature pattern appeared there was no significant effect of sleeping position upon night time body temperature, in line with previous reports. Once an adult-like night time temperature pattern appeared, infants sleeping supine reached significantly lower rectal temperatures than those sleeping prone or lateral. Babies sleeping supine moved significantly more during the night and were more likely to uncover their hands and arms. These findings suggest that supine sleepers are in a different physiological condition from those sleeping prone or lateral, which may be associated with their lower vulnerability to sudden unexpected infant death.     

Sleep position and bed-sharing in sudden infant deaths: an examination of autopsy findings

OBJECTIVE: To determine the effect of sleep position, sleep location, and bed-sharing on the incidence of sudden unexpected death in infancy and the frequency of significant autopsy findings. METHODS: We evaluated the cause of death in infants <1 year of age who died during sleep from January 1, 1986, through September 30, 1999. This retrospective series was compiled from log books and files of the Medical Examiner Office, Palm Beach County, Florida. RESULTS: The incidence of sudden unexpected infant death decreased 50% over the study period (P <.01). Of the 217 infants that fit the study criteria, 62.7% were sleeping prone (on the stomach), 9.7% were supine (on the back), 5.5% were on their side, 22.1% were in an unknown position, and 40.1% were bed-sharing. Significant autopsy findings that could explain death were documented by autopsy in 37.5% of all supine and side sleeping infants and only 14.0% of all prone sleeping infants (P <.001). Deaths of supine and side sleeping infants were more likely to be classified as a natural disease process other than sudden infant death syndrome (P <.01). Significant autopsy findings that could explain death were found in 47.6% of the infants sleeping alone in the supine or side position (P <.01), 18.2% of infants bed-sharing in the supine or side position, 16.5% of infants sleeping alone while prone, and 9.3% of infants bed-sharing while prone. CONCLUSIONS: Infant deaths associated with the prone position were less frequently explained by illness or disease than infant deaths associated with non-prone sleeping positions. Bed-sharing appears to increase the proportion of unexplained deaths, regardless of the position of the infant. The "Back to Sleep" campaign appears to be effective in reducing the incidence of unexpected sleeping infant deaths regardless of the certified cause of death.