Prenatal cigarette smoke exposure attenuates recovery from hypoxemic challenge in preterm infants

Evidence Base for 2022 Updated Recommendations for a Safe Infant Sleeping Environment to Reduce the Risk of Sleep-Related Infant Deaths

Every year in the United States, approximately 3500 infants die of sleep-related infant deaths, including sudden infant death syndrome (SIDS) (International Statistical Classification of Diseases and Related Health Problems 10th Revision [ICD-10] R95), ill-defined deaths (ICD-10 R99), and accidental suffocation and strangulation in bed (ICD-10 W75). After a substantial decline in sleep-related deaths in the 1990s, the overall death rate attributable to sleep-related infant deaths have remained stagnant since 2000, and disparities persist. The triple risk model proposes that SIDS occurs when an infant with intrinsic vulnerability (often manifested by impaired arousal, cardiorespiratory, and/or autonomic responses) undergoes an exogenous trigger event (eg, exposure to an unsafe sleeping environment) during a critical developmental period. The American Academy of Pediatrics recommends a safe sleep environment to reduce the risk of all sleep-related deaths. This includes supine positioning; use of a firm, noninclined sleep surface; room sharing without bed sharing; and avoidance of soft bedding and overheating. Additional recommendations for SIDS risk reduction include human milk feeding; avoidance of exposure to nicotine, alcohol, marijuana, opioids, and illicit drugs; routine immunization; and use of a pacifier. New recommendations are presented regarding noninclined sleep surfaces, short-term emergency sleep locations, use of cardboard boxes as a sleep location, bed sharing, substance use, home cardiorespiratory monitors, and tummy time. In addition, additional information to assist parents, physicians, and nonphysician clinicians in assessing the risk of specific bed-sharing situations is included. The recommendations and strength of evidence for each recommendation are published in the accompanying policy statement, which is included in this issue.

Home Cardiorespiratory Monitoring in Infants at Risk for Sudden Infant Death Syndrome (SIDS), Apparent Life-Threatening Event (ALTE) or Brief Resolved Unexplained Event (BRUE)

Sudden infant death syndrome (SIDS) is defined as the sudden death of an infant younger than one year of age which remains unexplained after a thorough case investigation, including performance of a complete autopsy, examination of the death scene, and review of the clinical history. About 90% of SIDS occur before six months of age, the peak incidence is between two and four months, and the median age for death is elven weeks. The clinical, social, and economic relevance of SIDS, together with the evidence that prevention of this syndrome was possible, has significantly stimulated research into risk factors for the development of SIDS in the hope of being able to introduce new effective preventive measures. This narrative review discusses the potential relationships between apparent life-threatening events (ALTE) or brief resolved unexplained events (BRUE) and SIDS development, and when a home cardiorespiratory monitor is useful for prevention of these conditions. A literature analysis showed that home cardiorespiratory monitoring has been considered a potential method to identify not only ALTE and BRUE but SIDS also. ALTE and BRUE are generally due to underlying conditions that are not detectable in SIDS infants. A true relationship between these conditions has never been demonstrated. Use of home cardiorespiratory monitor is not recommended for SIDS, whereas it could be suggested for children with previous ALTE or severe BRUE or who are at risk of the development of these conditions. However, use of home cardiorespiratory monitors assumes that family members know the advantages and limitations of these devices after adequate education and instruction in their use.

Ambulatory monitoring promises equitable personalized healthcare delivery in underrepresented patients

The pandemic has brought to everybody's attention the apparent need of remote monitoring, highlighting hitherto unseen challenges in healthcare. Today, mobile monitoring and real-time data collection, processing and decision-making, can drastically improve the cardiorespiratory-haemodynamic health diagnosis and care, not only in the rural communities, but urban ones with limited healthcare access as well. Disparities in socioeconomic status and geographic variances resulting in regional inequity in access to healthcare delivery, and significant differences in mortality rates between rural and urban communities have been a growing concern. Evolution of wireless devices and smartphones has initiated a new era in medicine. Mobile health technologies have a promising role in equitable delivery of personalized medicine and are becoming essential components in the delivery of healthcare to patients with limited access to in-hospital services. Yet, the utility of portable health monitoring devices has been suboptimal due to the lack of user-friendly and computationally efficient physiological data collection and analysis platforms. We present a comprehensive review of the current cardiac, pulmonary, and haemodynamic telemonitoring technologies. We also propose a novel low-cost smartphone-based system capable of providing complete cardiorespiratory assessment using a single platform for arrhythmia prediction along with detection of underlying ischaemia and sleep apnoea; we believe this system holds significant potential in aiding the diagnosis and treatment of cardiorespiratory diseases, particularly in underserved populations.

Design Implementation and Evaluation of a Mobile Continuous Blood Oxygen Saturation Monitoring System

Objective: In this study, we built a mobile continuous Blood Oxygen Saturation (SpO2) monitor, and for the first time, explored key design principles towards daily applications. Methods: We firstly built a customized wearable computer that can sense two-channel photoplethysmogram (PPG) signals, and transmit the signals wirelessly to smartphone. Afterwards, we explored many SpO2 model building principles, focusing on linear/nonlinear models, different PPG parameter calculation methods, and different finger types. Moreover, we further compared PPG sensor placement principles by comparing different hand configurations and different finger configurations. Finally, a dataset collected from eleven human subjects was used to evaluate the mobile health monitor and explore all of the above design principles. Results: The experimental results show that the root mean square error of the SpO2 estimation is only 1.8, indicating the effectiveness of the system. Conclusion: These results indicate the effectiveness of the customized mobile SpO2 monitor and the selected design principles. Significance: This research is expected to facilitate the continuous SpO2 monitoring of patients with clinical indications.

Maternal smoking and neurodevelopmental outcomes in infants <29 weeks gestation: a multicenter cohort study

OBJECTIVE

To compare neurodevelopmental outcomes of preterm infants at 18-21 months corrected age (CA) whose mothers smoked during pregnancy to those whose mothers did not smoke.

STUDY DESIGN

Preterm infants born at <29 weeks of gestation and evaluated at 18-21 months CA were included. Primary outcome was a composite outcome of death or neurodevelopmental impairment (NDI).

RESULTS

Of a total of 2760 infants, 699 met exclusion criteria. Of the remaining 2061 infants, 280 (13.6%) were exposed to maternal smoking and 1781 (86.4%) were not. The odds of the composite outcome of death or NDI (aOR 1.40; 95% CI: 1.03-1.91), NDI alone (aOR 1.43; 95% CI: 1.01-2.03), and Bayley-III motor score <85 (aOR 1.91; 95% CI: 1.31-2.81) were higher in exposed infants.

CONCLUSIONS

Exposure to maternal smoking was associated with adverse composite outcome of death or NDI, NDI alone and lower motor scores at 18-21 months CA.

Sudden infant death and social justice: A syndemics approach

Sudden unexpected infant death (SUID) and sudden infant death syndrome (SIDS) prevention has focused on modifying individual behavioural risk factors, especially bedsharing. Yet these deaths are most common among poor and marginalized people in wealthy countries, including U.S. Blacks, American Indians/Alaskan Natives, New Zealand Māori, Australian Aborigines, indigenous Canadians, and low-income British people. The United States now has the world's highest prevalence of SUID/SIDS, where even Whites' SIDS prevalence now approaches that of the Māori. Using public databases and the literature, we examine SUID/SIDS prevalence and the following risk factors in selected world populations: maternal smoking, preterm birth, alcohol use, poor prenatal care, sleep position, bedsharing, and formula feeding. Our findings suggest that risk factors cluster in high-prevalence populations, many are linked to poverty and discrimination and have independent effects on perinatal outcomes. Moreover, populations with the world's lowest rates of SUID/SIDS have low income-inequality or high relative wealth, yet have high to moderate rates of bedsharing. Employing syndemics theory, we suggest that disproportionately high prevalence of SUID/SIDS is primarily the result of socially driven, co-occurring epidemics that may act synergistically to amplify risk. SUID must be examined through the lens of structural inequity and the legacy of historical trauma. Emphasis on bedsharing may divert attention from risk reduction from structural interventions, breastfeeding, prenatal care, and tobacco cessation. Medical organizations play an important role in advocating for policies that address the root causes of infant mortality via poverty and discrimination interventions, tobacco control, and culturally appropriate support to families.

Factors Affecting the Target Oxygen Saturation in the First Minutes of Life in Preterm Infants

BACKGROUND

The aim of this study was to describe the effect of factors on time to reach a pulse oxygen saturation (SpO2) level of 90% in preterm infants in the delivery room.

METHODS

Preterm (<35 gestational age) infants who did not require supplemental oxygen were included in the study. Continuous recordings were taken by pulse oximetry during the first 15 min of life.

RESULTS

Of 151 preterm infants, 79 (52.3%) were female and 126 (83.5%) were delivered by cesarean section. Target saturation level (≥90%) was achieved faster in preductal measurements. Mean times taken to have a preductal and postductal SpO2 level of 90% were significantly lower in preterm babies born by vaginal delivery, with umbilical arterial pH ≥ 7.20 and whose mothers were non-smokers during pregnancy.

CONCLUSIONS

Differences in achievement of target saturation level were influenced by multiple factors (birth way, probe location, maternal smoking and umbilical blood gas pH) in the delivery room during resuscitation of preterm babies.

Prematurity and Sudden Unexpected Infant Deaths in the United States

BACKGROUND AND OBJECTIVES

Prematurity, a strong risk factor for sudden unexpected infant death (SUID), was addressed in recommendations by the American Academy of Pediatrics in 2011 for safe sleep education in NICUs. We documented associations between gestational age (GA) and SUID subsequent to these guidelines.

METHODS

Using the 2012-2013 US linked infant birth and death certificate period files, we documented rates per live births of sudden infant death syndrome, ill-defined and unspecified causes, accidental suffocation and strangulation in bed, and overall SUID by GA in postneonatal, out-of-hospital, and autopsied cases; compared survivors and cases; and estimated logistic regression models of associations between GA and SUID.

RESULTS

SUID cases were more likely than survivors to be <37 weeks' GA (22.61% vs 10.79%; P < .0001). SUID rates were 2.68, 1.94, 1.46, 1.16, 0.73, and 0.51 per 1000 live births for 24 to 27, 28 to 31, 32 to 33, 34 to 36, 37 to 38, and 39 to 42 weeks' GA, respectively. Logistic regression models additionally indicated declines in the risk for SUID as GA increased. Prenatal smoking, inadequate prenatal care, and demographics associated with poverty were strongly associated with SUID.

CONCLUSIONS

Despite the 2011 American Academy of Pediatrics recommendations for increased safe sleep education in the NICUs, SUID rates were inversely associated with GA in 2012 to 2013, suggesting that risk of SUID associated with prematurity has multiple etiologies requiring continued investigation, including biological vulnerabilities and the efficacy of NICU education programs, and that strategies to reduce SUID should be multifaceted.

Developmental toxicity of nicotine: A transdisciplinary synthesis and implications for emerging tobacco products

While the health risks associated with adult cigarette smoking have been well described, effects of nicotine exposure during periods of developmental vulnerability are often overlooked. Using MEDLINE and PubMed literature searches, books, reports and expert opinion, a transdisciplinary group of scientists reviewed human and animal research on the health effects of exposure to nicotine during pregnancy and adolescence. A synthesis of this research supports that nicotine contributes critically to adverse effects of gestational tobacco exposure, including reduced pulmonary function, auditory processing defects, impaired infant cardiorespiratory function, and may contribute to cognitive and behavioral deficits in later life. Nicotine exposure during adolescence is associated with deficits in working memory, attention, and auditory processing, as well as increased impulsivity and anxiety. Finally, recent animal studies suggest that nicotine has a priming effect that increases addiction liability for other drugs. The evidence that nicotine adversely affects fetal and adolescent development is sufficient to warrant public health measures to protect pregnant women, children, and adolescents from nicotine exposure.

SIDS and Other Sleep-Related Infant Deaths: Evidence Base for 2016 Updated Recommendations for a Safe Infant Sleeping Environment

Approximately 3500 infants die annually in the United States from sleep-related infant deaths, including sudden infant death syndrome (SIDS), ill-defined deaths, and accidental suffocation and strangulation in bed. After an initial decrease in the 1990s, the overall sleep-related infant death rate has not declined in more recent years. Many of the modifiable and nonmodifiable risk factors for SIDS and other sleep-related infant deaths are strikingly similar. The American Academy of Pediatrics recommends a safe sleep environment that can reduce the risk of all sleep-related infant deaths. Recommendations for a safe sleep environment include supine positioning, use of a firm sleep surface, room-sharing without bed-sharing, and avoidance of soft bedding and overheating. Additional recommendations for SIDS risk reduction include avoidance of exposure to smoke, alcohol, and illicit drugs; breastfeeding; routine immunization; and use of a pacifier. New evidence and rationale for recommendations are presented for skin-to-skin care for newborn infants, bedside and in-bed sleepers, sleeping on couches/armchairs and in sitting devices, and use of soft bedding after 4 months of age. In addition, expanded recommendations for infant sleep location are included. The recommendations and strength of evidence for each recommendation are published in the accompanying policy statement, "SIDS and Other Sleep-Related Infant Deaths: Updated 2016 Recommendations for a Safe Infant Sleeping Environment," which is included in this issue.

Interactive effects of maternal cigarette smoke, heat stress, hypoxia, and lipopolysaccharide on neonatal cardiorespiratory and cytokine responses

Maternal cigarette smoke (CS) exposure exhibits a strong epidemiological association with Sudden Infant Death Syndrome, but other environmental stressors, including infection, hyperthermia, and hypoxia, have also been postulated as important risk factors. This study examines whether maternal CS exposure causes maladaptations within homeostatic control networks by influencing the response to lipopolysaccharide, heat stress, and/or hypoxia in neonatal rats. Pregnant dams were exposed to CS or parallel sham treatments daily for the length of gestation. Offspring were studied at postnatal days 6-8 at ambient temperatures (T_a) of 33°C or 38°C. Within each group, rats were allocated to control, saline, or LPS (200 µg/kg) treatments. Cardiorespiratory patterns were examined using head-out plethysmography and ECG surface electrodes during normoxia and hypoxia (10% O₂). Serum cytokine concentrations were quantified from samples taken at the end of each experiment. Our results suggest maternal CS exposure does not alter minute ventilation (V̇e) or heart rate (HR) response to infection or high temperature, but independently increases apnea frequency. CS also primes the inflammatory system to elicit a stronger cytokine response to bacterial insult. High T_a independently depresses V̇e but augments the hypoxia-induced increase in V̇e Moreover, higher T_a increases HR during normoxia and hypoxia, and in the presence of an immune challenge, increases HR during normoxia, and reduces the increase normally associated with hypoxia. Thus, while most environmental risk factors increase the burden on the cardiorespiratory system in early life, hyperthermia and infection blunt the normal HR response to hypoxia, and gestational CS independently destabilizes breathing by increasing apneas.

Tobacco smoke in infants with bronchopulmonary dysplasia

Exposure to tobacco smoke has been not evaluated in children with bronchopulmonary dysplasia (BPD). We evaluate the association of in utero smoking (IUS) and environmental tobacco smoke (ETS) with the respiratory events of BPD and non-BPD children. Two hundred sixty-two children born before 35 weeks of gestational age (GA) and regularly followed up in our regional network for preterms were enrolled. They were paired according to their BPD status, their gestational age and birth weight (131 children with BPD and 131 without BPD, 28 mean weeks GA; mean weight 1000 g). Respiratory data were obtained prospectively during their first 2 years of life. A complementary questionnaire was completed by the parents about their child's respiratory health at the age of 2, their home environment, and tobacco status. IUS concerned 12.6 %; ETS, 48.8 % (67 % in BPD children treated with oxygen at home). No further influence on respiratory outcome could be found by exposure to intrauterine smoke or extrauterine tobacco smoke in this patient sample.

CONCLUSION

IUS and ETS exposures are as high in preterm children as in a general pediatric population. The highest exposure occurs among BPD infants treated with oxygen at home.

WHAT IS KNOWN

• Environmental tobacco smoke (ETS) and in utero smoking (IUS) are responsible for many morphological, functional, and clinical changes in children. • Children with bronchopulmonary dysplasia (BPD) have more respiratory events in their first years of life than preterm children without BPB, maybe triggered by ETS and IUS. What is New: • The exposition to ETS and IUS is high in preterm children with and without BDP, as high as in a general. • Pedaitric population, particularly in children with BPD and treated with oxygen at home. • No further influence on respiratory outcome could be found by exposure to ETS or IUS in our studied population.

Acute Neonatal Respiratory Failure

Acute respiratory failure requiring assisted ventilation is one of the most common reasons for admission to the neonatal intensive care unit. Respiratory failure is the inability to maintain either normal delivery of oxygen to the tissues or normal removal of carbon dioxide from the tissues. It occurs when there is an imbalance between the respiratory workload and ventilatory strength and endurance. Definitions are somewhat arbitrary but suggested laboratory criteria for respiratory failure include two or more of the following: PaCO₂ > 60 mmHg, PaO₂ < 50 mmHg or O₂ saturation <80 % with an FiO₂ of 1.0 and pH < 7.25 (Wen et al. 2004).

Maternal nicotinic exposure produces a depressed hypoxic ventilatory response and subsequent death in postnatal rats

In this study, we asked whether a “full term” prenatal nicotinic exposure (fPNE, 6 mg·kg⁻¹·day⁻¹ nicotinic delivery) over the full gestation, compared to a traditional PNE (tPNE) over the last two‐thirds of the gestation, caused a higher mortality following a remarkable depressed hypoxic ventilatory response (dHVR) independent of brain and pulmonary edema and change in serum corticosterone. P12‐14 pups pretreated with tPNE, fPNE or their vehicle (tCtrl and fCtrl) were exposed to 5% O₂ for up to 60 min followed by harvesting the brain and lungs or anesthetized to collect blood for detecting arterial blood pH/gases and serum cotinine and corticosterone levels. We found that fPNE had little effect on baseline V_E and heart rate, but consistently induced a dHVR and prolonged apnea that were rarely observed after tPNE. The severity of the dHVR in PNE pups were closely correlated to an earlier appearance of lethal ventilatory arrest (the hypoxia‐induced mortality). PNE did not induce brain and pulmonary edema, but significantly increased serum corticosterone levels similarly in tPNE and fPNE pups. Moreover, the accumulated nicotinic dose given to the individual was significantly higher in fPNE than tPNE pups, though there was no difference in serum cotinine levels and arterial blood pH/gases between the two groups. Our results suggest that nicotinic exposure at the early stage of gestation achieved by fPNE, rather than tPNE, is critical in generating the dHVR and subsequent death occurring independently of brain/pulmonary edema and changes in arterial blood pH/gases and serum corticosterone.

Our results suggest that nicotinic exposure at the early stage of gestation achieved by “full term” prenatal nicotinic exposure (fPNE), rather than traditional prenatal nicotinic exposure (tPNE), is critical in generating the depressed hypoxic ventilatory response (dHVR) and subsequent death. The fPNE‐induced cardiorespiratory impairement is independent of brain/pulmonary edema and changes in arterial blood pH/gases and serum corticosterone.

An optimized method for the estimation of the respiratory rate from electrocardiographic signals: implications for estimating minute ventilation

It is well-known that respiratory activity influences electrocardiographic (ECG) morphology. In this article we present a new algorithm for the extraction of respiratory rate from either intracardiac or body surface electrograms. The algorithm optimizes selection of ECG leads for respiratory analysis, as validated in a swine model. The algorithm estimates the respiratory rate from any two ECG leads by finding the power spectral peak of the derived ratio of the estimated root-mean-squared amplitude of the QRS complexes on a beat-by-beat basis across a 32-beat window and automatically selects the lead combination with the highest power spectral signal-to-noise ratio. In 12 mechanically ventilated swine, we collected intracardiac electrograms from catheters in the right ventricle, coronary sinus, left ventricle, and epicardial surface, as well as body surface electrograms, while the ventilation rate was varied between 7 and 13 breaths/min at tidal volumes of 500 and 750 ml. We found excellent agreement between the estimated and true respiratory rate for right ventricular (R(2) = 0.97), coronary sinus (R(2) = 0.96), left ventricular (R(2) = 0.96), and epicardial (R(2) = 0.97) intracardiac leads referenced to surface lead ECGII. When applied to intracardiac right ventricular-coronary sinus bipolar leads, the algorithm exhibited an accuracy of 99.1% (R(2) = 0.97). When applied to 12-lead body surface ECGs collected in 4 swine, the algorithm exhibited an accuracy of 100% (R(2) = 0.93). In conclusion, the proposed algorithm provides an accurate estimation of the respiratory rate using either intracardiac or body surface signals without the need for additional hardware.

Control of breathing activity in the fetus and newborn

Breathing movements have been demonstrated in the fetuses of every mammalian species investigated and are a critical component of normal fetal development. The classic sheep preparations instrumented for chronic fetal monitoring determined that fetal breathing movements (FBMs) occur in aggregates interspersed with long periods of quiescence that are strongly associated with neurophysiological state. The fetal sheep model also provided data regarding the neurochemical modulation of behavioral state and FBMs under a variety of in utero conditions. Subsequently, in vitro rodent models have been developed to advance our understanding of cellular, synaptic, network, and more detailed neuropharmacological aspects of perinatal respiratory neural control. This includes the ontogeny of the inspiratory rhythm generating center, the preBötzinger complex (preBötC), and the anatomical and functional development of phrenic motoneurons (PMNs) and diaphragm during the perinatal period. A variety of newborn animal models and studies of human infants have provided insights into age-dependent changes in state-dependent respiratory control, responses to hypoxia/hypercapnia and respiratory pathologies.

Assessing ventilatory control in infants at high risk of sleep disordered breathing: a study of infants with cleft lip and/or palate

Neonatal exposure to intermittent hypoxia results in altered ventilatory response to subsequent hypoxia in animal models. The effect of similar exposure in human infants is unknown. Our objective was to determine the impact of sleep disordered breathing (SDB) in early infancy on ventilatory response in infants. We recruited consecutive infants with cleft lip and/or palate (CL/P) to undergo ventilatory response testing using exposure to a hypoxic (15% O(2) ) gas mixture during sleep. This population is at high risk of SDB because of smaller airway caliber and abnormal palatal muscle attachments predisposing them to airway obstruction of ranging severity from birth. Ventilatory responses were compared between infants with a low apnea-hypopnea index (AHI; AHI < 15 events/hr) and a high AHI (AHI ≥ 15 events/hr). Testing was successfully completed in 22 of 23 infants who underwent testing at 4.4 ± 4.8 months. Infants with high AHI had lower weight z-scores, higher number of oxygen desaturation events during sleep, but similar oxygen saturation (S(p) O(2) ) nadir compared to infants with low AHI. The pattern of ventilatory response to hypoxia differed between the two groups; infants with high AHI had an earlier ventilatory decline and a blunted maximal ventilatory response to hypoxia. Infants with a high AHI use a different strategy to augment ventilation in response to hypoxia; while infants with a low AHI initially increased respiratory rate, tidal volume was the first parameter to increase in infants with high AHI. These results demonstrate that SDB in infancy is associated with altered ventilatory response to hypoxia.

Prenatal cigarette smoke exposure and postnatal respiratory responses to hypoxia and hypercapnia

Prenatal cigarette smoke (CS) exposure, in combination with hypoxia and/or hyperthermia can lead to gasping and attenuated recovery from hypoxia in 7 days old rat pups. We studied 95 unanesthetized spontaneously breathing 14 days old rat pups to investigate if the destabilizing effects of increased ambient temperature and prenatal CS exposure on respiratory control observed in 7 days old rats were still evident at day 14. This postnatal age was selected as it is beyond the analogous risk period for SIDS in human. Furthermore, we investigated if the breathing responses to hypercapnia are affected by prenatal CS exposure. Since high ambient (HA) temperature can lead to gasping and aberrant respiratory control, we recorded respiratory patterns at low (24-25°C) and high (29-30°C) ambient temperatures, and under hypoxic or hypercapnic states. No gasping was observed in 14 days old rat pups. During hypoxia, breathing frequency increased in the CS-exposed group under low and HA temperatures. Rectal temperature decreased only in the sham group in response to low ambient temperature hypoxia. At HA temperature, breathing frequency increased in both sham and CS-exposed groups during hypercapnia, however, it remained elevated during washout period only in the sham group. We demonstrate that prenatal CS exposure continues to have profound effects on respiratory and thermoregulatory responses to hypoxia and hypercapnia at day 14. The attenuated respiratory and thermoregulatory responses to acute hypoxia and hypercapnia on day 14 demonstrate a strong interaction between CS exposure, respiratory control, and thermoregulation during postnatal maturation.

SIDS and other sleep-related infant deaths: expansion of recommendations for a safe infant sleeping environment

Despite a major decrease in the incidence of sudden infant death syndrome (SIDS) since the American Academy of Pediatrics (AAP) released its recommendation in 1992 that infants be placed for sleep in a nonprone position, this decline has plateaued in recent years. Concurrently, other causes of sudden unexpected infant death occurring during sleep (sleep-related deaths), including suffocation, asphyxia, and entrapment, and ill-defined or unspecified causes of death have increased in incidence, particularly since the AAP published its last statement on SIDS in 2005. It has become increasingly important to address these other causes of sleep-related infant death. Many of the modifiable and nonmodifiable risk factors for SIDS and suffocation are strikingly similar. The AAP, therefore, is expanding its recommendations from being only SIDS-focused to focusing on a safe sleep environment that can reduce the risk of all sleep-related infant deaths including SIDS. The recommendations described in this report include supine positioning, use of a firm sleep surface, breastfeeding, room-sharing without bed-sharing, routine immunization, consideration of a pacifier, and avoidance of soft bedding, overheating, and exposure to tobacco smoke, alcohol, and illicit drugs. The rationale for these recommendations is discussed in detail in this technical report. The recommendations are published in the accompanying "Policy Statement--Sudden Infant Death Syndrome and Other Sleep-Related Infant Deaths: Expansion of Recommendations for a Safe Infant Sleeping Environment," which is included in this issue (www.pediatrics.org/cgi/doi/10.1542/peds.2011-2220).

Effects of prenatal exposure to cigarette smoke on use of xanthine and pneumogram evaluation at discharge in premature infants

OBJECTIVE

Prenatal exposure to cigarette smoke is associated with an increased risk of sudden infant death syndrome and possible rate increase of obstructive apnea in full-term infants but unknown in premature infants. Therefore, the objective was to study the effect of prenatal exposure to cigarette smoke on the use of methylxanthines and discharge pneumograms in premature infants.

METHODS

Preterm infants [gestational age (GA) ≤34 weeks] born between January 1997 and September 2007 were studied. A four-channel pneumogram was performed at discharge. Relevant clinical data were collected from the infant's records. Infants with prenatal exposure to cigarette smoke were compared with infants not exposed (controls).

RESULTS

A total of 1656 infants were studied: 263 infants {birth weight (BW) (mean ± SD) 1682 ± 566 g, GA 31.0 ± 2.8 weeks} exposed to prenatal cigarette smoke and 1393 infants (BW 1638 ± 575 g, GA 31.1 ± 2.7 weeks) not exposed. Baseline patient characteristics were similar between the two groups. When comparing the smoking versus control groups, there was no significant difference in the infants for the following: xanthine therapy and abnormal pneumograms; presence of central, obstructed or mixed apnea and home discharge on monitors, oxygen and xanthines.

CONCLUSIONS

Prenatal exposure to cigarette smoke was not associated with increased use of xanthines or abnormal pneumogram in premature infants.

Ambient air pollution and apnea and bradycardia in high-risk infants on home monitors

BACKGROUND

Evidence suggests that increased ambient air pollution concentrations are associated with health effects, although relatively few studies have specifically examined infants.

OBJECTIVE

We examined associations of daily ambient air pollution concentrations with central apnea (prolonged pauses in breathing) and bradycardia (low heart rate) events among infants prescribed home cardiorespiratory monitors.

METHODS

The home monitors record the electrocardiogram, heart rate, and respiratory effort for detected apnea and bradycardia events in high-risk infants [primarily premature and low birth weight (LBW) infants]. From August 1998 through December 2002, 4,277 infants had 8,960 apnea event-days and 29,450 bradycardia event-days in > 179,000 days of follow-up. We assessed the occurrence of apnea and bradycardia events in relation to speciated particulate matter and gaseous air pollution levels using a 2-day average of air pollution (same day and previous day), adjusting for temporal trends, temperature, and infant age.

RESULTS

We observed associations between bradycardia and 8-hr maximum ozone [odds ratio (OR) = 1.049 per 25-ppb increase; 95% confidence interval (CI), 1.021-1.078] and 1-hr maximum nitrogen dioxide (OR =1.025 per 20-ppb increase; 95% CI, 1.000-1.050). The association with ozone was robust to different methods of control for time trend and specified correlation structure. In secondary analyses, associations of apnea and bradycardia with pollution were generally stronger in infants who were full term and of normal birth weight than in infants who were both premature and LBW.

CONCLUSIONS

These results suggest that higher air pollution concentrations may increase the occurrence of apnea and bradycardia in high-risk infants.

Relationship of maternal snuff use and cigarette smoking with neonatal apnea

BACKGROUND

Maternal smoking is associated with disturbed cardiorespiratory control in the infant. Despite lacking knowledge of whether the harmful effects of smoking are caused by combustion products in tobacco smoke or by nicotine, it has been argued that nicotine-replacement therapy during pregnancy is safer than smoking.

OBJECTIVE

The goal of this study was to investigate if the disturbances in cardiorespiratory control associated with maternal smoking are also seen in infants prenatally exposed to snuff. We hypothesized that prenatal nicotine exposure (via moist snuff) causes disturbances in autonomic control and thereby increases the risk of apnea in the newborn.

METHODS

In a nationwide Swedish cohort study, we studied associations between maternal tobacco use during pregnancy and neonatal apnea. Of 609 551 live-born singleton infants, 7599 were born to snuff-using mothers, 41 391 and 16 928 were born to light (1-9 cigarettes per day) and heavy (≥ 10 cigarettes per day) smokers, respectively. Logistic regression was used to calculate odds ratios, using 95% confidence intervals.

RESULTS

Compared with infants of nontobacco users, infants with prenatal exposure to snuff were at an increased risk of apnea even after adjustment for differences in gestational age (odds ratio: 1.96 [95% confidence interval: [1.30-2.96]) Smoking was associated with increased risk of apnea before, but not after, adjusting for gestational age.

CONCLUSIONS

Snuff use during pregnancy is associated with a higher risk of neonatal apnea than smoking. Maternal use of snuff or nicotine-replacement therapy cannot be regarded as an alternative to smoking during pregnancy.

Prenatal tobacco exposure influences cerebral oxygenation in preterm infants

AIM

Our aim was to determine the influence of prenatal tobacco exposure on regional cerebral tissue oxygen saturation (r(c)SO(2)) and fractional tissue oxygen extraction (FTOE) in preterm infants. We hypothesized that as a result of vasoconstriction caused by prenatal tobacco exposure r(c)SO(2) would be lower and FTOE would be higher during the first days after birth in infants exposed to tobacco during pregnancy.

METHODS

Sixty preterms were included in this prospective, observational cohort study (median gestational age 29.9 weeks, range 26.0-31.8, median birth weight 1248 g, range 615-2250). Fourteen infants had been exposed to tobacco during pregnancy. All mothers smoked more than five cigarettes a day till delivery. We measured r(c)SO(2) and transcutaneous arterial oxygen saturation (tcSaO(2)) in all infants on days 1-5, 8, and 15. FTOE was calculated: FTOE=(tcSaO(2)-r(c)SO(2))/tcSaO(2).

RESULTS

In preterm infants exposed to tobacco during pregnancy, r(c)SO(2) was lower during days 1, 2, and 8 after birth, median 73% versus 81%, 73% versus 80% and 71% versus 78% respectively. FTOE was higher during days 1 and 8 after birth, median 0.24 versus 0.15 and 0.26 versus 0.19 respectively. On the second day, FTOE tended to be higher, 0.18 versus 0.14.

CONCLUSIONS

During the first two days and day 8 after birth cerebral oxygen saturation is lower and oxygen extraction higher in preterm infants following prenatal tobacco exposure. Our data suggest that prenatal tobacco exposure may have an effect on cerebral oxygenation of the infant.

Maternal hypoxia increases the activity of MMPs and decreases the expression of TIMPs in the brain of neonatal rats

A recent study has shown that increased activity of matrix metalloproteinases-2 and metalloproteinases-9 (MMP-2 and MMP-9) has detrimental effect on the brain after neonatal hypoxia. The present study determined the effect of maternal hypoxia on neuronal survivability and the activity of MMP-2 and MMP-9, as well as the expression of tissue inhibitors of metalloproteinase 1 and 2 (TIMP-1 and TIMP-2) in the brain of neonatal rats. Pregnant rats were exposed to 10.5% oxygen for 6 days from the gestation day 15 to day 21. Pups were sacrificed at day 0, 4, 7, 14, and 21 after birth. Body weight and brain weight of the pups were measured at each time point. The activity of MMP-2 and MMP-9 and the protein abundance of TIMP-1 and TIMP-2 were determined by zymography and Western blotting, respectively. The tissue distribution of MMPs was examined by immunofluorescence staining. The neuronal death was detected by Nissl staining. Maternal hypoxia caused significant decreases in body and brain size, increased activity of MMP-2 at day 0, and increased MMP-9 at day 0 and 4. The increased activity of the MMPs was accompanied by an overall tendency towards a reduced expression of TIMPs at all ages with the significance observed for TIMPs at day 0, 4, and 7. Immunofluorescence analysis showed an increased expression of MMP-2, MMP-9 in the hippocampus at day 0 and 4. Nissl staining revealed significant cell death in the hippocampus at day 0, 4, and 7. Functional tests showed worse neurobehavioral outcomes in the hypoxic animals.