Название: Human Milk: Composition, Clinical Benefits and Future Opportunities
Автор: Группа авторов
Издательство: Ingram
Жанр: Медицина
Серия: Nestlé Nutrition Institute Workshop Series
isbn: 9783318063417
isbn:
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34Lucas A, Brooke OG, Morley R, et al: Early diet of preterm infants and development of allergic or atopic disease: randomised prospective study BMJ 1990; 300: 837–840.
State of Breastfeeding in the World
Donovan SM, German JB, Lönnerdal B, Lucas A (eds): Human Milk: Composition, Clinical Benefits and Future Opportunities. Nestlé Nutr Inst Workshop Ser, vol 90, pp 13–32, (DOI: 10.1159/000490322)
Nestlé Nutrition Institute, Switzerland/S. Karger AG., Basel, © 2019
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Michael W. Woolridge
Great Ormond Street Institute of Child Health, University College London, London, UK
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Abstract
Currently accepted “best practice” for managing breastfeeding effectively (WHO/UNICEF) is largely based on a historical view of how babies remove milk from the breast, which had persisted for several centuries. The collective wisdom was verified by imaging studies in the 1950s and 1980s, to reach a consensus view – clinical management principles, based on such research, have proved highly effective. Over the past decade, the mechanics of suckling, and how the baby removes milk from the breast, have been revisited, using modern imaging technology and by the application of engineering-based techniques, which seek to develop explanatory models of how suckling works. While the imaging studies have caused us to expand our view of the process, the engineering-based models have proved somewhat contradictory, tending to undermine the new consensus. Such models are complex, mathematically difficult to evaluate, and without simple lessons by which clinicians/practitioners can update their practice. This presentation will seek to demonstrate the current agreement between imaging studies, and elucidate recent engineering-based models of milk extraction, to achieve a fresh consensus – a “revised suckling physiology.” Certain limitations of the engineering-based models will be addressed, showing why they do not yet provide a definitive explanation of how babies remove milk from the breast. The encouraging news, however, is that current “best practice” for breastfeeding does not need to be updated; in fact, a new conclusion indicates that the guiding principles are even more relevant than before.
© 2019 Nestlé Nutrition Institute, Switzerland/S. Karger AG, Basel
Introduction
For the best part of four centuries, the medical world was secure in its view of how babies fed and removed milk from the breast – the terms “sucking” and “suckling” became mutually replaceable, even though they describe separate processes. Two commonly accepted facts remain today: first, the baby generates high levels of suction pressure in the oral cavity, so that any object placed in a baby’s mouth (bottle-teat, finger, pacifier) cannot easily be removed. Second, the baby’s tongue moves in a wave-like manner, with positive pressure being exerted rhythmically by the dorsum of the tongue surface to the underside of the nipple/breast complex held in the baby’s mouth; this is regarded as a type feature of the baby, taken to indicate its neurodevelopmental maturity.
The latter tongue movements, originally identified by practical observation [1–3], were later visualized using various techniques including cineradiography [4], 2D ultrasound [5, 6], direct filming [7] and, most recently, 3D ultrasound [8]. All such methods were unambiguous in observing peristaltic tongue movements (PTMs), on the basis of which it was assumed that they played a role in expressing milk from the breast; we have since confirmed that this collective view is essentially correct [9, 10].
Two studies, principally Eishima [7] and Geddes et al. [11], identified a novel feature of infant feeding, involving a localized drawing down of the central region of the tongue, adjacent to the nipple tip. To this movement was imputed the ability to generate increased (added) suction at the nipple surface, claimed to play a predominant role in milk extraction from the breast; subsequent studies have extended and elaborated on these claims [12–14]. We can similarly confirm that these authors are correct in their observations, and in their proposition that the action aids milk extraction; nonetheless, some vital caveats need to be considered when evaluating the full validity of their claims.
What We Already Know
Seven principal forces are present and active during breastfeeding, the first three affect the pressure of milk within the breast; all but one is active in milk transfer, while one plays a key role in retaining the breast within the baby’s mouth.
(1) Atmospheric pressure is an important force in the process, although it is eclipsed by the positive pressure created by (2) the mother’s “let-down” or milk ejection reflex (MER). The MER creates phasic (intermittent) increases in positive pressure in the milk held within the breast, while also causing the milk ducts to dilate, so providing less resistance to the flow of milk to the nipple surface. Because breastfeeding is such a highly dynamic form of milk extraction, atmospheric pressure is more likely to play a role in milk extraction by breast pump (being less dynamic). These two forces constitute one side of an active pressure gradient.
A less obvious process creating positive pressure in the breast is (3) the compressive pressure of the baby’s lips against the СКАЧАТЬ