Characterisation of sucking dynamics of breastfeeding preterm infants: a cross sectional study

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.

Evolution, diversification and function of the maternal-infant dyad in mammalian feeding

The evolution of the mother/infant dyad providing a source of nutrition for infants is essential for the origin and subsequent diversification of mammals. Despite the importance of this dyad, research on maternal and infant function is often treated independently. Our goal is to synthesize the work on maternal and infant function, discuss our own studies of suckling, and compare the origins of lactation and suckling with their ensuing diversification. Our central premise is that while extensive work has demonstrated variation across mammals in the maternal aspect of this system, very little has been done to address how this relates to infant function. We start with a discussion of the fundamental anatomy and physiology of both mother and infant. We next discuss the origin of mammary glands and milk, and infant suckling, which is distinct from their subsequent diversification. We then discuss the diversification of maternal and infant function, highlighting the evolutionary diversity present in maternal function (both anatomically and physiologically), before arguing that the diversity of infant function is unexplored, and needs to be better studied in the future. We end by discussing some of the holes in our understanding, and suggestions for future work that can address these lacunae. This article is part of the theme issue 'Food processing and nutritional assimilation in animals'.

Non-Nutritive Suckling System for Real-Time Characterization of Intraoral Vacuum Profile in Full Term Neonates

Infant breastfeeding diagnostics remain subjective due to the absence of instrumentation to objectively measure and understand infant oral motor skills and suckling characteristics. Qualitative diagnostic exams, such as the digital suck assessment which relies upon a clinician's gloved finger inserted into the infant's mouth, produce a diversity of diagnoses and intervention pathways due to their subjective nature. In this paper, we report on the design of a non-nutritive suckling (NNS) system which quantifies and analyzes quantitative intraoral vacuum and sucking patterns of full-term neonates in real time. In our study, we evaluate thirty neonate suckling profiles to demonstrate the technical and clinical feasibility of the system. We successfully extract the mean suck vacuum, maximum suck vacuum, frequency, burst duration, number of sucks per burst, number of sucks per minute, and number of bursts per minute. In addition, we highlight the discovery of three intraoral vacuum profile shapes that are found to be correlated to different levels of suckling characteristics. These results establish a framework for future studies to evaluate oromotor dysfunction that affect the appearance of these signals based on established normal profiles. Ultimately, with the ability to easily and quickly capture intraoral vacuum data, clinicians can more accurately perform suckling assessments to provide timely intervention and assist mothers and infants towards successful breastfeeding outcomes.

Adaptation of a clinical reasoning model for use in inflammatory conditions of the lactating breast: a retrospective mixed-methods study

Background

Many potential factors associated with Inflammatory Conditions of the Lactating Breast (ICLB) have been reported in the literature, by lactating mothers and clinicians. Clinicians, including general practitioners, lactation consultants and physiotherapists, require a clinical reasoning model that summarises associated or linked factors, to aid in the assessment, treatment, and prevention of ICLB. Thus, we aimed to adapt the existing Breastfeeding Pain Reasoning Model (BPRM), for use in the management of ICLB, using prior research and clinical audit data to guide adaptation. The existing BPRM categorises contributing factors for breastfeeding nipple pain, rather than ICLB.

Methods

Factors linked with ICLB were identified from prior research and considered for inclusion into the existing model. Clinical data from a retrospective audit of ICLB patient notes at a private physiotherapy practice were also examined. Any factors identified from prior research that could not be identified in the clinical notes were not considered for inclusion into the existing model. Additional factors from the clinical notes that appeared repeatedly were considered for inclusion into the adaptation of the BPRM. A draft adapted model was created comprising all eligible factors, considering their counts and percentages as calculated from the clinical data. The research team iteratively examined all factors for appropriate categorisation and modification within the adapted model.

Results

Prior research and data from 160 clinical notes were used to identify factors for inclusion in the adapted model. A total of 57 factors, 13 pre-existing in the BPRM and 44 extra identified from the prior research or clinical audit, comprised the draft adapted model. Factor consolidation and terminology modification resulted in a total of 34 factors in the final proposed adapted ICLB model. The three main categories, CNS modulation, External influences and Local stimulation, from the existing model were maintained, with one minor terminology change to the former Local stimulation category, resulting in 'Local influences' category. Terminology for five subcategories were modified to better reflect the types of factors for ICLB. The most common factors in the adapted model, calculated from the clinical audit population of mothers with ICLB, were employment (85%), high socioeconomic status (81%), antibiotic use during breastfeeding (61%), history of an ICLB (56%), any breast pump use (45%), multiparity (43%), birth interventions (35%), decreased milk transfer (33%), breastfeeding behaviour and practices (33%), nipple pain (30%) and fit and hold (attachment and positioning) difficulty (28%).

Conclusion

An ICLB-specific linked factors model is proposed in this paper. Clinicians treating mothers with ICLB can use this model to identify influencing and determining factors of ICLB clinical presentations and provide targeted education and effective treatment plans.

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.

Variability in Swallowing Biomechanics in Infants with Feeding Difficulties: A Videofluoroscopic Analysis

Clinicians performing feeding evaluations in infants often report swallow variability or inconsistency as concerning. However, little is known about whether this represents pathological incoordination or normal physiologic variance in a developing child. Our retrospective study explored quantitative videofluoroscopic measures in 50 bottle-fed infants (0-9 months) referred with feeding concerns. Our research questions were as follows: Is it possible to assess swallow to swallow variability in an infant with feeding concerns, is there variability in pharyngeal timing and displacement in infants referred for videofluoroscopy, and is variability associated with aspiration risk? Measures were taken from a mid-feed, 20-s loop recorded at 30 frames per second. Each swallow within the 20-s loop (n = 349 swallows) was analysed using quantitative digital measures of timing, displacement and coordination (Swallowtail™). Two blinded raters measured all swallows with strong inter-rater reliability (ICC .78). Swallow frequency, suck-swallow ratio, residue and aspiration were also rated. Variability in timing and displacement was identified across all infants but did not correlate with aspiration (p > .05). Sixteen infants (32%) aspirated. Across the cohort, swallow frequency varied from 1 to 15 within the 20-s loops; suck-swallow ratios varied from 1:1 to 6:1. Within-infant variability in suck-swallow ratios was associated with higher penetration-aspiration scores (p < .001). In conclusion, pharyngeal timing and displacement variability is present in infants referred with feeding difficulties but does not correlate with aspiration. Suck-swallow ratio variability, however, is an important risk factor for aspiration that can be observed at bedside without radiation. These objective measures provide insight into infant swallowing biomechanics and deserve further exploration for their clinical applicability.

Nine Levels of Explanation : A Proposed Expansion of Tinbergen's Four-Level Framework for Understanding the Causes of Behavior

Tinbergen's classic "On Aims and Methods of Ethology" (Zeitschrift für Tierpsychologie, 20, 1963) proposed four levels of explanation of behavior, which he thought would soon apply to humans. This paper discusses the need for multilevel explanation; Huxley and Mayr's prior models, and others that followed; Tinbergen's differences with Lorenz on "the innate"; and Mayr's ultimate/proximate distinction. It synthesizes these approaches with nine levels of explanation in three categories: phylogeny, natural selection, and genomics (ultimate causes); maturation, sensitive period effects, and routine environmental effects (intermediate causes); and hormonal/metabolic processes, neural circuitry, and eliciting stimuli (proximate causes), as a respectful extension of Tinbergen's levels. The proposed classification supports and builds on Tinbergen's multilevel model and Mayr's ultimate/proximate continuum, adding intermediate causes in accord with Tinbergen's emphasis on ontogeny. It requires no modification of Standard Evolutionary Theory or The Modern Synthesis, but shows that much that critics claim was missing was in fact part of Neo-Darwinian theory (so named by J. Mark Baldwin in The American Naturalist in 1896) all along, notably reciprocal causation in ontogeny, niche construction, cultural evolution, and multilevel selection. Updates of classical examples in ethology are offered at each of the nine levels, including the neuroethological and genomic findings Tinbergen foresaw. Finally, human examples are supplied at each level, fulfilling his hope of human applications as part of the biology of behavior. This broad ethological framework empowers us to explain human behavior-eventually completely-and vindicates the idea of human nature, and of humans as a part of nature.

25 Years of Research in Human Lactation: From Discovery to Translation

Researchers have recently called for human lactation research to be conceptualized as a biological framework where maternal and infant factors impacting human milk, in terms of composition, volume and energy content are studied along with relationships to infant growth, development and health. This approach allows for the development of evidence-based interventions that are more likely to support breastfeeding and lactation in pursuit of global breastfeeding goals. Here we summarize the seminal findings of our research programme using a biological systems approach traversing breast anatomy, milk secretion, physiology of milk removal with respect to breastfeeding and expression, milk composition and infant intake, and infant gastric emptying, culminating in the exploration of relationships with infant growth, development of body composition, and health. This approach has allowed the translation of the findings with respect to education, and clinical practice. It also sets a foundation for improved study design for future investigations in human lactation.

No long-term effect of oral stimulation on the intra-oral vacuum in healthy premature infants

AIM

Exclusive breastfeeding is recommended for the first 6 months of life, but the breastfeeding rate in premature infants is low. We examined the effect of oral stimulation on infant's strength of suction and the relation between this intra-oral vacuum and breastfeeding duration.

METHOD

Between 2016 and 2018, 211 infants in a Danish neonatal unit were randomised 1:1 and of these 108 to oral stimulation intervention and 103 to control. Suction was measured as peak vacuum at enrolment and a corrected age of 6 weeks. Breastfeeding duration was registered.

RESULTS

Vacuum increased from enrolment to a corrected age of 6 weeks in all infants, and no effect of oral stimulation intervention was demonstrated P = .08. Infants born ≤32 gestational weeks had lower vacuum compared with infants born after, 350 vs 398 mbar P < .001. For infants born after 32 gestational weeks, the odds ratio for exclusive breastfeeding at 6 months was 1.99 per 100 mbar increase in vacuum P = .01.

CONCLUSION

In our study, infant's intra-oral vacuum increased with age and was not affected by the oral stimulation intervention. For infants born after 32 gestational weeks, the exclusive breastfeeding rate was positively associated with a strong vacuum.

Estimates of Preterm Infants' Breastfeeding Transfer Volumes Are Not Reliably Accurate

BACKGROUND

Adequate human milk nutrition is critical for infant growth and neurodevelopment; however, low milk transfer volumes are common when establishing preterm breastfeeding. Despite clinical assessments of milk transfer volumes at the breast being inaccurate, measurement of feed volume via test weighing is rarely carried out either routinely or in cases where infant weight gain is inadequate.

PURPOSE

To assess the accuracy of the Preterm Breastfeeding Assessment Tool (PBAT) in determining transfer volumes and examine factors associated with PBAT accuracy.

METHODS

Pre/postfeed weights were performed using electronic scales and PBAT scores recorded for 1186 breastfeeds in 60 preterm infants born less than 33/40 and 33 to 39/40 postmenstrual age. Measured milk intake volumes were converted to percent prescribed feed volume and compared with PBAT estimates of milk transfer.

RESULTS

The PBAT is accurate in identifying when no milk is transferred at the breast but not in estimating transfer of half or the full prescribed volume (accuracy 26% and 47%, respectively). Wide ranges of transfer volumes (11-75 mL) were observed within and between infants, and for 20% of breastfeeds, no milk was transferred. Preterm Breastfeeding Assessment Tool accuracy decreased with each 1-week increase in birth gestation (odds ratio = 0.82; 95% confidence interval, 0.71-0.94; P = .004).

IMPLICATIONS FOR PRACTICE

When establishing breastfeeding, test weighing facilitates adequate nutrition by guiding appropriate complementary feeding. For mothers breastfeeding several times per day in preparation for discharge home, test weighing may offer a useful tool for developing maternal confidence in assessing milk transfer. Preterm Breastfeeding Assessment Tool is inaccurate in assessing preterm infants' milk transfer volumes when breastfeeding.

IMPLICATIONS FOR RESEARCH

While studies have typically focused on medically stable infants, test weighing offers a useful tool to examine breastfeeding efficacy and inform nutritional management of preterm infants with complications such as chronic lung and cardiac disease.

Iron delivery from liquid-core hydrogels within a therapeutic nipple shield

To aid oral therapeutic administration to infants, a novel delivery technology, referred to as a Therapeutic Nipple Shield (TNS), was previously developed. It consists of a silicone nipple shield device and a dosage form containing a therapeutic (or Active Pharmaceutical Ingredient (API)) to enable delivery during breastfeeding. A range of dosage forms were investigated in past literature, but sufficient API release into human milk had not been achieved. The presented work illustrates the delivery of iron sulphate pentahydrate from liquid-core sodium alginate hydrogels, inserted into a commercially available ultra-thin silicone nipple shield into human milk during in-vitro breastfeeding simulation. Release of iron was quantified employing absorbance measurements of a salicylic assay. An absolute recovery of 44.35 ± 5.43% of loaded iron(III)sulphate pentahydrate was obtained after 10.58 ± 0.09 g of human milk had passed through the nipple shield. This finding is superior to previous investigations involving the delivery of zinc from rapidly disintegrating tablets and non-woven fibres within a TNS. Due to their superior delivery properties, ease of fabrication and cost-efficiency, liquid-core sodium alginate hydrogels consequently represent a promising dosage form for use as part of the TNS. Further improvements can be made to enhance handling stability and shelf-life characteristics.

Effect of vacuum-release teat versus standard teat use on feeding milestones and breastfeeding outcomes in very preterm infants: A randomized controlled trial

Background

Breast milk is important to infant health, yet shorter breastfeeding duration is reported for preterm infants. Both breast and bottle feeds are given in the neonatal unit, with full oral feeding often the last milestone to be achieved prior to discharge home. Unlike standard bottle teats, a vacuum release teat requires the application of negative intra-oral pressure to release milk, and so may facilitate breastfeeding in preterm infants. The objective of this study was to determine the effect of vacuum release teat use on timing of achievement of the first full oral feed and on first completion of 24 h full oral feeds. Feeding method at discharge home, 2 weeks, 6 weeks and 12 weeks corrected gestational age were also examined.

Methods

A randomized controlled trial was completed with mothers of preterm infants born 24–33 weeks gestation in the neonatal unit of a tertiary women’s hospital. Infants were randomized to one of two parallel groups using a vacuum release teat or standard teat for oral feeds when the mother was not available to breastfeed. Test weights were completed for all oral feeds. It was not possible to blind participants, care givers and outcome assessors to group assignment due to the nature of the study.

Results

The groups did not differ with regard to timing of achievement of first full oral feed or 24 h of full oral feeds. Significantly more infants in the vacuum release teat group were exclusively fed breast milk at discharge from hospital and breastfed at 3 months corrected gestational age.

Conclusions

Use of a vacuum release teat when the mother is not available to breastfeed may promote preterm breastfeeding skills, resulting in higher rates of exclusivity and longer breastfeeding duration.

Trial registration

The trial is registered with the Australian New Zealand Clinical Trials Registry ACTRN12615000245594.

Changes in R0/R∞ ratio and membrane capacitance are associated with milk removal from the breast

Perceived low milk supply is a common reason for introducing supplementary feeds, which in turn serves to further diminish the milk supply. Current methods of measuring milk production and milk transfer from the breast to the infant are inaccessible to the mothers. There is a need for an inexpensive, portable device to enable mothers to measure milk transfer to either confirm their milk production is adequate or identify breastfeeding issues early. The aim of this study was to examine changes in bioimpedance spectroscopy associated with milk removal from the human lactating breast using an electric breast pump. Thirty lactating women participated in 2 research sessions performed in random order over 2 weeks. Milk flow rate and volume were measured during pumping. All mothers completed 24-hour milk profiles. Breasts were monitored using bioimpedance spectroscopy. Analysis was performed using linear mixed effects models to investigate the relationship between both proportional change in membrane capacitance (C_m) and R0/R∞ with milk removal. There was an inverse relationship between R0/R∞ and milk removed (p<0.001). A positive relationship was also observed between C_m and both volume of milk removed (P<0.001) and percentage of available milk removed (p<0.001). This study has shown that changes in bioimpedance are related to the volume of milk removed from the breast during pumping. This modality may hold promise for the measurement of the effectiveness of the breastfeeding infant in removing milk from the breast.

Preterm Infant Feeding: A Mechanistic Comparison between a Vacuum Triggered Novel Teat and Breastfeeding

The goal for preterm infants is to achieve full oral feeds quickly and ultimately progress to full breastfeeding. Supplementary oral feeds are often given when the mother is not available to breastfeed. Bottles typically deliver milk in a different fashion compared to breastfeeding, which is thought to hamper transition to full breastfeeding. The aim of this study was to compare the sucking dynamics of preterm infants fed at the breast to feeding with an experimental novel teat (NT) designed to release milk only upon the application of vacuum. Simultaneous ultrasound imaging of the infant oral cavity and measurement of intra-oral vacuum was performed during a breastfeed and a feed with the NT. Test weighs were used to measure milk intake. Linear mixed effects models were performed to investigate differences by feed type, and simultaneous linear regression was performed to investigate individual patterns. Tongue movement was not different between breastfeeding and the NT. Intra-oral vacuums (median (interquartile range: IQR)) were significantly lower with the NT (Baseline vacuum: -5.8 mmHg (-11.0, 0.1); Peak: 40.0 mmHg (-54.6, -27.1)) compared to breastfeeding (Baseline: -31.1 mmHg (-60.0, -12.7); Peak: -106.2 mmHg (-153.0, -65.5)). Milk intake was significantly higher with the NT (33 mL (22.5, 42.5)) compared to the breastfeed (12 mL (3, 15.5)). The novel teat encouraged a similar tongue action to breastfeeding, and infants transferred a greater volume of milk with the novel teat. Intra-oral vacuums were lower in strength with the novel teat compared to the breast. Use of the novel teat for the training of sucking dynamics in preterm infants has the potential to improve breastfeeding success and requires further investigation.