A review of the anatomy of the upper airway in early infancy and its possible relevance to SIDS

The Ogival Palate: A New Risk Marker of Sudden Unexpected Death in Infancy?

OBJECTIVE

Ogival palate (i.e., a narrow and high-arched palate) is usually described in obstructive breath disorder but has been found in infants unexpectedly deceased. We studied the association between ogival palate and sudden unexpected death in infancy (SUDI) on the basis of a computed tomography (CT) evaluation.

METHODS

We conducted a monocentric case-control study of children under 2 years of age who died of SUDI, for which a head CT scan and an autopsy were performed between 2011 and 2018. Each case was matched by sex and age (± 30 days) to two controls selected among living children in the same center who benefited from a cranio-encephalic CT scan. Four parameters of the hard palate were measured by CT: height, width, length, and sagittal angle; the height/width ratio was calculated. The presence of an ogival palate was also subjectively evaluated by the radiologists, independently from the measurements. Standardized odds ratios (OR) were calculated using conditional logistic regression models, all expressed for +1 standard deviation (SD).

RESULTS

Thirty-two deceased children were matched to 64 living control children. Mean ages were 5.0 and 5.3 months, respectively. Twenty-eight cases were considered to have died as a result of SIDS. The mean heights of the hard palate were significantly higher in the deceased children [4.1 (± 0.7) millimeters (mm)] than in the living children [3.2 (± 0.6) mm], with OR (+1SD) = 4.30 (95% confidence interval [CI], 2.04-9.06, P = 0.0001). The mean widths of the hard palate were 21.0 (± 1.9) mm and 23.2 (± 2.1) mm, respectively, with OR = 0.15 (95% CI, 0.06-0.40, P = 0.0001). The mean sagittal angles were significantly more acute in deceased children [134.5° (± 9.3)] than in living children [142.9° (± 8.1)], with OR = 0.28 (95% CI, 0.14-0.56, P = 0.0003). The mean height/width ratios were 19.8 (± 3.7) and 14.1 (± 3.3), respectively, with OR = 6.10 (95% CI, 2.50-14.9, P = 0.0001). The hard palate was subjectively considered as ogival in 59.4% (19/32) of the cases versus 12.5% (8/64) of the controls.

CONCLUSION

Radiological features of the ogival palate were strongly associated with SUDI. This observation still needs to be confirmed and the corresponding clinical features must be identified.

Risk and Preventive Factors for SUDI: Need We Adjust the Current Prevention Advice in a Low-Incidence Country

Background: The incidence of Sudden Unexpected Death in Infancy (SUDI) is low in the Netherlands, with an incidence rate of 0.18 per 1,000 live births. Therefore, prevention advice may receive less attention, potentially leading to increasing incidence rates. It is currently unknown whether the risks for SUDI changed in the Netherlands, and if other risk factors might be present. The aim of this study was to examine the current risks and preventive factors for SUDI in Dutch infants, in order to determine if it is necessary to adapt the prevention advice toward the current needs. Methods: A case-control study was conducted comparing SUDI cases aged <12 months from 2014-2020 in the Netherlands (n = 47), to a Dutch national survey control group from 2017 including infants <12 months of age (n = 1,192). Results: Elevated risks for several well-known factors were observed, namely: duvet use (aOR = 8.6), mother smoked during pregnancy (aOR = 9.7), or after pregnancy (aOR = 5.4) and the prone sleeping position (aOR = 4.6). Reduced risks were observed for the well-known factors: room-sharing (aOR = 0.3), sleep sack use (aOR = 0.3), breastfeeding (aOR = 0.3), and the use of a pacifier (aOR = 0.4). For infants <4 months, the risk for SUDI was higher when bed-sharing (aOR = 3.3), and lower when room-sharing (aOR = 0.2) compared to older infants. For older infants, the sleep sack was found to be more protective (aOR = 0.2). A high risk for SUDI when bed-sharing was found when mother smoked, smoked during pregnancy, or if the infant did not receive any breastfeeding (respectively aOR = 17.7, aOR = 10.8, aOR = 9.2). Conclusions: Internationally known factors related to the sudden unexpected death of infants were also found in this study. Relatively new findings are related to specific groups of infants, in which the strengths of these risk factors differed. In a low-incidence country like the Netherlands, renewed attention to the current prevention advice is needed. Furthermore, additional attention for prevention measures in low educated groups, and additional advice specifically targeting high-risk groups is recommended.

How might non nutritional sucking protect from sudden infant death syndrome

Epidemiology has identified an association between the use of pacifiers and protection from sudden infant death syndrome (SIDS). The use of pacifiers for SIDS prevention fails to gain adoption partly because there is no widely accepted physiologic mechanism to explain the epidemiologic association. Additionally, the scientific literature available on pacifier use focuses largely on the probable adverse effects. We hypothesize that pacifier use and all other forms of non-nutritional sucking (specifically digit sucking, also known as thumb sucking) is a life saving defense mechanism meant to splint open and stabilize the collapsible portion of the upper airway in infants.The main objective of this review article is to propose a mechanism to explain how pacifiers might help prevent SIDS. If the medical community accepts this mechanism, it can help promote pacifier use by the public and potentially reduce the incidence of SIDS.

Sudden deaths in adult-worn baby carriers: 19 cases

Soft infant carriers such as slings have become extremely popular in the west and are usually considered safe. We report 19 cases of sudden unexpected death in infancy (SUDI) linked to infant carrier. Most patients were healthy full-term babies less than 3 months of age, and suffocation was the most frequent cause of death.

CONCLUSION

Infant carriers represent an underestimated cause of death by suffocation in neonates.

WHAT IS KNOWN

• Sudden unexpected deaths in infancy linked to infant carrier have been only sparsely reported.

WHAT IS NEW

• We report a series of 19 cases strongly suggesting age of less than 3 months as a risk factor and suffocation as the mechanism of death.

Gut Microbiota and Immunity: Possible Role in Sudden Infant Death Syndrome

The gut microbiome influences the development of the immune system of young mammals; the establishment of a normal gut microbiome is thought to be important for the health of the infant during its early development. As the role of bacteria in the causation of sudden infant death syndrome (SIDS) is backed by strong evidence, the balance between host immunity and potential bacterial pathogens is likely to be pivotal. Bacterial colonization of the infant colon is influenced by age, mode of delivery, diet, environment, and antibiotic exposure. The gut microbiome influences several systems including gut integrity and development of the immune system; therefore, gut microflora could be important in protection against bacteria and/or their toxins identified in SIDS infants. The aims of the review are to explore (1) the role of the gut microbiome in relation to the developmentally critical period in which most SIDS cases occur; (2) the mechanisms by which the gut microbiome might induce inflammation resulting in transit of bacteria from the lumen into the bloodstream; and (3) assessment of the clinical, physiological, pathological, and microbiological evidence for bacteremia leading to the final events in SIDS pathogenesis.

The evolution and development of human swallowing: the most important function we least appreciate

As mammals evolved, the larynx accrued added importance in new activities such as effectuating intra-abdominal pressure control during the transition from egg-laying to birthing and control of intrathoracic stabilization as movement of the upper limb required rib stabilization during climbing. The proper development of the larynx during the embryonic period is crucial to its later normal function. The permanent intersection of the respiratory and digestive pathways has created a de novo aerodigestive tract; a first of its kind in mammals. The lowered position of the human larynx has provided a greatly expanded supralaryngeal portion of the pharynx.

Are baby hammocks safe for sleeping babies? A randomised controlled trial

AIM

Two reports of infants found dead after sleeping in baby hammocks have raised international concern about the safety of infant hammocks. We therefore tested whether hammock sleep affected oxygenation in infants, when they were at an age of high risk of sudden, unexpected infant death.

METHODS

Healthy, full-term 4- to 8-week-old infants were randomised to sleep either in a commercially available hammock (n = 14) or a standard bassinet (n = 9), and sleep state, oxygen desaturation (a fall in peripheral haemoglobin oxygen saturation (SpO2 ) ≥ 4%, for ≥ 4 sec from baseline to nadir), apnoea and hypopnoea, and mean SpO2 were analysed.

RESULTS

There was no significant difference in mean SpO2 (both 98.5%) or rate of oxygen desaturation events between the hammock and the bassinet cot (mean ± SD, 24 ± 20 vs. 28 ± 23 events per hour), but infants slept less in the hammock (59 ± 31 vs. 81 ± 34 min, p < 0.02).

CONCLUSION

When correctly used, the hammock sleep position did not compromise the upper airway of sleeping infants. The significance of shorter duration of sleep in the hammocks is unclear. These findings should not be applied to all baby hammocks, nor to older babies, particularly once the infant can roll. Given that it is not possible to predict when an infant will be able to roll, we strongly recommend that hammocks should not be used for unsupervised sleep.

Gut microbiome in sudden infant death syndrome (SIDS) differs from that in healthy comparison babies and offers an explanation for the risk factor of prone position

The role of bacteria in the causation of sudden infant death syndrome (SIDS) is gaining acceptance. Mainstream research favouring respiratory compromise has failed to provide a plausible pathogenetic mechanism despite many years of investigation and thousands of research papers. Bacterial colonisation of the colon of the human infant is influenced by many factors including age, mode of delivery, diet, environment, and antibiotic exposure. The gut microbiome influences development of the immune system. The gut microflora could be important in protection against the bacteria and/or their toxins purportedly involved in SIDS pathogenesis. The aim was to perform a preliminary investigation of the gut microflora in sudden infant death syndrome (SIDS) compared with live comparison babies. The intestinal contents from 52 SIDS, and 102 faecal samples from age-matched live comparison infants were screened by PCR to target 16s RNA genes of Clostridium innocuum, Cl. Perfringens, Cl. difficile, Bacteroides thetaiotaomicron and Staphylococcus aureus. Gut colonisation of the babies with these bacteria was analysed in relation to age, gender and type of feeding; and for SIDS babies sleeping position. Cl. difficile, Cl. innocuum and B. thetaiotaomicron were significantly associated with SIDS with 25%, 46% and 30% of cases PCR positive for these respective bacteria compared with only 6%, 23% and 8.8% respectively in the comparison group. SIDS babies had dual colonisation by both Cl. perfringens and Cl. difficile significantly more often than comparison babies and also with triple colonisation by Cl. perfringens, Cl. difficile and Cl. innocuum. SIDS babies were more often colonised by S. aureus than comparison babies. In addition, SIDS babies found prone were significantly more likely to be colonised by S. aureus than for other positions recorded (OR = ∞; CI = 2·04 - ∞). No significant differences between breast and bottle-fed SIDS babies was observed in regard to each clostridial bacterium, or S. aureus, however Cl. innocuum was found to be significantly associated with formula feeding in the comparison cohort. Comparison of breast and formula feeding of SIDS babies with live comparison babies revealed significant differences with regards to some of the clostridial bacteria. Age-specific differences in gut bacterial microbiome were observed in both SIDS and comparison healthy babies. This study gives an insight into differences in the gut bacterial microbiome of SIDS babies compared with healthy babies. These differences could be important in contributing to a baby's susceptibility to infection and therefore to SIDS. The association of S. aureus colonisation with prone sleep position supports the hypothesis that prone sleep position could increase the risk of ingestion/inhalation of bacteria contaminating the sleeping surface and could account for the increased risk of SIDS in babies who are put to sleep prone. The study provides impetus for broader studies into the gut microbiome of babies and could lead to effective approaches to SIDS prevention.

Nasal versus oronasal raised volume forced expirations in infants--a real physiologic challenge

Raised volume rapid thoracoabdominal compression (RTC) generates forced expiration (FE) in infants typically from an airway opening pressure of 30 cm H(2)O (V(30)). We hypothesized that the higher nasal than pulmonary airway resistance limits forced expiratory flows (FEF(%)) during (nasal) FE(n), which an opened mouth, (oronasal) FE(o), would resolve. Measurements were performed during a brief post-hyperventilation apnea on 12 healthy infants aged 6.9-104 weeks. In two infants, forced expiratory (FEFV) flow volume (FV) curves were generated using a facemask that covered the nose and a closed mouth, then again with a larger mask with the mouth opened. In other infants (n = 10), the mouth closed spontaneously during FE. Oronasal passive expiration from V(30) generated either the inspiratory capacity (IC) or by activating RTC before end-expiration, the slow vital capacity ((j) SVC). Peak flow (PF), FEF(25), FEF(50), FEF(25-75), FEV(0.4), and FEV(0.5) were lower via FE(n) than FE(o) (P < 0.05), but the ratio of expired volume at PF and forced vital capacity (FVC) as percent was higher (P < 0.05). FEF(75), FEF(85), FEF(90), FVC as well as the applied jacket pressures were not different (P > 0.05). FEFV curves generated via FE(o) exhibited higher PF than FV curves of IC (P < 0.05); PF of those produced via FE(n) were not different from FV curves of IC (P > 0.05) but lower than those of (j) SVC (P < 0.05). In conclusion, the higher nasal than pulmonary airways resistance unequivocally affects the FEFV curves by consistently reducing PF and decreases mid-expiratory flows. A monitored slightly opened mouth and a gentle anterior jaw thrust are physiologically integral for raised volume RTC in order to maximize the oral and minimize nasal airways contribution to FE so that flow limitation would be in the pulmonary not nasal airways.

Otolaryngological aspects of sudden infant death syndrome

INTRODUCTION

Sudden infant death syndrome (SIDS) is characterized by the sudden death of an apparently otherwise healthy infant, typically during sleep, and with no obvious case after a thorough post-mortem and scene death examination.

OBJECTIVE

To address the problem from the otolaryngologist's perspective, describe relevant pathologies, discuss controversies and suggest preventive measures in high-risk populations.

METHODOLOGY

A MEDLINE search and hand search were conducted to identify reports published between 1969 and 2011 in the English language on the pathophysiology of SIDS related to the head and neck organs. Search terms included SIDS (MeSH term), SIDS and pathophysiology (text words), and SIDS and autopsy (text words).

DISCUSSION

A growing number of reports suggested head and neck organs involvement in SIDS autopsies. Laryngeal, oropharyngeal, maxillofacial, otologic, cervical vascular abnormalities and infectious etiologies, were recognized and discussed.

CONCLUSIONS

Otolaryngologists should be aware of relevant pathologies, as some are treatable, if identified early enough in infancy. A proactive risk-management approach is warranted in infants presenting with certain abnormalities reviewed here.

A perspective on SIDS pathogenesis. the hypotheses: plausibility and evidence

Several theories of the underlying mechanisms of Sudden Infant Death Syndrome (SIDS) have been proposed. These theories have born relatively narrow beach-head research programs attracting generous research funding sustained for many years at expense to the public purse. This perspective endeavors to critically examine the evidence and bases of these theories and determine their plausibility; and questions whether or not a safe and reasoned hypothesis lies at their foundation. The Opinion sets specific criteria by asking the following questions: 1. Does the hypothesis take into account the key pathological findings in SIDS? 2. Is the hypothesis congruent with the key epidemiological risk factors? 3. Does it link 1 and 2? Falling short of any one of these answers, by inference, would imply insufficient grounds for a sustainable hypothesis. Some of the hypotheses overlap, for instance, notional respiratory failure may encompass apnea, prone sleep position, and asphyxia which may be seen to be linked to co-sleeping. For the purposes of this paper, each element will be assessed on the above criteria.

Potential Mechanisms of Failure in the Sudden Infant Death Syndrome

Current evidence suggests that multiple neural mechanisms contribute to the fatal lethal event in SIDS. The processes may develop from a range of otherwise seemingly-innocuous circumstances, such as unintended external airway obstruction or accidental extreme flexion of the head of an already-compromised structure of the infant upper airway. The fatal event may occur in a sleep state which can suppress muscle tone essential to restore airway patency or exert muscle action to overcome a profound loss of blood pressure. Neural processes that could overcome those transient events with reflexive compensation appear to be impaired in SIDS infants. The evidence ranges from subtle physiological signs that appear very early in life, to autopsy findings of altered neurotransmitter, including serotonergic, systems that have extensive roles in breathing, cardiovascular regulation, and thermal control. Determination of the fundamental basis of SIDS is critical to provide biologic plausibility to SIDS risk reduction messages and to develop specific prevention strategies.

Effect of pacifier use on mandibular position in preterm infants

AIM

It has been hypothesized that the association of pacifier use with reduced risk of sudden infant death is mediated by forward movement of the mandible and tongue that helps open the upper airway. Our aim was to examine whether the mandible is moved forward when an infant is sucking on a pacifier, and if so, whether the mandible remains advanced after the pacifier is removed.

METHODS

In sixty clinically stable premature infants (corrected gestation age 36.5 +/- 0.3 weeks, mean +/- SEM) the distance from each ear where the pinna met the cheek to the most prominent point of the chin was measured bilaterally, and the average was used as an index of mandibular position. Mandibular position was determined before and after allowing the infants to suck on a pacifier for 10-15 min, and after removing the pacifier.

RESULTS

There was a significant forward movement of the mandible when the infants were sucking on the pacifier (59.5 +/- 0.7 vs. 58.6 +/- 0.7 mm, p = 0.001), with no significant change after the pacifier was removed.

CONCLUSIONS

Pacifier use in preterm infants was associated with a small significant forward displacement of the jaw. These data suggest that pacifier use may help protect the upper airway.

Smaller mandibular size in infants with a history of an apparent life-threatening event

OBJECTIVES

To examine small mandibular size and preference for a hand-to-chin posture as salient characteristics in infants with a history of an apparent life-threatening event (ALTE).

STUDY DESIGN

This was a prospective case-control study of term infants, from birth to 6 months of age, admitted post-ALTE and matched 1:2 with healthy control infants (age within 2 weeks and weight within 0.5 kg). Infants with confirmed gastroesophageal reflux and congenital anomalies, including severe micrognathia, were excluded.

RESULTS

Infants with a history of an ALTE (n = 25) were matched to 47 healthy controls. Infants with a history of an ALTE had mandibular indices (larger index indicates a smaller mandible) that were 3.8 mm greater on the left side (95% CI: 2.0-5.6, P < .001) and 4.2 mm greater on the right side (95% CI: 2.7-5.6, P < .001) adjusting for length and non-white race. Controlling for matching and length, a 1-mm increase in the average mandibular index increased the odds of an ALTE by 62% (OR = 1.62, 95% CI: 1.22-2.44, P < .001).

CONCLUSIONS

Smaller mandibular size was associated with ALTE, suggesting airway obstruction as a potential cause of ALTE. The association of this characteristic with ALTE also offers the potential for prospective quantification of ALTE risk.

Endoscopic findings in children with obstructive sleep apnea: effects of age and hypotonia

Obstructive sleep apnea (OSA) syndrome is a common disorder among children and is often associated with significant morbidity. The causes of OSA are related to either fixed upper airway abnormalities such as adenotonsillar hypertrophy, or dynamic airway abnormalities such as laryngomalacia and pharyngeal wall collapse. The aim of the present study was to determine the prevalence of dynamic upper airway abnormalities, based on endoscopic findings, in normotonic and hypotonic children with polysomnographically documented OSA. The records of 39 consecutive children with OSA who underwent bronchoscopy (22 with normal tone, and 17 with hypotonia) were reviewed. The prevalence of dynamic defects among children with normal tone decreased with age. All 7 patients less than 1 year old had dynamic abnormalities (isolated or combined fixed/dynamic), compared to only 66% (6/9) of patients between 1-2 years old, and 17% (1/6) of children more than 2 years old. In contrast, dynamic abnormalities were very common among hypotonic children, independent of age. Since children with dynamic defects are less likely to respond to surgical treatments, it would be appropriate to identify these children prior to any intervention. Due to the higher frequency of dynamic defects in both infants (< 1 year) and hypotonic children, it may be appropriate to include endoscopy as part of the diagnostic evaluation of OSA in these subgroups.

Physiology of breathing and related pathological processes in infants

There is little information describing control of breathing in the fetus and infant. The available data have largely been drawn from studies in animals and awake adults. Although the hierarchy of control of breathing is the same in adults and infants, feedback emphasis is different, with behavioral states and the sleep/wake cycle primary in the fetus and infant and integrated chemoreceptor response primary in the older child and adult. Control of breathing during the transition from the fetal state to a breathing child and the process of maturation are very different from that in adults. The article begins with an overview of the changes in the systems responsible for breathing at the developmental stages from fetus to neonate, with differences highlighted. It then discusses the possible pathology related to difficulties in negotiating this transition period, including apnea, sudden infant death syndrome, and chemoreceptor control abnormalities.

Simple car seat insert to prevent upper airway narrowing in preterm infants: a pilot study

OBJECTIVES

To test prospectively the hypothesis that an infant car seat modification to allow the infant's head to rest in a neutral position on the trunk would prevent narrowing of the upper airway and thus reduce oxygen desaturation in preterm infants who are restrained in car seats.

METHODS

Seventeen preterm infants who were approved for discharge were evaluated in a car seat for newborns, with and without a foam insert that provided a slot for the back of the infants' head. Respiration timed inspiratory radiographs for assessment of upper airway dimensions were taken during quiet sleep in each position. Infants were monitored in each position for 30 minutes with continuous polygraphic recording of respiratory, cardiac, and nasal airflow activity and pulse oximetry.

RESULTS

Placement of the insert in the car seat was associated with a larger upper airway space (mean +/- standard deviation, 5.2 +/- 1.3 vs 3.6 +/- 1.4 mm). This radiologic improvement was associated with a significant reduction in the frequency of episodes of oxygen desaturation to <85% (1.5 +/- 2.1 vs 3.5 +/- 3.5 episodes/infant), of bradycardia <90 bpm (0.1 +/- 0.3 vs 1 +/- 1.7), and of arousal (median [25th, 75th], 2.5 [1.3, 4.0] vs 5.0 [4.0, 7.0]).

CONCLUSIONS

The cause of oxygen desaturation in preterm infants who are restrained in car seats is multifactorial. The present data strongly support the hypothesis that flexion of the head on the body is a significant contributor to these episodes and that the mechanism is posterocephalic displacement of the mandible, leading to narrowing of the upper airway. Critically, this pilot study demonstrates that the frequency of episodes of desaturation in a standard newborn car seat can be substantially reduced by placement of a simple foam insert that allows the infant to maintain the head in a neutral position on the trunk during sleep.

Nasal obstruction in sleep-disordered breathing

It has been 30 years since Cottle suggested that "sleeping patterns are in great measure dependent on good nasal function" [1]. During this time, we have identified the OSAHS and related forms of sleep-disordered breathing such as UARS, and better appreciate the clinical sequelae of recurrent arousals and sleep fragmentation. Yet the exact role that obstructed nasal breathing plays in the pathogenesis of such sleep disorders remains presumptive, and robust clinical studies to corroborate this theory remain elusive; however, patients who may benefit most from correction of nasal obstruction as a sole intervention may be those with the mildest forms of sleep-disordered breathing without other significant predisposing anatomic abnormalities. Clearly, more stringently controlled studies [17,105] are needed, particularly in these types of patients. Until such time, it is reasonable to address issues of nasal obstruction as an adjunct to surgical and nonsurgical treatment in all patients who are diagnosed with a sleep-related breathing disorder.