Interaction between nonnutritive sucking and respiration in preterm infants

The effect of nonnutritive sucking bursts (NNSBs) on respiratory frequency was sequentially evaluated in 12 healthy preterm infants. Studies were performed during active sleep in infants between 32 and 37 weeks postconceptional age. The duration of NNSBs was classified as follows: (a) less than 3 s, (b) between 3 and 6 s, and (c) greater than 6 s. NNSBs of each duration were found at all ages, although NNSBs greater than 6 s were the least frequently observed. Respiratory rate increased significantly during NNSBs of less than 3 s, and also in those of 3-6 s duration. There was no significant effect on respiratory frequency of sucking bursts longer than 6 s. Our results document an early interaction between these two motor rhythms, which is influenced by the length of the NNSB. Moreover, they indicate that the decrease in respiratory frequency reported in a similar group of preterm infants during feeding should not be interpreted as an effect of sucking per se.     

Non-nutritive sucking in sick preterm infants

BACKGROUND: Non-nutritive sucking (NNS) by the newborn infant is a fundamental behaviour and is one of the first coordinated muscular activities in the fetus. Aims: Our objective is to study the NNS pattern in prematurely born infants, who had various conditions commonly associated with immaturity. METHOD: A specially designed computer-based method that analyses and quantifies components of the NNS pattern was used. SUBJECTS: The pattern of 51 clinically stable prematurely born infants (gestational ages 26-35 weeks) making a total of 206 observations were analysed and findings were compared with those obtained from 58, healthy preterm infants. RESULTS: The rhythmic NNS pattern of alternating sucking and pauses was elicited in all examined infants, the earliest at post-menstrual age (PMA) 26 weeks. The role of PMA, the dominant predictor for several sucking variables seen in the control group, became diminished for the infants with risk factors but changes were otherwise similar. The infants' sucking activity and sucking frequency increased and the variability of the pattern declined with increased PMA and weight. Follow-up of a subgroup of infants revealed fewer sucking bursts per minute, slower sucking frequency and a greater variability of the frequency and amplitudes in those infants who developed sequelae. CONCLUSIONS: It would, thus, appear that the NNS pre-programmed rhythm generator, primarily modulated by maturation in healthy preterm infants, becomes affected by known risk associated events and in infants who later develop sequelae. Quantification of the NNS pattern in preterm infants may be a valuable future component of their evaluation.     

Development of sucking rhythm in preterm infants

We studied the ontogeny and temporal organization of non-nutritive sucking during active sleep in 6 healthy preterm infants (mean birthweight 1.1 kg (range 0.8-1.3 kg) gestational age 28.6 weeks (range 26-30 w] from 30 to 35 weeks of post-menstrual (PM) age. Recognizable rhythmical sucking bursts were recorded at 28 weeks in one infant and by 31-33 weeks in the others. Results were analyzed for the periods 30-31, 32-33 and 34-35 PM weeks. The number of bursts/min increased with age, while the duration of each burst was stable (mean 4.1 s). The pause between bursts decreased. Sucking pace within bursts increased with age which resulted in an increase in the overall rate of sucking. The coefficient of variation (CV) for intersuck time within bursts and for interburst time was computed to examine the stability of the sucking rhythm. For intersuck time the CV was relatively low and constant across ages. However, for interburst time CV was relatively large across ages. Thus, there appears to be a stability of the intraburst sucking rhythm from 30 weeks of gestation, whereas the interburst rhythm is less regular. This documentation of temporal organization in sucking from 30 weeks is one of the earliest indications of an intrinsic rhythm in human behavior.     

Stimulation of sucking and swallowing to promote oral feeding in premature infants

AIM: To study the effect of stimulation of sucking and swallowing on weaning from nasogastric (NG) feeding and length of hospital stay in premature infants. METHOD: Randomized controlled trial with blinded evaluation. Premature infants on NG feeds and post-menstrual age (PMA) less than 36 weeks who had poor ability to suck were randomized to receive one daily session of stimulation according to Vojta or no intervention other than standard nursing care. RESULTS: Of 36 infants, 18 received stimulation and 18 were observed without intervention. Mean gestational age at birth was 32.2 weeks (SD 2.4) versus 31.4 (2.3) weeks, p = 0.27, and PMA at study entry 35.1 weeks (0.8) versus 34.4 (0.9) weeks, p = 0.01, respectively. NG feeding was discontinued at 36.8 weeks (0.9) versus 36.3 (0.9) weeks' PMA, p = 0.25, and they were discharged at 37.8 weeks (0.9) versus 37.7 (1.3) weeks, p = 0.81. CONCLUSION: The stimulation programme did not result in earlier weaning from NG feeding or earlier discharge. However, such studies may need to be large to limit the possibility of type II errors.     

Transcutaneous oxygen tension during nonnutritive sucking in preterm infants

The effects of nonnutritive sucking on transcutaneous oxygen tension, heart rate, and respiratory rate were studied sequentially in 14 sleeping preterm infants breathing room air. Transcutaneous oxygen tension increased during nonnutritive sucking in infants between 32 and 35 weeks postconceptional age, but not in those between 36 and 39 weeks. This response was not associated with a change in respiratory rate or sleep state, although heart rate tended to increase. These data offer further support for the beneficial effects of nonnutritive sucking in preterm infants.     

Evaluation of beneficial effects of nonnutritive sucking in preterm infants

The effects of nonnutritive sucking (NNS) were studied in 40 preterm infants weighing less than or equal to 1800 g and of less than or equal to 35 weeks gestation by using a pacifier. The provision of NNS accelerated the maturation of sucking resulting in a faster transition from gavage to oral feedings. Treated infants (20) were ready for bottle feeds 1.54 days earlier, took their bottle feeds 1.5 min/30 ml faster and were transferred out of the nursery on an average .5 days earlier than the control infants. No adverse effects due to NNS were observed throughout the period of study. This resulted in an earlier union with their mother, less maternal deprivation and decreased work load on the nursery staff. Used judiciously this simple and safe modality of providing a pacifier for NNS during tube feeding may be useful in the management of preterm infants.     

非营养性吸吮在机械通气治疗早产儿中的应用

目的：探讨非营养性吸吮在需要机械通气辅助治疗的早产儿中的作用。方法：将68例需要机械通气辅助治疗的早产儿随机分为观察组（n=35）和对照组（n=33）。观察组进行非营养性吸吮,对照组不进行非营养性吸吮。比较两组患儿达全胃肠道喂养时间、恢复至出生体重时间、体重增长速度、住院时间、喂养耐受性、机械通气并发症等。结果：与对照组比较,观察组达全胃肠道营养时间及住院时间缩短（P0.05）。结论：在需要机械通气治疗的早产儿中采用非营养性吸吮可加快其生长发育速度、缩短住院时间,并能提高喂养耐受性,而机械通气并发症发生率没有上升。     

Patterned orocutaneous therapy improves sucking and oral feeding in preterm infants

AIM: To determine whether NTrainer patterned orocutaneous therapy affects preterm infants' non-nutritive suck and/or oral feeding success. SUBJECTS: Thirty-one preterm infants (mean gestational age 29.3 weeks) who demonstrated minimal non-nutritive suck output and delayed transition to oral feeds at 34 weeks post-menstrual age. INTERVENTION: NTrainer treatment was provided to 21 infants. The NTrainer promotes non-nutritive suck output by providing patterned orocutaneous stimulation through a silicone pacifier that mimics the temporal organization of suck. METHOD: Infants' non-nutritive suck pressure signals were digitized in the NICU before and after NTrainer therapy and compared to matched controls. Non-nutritive suck motor pattern stability was calculated based on infants' time- and amplitude-normalized digital suck pressure signals, producing a single value termed the Non-Nutritive Suck Spatiotemporal Index. Percent oral feeding was the other outcome of interest, and revealed the NTrainer's ability to advance the infant from gavage to oral feeding. RESULTS: Multilevel regression analyses revealed that treated infants manifest a disproportionate increase in suck pattern stability and percent oral feeding, beyond that attributed to maturational effects alone. CONCLUSION: The NTrainer patterned orocutaneous therapy effectively accelerates non-nutritive suck development and oral feeding success in preterm infants who are at risk for oromotor dysfunction.     

Coordination of suck-swallow and swallow respiration in preterm infants

Safe oral feeding of infants necessitates the coordination of suck-swallow-breathe. Healthy full-term infants demonstrate such skills at birth. But, preterm infants are known to have difficulty in the transition from tube to oral feeding. AIM: To examine the relationship between suck and swallow and between swallow and breathe. It is hypothesized that greater milk transfer results from an increase in bolus size and/or swallowing frequency, and an improved swallow-breathe interaction. METHODS: Twelve healthy preterm (<30 wk of gestation) and 8 full-term infants were recruited. Sucking (suction and expression), swallowing, and respiration were recorded simultaneously when the preterm infants began oral feeding (i.e. taking 1-2 oral feedings/d) and at 6-8 oral feedings/d. The full-term infants were similarly monitored during their first and 2nd to 4th weeks. Rate of milk transfer (ml/min) was used as an index of oral feeding performance. Sucking and swallowing frequencies (#/min), average bolus size (ml), and suction amplitude (mmHg) were measured. RESULTS: The rate of milk transfer in the preterm infants increased over time and was correlated with average bolus size and swallowing frequency. Average bolus size was not correlated with swallowing frequency. Bolus size was correlated with suction amplitude, whereas the frequency of swallowing was correlated with sucking frequency. Preterm infants swallowed preferentially at different phases of respiration than those of their full-term counterparts. CONCLUSION: As feeding performance improved, sucking and swallowing frequency, bolus size, and suction amplitude increased. It is speculated that feeding difficulties in preterm infants are more likely to result from inappropriate swallow-respiration interfacing than suck-swallow interaction.     

The relationship between birth weight and feeding maturation in preterm infants

Aim: To report changes in ingestive behaviour from 35 to 40 weeks post-conceptual age and examine the association between birth weight and feeding maturation in preterm infants.
Methods: One hundred and four preterm infants born 24 to 34 weeks gestational age were studied. Feeding maturation was assessed as the change from 35 to 40 weeks post-conceptual age in the number of sucks over 5 min, sucking bursts, sucks per burst, time between bursts and maximum pressure during a suck (Pmax). The association between birth weight and each sucking behaviour was examined after adjusting for potential confounders.
Results: Significant changes in feeding maturation occurred between 35 and 40 weeks. Birth weight was positively associated with change in Pmax and change in number of sucks per burst for extremely premature infants born 24 to <29 weeks gestational age but not for very premature infants born ≥29 to 34 weeks. The association between birth weight and change in Pmax for extremely premature infants remained significant after adjustment (adjusted beta = 0.128 mmHg increase in change in maximum sucking pressure per every 1 g of birth weight, 95% CI = 0.017, 0.239, p = 0.03).
Conclusion: Birth weight is positively associated with maturation in maximum sucking pressure among infants born extremely premature.     

Developmental maturation of gastro-oesophageal reflux in preterm infants

The frequency and duration of gastro-oesophageal reflux were examined in 40 preterm infants and compared with a previously published healthy cohort of 74 term infants. Selection required that the infants were born between 24 and 32 weeks' gestation, had a normal head ultrasound and were studied at term post-menstrual age. Multi-channel pen recordings of sleep state, movement, breathing and acid reflux were made. In term and preterm infants the frequency and duration of reflux were greatest in active sleep, rare in quiet sleep and significantly less in preterm than term infants in wakefulness and active sleep ( p <0.05). The fewer and shorter episodes in preterm infants could not be explained by sleep state, movement, gestational or postnatal age, days intubated, days on oxygen or the lowest pH of reflux episodes.     

Nonnutritive sucking during gavage feeding enhances growth and maturation in premature infants

The effects of nonnutritive sucking (NNS) by means of a pacifier during gavage feeding were studied in 30 premature infants whose birth weight was less than 1,500 g. The addition of NNS accelerated the maturation of the sucking reflex, facilitating a more rapid transition from gavage to oral feedings. Additionally, NNS decreased intestinal transit time and caused a more rapid weight gain despite comparable caloric intake resulting in a shortened hospital stay. Although the physiologic mechanisms resulting from this form of oral stimulation remain to be investigated, our data suggest that NNS may be an important factor to consider in the feeding of premature infants.     

Non-nutritive sucking in full-term and preterm infants studied at term conceptional age

Non-nutritive sucking (NNS) patterns in full-term newborn and preterm infants were studied at term conceptional age. The preterm group showed a distinct NNS pattern with a higher frequency and lower amplitude. In the preterm group, gender differences were observed, the girls having higher frequency and larger amplitude. The full-term infants' NNS patterns were also related to pacifier use during early childhood. Experience, gender, maturity and level of tension are suggested as explanatory factors for differences in NNS patterns.     

Characterization of the developmental stages of sucking in preterm infants during bottle feeding

It is acknowledged that the difficulty many preterm infants have in feeding orally results from their immature sucking skills. However, little is known regarding the development of sucking in these infants. The aim of this study was to demonstrate that the bottle-feeding performance of preterm infants is positively correlated with the developmental stage of their sucking. Infants' oral-motor skills were followed longitudinally using a special nipple/bottle system which monitored the suction and expression/compression component of sucking. The maturational process was rated into five primary stages based on the presence/absence of suction and the rhythmicity of the two components of sucking, suction and expression/compression. This five-point scale was used to characterize the developmental stage of sucking of each infant. Outcomes of feeding performance consisted of overall transfer (percent total volume transfered/volume to be taken) and rate of transfer (ml/min). Assessments were conducted when infants were taking 1-2, 3-5 and 6-8 oral feedings per day. Significant positive correlations were observed between the five stages of sucking and postmenstrual age, the defined feeding outcomes, and the number of daily oral feedings. Overall transfer and rate of transfer were enhanced when infants reached the more mature stages of sucking. We have demonstrated that oral feeding performance improves as infants' sucking skills mature. In addition, we propose that the present five-point sucking scale may be used to assess the developmental stages of sucking of preterm infants. Such knowledge would facilitate the management of oral feeding in these infants.     

The role of swallowing during active sleep in the clearance of reflux in term and preterm infants

OBJECTIVES: To investigate swallowing and peristalsis in sleep and during gastroesophageal reflux (GER) in both healthy term and preterm infants at term equivalent age. STUDY DESIGN: Multichannel recordings were made in 12 healthy term and 11 preterm infants, under the same conditions, after feeding. Sleep state, cardiorespiratory variables, esophageal pH, and pharyngeal swallowing and peristalsis were measured. GER was defined as pH <4 for > or = 15 seconds, and swallows were classified as pharyngeal only, primary peristalsis (propagated, dropped, interrupted), or secondary peristalsis. RESULTS: Spontaneous swallowing rate was not significantly different between term and preterm infants and was sleep state-related, occurring in active sleep but rarely in quiet sleep. In response to acid GER, term infants significantly increased pharyngeal swallowing from a median of 0.7 (25th-75th interquartile range, 0.5-0.9) to 1.7 (1.0-3.0) swallows/min and secondary peristalsis from a median of 0.5 (25th-75th interquartile range, 0.3-0.8) to 1.1 (0.8-2.0) waves/min (P <.05). In contrast, the preterm infants demonstrated a significantly higher proportion of fully propagated peristaltic swallows compared with the term infants (53% and 27%, respectively) (P <.05). CONCLUSION: The occurrence of swallowing is sleep state-related. In active sleep, term infants clear GER by increasing swallowing and secondary peristalsis, whereas preterm infants at term equivalent age clear GER by increasing propagated peristalsis. This method of clearance would explain the mechanism by which preterm infants have significantly shorter episodes of reflux than term infants.