Posted by: Indonesian Children | November 13, 2010

Sucking and Swallowing

Sucking and Swallowing

There are two basic forms of sucking, including nonnutritive sucking (NNS) when no nutrient is involved (i.e., pacifier or finger) and nutritive sucking when a nutrient such as milk is ingested from a bottle or breast. Lau  defines mature nutritive sucking to include the rhythmic alternation of suction (negative intraoral pressure that draws milk into the oral cavity) and expression, which is characterized by the compression and stripping force applied by the tongue against the nipple to eject milk into the mouth.
Mature sucking is attained sequentially into the following five primary stages:
  1. Stage 1) arrhythmic expression with no suction
  2. Stage 2) transition to rhythmic expression and appearance of arrhythmic suction
  3. Stage 3) emergence of rhythmic suction
  4. Stage 4) progression to an alternating pattern of suction and expression, with concomitant increases in suction amplitude and duration of sucking bursts
  5. Stage 5). This sequential development of nutritive sucking is correlated with postmenstrual age and oral feeding performance defined by Lau  as the rate of milk transfer (ml/min) and the ability to complete their feeding within a 20 min feed session.
NNS indirectly provides benefits to the attainment of oral feeding skills. For example, a pacifier offered during gavage feeding improved feeding tolerance, accelerates the transition from tube to oral feed, increased weight gain, reduced length of stay, predictive of feeding readiness/feeding problems , improves breastfeeding scores , and increases gastric motility (tachygastria). The observation of an apparently mature NNS pattern with alternating suction and expression does not guarantee the production of a mature pattern of suck during bottle feeding . For such infants, the coordination necessary for suck–swallow–respiration to support safe oral feeding is likely underdeveloped.
During NNS, the demands on swallowing are minimal, as the infant need only handle their own secretions. Thus, NNS and respiration can operate independently from one another. However, during nutritive swallow, swallowing occurs frequently and the suck–swallow–respiration event must be closely linked (dependent on each other) to avoid aspiration. Immature nutritive swallow does not reflect immature sucking ability only, but may also reflect the state of coordination of suck–swallow–respiration. NNS provides a good index of fundamental suck skills, but is not inclusive of the additional coordinative skill set produced by additional CPGs involved in airway protection during nutritive feeds .
Swallowing
With neuromuscular maturation, the swallowing process becomes more rapid and adaptable in handling larger and more varied bolus sizes. More rapid swallowing rates are correlated with higher tongue force and higher intrabolus pressures to propel the bolus to the posterior pharynx and trigger the swallowing reflex. Such observations reinforce the close link between sucking and swallowing and suggest the operation of a dynamic neural sensorimotor control mechanism to sense and allocate activity patterns among at least three brainstem pattern-generating networks to achieve safe swallow. Driving intraoral and pharyngeal sensory afferents mediated by the trigeminal and glossopharyngeal system during suck can initiate or modulate a swallow. Safe swallowing occurs with the proper timing of the epiglottis, aryepiglottic folds, and true vocal folds to effect tracheal closure to prevent tracheal penetration/aspiration into the lungs. Penetration and aspiration may occur prior to swallowing due to poor bolus formation, during swallow due to incomplete laryngeal closure, or following a swallow because of residual liquid or bolus material pooled around the valleculae and pyriform sinuses due to poor pharyngeal clearance.
Advanced swallow assessment technologies
The brainstem plays an important role in breathing–swallowing coordination (BSC); however, the role of suprabulbar structures is unclear during the first year of life . Nonnutritive swallowing occurs frequently during sleep in infants and is vital for fluid clearance and airway protection. Swallowing is also associated with prolonged apnea in some clinical populations. A recent study examined the temporal relations between swallowing, respiratory pauses, and arousal in six preterm infants at term using multichannel polysomnography and a pharyngeal pressure sensor . Results showed that swallows occurred more frequently during respiratory pauses and arousal than during control periods. Most swallows occurred after the respiratory pause onset and were linked to arousal from sleep; thus, the swallow does not appear to trigger the pause in respiration. Swallows not associated with the respiratory pause were observed consistently during the expiratory phase of the respiratory cycle. Nixon et al.  concluded that swallowing and associated arousal may serve to protect the airway during sleep with medically stable preterm infants manifesting the mature pattern of respiratory–swallow coordination at term.
Studies on the dynamics of pharyngoesophageal motility have benefited from the application of pharyngo-UES-esophageal micromanometry in human preterm neonates and infants. Esophageal micromanometry has also proven effective in evaluating the relation between spatial (height) and temporal (duration) characteristics of acid reflux events (AREs) in preterm and term infants with chronic lung disease. On the basis of a sample of 511 AREs from nine preterm infants, 80% of AREs were found to reach the distal esophagus compared with other esophageal segments. One-third of AREs were associated with symptoms and the average acid clearance time was significantly prolonged with symptomatic AREs versus nonsymptomatic AREs by 3.5-fold. This finding suggests that the presence of the acid in the esophagus leads to the expression of symptoms (i.e., cough, gag, arching head and neck) and implies that aversive stimulation of sensory and motor fibers is involved in the pathogenesis of such symptoms.
Reference :
  • Jean A. Brainstem control of swallowing: localization and organization of the central pattern generator for swallowing. In: Taylor A, editor. Neurophysiology of the jaws and teeth. London: MacMillan Press; 1990. pp. 294–321.
  • Mistry S, Hamdy S Neural control of feeding and swallowing. Phys Med Rehabil Clin N Am. 2008;19:709–728. [PubMed] Excellent review of the neuroanatomy, neural control, and central pattern generation of feeding and swallowing.
  • Bingham PM, Thomas CS, Ashikaga T, Abbasi S. Nonnutritive sucking measure predicts feeding skills in tube-fed premature infants [abstract] Pediatr Acad Soc. 2008;3778:1.
  • Volkmer AS, Fiori H Nonnutritive sucking with a pacifier in preterm infants [abstract] Pediatr Acad Soc. 2008;3535:1. Recent report of a randomized study of the effects of pacifier use on breastfeeding. Babies who were given pacifiers manifest significantly improved breastfeeding scores at the 2-week measurement interval, compared with a control group.
  • Abbasi S, Sivieri E, Samuel-Collins N, Gerdes JS Effect of nonnutritive sucking on gastric motility of preterm neonates [abstract] Pediatr Acad Soc. 2008;5840:22. This study shows the potential interaction between trigeminal–facial–hypoglossal activation and gastric motility, evidence of cross-system interactions between central pattern generating networks.
  • Lau C, Kusnierczyk I. Quantitative evaluation of infant’s nonnutritive and nutritive sucking. Dysphagia. 2001;16:58–67. [PubMed]

 


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