Pacifier Stiffness Alters the Dynamics of the Suck Central Pattern Generator

The Impact of Varying Nipple Properties on Infant Feeding Physiology and Performance Throughout Ontogeny in a Validated Animal Model

Infant feeding requires successful interactions between infant physiology and the maternal (or bottle) nipple. Within artificial nipples, there is variation in both nipple stiffness and flow rates, as well as variation in infant physiology as they grow and mature. However, we have little understanding into how infants interact with variable nipple properties to generate suction and successfully feed. We designed nipples with two different stiffnesses and hole sizes and measured infant feeding performance through ontogeny using a pig model. We evaluated their response to nipple properties using high-speed X-Ray videofluoroscopy. Nipple properties substantially impacted sucking physiology and performance. Hole size had the most profound impact on the number of sucks infants took per swallow. Pressure generation generally increased with age, especially in nipples where milk acquisition was more difficult. However, most strikingly, in nipples with lower flow rates the relationship between suction generation and milk acquisition was disrupted. In order to design effective interventions for infants with feeding difficulties, we must consider how variation in nipple properties impacts infant physiology in a targeted manner. While reducing flow rate may reduce the frequency an infant aspirates, it may impair systems involved in sensorimotor integration.

Conformity between Pacifier Design and Palate Shape in Preterm and Term Infants Considering Age-Specific Palate Size, Facial Profile and Lip Thickness

This retrospective case-control study is the first to examine the spatial conformity between pacifiers and palates in 39 preterm infants (12 females, 27 males) and 34 term infants (19 females, 15 males), taking into account the facial-soft-tissue profile and thickness. The shape of 74 available pacifiers was spatially matched to the palate, and conformity was examined using width, height, and length measurements. In summary, the size concept of pacifiers is highly variable and does not follow a growth pattern, like infant palates do. Pacifiers are too undersized in width, length, and height to physiologically fit the palate structures from 0 to 14 months of age. There are two exceptions, but only for premature palates: the palatal depth index at 9−11 months of age, which has no clinical meaning, and the nipple length at <37 weeks of age, which bears a resemblance to the maternal nipple during non-nutritive sucking. It can be concluded that the age-size concept of the studied pacifiers does not correspond to any natural growth pattern. Physiologically aligned, pacifiers do not achieve the age-specific dimensions of the palate. The effects attributed to the products on oral health in term infants cannot be supposed.

Associations of gestational phthalate exposure and non-nutritive suck among infants from the Puerto Rico Testsite for Exploring Contamination Threats (PROTECT) birth cohort study

BACKGROUND

Infant non-nutritive suck (NNS), or sucking on a pacifier with no nutrients being delivered, has been used as in index of brain function and has been linked to subsequent neurodevelopment. Yet, no data are available connecting NNS to environmental exposures in utero. The goal of this study was to examine the relationship between gestational exposure to phthalates (a group of chemicals found in personal care products, PVC plastics, and other products) and NNS among infants in a birth cohort study in Puerto Rico.

METHODS

Urinary phthalate metabolite levels were measured in women at up to three time points in pregnancy as a measure of in utero exposure to the child. We calculated the geometric mean of each metabolite for each woman as a measure of exposure across gestation. Infants had their NNS sampled using our custom research pacifier between 4-6 (± 2 weeks) weeks of age, yielding the following NNS dependent measures: cycles/burst, frequency, amplitude, bursts/min, and cycles/min.

RESULTS

Two hundred and eight mother-infant dyads completed this study We used multiple linear regression to assess associations between individual phthalate metabolites and NNS measurements, adjusting for infant sex, birthweight, and urinary specific gravity. An interquartile range (IQR) increase in mono carboxyisononyl phthalate across pregnancy was associated with 3.5% (95%CI: -6.2, -0.8%) lower NNS frequency and 8.9% (0.6, 17.3%) higher NNS amplitude. Similarly, an IQR increase in mono-2-ethylhexyl phthalate was also associated with 3.4% (-6.5, -0.2%) lower NNS frequency, while an IQR increase in di-2-ethylhexyl terephthalate metabolites was associated with 11.2% (2.9, 19.5%) higher NNS amplitude. Gestational exposure to phthalates may alter NNS amplitude and frequency in full-term infants. These findings indicate that the infants may be increasing their NNS amplitude to compensate for their slower NNS frequency. These preliminary findings could have important clinical implications for earlier detection of exposure-related deficits in neurofunction as well as implications for subsequent neurodevelopment and related interventions.

Abnormal Nutritive Sucking as an Indicator of Neonatal Brain Injury

A term neonate is born with the ability to suck; this neuronal network is already formed and functional by 28 weeks gestational age and continues to evolve into adulthood. Because of the necessity of acquiring nutrition, the complexity of the neuronal network needed to suck, and neuroplasticity in infancy, the skill of sucking has the unique ability to give insight into areas of the brain that may be damaged either during or before birth. Interpretation of the behaviors during sucking shows promise in guiding therapies and how to potentially repair the damage early in life, when neuroplasticity is high. Sucking requires coordinated suck-swallow-breathe actions and is classified into two basic types, nutritive and non-nutritive. Each type of suck has particular characteristics that can be measured and used to learn about the infant's neuronal circuitry. Basic sucking and swallowing are present in embryos and further develop to incorporate breathing ex utero. Due to the rhythmic nature of the suck-swallow-breathe process, these motor functions are controlled by central pattern generators. The coordination of swallowing, breathing, and sucking is an enormously complex sensorimotor process. Because of this complexity, brain injury before birth can have an effect on these sucking patterns. Clinical assessments allow evaluators to score the oral-motor pattern, however, they remain ultimately subjective. Thus, clinicians are in need of objective measures to identify the specific area of deficit in the sucking pattern of each infant to tailor therapies to their specific needs. Therapeutic approaches involve pacifiers, cheek/chin support, tactile, oral kinesthetic, auditory, vestibular, and/or visual sensorimotor inputs. These therapies are performed to train the infant to suck appropriately using these subjective assessments along with the experience of the therapist (usually a speech therapist), but newer, more objective measures are coming along. Recent studies have correlated pathological sucking patterns with neuroimaging data to get a map of the affected brain regions to better inform therapies. The purpose of this review is to provide a broad scope synopsis of the research field of infant nutritive and non-nutritive feeding, their underlying neurophysiology, and relationship of abnormal activity with brain injury in preterm and term infants.

Effect of Pacifier Design on Nonnutritive Suck Maturation and Weight Gain in Preterm Infants: A Pilot Study

Background

Pacifiers are effective in promoting oral feeding by increasing the maturation of nonnutritive sucking to nutritive suck in preterm neonates. It is unclear whether pacifier design can influence suck dynamics and weight loss during the first week of life.

Objectives

This pilot study examined the feasibility of studying the effect of pacifier design on suck maturation and weight loss in preterm neonates.

Methods

Twenty-five preterm neonates (mean [SD] birth weight 1791 [344.9] grams, mean [SD] gestational age 33.1 [1.2] weeks) were studied in a single newborn intensive care unit. Neonates were assigned to either an orthodontic pacifier (n = 13) or a bulb-shaped pacifier (n = 12) immediately after birth. Suck dynamics (cycles per minute, total compressions per minute, cycle bursts, and amplitude) were assessed with an NTrainer (Innara Health, Olathe, Kansas). Weight was recorded during the first week of life on day 1.2 (±2.5 days) and day 6.0 (±2.1 days). Descriptive statistics were applied to analyze data.

Results

No significant differences were seen between groups with respect to birth weight and gestational age. Reproducible nonnutritive sucking measurements could be obtained with the NTrainer, with both types of pacifiers. No differences were detected in nonnutritive sucking dynamics or weight loss over time within each group or between groups.

Conclusions

Data indicate that it is feasible to measure nonnutritive sucking dynamics and associated weight loss in relation to pacifier design in preterm neonates. Larger trials over longer time periods are needed to determine whether pacifier design influences suck dynamics and maturation, oromotor function, feeding/weight loss, and dental formation in preterm neonates. (Curr Ther Res Clin Exp. 2020; 81:XXX–XXX)

Sucking versus swallowing coordination, integration, and performance in preterm and term infants

Mammalian infants must be able to integrate the acquisition, transport, and swallowing of food to effectively feed. Understanding how these processes are coordinated is critical, as they have differences in neural control and sensitivity to perturbation. Despite this, most studies of infant feeding focus on isolated processes, resulting in a limited understanding of the role of sensorimotor integration in the different processes involved in infant feeding. This is especially problematic in the context of preterm infants, as they are considered to have pathophysiological brain development and often experience feeding difficulties. Here, we use an animal model to study how the different properties of food acquisition, transport, and swallowing differ between term and preterm infants longitudinally through infancy to understand which processes are sensitive to variation in the bolus being swallowed. We found that term infants are better able to acquire milk than preterm infants, and that properties of acquisition are strongly correlated with the size of the bolus being swallowed. In contrast, behaviors occurring during the pharyngeal swallow, such as hyoid and soft palate movements, show little to no correlation with bolus size. These results highlight the pathophysiological nature of the preterm brain and also demonstrate that behaviors occurring during oral transport are much more likely to respond to sensory intervention than those occurring during the "pharyngeal phase."NEW & NOTEWORTHY Physiological maturation of infant feeding is clinically and developmentally significant, but seldom examined as an integrated function. Using longitudinal high-speed videofluoroscopic data, we found that properties of sucking, such as the length of the suck, are more sensitive to swallow physiology than those associated with the pharyngeal swallow itself, such as hyoid excursion. Prematurity impacted the function and maturation of the feeding system, resulting in a physiology that fundamentally differs from term infants by weaning.

Changes in non-nutritive suck between 3 and 12 months

BACKGROUND

Non-nutritive suck (NNS) is one piece of the complex oral feeding process, yet there is paucity on how it develops throughout the first year of life.

AIMS

To determine changes in infant NNS between 3 and 12 months of age.

STUDY DESIGN

Twenty-six full-term infants (65% male) completed this study. All infants were offered our custom research pacifier to attain a quantitative analysis of their suck pattern. Based on quantitative analyses of NNS cycle count, the best 2 min of infants' suck were selected and analyzed.

OUTCOME MEASURES

NNS duration, amplitude, cycles/burst, frequency, cycles, and bursts.

RESULTS

NNS duration, bursts, cycles/burst and cycles significantly decreased from 3 to 12 months, yet amplitude significantly increased over the same time period. Additionally, no significant differences were evident for NNS frequency. Three-month-old infants produced a median of 4.50 suck bursts per minute that contained 9.60 cycles/burst, resulting in a burst duration of 4.74 s. The median NNS frequency was 2.09 Hz, with an average amplitude of 14.05 cmH₂0. Twelve-month-old infants produced a median of 2.50 suck bursts that contained 3.75 cycles/burst, resulting in a burst duration of 1.67 s. The median NNS frequency was 2.11 Hz with an amplitude of 19.75 cmH₂0.

CONCLUSION

Full-term infants significantly change their NNS duration, amplitude, burst number, cycles/burst and cycle number with no significant changes present in NNS frequency between 3 and 12 months. Knowledge of NNS emergence and maturation during the first year of life is imperative for proper NNS assessment so that healthcare professionals can identify delays.

Motor Learning, Neuroplasticity, and Strength and Skill Training: Moving From Compensation to Retraining in Behavioral Management of Dysphagia

Purpose Learning a motor skill and regaining a motor skill after it is lost are key tenets to the field of speech-language pathology. Motor learning and relearning have many theoretical underpinnings that serve as a foundation for our clinical practice. This review article applies selective motor learning theories and principles to feeding and swallowing across the life span. Conclusion In reviewing these theoretical fundamentals, clinical exemplars surrounding the roles of strength, skill, experience, compensation, and retraining, and their influence on motor learning and plasticity in regard to swallowing/feeding skills throughout the life span are discussed.

Changes in infant non-nutritive sucking throughout a suck sample at 3-months of age

The goal of this study was to compare how infants’ non-nutritive suck (NNS) changes throughout a suck sample. Fifty-four full-term infants (57% male) completed this study at, on average, 3.03 (SD .31) months of age. These infants sucked on our custom research pacifier for approximately five minutes. Infants produced, on average, 14.50 suck bursts during the sample. NNS data was pooled across subjects and breakpoint analyses were completed to determine if there were changes in their NNS patterning. Breakpoints were evident for NNS cycles per burst at burst numbers 18 and 34, and for amplitude (cmH₂0) at burst numbers 18 and 29. No breakpoints were present for NNS frequency. Infants exhibit changes in their suck physiology across burst number. When assessing suck, developmental specialists should observe more than one suck burst to attain a more valid and appropriate scope of the infant’s suck ability.

Preterm Neurodevelopmental Outcomes Following Orosensory Entrainment Intervention

Previous research indicates that the NTrainer, a pressurized pacifier programmed to produce pulsed pneumotactile stimulation during gavage feeds, has been found to facilitate non-nutritive suck development and shorten the length of hospital stay when used in the Neonatal Intensive Care Unit (NICU). Four groups of children, including infants of diabetic mothers (IDM), healthy controls (HI), and those with respiratory distress syndrome (RDS), or chronic lung disease (CLD), were randomly assigned to an NTrainer therapy or sham 'control' condition when in the NICU. At 30 months of age, 113/223 study participants were assessed using standardized language, motor, and cognitive assessments. No significant group differences were evident between the NTrainer and sham groups in language, motor, or cognitive functioning. The NTrainer did not improve nor adversely impact language, cognition, or motor outcomes.

Not All Pacifiers Are Created Equal: A Mechanical Examination of Pacifiers and Their Influence on Suck Patterning

PURPOSE

Many pacifier companies advertise that their product is the "best choice" to support proper sucking, feeding, and dental development; however, very little evidence exists to support these claims. As the primary differences across pacifiers are structural and mechanical, the goals of this study were to measure such properties of commercially available pacifiers and to examine how these properties alter suck patterning in healthy, full-term infants.

METHOD

Seven commonly utilized pacifiers were mechanically tested for pull and compression stiffness levels and categorized into nipple shape types based on their aspect ratio. Next, 3 pacifiers (Soothie, GumDrop, and Freeflow) with the most salient differences in pull stiffness levels with 2 different pacifier nipple types were tested clinically on 16 full-term infants (≤ 6 months old) while measuring non-nutritive suck (NNS).

RESULTS

A repeated measures analysis of variance revealed significant differences between NNS burst duration (p = .002), NNS cycles per burst (p = .002), and NNS cycles per minute (p = .006) and pacifier type. With each significant dependent measure, pairwise comparisons showed that the GumDrop and Freeflow pacifiers differed significantly on these measures.

CONCLUSIONS

Pacifier compression, pull stiffness, and nipple shape type yield different NNS dynamics. These findings motivate further investigation into pacifier properties and suck patterning in young infants.

The physiologic coupling of sucking and swallowing coordination provides a unique process for neonatal survival

AIM

Although the coordination of sucking and swallowing is critical for successful oral intake in neonates, the mechanisms that facilitate this coordination are not well understood. This investigation sought to clarify the mechanisms that facilitate this coordination, by comparing sucks that were coordinated with swallows and sucks that were completed in isolation.

METHODS

Ten neonates with a median gestational age of 28.2 weeks, ranging from 27.0 to 35.0 weeks, were recruited from the neonatal nurseries at Nationwide Children's Hospital, Columbus, Ohio, USA. They were evaluated while bottle-feeding at term gestation for differences in characteristics between sucks that were coupled and not coupled with swallows. Suction was evaluated using an intra-oral pressure transducer, and swallows were identified using a micromanometry pharyngeal catheter. Linear mixed models were applied to distinguish sucking characteristics.

RESULTS

Suction exhibited an antiphase relationship with the generation and release of positive pharyngeal pressure during the swallow. Coupled sucks had lower suction generation and release rates (p < 0.0001), lower suction amplitude (p = 0.004), longer suction duration (p < 0.0001) and higher milk ejection pressure (p < 0.0001).

CONCLUSION

The coordination of unique sucking and swallowing movement patterns may be achieved by the infant adapting sucking kinematics around the lingual patterns that facilitate the pharyngeal swallow.

Effects of pacifier and taste on swallowing, esophageal motility, transit, and respiratory rhythm in human neonates

BACKGROUND

Pacifier use is widely prevalent globally despite hygienic concerns and uncertain mechanistic effects on swallowing or airway safety.

AIMS

The effects of pacifier and taste interventions on pharyngo-esophageal motility, bolus transit, and respiratory rhythms were investigated by determining the upper esophageal sphincter (UES), esophageal body, esophagogastric junction (EGJ) motor patterns and deglutition apnea, respiratory rhythm disturbances, and esophageal bolus clearance.

METHODS

Fifteen infants (six males; median gestation 31 weeks and birth weight 1.4 kg) underwent high-resolution impedance manometry at 43 (41-44) weeks postmenstrual age. Manometric, respiratory, and impedance characteristics of spontaneous swallows, pacifier-associated dry swallowing and taste (pacifier dipped in 3% sucrose)-associated swallowing were analyzed. Linear mixed and generalized estimating equation models were used. Data are presented as mean ± SEM, %, or median (IQR).

KEY RESULTS

Pharyngo-esophageal motility, respiratory, and impedance characteristics of 209 swallows were analyzed (85 spontaneous swallows, 63 pacifier- swallows, 61 taste- swallows). Basal UES and EGJ pressures decreased upon pacifier (p < 0.05) and taste interventions (p < 0.05); however, esophageal motility, respiratory rhythm, and impedance transit characteristics were similar with both interventions.

CONCLUSIONS & INFERENCES

Oral stimulus with pacifier or taste interventions decreases UES and EGJ basal pressure, but has no effects on pharyngo-esophageal motility, airway interactions, or esophageal bolus transit. A decrease in central parasympathetic-cholinergic excitatory drive is likely responsible for the basal effects.

Nipple Shields

Mothers have used nipple shields for centuries for various breastfeeding issues and problems. Shield use has become controversial, but many clinicians recommend the use of nipple shields under varying circumstances despite the absence of any professionally peer-reviewed or generally agreed-upon guidelines, protocols, policies, or clinical algorithms. Judicious use of nipple shields can salvage the breastfeeding process, and most mothers have found them to be helpful. However, some mothers and studies have reported problems with shields. There remain many questions regarding the effect of nipple shield use on infant feeding behaviors relative to the imprinting that may be affected by presenting a superstimulus to an infant during a sensitive or critical period of time. This raises more questions than answers.

Clarifying nipple confusion

Nipple confusion, an infant's difficulty with or preference for one feeding mechanism over another after exposure to artificial nipple(s), has been widely debated. This is in part due to conflicting statements, one by the American Academy of Pediatrics in 2005 suggesting that infants should be given a pacifier to protect against Sudden Infant Death Syndrome, and the other by the World Health Organization in 2009 stating that breastfeeding infants should never be given artificial nipples. Despite the limited and inconsistent evidence, nipple confusion is widely believed by practitioners. Therefore, there is a unique opportunity to examine the evidence surrounding nipple confusion by assessing the research that supports/refutes that bottle feeding/pacifier use impedes breastfeeding efficacy/success/duration. This review examined 14 articles supporting and refuting nipple confusion. These articles were reviewed using the Johns Hopkins Nursing Evidence-Based Practice Rating Scale. Based on our review, we have found emerging evidence to suggest the presence of nipple confusion only as it relates to bottle usage and found very little evidence to support nipple confusion with regards to pacifier use. The primary difficulty in conclusively studying nipple confusion is establishing causality, namely determining whether bottles'/pacifiers' nipples are causing infants to refuse the breast or whether they are simply markers of other maternal/infant characteristics. Future research should focus on prospectively examining the causality of nipple confusion.

Frequency-modulated orocutaneous stimulation promotes non-nutritive suck development in preterm infants with respiratory distress syndrome or chronic lung disease

OBJECTIVE

For the premature infant, extrauterine life is a pathological condition, which greatly amplifies the challenges to the brain in establishing functional oromotor behaviors. The extent to which suck can be entrained using a synthetically patterned orocutaneous input to promote its development in preterm infants who manifest chronic lung disease (CLD) is unknown. The objective of this study was to evaluate the effects of a frequency-modulated (FM) orocutaneous pulse train delivered through a pneumatically charged pacifier capable of enhancing non-nutritive suck (NNS) activity in tube-fed premature infants.

STUDY DESIGN

A randomized trial to evaluate the efficacy of pneumatic orocutaneous stimulation 3 × per day on NNS development and length of stay (LOS) in the neonatal intensive care unit among 160 newborn infants distributed among three sub-populations, including healthy preterm infants, respiratory distress syndrome (RDS) and CLD. Study infants received a regimen of orocutaneous pulse trains through a PULSED pressurized silicone pacifier or a SHAM control (blind pacifier) during gavage feeds for up to 10 days.

RESULT

Mixed modeling, adjusted for the infant's gender, gestational age, postmenstrual age and birth weight, was used to handle interdependency among repeated measures within subjects. A significant main effect for stimulation mode (SHAM pacifier vs PULSED orosensory) was found among preterm infants for NNS bursts per min (P=0.003), NNS events per min (P=0.033) and for total oral compressions per min (NNS+nonNNS) (P=0.016). Pairwise comparison of adjusted means using Bonferroni adjustment indicated RDS and CLD infants showed the most significant gains on these NNS performance indices. CLD infants in the treatment group showed significantly shorter LOS by an average of 2.5 days.

CONCLUSION

FM PULSED orocutaneous pulse train stimuli delivered through a silicone pacifier are effective in facilitating NNS burst development in tube-fed RDS and CLD preterm infants, with an added benefit of reduced LOS for CLD infants.

Short-Term Effects of Pacifier Texture on NNS in Neurotypical Infants

The dense representation of trigeminal mechanosensitive afferents in the lip vermilion, anterior tongue, intraoral mucosa, and temporomandibular joint allows the infant's orofacial system to encode a wide range of somatosensory experiences during the critical period associated with feed development. Our understanding of how this complex sensorium processes texture is very limited in adults, and the putative role of texture encoding in the infant is unknown. The purpose of this study was to examine the short-term effects of a novel textured pacifier experience in healthy term infants (N = 28). Nonnutritive suck (NNS) compression pressure waveforms were digitized in real time using a variety of custom-molded textured pacifiers varying in spatial array density of touch domes. MANCOVA, adjusted for postmenstrual age at test and sex, revealed that infants exhibited an increase in NNS burst attempts at the expense of a degraded suck burst structure with the textured pacifiers, suggesting that the suck central pattern generator (sCPG) is significantly disrupted and reorganized by this novel orocutaneous experience. The current findings provide new insight into oromotor control as a function of the oral somatosensory environment in neurotypically developing infants.

Perioral movements and sucking pattern during bottle feeding with a novel, experimental teat are similar to breastfeeding

OBJECTIVE

To measure intraoral pressure and perioral movement in infants during breastfeeding (BF) and feeding with experimental teat (ET). The teat has a wide base, firm shaft and a valve at the base, such that milk flows only when the baby provides a hold pressure.

STUDY DESIGN

Twenty healthy term infants, between 1 and 8 months old, were enrolled in the study. Feeding sessions (BF and ET) were recorded using a digital video camera. During both BF and ET feeding sessions, recordings during feeding were taken of jaw and throat movements (n=20) as well as intraoral pressure (n=18). The efficiency of milk transfer and the angle of the mouth were also measured.

RESULT

There was no significant difference in either the jaw or throat movements between BF and ET. The sucking burst pattern, the efficiency (ml min(-1)), and the angle of the mouth did not differ between both feeding methods. The intraoral negative pressure observed during ET was significantly smaller than that observed during BF.

CONCLUSION

There were no significant differences in perioral movements. Although the value was smaller, a hold pressure was observed during ET. From these results, the novel, ET may decrease BF problems related to bottle use.

The accessibility of a new oral motor pacifier to infants

OBJECTIVE

The aim of the present study was to examine whether infants would accept an oral motor pacifier (OMP).

CHILDREN AND METHODS

Sixteen infants were examined for their immediate acceptance of an OMP. The pacifier was regarded as accepted, if the child took it in the mouth and kept it there actively, i.e. sucked it in one way or other. Their parents were informed verbally and in writing literally about how to offer the OMP to the child and how to use it. The OMP was presented to the child and the child permitted to insert it into her/his mouth by her/himself or if the child failed to do so, the OMP was gently put to the child's mouth. The subjects' reactions were structurally evaluated in terms of 11 statements. The parents of the children received a structured questionnaire with a space for optional free comments and personal opinions.

RESULTS

The median age (6 females, 10 males) was 18 months (mean 19.2 months, s.d. 10.6 and range 2-38 months). The statement scores showed no significant differentiation based on the age of the subject. The parents' reports indicated that 14 (87.5%) of the 18 subjects accepted the OMP, 13 (81.3%) enjoyed watching the pacifier as it was shown to them, and 11 (68.8%) explored it with their fingers while holding it in their hands.

CONCLUSION

The vast majority of the children accepted the new OMP either at the first trial or after a few trials.

Frequency Modulation and Spatiotemporal Stability of the sCPG in Preterm Infants with RDS

The nonnutritive suck (NNS) is an observable and accessible motor behavior which is often used to make inference about brain development and pre-feeding skill in preterm and term infants. The purpose of this study was to model NNS burst compression pressure dynamics in the frequency and time domain among two groups of preterm infants, including those with respiratory distress syndrome (RDS, N = 15) and 17 healthy controls. Digitized samples of NNS compression pressure waveforms recorded at a 1-week interval were collected 15 minutes prior to a scheduled feed. Regression analysis and ANOVA revealed that healthy preterm infants produced longer NNS bursts and the mean burst initiation cycle frequencies were higher when compared to the RDS group. Moreover, the initial 5 cycles of the NNS burst manifest a frequency modulated (FM) segment which is a significant feature of the suck central pattern generator (sCPG), and differentially expressed in healthy and RDS infants. The NNS burst structure revealed significantly lower spatiotemporal index values for control versus RDS preterm infants during FM, and provides additional information on the microstructure of the sCPG which may be used to gauge the developmental status and progression of oromotor control systems among these fragile infants.

Central pattern generation involved in oral and respiratory control for feeding in the term infant

PURPOSE OF REVIEW

Drinking and eating are essential skills for survival and benefit from the coordination of several pattern generating networks and their musculoskeletal effectors to achieve safe swallows. Oralpharyngoesophageal motility develops during infancy and early childhood, and is influenced by various factors, including neuromuscular maturation, dietary and postural habits, arousal state, ongoing illnesses, congenital anomalies, and the effects of medical or surgical interventions. Gastroesophageal reflux is frequent in neonates and infants, and its role in neonatal morbidity including dysphagia, chronic lung disease, or apparent life-threatening events is not well understood. This review highlights recent studies aimed at understanding the development of oral feeding skills, and cross-system interactions among the brainstem, spinal, and cerebral networks involved in feeding.

RECENT FINDINGS

Functional linkages between suck-swallow and swallow-respiration manifest transitional forms during late gestation through the first year of life, which can be delayed or modified by sensory experience or disease processes, or both. Relevant central pattern generator (CPG) networks and their neuromuscular targets attain functional status at different rates, which ultimately influences cross-system CPG interactions. Entrainment of trigeminal primary afferents accelerates pattern genesis for the suck CPG and transition-to-oral feed in the RDS preterm infant.

SUMMARY

The genesis of within-system CPG control for rate and amplitude scaling matures differentially for suck, mastication, swallow, and respiration. Cross-system interactions among these CPGs represent targets of opportunity for new interventions, which optimize experience-dependent mechanisms to promote safe swallows among newborn and pediatric patients.

Modulation, adaptation, and control of orofacial pathways in healthy adults

Although the healthy adult possesses a large repertoire of coordinative strategies for oromotor behaviors, a range of nonverbal, speech-like movements can be observed during speech. The extent of overlap among sensorimotor speech and nonspeech neural correlates and the role of neuromodulatory inputs generated during oromotor behaviors are unknown. The focus of this review is to consider the adaptive capacity of the orofacial substrate, and the neural correlates of kinematic parameter encoding at cortical and subcortical levels subserving oromotor behaviors. Special emphasis is directed toward distributed neural networks that are dynamically modulated by environment and task related demands.

LEARNING OUTCOMES

Readers will (1) gain a better understanding of healthy adult orofacial pathways, (2) be able to identify orofacial pathway components that contribute to sensorimotor integration, and (3) better understand the flexible connectivity among distributed neural networks subserving oromotor behavior.

The Complexity of Transitioning to Oral Feeds in Preterm Infants

Transitioning to oral feeds is one of the final tasks that preterm infants need to accomplish before discharge from the neonatal intensive care unit. There are many types of pacifiers and nipples used to accelerate and encourage the development of feeding skills; however, little is known about the impact of the mechanical properties of these nipples on feeding among preterm infants, who often must endure prolonged periods of sensory deprivation, maladaptive inputs, and motor restriction. Many feeding specialists alternate between different nipple types on a trial-and-error basis in an attempt to find the most appropriate nipple type for the infant. Given the complexity of feeding, a more comprehensive understanding of the multiple neural interactions among suck, swallow, airway protection, pharyngoespophageal motility, and digestive mechanisms is needed. Delay or disruption of these processes during a critical phase in late gestation may prevent infants from transitioning successfully to oral feeds and may lead to poor neurodevelopmental outcomes.

Synthetic orocutaneous stimulation entrains preterm infants with feeding difficulties to suck

BACKGROUND

Prematurity can disrupt the development of a specialized neural circuit known as suck central pattern generator (sCPG), which often leads to poor feeding skills. The extent to which suck can be entrained using a synthetically patterned orocutaneous input to promote its development in preterm infants who lack a functional suck is unknown.

OBJECTIVE

To evaluate the effects of a new motorized 'pulsating' pacifier capable of entraining the sCPG in tube-fed premature infants who lack a functional suck and exhibit feeding disorders.

METHODS

Prospective cohort study of 31 preterm infants assigned to either the oral patterned entrainment intervention (study) or non-treated (controls) group, matched by gestational age, birth weight, oxygen supplementation history and oral feed status. Study infants received a daily regimen of orocutaneous pulse trains through a pneumatically controlled silicone pacifier concurrent with gavage feeds.

RESULTS

The patterned orocutaneous stimulus was highly effective in accelerating the development of non-nutritive suck (NNS) in preterm infants. A repeated-measure multivariate analysis of covariance revealed significant increases in minute rates for total oral compressions, NNS bursts, and NNS cycles, suck cycles per burst, and the ratiometric measure of NNS cycles as a percentage of total ororhythmic output. Moreover, study infants also manifest significantly greater success at achieving oral feeds, surpassing their control counterparts by a factor of 3.1 x (72.8% daily oral feed versus 23.3% daily oral feed, respectively).

CONCLUSION

Functional expression of the sCPG among preterm infants who lack an organized suck can be induced through the delivery of synthetically patterned orocutaneous pulse trains. The rapid emergence of NNS in treated infants is accompanied by a significant increase in the proportion of nutrient taken orally.

Pacifier Stiffness Alters the Dynamics of the Suck Central Pattern Generator

Variation in pacifier stiffness on non-nutritive suck (NNS) dynamics was examined among infants born prematurely with a history of respiratory distress syndrome. Three types of silicone pacifiers used in the NICU were tested for stiffness, revealing the Super Soothie™ nipple is 7 times stiffer than the Wee™ or Soothie™ pacifiers even though shape and displaced volume are identical. Suck dynamics among 20 preterm infants were subsequently sampled using the Soothie™ and Super Soothie™ pacifiers during follow-up at approximately 3 months of age. ANOVA revealed significant differences in NNS cycles/min, NNS amplitude, NNS cycles/burst, and NNS cycle periods as a function of pacifier stiffness. Infants modify the spatiotemporal output of their suck central pattern generator when presented with pacifiers with significantly different mechanical properties. Infants show a non-preference to suck due to high stiffness in the selected pacifier. Therefore, excessive pacifier stiffness may decrease ororhythmic patterning and impact feeding outcomes.