Development of Suck and Swallow Mechanisms in Infants

Abstract

Preterm infants' hospital discharge is often delayed due to their inability to feed by mouth safely and competently. No evidence-based supported guidelines are currently available for health-care professionals caring for these infants. Available interventions advocating benefits are not readily acknowledged for lack of rigorous documentation inasmuch as any improvements may ensue from infants' normal maturation. Through research, a growing understanding of the development of nutritive sucking skills has emerged, shedding light on how and why infants may encounter oral feeding difficulties due to the immaturity of specific physiologic functions. Unfortunately, this knowledge has yet to be translated to the clinical practice to improve the diagnoses of oral feeding problems through the development of relevant assessment tools and to enhance infants' oral feeding skills through the development of efficacious preventive and therapeutic interventions. This review focuses on the maturation of the various physiologic functions implicated in the transport of a bolus from the oral cavity to the stomach. Although infants' readiness for oral feeding is deemed attained when suck, swallow, and respiration are coordinated, we do not have a clear definition of what coordination implies. We have learned that each of these functions encompasses a number of elements that mature at different times and rates. Consequently, it would appear that the proper functioning of sucking, the swallow processing, and respiration need to occur at two levels: first, the elements within each function must reach an appropriate functional maturation that can work in synchrony with each other to generate an appropriate suck, swallow process, and respiration; and second, the elements of all these distinct functions, in turn, must be able to do the same at an integrative level to ensure the safe and efficient transport of a bolus from the mouth to the stomach.

Figure 1

A five-stage descriptive scale of the development of VLBW infants’ nutritive sucking defined by the sequential presence/absence of the suction and expression components of sucking and their respective rhythmicity. At the earlier stages (1 to 3), infants readily shift from using either pattern (A) or (B).

Figure 2

Temporal appearance of characteristics of the Expression and Suction components of nutritive sucking as per stages described in Figure 1

Figure 3

Percent distribution of OFS levels by GA strata at introduction of oral feeding (reproduced by permission Karger Publishers)

Figure 4

Schematic of sucking, pharyngeal swallow and respiratory airflow during nutritive (A) and nonnutritive (B) sucking

Figure 5

Tracings of nonnutritive and nutritive sucking monitored 3 min apart during same feeding sessions of an infant born at 33^1/7 weeks GA, introduced to oral feeding at 34^2/7 weeks PMA, and attaining 8 oral feedings per day at 36^1/7 weeks PMA