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.     

Interventions to improve the oral feeding performance of preterm infants

Aim: Preterm infants have difficulty oral feeding. We hypothesized that a specific sucking and swallowing exercises vs. no intervention accelerate the attainment of independent oral feeding through a faster maturation of infants’ oral feeding skills (OFS). Methods: Very low birthweight infants were randomized to a control, sucking and swallowing groups. Sucking consisted of active sucking on a pacifier, and swallowing of placing a milk bolus (0.05–0.2 mL) on the tongue where the bolus rests prior to entering the pharynx. Primary outcome was days from start to independent oral feeding (SOF‐IOF). Secondary outcomes included overall transfer (OT, % volume taken/volume prescribed), proficiency (PRO, % volume taken at 5 min/volume prescribed), rate of transfer (RT, mL/min) over the entire feeding and infants’ OFS levels. OFS levels were defined by PRO and RT. Results: Days from SOF to IOF vs controls (21 ± 2) were similar for the sucking group (19 ± 2) and shorter for the swallowing group (15 ± 2; p = 0.019). Only the latter infants demonstrated more mature OFS levels than controls. Conclusion: The swallowing exercise is an efficacious intervention in facilitating the attainment of independent oral feeding, but not the sucking exercise. We speculate that the swallowing benefit resulted from an accelerated maturation of infants’ OFS levels.     

Does the choice of bottle nipple affect the oral feeding performance of very‐low‐birthweight (VLBW) infants?

Background: There is a continuous debate regarding the best bottle nipple to be used to enhance the bottle-feeding performance of a preterm infant. Aim: To verify that feeding performance can be improved by using the bottle nipple with the physical characteristics that enhance infants' sucking skills. Methods: Ten “healthy” VLBW infants (941±273 g) were recruited. Feeding performance was monitored at two time periods, when taking 1-2 and 6-8 oral feedings/d. At each time and within 24 h, performance was monitored using three different bottle nipples offered in a randomized order. Rate of milk transfer (ml/min) was the primary outcome measure. The sucking skills monitored comprised stage of sucking, suction amplitude, and duration of the generated negative intraoral suction pressure. Results: At both times, infants demonstrated a similar rate of milk transfer among all three nipples. However, the stage of sucking, suction amplitude, and duration of the generated suction were significantly different between nipples at 1-2, but not 6-8 oral feedings/d.

Conclusion: We did not identify a particular bottle nipple that enhanced bottle feeding in healthy VLBW infants. Based on the notion that afferent sensory feedback may allow infants to adapt to changing conditions, we speculate that infants can modify their sucking skills in order to maintain a rate of milk transfer that is appropriate with the level of suck-swallow-breathe coordination achieved at a particular time. Therefore, it is proposed that caretakers should be more concerned over monitoring the coordination of suck-swallow-breathe than over the selection of bottle nipples.     

The maturation and coordination of sucking,swallowing, and respiration in preterm infants

OBJECTIVES: Our objectives were to establish normative maturational data for feeding behavior of preterm infants from 32 to 36 weeks of postconception and to evaluate how the relation between swallowing and respiration changes with maturation. STUDY DESIGN: Twenty-four infants (28 to 31 weeks of gestation at birth) without complications or defects were studied weekly between 32 and 36 weeks after conception. During bottle feeding with milk flowing only when infants were sucking, sucking efficiency, pressure, frequency, and duration were measured and the respiratory phase in which swallowing occurs was also analyzed. Statistical analysis was performed by repeated-measures analysis of variance with post hoc analysis. RESULTS: The sucking efficiency significantly increased between 34 and 36 weeks after conception and exceeded 7 mL/min at 35 weeks. There were significant increases in sucking pressure and frequency as well as in duration between 33 and 36 weeks. Although swallowing occurred mostly during pauses in respiration at 32 and 33 weeks, after 35 weeks swallowing usually occurred at the end of inspiration. CONCLUSIONS: Feeding behavior in premature infants matured significantly between 33 and 36 weeks after conception, and swallowing infrequently interrupted respiration during feeding after 35 weeks after conception.     

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.     

Développement de l'oralité chez le nouveau-né prématuré

Preterm infants cannot readily transition from tube to oral feeding. Such difficulty often delays their discharge from the hospital and mother-infant reunion. Therefore, understanding the development of the necessary skills preterm infants need to acquire for safe and successful oral feeding is essential. It is now recognized that a mature sucking pattern consisting of the rhythmic alternation of suction and expression is not sufficient for an infant to feed by mouth safely. Rather, an adequate coordination of sucking, swallowing, and respiration appear to be crucial if the infant is to feed with no episodes of desaturation, apnea, bradycardia, and/or aspiration. Studies have shown the benefits of some interventions in facilitating oral feeding in the preterm infant. However, it remains to be determined whether these effects can be generalized.     

The reliability of the Neonatal Oral-Motor Assessment Scale.

OBJECTIVES: Sucking problems in preterm infants can be specified by means of visual observation. The Neonatal Oral-Motor Assessment Scale (NOMAS) is the visual observation method most commonly used to assess the non-nutritive sucking (NNS) and nutritive sucking (NS) skills of infants up to approximately 8 weeks postterm. During the first 2 min of a regular feeding the infant's sucking skill is assessed, either immediately or on video. Although NOMAS has been used since 1993, little is known about the method's reliability. The aim of our study was to determine the test-retest and inter-rater reliability of NOMAS. METHODS: The 75 infants included in this study were born at 26-36 weeks postmenstrual age (PMA). Four observers participated in the study. They were trained and certified to administer NOMAS in the Netherlands by M.M. Palmer between 2000 and 2002. RESULTS: We found the test-retest agreement of NOMAS to be 'fair' to 'almost perfect' (Cohen's kappa [kappa] between 0.33 and 0.94), whereas the inter-rater agreement with respect to the diagnosis was 'moderate' to 'substantial' (Cohen's kappa, between 0.40 and 0.65). As a diagnostic tool, however, the current version of NOMAS cannot be used for both full-term and preterm infants. For a measuring instrument such as NOMAS, one should aim at reliability coefficients for inter-rater and test-retest agreement of at least 0.8. A Cohen's kappa of 0.6 or less we find unacceptable. Nonetheless, by observing sucking and swallowing according to a protocol much useful information can be gathered about the development of an infant's sucking skills. For instance, whether the infant is able to co-ordinate sucking and swallowing, whether the infant can maintain sucking, swallowing and breathing during the continuous phase and whether the infant is able to suck rhythmically with equally long bursts. In addition, NOMAS offers useful aids for intervention. CONCLUSIONS: NOMAS should be re-adjusted in order to improve inter-rater agreement, and at the same time current insights into the development of sucking and swallowing should be incorporated in the method.     

Oral and nonoral sensorimotor interventions facilitate suck-swallow-respiration functions and their coordination in preterm infants

Background

Preterm infants are at high risk of encountering oral feeding difficulties. Early sensorimotor interventions may improve oral feeding skills in preterm infants.

Aim

To further explore the effects of an oral (O), tactile/kinesthetic (T/K), and combined (O + T/K) sensorimotor intervention on preterm infants' nutritive sucking, swallowing and their coordination with respiration.

Study design

Seventy-five infants (29 [0.3, standard error of mean, SEM] weeks gestation, 49 males/26 females) were randomly assigned to an O group involving sensorimotor input to the oral structures; a T/K group involving sensorimotor input to the trunk and limbs; a combined (O + T/K) group; and a control group.

Outcome measures

Stage of sucking, suction and expression amplitudes (mm Hg), suck–swallow ratio, stability of suck–swallow interval, and swallow–respiration patterns.

Results

The O group had significantly more advanced sucking stages, and greater suction and expression amplitudes than controls [p ≤ 0.035, effect size (ES) > 0.6]. The suck–swallow ratio and stability of suck–swallow intervals did not significantly differ among groups (p ≥ 0.181, ES ≤ 0.3). The three interventions led to fewer swallows bracketed by prolonged respiratory pauses compared to controls (pause–swallow–pause, p ≤ 0.044, ES ≥ 0.7). The T/K and combined (O + T/K) groups had greater occurrence of swallows bracketed by expiration than the control and O groups (expiration–swallow–expiration, p ≤ 0.039, ES ≥ 0.3).

Conclusion

The O intervention enhanced specific components of nutritive sucking. All three interventions resulted in improved swallow–respiration coordination. Sensorimotor interventions have distributed beneficial effects that go beyond the specific target of input.     

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.     

Assessment of sensorial oral stimulation in infants with suck feeding disabilities

A non-randomised single blind study was undertaken to determine the clinical and physiological changes in suck feeding after sensorial oral stimulation, in fourteen patients age 9 to 210 days old with sucking alterations. Patients lacked at least one of the five oral reflexes, plus two or more abnormal sucking sings or at least one abnormal sucking sign, plus two or more abnormal oral reflexes. Oral sensorial therapy was performed thrice daily for five days. The number of absent oral reflexes, number of abnormal sucking signs, volume of milk for nursing and sucking rate, were registered. Differences of medians were tested using Freidman's test and differential of proportions using Cochran's Q test. After therapy, oral reflexes were recovered (2, 0–4 vs. 5,5–5, p=0.0000, median rank of absence oral reflexes) and the number of abnormal sucking signs decreased (6,1–9 vs. 1, 0–4; p=0.0000). There were statistically significant improvements in patients who had lost launch up nipple ability (p=0.005), delay at the beginning of sucking (p=0.0022), drawing of milk from the mouth (p=0.0001), cyanosis (p=0.0084), weaning (p=0.0004) and prolonged sucking (p=0.0038). Even in patients with moderate improvement, no statistical differences were observed in nipple rooting (p=0.09) and coughing (p=0.09). No changes were observed in patients who had cried (p=0.31) and spitted (p=0.51) during feeding. At the end of therapy, volumes of consumed milk were increased at each feeding (10 ml, 0–40 vs. 50 ml, 25–60; p=0.0001). Sucking rates also increased (22 sucks/minute, 10–35 vs. 40.5, 35–48; p=0.0044). Oral sensorial and motor stimulation normalise oral motor reflexes, diminish the clinical abnormal sucking signs and increase milk volumes ingested for nursing.     

Nutritive sucking pattern--from very low birth weight preterm to term newborn

The contribution of maturation and stimulation to the development of oral feeding was investigated, with two main objectives: (1) to analyze the nutritive sucking pattern of very-low-birth-weight newborns from their first oral feeding to the acquisition of independent oral feeding, and (2) to compare the nutritive sucking patterns of these babies, after feeding autonomy, with healthy term newborns.

Methods

Two groups were considered for analysis. Group 1: N = 15 Very-Low-Birth-Weight (VLBW), gestacional age (GA) = 28.15 ± 1.5, birth weight (BW) = 1178.3 ± 174.4. The intervention program began at 30.19 ± 1.52 weeks GA. Group 2: N = 25 term newborns, healthy, GA = 39.04 ± 1.2, BW = 3370.42 ± 310.76. Repeated measures of the following variables were taken (weekly for group 1): suction efficacy (SEF), rhythm of milk transfer (RMT), suctions, bursts and pauses. Group 2 was analysed only once between the 2nd and 5th day of life.

Results

Group 1 has revealed a minimal suction number at 32 GA weeks (82 ± 77.6) and maximal suction number at 36-37 GA weeks (162.7 ± 60.7). The number of sucks seemed to be dependent of weight (p = 0.005), duration of intervention (p = 0.001) and chronological age (p = 0.000). Significant statistical effects of gestational age were not observed (p = 0.904). Sucks in bursts represented 77% at the beginning of oral feeding (32 weeks GA), and 96% at 33 weeks GA, remaining constant thereafter. The number of sucks and bursts increased with GA and weeks of feeding. The mean duration of the pauses decreased from first to fourth week of feeding (week1 = 14.1 ± 9.1 and week4 = 6.4 ± 1.4 s). The sucking efficacy (SEF) was better explained by weight (p = 0.000), number of sucks in 5 min (p = 0.025) and chronological age (p = 0.044). Gestational age (p = 0.051) and nutritive intervention duration (NDI) (p = 0.110) did not contribute to explain SEF. Despite the observation of significant statistical differences between groups regarding GA (35.9/39.08; p = 0.00), chronological age (53.3/2.5; p = 0.00) and weight (1875/3360; p = 0.00), the nutritive suction pattern was not statistically different between groups after feeding autonomy.

Conclusion

in VLBW oral feeding before 32 weeks GA allows the attainment of a mature nutritive suction pattern before term (37-40 weeks). Experience seems to be one of the influencing factors in the change of the nutritive suction pattern.     

Mechanisms of feeding efficiency in preterm infants

Nutritive sucking was studied in 18 preterm infants. Differences in feeding efficiency could not be explained by differences in sucking rate. Quick efficient drinking, however, was characterized by long sucking bursts and by a large amount of milk intake during each sucking movement. Slow inefficient drinking was characterized by short sucking bursts and by a small amount of milk intake during each sucking movement.     

Feeding efficiency and respiratory integration in infants with acute viral bronchiolitis

OBJECTIVE: To examine the effects of bronchiolitis on feeding efficiency and respiratory integration. STUDY DESIGN: We studied 21 infants with bronchiolitis and 21 bottle-fed healthy infants who formed a comparison group. Repeat evaluations of half the bronchiolitis group were performed during recovery. During each feeding study we measured the duration and frequency of sucking, the frequency of single and multiple swallows, the respiratory rate, the postswallow respiratory direction, and the suck and swallow volumes. RESULTS: The infants with bronchiolitis devoted significantly less time to sucking than their healthy peers (P <.05), and the mean suck volume was reduced. Although the frequency of swallowing was slightly higher, the volume of milk consumed per swallow was almost half the amount consumed by the comparison group (P <.01). Coordination of breathing with swallowing was also less effective (P <.01). CONCLUSION: Although most aspects of feeding are less efficient during periods of respiratory illness, others are preserved or recover rapidly. Coordination of breathing during feeding is also significantly impaired.     

The preterm piglet – a model in the study of oesophageal development in preterm neonates

Aim: Preterm infants have difficulty in attaining independent oral feeding. This can ensue from inadequate sucking, swallowing and/or respiration. In impeding bolus transport, immature oesophageal motility may also be a cause. As studies on the development of oesophageal motility are invasive in preterm infants, the preterm piglet was investigated as a potential research model. Methods: Oesophageal motility (EM) of term (n = 6) and preterm (n = 15) piglets were monitored by manometry for 10 min immediately following bottle feeding on days 1–2 and 3–4 of life. Results: Piglets’ oral feeding performance and EM were similar to those of their human counterparts. Term piglets readily completed their feeding, whereas their preterm counterparts did not. They also presented with greater peristaltic activity and propagating velocity. Peristaltic activity remained unchanged over time in preterm piglets, but an increase in synchronous and decrease in incomplete motor activity were noted. Preterm piglets that developed symptoms analogous to necrotizing enterocolitis (NEC) demonstrated uncharacteristic oesophageal activity. Conclusion: Immature EM may cause oral feeding difficulties. NEC‐like symptoms may adversely affect EM. The piglet is a valid research model for studying human infant oral feeding and oesophageal development.     

Clinical effects of oral motor intervention combined with non-nutritive sucking on oral feeding in preterm infants with dysphagia

ObjectiveTo explore the effectiveness of oral motor intervention combined with non-nutritive sucking in treating premature infants with dysphagia.MethodsSixty preterm infants admitted to the neonatal intensive care unit of the present study's hospital were selected and randomly divided into the control and intervention groups. The control group was given non-nutritive sucking intervention alone, while the intervention group was given oral motor intervention combined with non-nutritive sucking. The oral motor ability, milk sucking amount and sucking rate, feeding efficiency and outcomes, and the occurrence of adverse reactions were measured and compared.ResultsCompared to first-day interventions, preterm infant oral feeding readiness assessment scale-Chinese version (PIOFRAS-CV) scores of the two groups significantly increased after 14 days of intervention, and this score was higher in the intervention group compared to the control group. Similarly, after 14 days of intervention, the intervention group's milk sucking rate and amount were significantly higher than the control group. Also, after the intervention, the intervention group's total oral feeding weeks were considerably lower, while the feeding efficiency and body weight were significantly higher than the control group. Moreover, the overall adverse reaction rate in the intervention group was lower than that in the control group.ConclusionsOral motor intervention combined with non-nutritive sucking can significantly improve the oral motor ability of premature newborns, promote the process of oral feeding, improve the outcome of oral feeding, and reduce the occurrence of adverse effects. The combined intervention seems to have a beneficial effect on oral feeding proficiency in preterm infants.     

Sipping/lapping is a safe alternative feeding method to suckling for preterm infants

Aim: To determine whether sipping/lapping is a safe alternative to suckle bottle-feeding without any hydrostatic pressure, in terms of physiological stability and the relationship between swallowing and respiration. In addition, tongue movement was compared between sipping/lapping and suckling (bottle- and breastfeeding). Methods: Eighteen infants (30-35 wk of gestation at birth) were studied while sipping/lapping and suckling a bottle without any hydrostatic pressure at different feeding sessions on the same day of the first oral feeding. The postmenstrual age at the time of study was 34.6±0.2 wk. We evaluated the amounts ingested and administration times. The heart rate, O₂ saturation (SpO₂), and relationship between swallowing and respiration were examined while feeding. Tongue movements were also observed by ultrasonography. Statistical analysis was performed by a paired t-test. Results: The amounts ingested and intake volume per minute were lower while sipping/lapping compared to suckling. The overall heart rate and SpO₂ showed no statistically significant difference. The frequency of swallows followed by inspiration (27.6±0.8% and 31.0±1.3%) and swallows followed by expiration (46.4±0.9% and 45.4±1.4%, sipping and suckling, respectively) also showed no difference. Tongue movements while sipping/lapping differed from those while suckling a bottle or breast.

Conclusion: Because physiological parameters and the relationship between swallowing and respiration while sipping/lapping are comparable to those while suckle bottle-feeding without any hydrostatic pressure, sipping/lapping is a safe alternative feeding method to suckle bottle-feeding, even in preterm infants.     

Coordination of sucking, swallowing, and breathing and oxygen saturation during early infant breast-feeding and bottle-feeding

This prospective study compared the coordination of sucking, swallowing, and breathing and its relationship to oxygen saturation in infants during breast-feeding and bottle-feeding. After 4 to 6 wk of exclusive breast-feeding, infants began bottle-feedings of expressed human milk using one of two systems: a soft-walled bottle and nipple (system 1, Playtex) or a hard-walled bottle and nipple (system 2, Avent). Infants' sucking, swallowing, breathing, and oxygenation were measured during breast-feeding and bottle-feeding, and coordination of these activities during breast-feeding and bottle-feeding were compared. During breast-feeding, swallowing occurred nonrandomly between breaths and did not interfere with breathing. The same distribution of swallowing occurred in infants fed with system 1, while swallowing occurred randomly in infants fed with system 2. Swallowing significantly increased during bottle-feeding among infants using system 2, but decreased among infants using system 1. Infants using system 2 also had a greater instability in the coordination of sucking, swallowing, and breathing and more perturbation of breathing. Oxygen saturation was significantly higher in infants fed with system 1 compared with system 2. These results suggest that the overall feeding pattern and oxygenation of system 1 are closer to the physiologic norm than system 2.     

Comparison of sucking patterns at introduction of oral feeding and at term in Israeli and American preterm infants

BACKGROUND: It has been hypothesized that early initiation of oral feeding in premature infants may enhance the maturation of sucking patterns. AIM: To compare preterm infant sucking characteristics in urban level III neonatal care units in the USA and Israel. The two hospitals have different practices regarding the introduction of oral feeding. METHODS: Infants were assessed at 34-35 wk postconceptional age (PCA) and at term. Sucking parameters were assessed with the Kron's Nutritive Sucking Apparatus. RESULTS: 70 infants (38 Americans and 32 Israelis) participated in the study. Oral feedings were initiated earlier (32.6 +/- 4.3 vs 34.5 +/- 1.8 wk PCA, p < 0.01) and full oral feedings were reached earlier (35.4 +/- 2.8 vs 36.5 +/- 2.5 wk PCA, p < 0.05) in the USA infants. American preterm infants produced significantly more sucks (p < 0.001), had a higher suck rate (p < 0.001), more sucks per burst (p < 0.05), and a shorter interburst width (p < 0.01) at 34 wk PCA than Israeli infants. At term, American infants produced significant more sucks (p < 0.001), higher suck rate (p < 0.001), shorter intersuck width (p < 0.001), and a shorter interburst width (p < 0.05) than the Israeli infants of the same PCA. CONCLUSION: Different practices in the care of preterm infants, such as postconceptional age at introduction of oral feeding, may play a role in the development of feeding and feeding organization at term.     

Sucking and breathing patterns during breast- and bottle-feeding in term neonates. Effects of nutrient delivery and composition

We attempted to determine whether differences in milk composition or flow rate are the primary determinants in altering breathing pattern during nipple-feeding. In the first phase of the study, 15 neonates were studied during breast-feeding and bottle-feeding; in the second phase, 15 were evaluated during bottle-feeding of expressed human milk and formula. A reduction in inspiratory duration was observed with all feeding regimens. Moreover, significant prolongation in expiratory duration and reduction in breathing frequency were observed during bottle-feeding of formula and expressed human milk (compared with control); these effects were greater with formula feeding. Higher sucking frequency was observed during breast-feeding compared with bottle-feeding; no difference in suckling frequency or sucking pressure was observed between bottle-feeding of expressed human milk and formula. We conclude that most of the differences in sucking and breathing patterns between breast- and bottle-feeding can be attributed to nutrient delivery rather than nutrient composition.