Effects of nasal continuous positive-airway pressure on nutritive swallowing in lambs

Safety of Bottle-Feeding Under Nasal Respiratory Support in Preterm Lambs With and Without Tachypnoea

Aim: Convalescing preterm infants often require non-invasive respiratory support, such as nasal continuous positive airway pressure or high-flow nasal cannulas. One challenging milestone for preterm infants is achieving full oral feeding. Some teams fear nasal respiratory support might disrupt sucking–swallowing–breathing coordination and induce severe cardiorespiratory events. The main objective of this study was to assess the safety of oral feeding of preterm lambs on nasal respiratory support, with or without tachypnoea.

Methods: Sucking, swallowing and breathing functions, as well as electrocardiogram, oxygen haemoglobin saturation, arterial blood gases and videofluoroscopic swallowing study were recorded in 15 preterm lambs during bottle-feeding. Four randomly ordered conditions were studied: control, nasal continuous positive airway pressure (6 cmH₂O), high-flow nasal cannulas (7 L•min^–1), and high-flow nasal cannulas at 7 L•min^–1 at a tracheal pressure of 6 cmH₂O. The recordings were repeated on days 7–8 and 13–14 to assess the effect of maturation.

Results: None of the respiratory support impaired the safety or efficiency of oral feeding, even with tachypnoea. No respiratory support systematically impacted sucking–swallowing–breathing coordination, with or without tachypnoea. No effect of maturation was found.

Conclusion: This translational physiology study, uniquely conducted in a relevant animal model of preterm infant with respiratory impairment, shows that nasal respiratory support does not impact the safety or efficiency of bottle-feeding or sucking–swallowing–breathing coordination. These results suggest that clinical studies on bottle-feeding in preterm infants under nasal continuous positive airway pressure and/or high-flow nasal cannulas can be safely undertaken.

Nasal respiratory support and tachypnea and oral feeding in full-term newborn lambs

Newborn infants with respiratory difficulties frequently require nasal respiratory support such as nasal continuous positive airway pressure (nCPAP) or high-flow nasal cannulae (HFNC). Oral feeding of these infants under nasal respiratory support remains controversial out of fear of aspiration and cardiorespiratory events. The main objective of this study was to evaluate the safety of oral feeding under different types of nasal respiratory support in newborn lambs without or with tachypnea. Eight lambs aged 4-5 days were instrumented to record sucking, swallowing, respiration, ECG, oxygen saturation, and arterial blood gases. Each lamb was given two bottles of 30 mL of milk with a pause of 30 s under videofluoroscopy in four conditions [no respiratory support, nCPAP 6 cmH₂O, HFNC 7 L/min, HFNC_CPAP (= HFNC 7 L/min + CPAP 6 cmH₂O)] administered in random order. The study was conducted in random order over 2 days, with or without standardized tachypnea induced by thoracic compression with a blood pressure cuff. Generalized linear mixed models were used to compare the four nasal respiratory supports in terms of safety (cardiorespiratory events and aspiration), sucking-swallowing-breathing coordination, and efficacy of oral feeding. Results reveal that no nasal respiratory support impaired the safety of oral feeding. Most of the few laryngeal penetrations we observed occurred with HFNC_CPAP. Nasal CPAP modified sucking-swallowing-breathing coordination, whereas the efficiency of oral feeding decreased under HFNC_CPAP. Results were similar with or without tachypnea. In conclusion, oral feeding under nasal respiratory support is generally safe in a term lamb, even with tachypnea.NEW & NOTEWORTHY The practice of orally feeding newborns suffering from respiratory problems while on nCPAP or HFNC remains controversial for fear of triggering cardiorespiratory events or aspiration pneumonia, or aggravating chronic lung disease. The present results show that bottle-feeding is generally safe in full-term lambs under nasal respiratory support, both without and with tachypnea.

Physiological Basis of Neonatal Aerodigestive Difficulties in Chronic Lung Disease

In the United States, preterm birth rates have steadily increased since 2014. Despite the recent advances in neonatal-perinatal care, more than 40% of very low-birth-weight infants develop chronic lung disease (CLD) and almost 25% have feeding difficulties resulting in delayed achievement of full oral feeds and longer hospital stay. Establishment of full oral feeds, a major challenge for preterm infants, becomes magnified among those on respiratory support and/or with CLD. The strategies to minimize aerodigestive disorders include supporting nonnutritive sucking, developing infant-directed feeding protocols, sensory oromotor stimulation, and early introduction of oral feeds.

Clinical characteristics of premature infants who orally feed on continuous positive airway pressure

BACKGROUND

Between 32 and 34 weeks postconceptional age (PCA), premature infants typically achieve neuromuscular maturation to initiate the coordination of a nutritive suck triad. Many premature infants also require intubation, which has been associated with dysphagia in adults and infants. At our institution, despite these factors, some infants have been noted to tolerate oral feeds while on continuous positive airway pressure (CPAP).

AIMS

Compare the clinical characteristics and duration of intubation in infants that initiate oral feedings on CPAP to infants that did not begin oral feeding on CPAP.

STUDY DESIGN

Retrospective case control study.

SUBJECTS

Infants with gestational age < 32 weeks who required CPAP at 32 weeks PCA.

OUTCOME MEASURES

Oral feeding was defined as any oral feed ≥5 ml. Duration of intubation was defined as the number of intubated days prior to 32 weeks PCA.

RESULTS

Of the 243 infants on CPAP at 32 weeks PCA, 31% (n = 76) began oral feeding on CPAP. Infants who initiated oral feeding on CPAP were of younger gestational age at birth (median 26 versus 27 weeks, p < 0.001) and remained intubated for longer (median 10.5 versus 2 days, p < 0.001).

CONCLUSIONS

Infants who began oral feeding on CPAP had lower gestational age and longer duration of intubation than infants who started oral feeding off CPAP.

Nasal continuous positive airway pressure influences bottle-feeding in preterm lambs

BackgroundIn preterm infants, the time from initiation to full oral feeding can take weeks, which represents a very worrisome problem in neonatal medicine. Although current knowledge suggests that oral feeding should be introduced early, this is often delayed due to the need for prolonged nasal continuous positive airway pressure (nCPAP). Indeed, most caregivers fear that nCPAP could disrupt sucking-swallowing-breathing coordination and induce tracheal aspiration. The goal of the present study was to assess the impact of nCPAP delivered by the Infant Flow System on the physiology of sucking-swallowing-breathing coordination during bottle-feeding in preterm lambs over 24 h.MethodsSeventeen lambs (8 control, 9 nCPAP of 6 cmH₂O) born 14 days prematurely were instrumented to record sucking, swallowing, respiration, ECG, and oxygenation. They were fed via a nasogastric tube for the first 5 days of life until introduction of bottle-feeding every 4 h for 24 h.ResultsnCPAP increased the feeding efficiency while maintaining higher oxygenation without any deleterious cardiorespiratory events. However, coughs were observed in lambs under nCPAP immediately following bottle-feeding and may be related to the high milk flow in preterm lambs.ConclusionFurther studies documenting tracheal aspirations are needed, especially in preterm lambs under nCPAP for moderate respiratory difficulties, to further inform future clinical studies.

Effect of nasal continuous positive airway pressure on the pharyngeal swallow in neonates

OBJECTIVE

Feeding neonates orally while on nasal continuous positive airway pressure (nCPAP) is a common practice. We hypothesize that pressurized airflow provided by nCPAP will alter the swallowing mechanism in neonates, increasing the risk of aspiration during oral feeding.

STUDY DESIGN

Infants receiving nCPAP with a RAM cannula and tolerating at least 50% of their feeding orally were included in the study (one term; six preterm infants). Each participant underwent a videofluoroscopic swallow study while on nCPAP and off nCPAP. A non-parametric signed-rank test was used for paired data.

RESULT

The incidence of deep penetration (P=0.03) and aspiration (P=0.01) decreased significantly off-nCPAP compared with on-nCPAP. However, the incidence of mild penetration (P=0.65) and nasopharyngeal reflux (P=0.87) remained the same under both conditions.

CONCLUSION

Oral feeding while on-nCPAP significantly increases the risk of laryngeal penetration and tracheal aspiration events. We recommend caution when initiating oral feedings on nCPAP.

Effects of Nasal Continuous Positive Airway Pressure and High-Flow Nasal Cannula on Sucking, Swallowing, and Breathing during Bottle-Feeding in Lambs

The use of prolonged respiratory support under the form of high-flow nasal cannula (HFNC) or nasal continuous positive airway pressure (nCPAP) is frequent in newborn infants. Introduction of oral feeding under such nasal respiratory support is, however, highly controversial among neonatologists, due to the fear that it could disrupt sucking, swallowing, and breathing coordination and in turn induce cardiorespiratory events. The recent observation of tracheal aspirations during bottle-feeding in preterm infants under nCPAP justifies the use of animal models to perform more comprehensive physiological studies on the subject, in order to gain further insights for clinical studies. The objective of this study was to assess and compare the impact of HFNC and nCPAP on bottle-feeding in newborn lambs, in terms of bottle-feeding efficiency and safety as well as sucking-swallowing-breathing coordination. Eight full-term lambs were instrumented to record sucking, swallowing, and respiration as well as electrocardiogram and oxygenation. Lambs were bottle-fed in a standardized manner during three randomly ordered conditions, namely nCPAP 6 cmH₂O, HFNC 7 L/min, and no respiratory support. Results revealed that nCPAP decreased feeding duration [25 vs. 31 s (control) vs. 57 s (HFNC), p = 0.03] and increased the rate of milk transfer [2.4 vs. 1.9 mL/s (control) vs.1.1 mL/s (HFNC), p = 0.03]. No other indices of bottle-feeding safety or sucking-swallowing-breathing coordination were significantly altered by HFNC or nCPAP. In conclusion, our results obtained in full-term newborn lambs suggest that: (i) nCPAP 6 cmH₂O, but not HFNC 7 L/min, increases bottle-feeding efficiency; (ii) bottle-feeding is safe under nCPAP 6 cmH₂O and HFNC 7 L/min, with no significant alteration in sucking-swallowing-breathing coordination. The present informative and reassuring data in full-term healthy lambs must be complemented by similar studies in preterm lambs, including mild-to-moderate respiratory distress alleviated by respiratory support in order to mimic preterm infants with bronchopulmonary dysplasia and pave the way for clinical studies.

New insights into sucking, swallowing and breathing central generators: A complexity analysis of rhythmic motor behaviors

Sucking, swallowing and breathing are dynamic motor behaviors. Breathing displays features of chaos-like dynamics, in particular nonlinearity and complexity, which take their source in the automatic command of breathing. In contrast, buccal/gill ventilation in amphibians is one of the rare motor behaviors that do not display nonlinear complexity. This study aimed at assessing whether sucking and swallowing would also follow nonlinear complex dynamics in the newborn lamb. Breathing movements were recorded before, during and after bottle-feeding. Sucking pressure and the integrated EMG of the thyroartenoid muscle, as an index of swallowing, were recorded during bottle-feeding. Nonlinear complexity of the whole signals was assessed through the calculation of the noise limit value (NL). Breathing and swallowing always exhibited chaos-like dynamics. The NL of breathing did not change significantly before, during or after bottle-feeding. On the other hand, sucking inconsistently and significantly less frequently than breathing exhibited a chaos-like dynamics. Therefore, the central pattern generator (CPG) that drives sucking may be functionally different from the breathing CPG. Furthermore, the analogy between buccal/gill ventilation and sucking suggests that the latter may take its phylogenetic origin in the gill ventilation CPG of the common ancestor of extant amphibians and mammals.

Eating in "SINC": Safe Individualized Nipple-Feeding Competence, a Quality Improvement Project to Explore Infant-Driven Oral Feeding for Very Premature Infants Requiring Noninvasive Respiratory Support

Oral feeding is a developmental task for all premature infants. often, independent nipple feeding is the last barrier to discharge home from the NICU. A relationship exists between consistent, infant-driven feeding management practices and improved feeding performance. Conversely, a random approach to feeding may contribute to poor short-term and long-term clinical outcomes. We report a quality improvement project that was undertaken across five NICUs in an urban setting. our aim was to safely initiate and advance nipple feeding for very preterm neonates (born at <32 weeks gestation) who had a respiratory morbidity requiring nasal continuous positive airway pressure therapy. A novel algorithm entitled "eating in SINC: Safe individualized nipple-Feeding Competence" was developed. Safe individualized nipple-feeding competence involves the baby, the parents, and the health care team by using infant-driven strategies, common language, and developmentally appropriate goals while supporting fragile neonates to be skilled feeders.

Oral Alimentation in Neonatal and Adult Populations Requiring High-Flow Oxygen via Nasal Cannula

Use of high-flow oxygen via nasal cannula (HFO2-NC) is increasingly common in intensive care unit (ICU) settings. Despite the critical interface between respiration and swallowing, and the high acuity of patients in ICUs, the impact of HFO2-NC on feeding and swallowing is unknown. The present prospective, single-center, cohort study investigated the impact of HFO2-NC use on oral alimentation in neonatal and adult ICU patients. Oral alimentation status was evaluated in 100 consecutive ICU inpatients (50 neonatal and 50 adult) requiring HFO2-NC. Participant characteristics, respiratory support, successful initiation of oral feeding in neonates, and successful resumption of oral feeding in adults were recorded. Seventeen of 50 (34 %) neonates requiring HFO2-NC were deemed developmentally and medically appropriate by the neonatologist and nursing to begin oral alimentation. All 17 (100 %) were successful with initiation of oral feedings. Thirty-three of 50 (66 %) continued nil per os due to prematurity or medical conditions precluding oral alimentation at time of data collection. Thirty-nine of 50 (78 %) adults requiring HFO2-NC were deemed medically appropriate by the intensivist and nursing to resume oral alimentation (n = 34) or with a functional swallow without aspiration on FEES (n = 5). All 39 (100 %) resumed oral alimentation successfully. Eleven of 50 (22 %) continued nil per os due to severe respiratory issues precluding both swallow testing and oral alimentation at time of data collection. All developmentally and medically appropriate neonatal and adult patients requiring HFO2-NC were successful with either the introduction or resumption of oral alimentation. Patients requiring HFO2-NC who are identified as having feeding or swallowing issues should be referred for swallowing evaluations using the same criteria as patients who do not require HFO2-NC, as it is not the use of HFO2-NC but rather patient-specific determinants of feeding and swallowing readiness and their underlying medical conditions that impact readiness for oral alimentation status.

Effects of Moderate Hyperbilirubinemia on Nutritive Swallowing and Swallowing-Breathing Coordination in Preterm Lambs

BACKGROUND

Hyperbilirubinemia (HB) occurs in 90% of preterm newborns. HB induces acute neurological disorders (somnolence, abnormal tone, feeding difficulties, auditory dysfunction) and alterations in respiratory control. These findings suggest brainstem neurotoxicity that could also affect swallowing centers.

OBJECTIVE

To test the hypothesis that HB impairs nutritive swallowing (NS) and swallowing-breathing coordination.

METHODS

Two groups of preterm lambs (born 14 days prior to term), namely control (n = 6) and HB (n = 5), were studied. On day 5 of life (D0), moderate HB (150-250 µmol/l) was induced during 17 h in the HB group. Swallowing was assessed via recording of pharyngeal pressure and respiration by respiratory inductance plethysmography and pulse oximetry. The effect of HB on NS was assessed during standardized bottle-feeding. A second recording was performed 48 h after recovery from HB (D3).

RESULTS

Swallows were less frequent (p = 0.003) and of smaller volume (p = 0.01) in HB lambs while swallowing frequency was decreased (p = 0.004). These differences disappeared after HB normalization. Swallowing-breathing coordination was impaired in HB lambs, with a decrease in percent time with NS burst-related apneas/hypopneas at D0 and D3. Simultaneously, HB lambs tended to experience more severe desaturations (<80%) during bottle-feeding. Finally, following bottle-feeding, the respiratory rate was significantly lower, along with an increased apnea duration in HB lambs.

CONCLUSIONS

Swallowing and swallowing-breathing coordination are altered by acute moderate HB in preterm lambs. Decreased efficiency at bottle-feeding is accompanied by continuation of breathing during swallow bursts, which may promote lung aspiration.

Safety and Efficacy of Oral Feeding in Infants with BPD on Nasal CPAP

Safety and efficacy of oral feeding was examined in infants with bronchopulmonary dysplasia (BPD) on nasal continuous positive airway pressure (NCPAP). We hypothesized that repetitive oral feeding enhances aero-digestive outcomes and reduces resource utilization. Data from infants with BPD (37-42 weeks post menstrual age) that were orally fed while on NCPAP (n = 26) were compared with those that were exclusively gavage fed on NCPAP (n = 27). Subject assignment was random and physician practice based. Specifically, we compared the differences in aero-digestive milestones, resource utilization, and safety metrics. Demographic characteristics such as gender distribution, gestational age, and birth weight, clinical characteristics such as frequency of intraventricular hemorrhage and patent ductus arteriosus needing surgical ligation were similar in both groups (p > 0.05). Characteristics of respiratory support and airway milestones were similar in both groups (p > 0.05). However, infants in NCPAP-oral fed group had earlier acquisition of full oral feeding milestone by 17 days (median) versus infants who were not orally fed during NCPAP (p < 0.05). Discharge weights and the frequency of gastrostomy tube placement were also similar in both groups (p > 0.05). There were no tracheostomies in either group. There was no incidence of clinically significant aspiration pneumonia in infants during the period of the oral feeding while on NCPAP. Controlled introduction of oral feedings in infants with BPD during NCPAP is safe and may accelerate the acquisition of oral feeding milestones.

Nasal continuous positive airway pressure inhibits gastroesophageal reflux in newborn lambs

Background

Using esophageal pHmetry, nasal CPAP (nCPAP) has been shown to decrease acid gastroesophageal reflux (GER) in adult humans. Although both GER (mainly non-acid) and nCPAP use are very frequent in newborns, the effect of nCPAP on GER in early life is unknown. Having recently shown that the newborn lamb is a unique model for studying neonatal GER, our main objective was to assess the effect of nCPAP on GER in newborn lambs.

Methods

Eight newborn lambs, aged 2–3 days, were studied. Continuous esophageal pH-Impedance monitoring and polysomnography were performed for six hours during both spontaneous breathing and nCPAP application at 6 cmH₂O (nCPAP6), in a randomized order. Results were compared in the two experimental conditions, as well as without CPAP during the following 6 hours.

Results

i) nCPAP₆ virtually abolished GER [mean ±SD reflux number for 6 h = 9.1±8.6 without nCPAP₆ vs. 0.6±1 with nCPAP₆, P<0.05]; ii) GER number was also reduced during the 6 h-period following nCPAP6 application (18±16 without nCPAP₆ vs. 7±8.1 with nCPAP₆, P<0.05); iii) nCPAP₆ decreased the depth and duration of lower esophageal sphincter relaxation.

Conclusions

nCPAP inhibits GER in the newborn lamb. Further clinical studies using different levels of nasal CPAP are needed to confirm this result in human infants.

Effects of reflux laryngitis on non-nutritive swallowing in newborn lambs

Reflux laryngitis in infants may be involved not only in laryngeal disorders, but also in disorders of cardiorespiratory control through its impact on laryngeal function. Our objective was to study the effect of reflux laryngitis on non-nutritive swallowing (NNS) and NNS-breathing coordination. Two groups of six newborn lambs, randomized into laryngitis and control groups, were surgically instrumented for recording states of alertness, swallowing and cardiorespiratory variables without sedation. A mild to moderate reflux laryngitis was induced in lambs from the experimental group. A significant decrease in the number of NNS bursts and apneas was observed in the laryngitis group in active sleep (p=0.03). In addition, lower heart and respiratory rates, as well as prolonged apnea duration (p<0.0001) were observed. No physiologically significant alterations in NNS-breathing coordination were observed in the laryngitis group. We conclude that a mild to moderate reflux laryngitis alters NNS burst frequency and autonomous control of cardiac activity and respiration in lambs.

Absence of effect of nasal continuous positive airway pressure on the esophageal phase of nutritive swallowing in newborn lambs

OBJECTIVES

It is presently recommended that oral feeding be started in premature infants as soon as possible, often at an age at which nasal continuous positive airway pressure (nCPAP) is still required for ventilatory support. Our previous data showed that application of nCPAP up to 10 cmH2O in full-term lambs had no deleterious effect on cardiorespiratory safety, feeding efficiency, or on nutritive swallowing-breathing coordination. Besides fear of swallowing-breathing coordination disturbances, esophageal motility disruption by nCPAP could be a reason to delay oral feeding. To our knowledge, no study has focused on the effects of nCPAP on esophageal motility in the neonatal period. The aim of the present study was therefore to further assess the effects of nCPAP on oral feeding by assessing its effects on the esophageal phase of nutritive swallowing (nutritive esophagodeglutition).

METHODS

Six full-term lambs, ages 2 to 3 days, underwent esophageal multichannel intraluminal impedance-pH monitoring. Lambs were bottle-fed under 2 randomized conditions, namely spontaneous breathing and nCPAP 6 cmH(2)O.

RESULTS

Beyond confirmation of unaltered feeding efficiency, analysis of multiple variables measured by impedance monitoring revealed that nCPAP 6 does not alter nutritive esophagodeglutition in any way (nCPAP vs spontaneous breathing, P > 0.1 for all variables).

CONCLUSIONS

offering further support to neonatologists pleading for initiation of oral feeding in infants still on nCPAP, the present results set the foundations for similar clinical studies in preterm human infants to confirm the absence of effects of nCPAP on nutritive swallowing.

Effects of postnatal environmental tobacco smoke on non-nutritive swallowing-breathing coordination in newborn lambs

While prenatal environmental tobacco smoke (ETS) exposure is a well-known risk factor for sudden infant death syndrome, the effect of postnatal ETS exposure is less clear. The objective of this study was to investigate the effect of postnatal ETS exposure on non-nutritive swallowing (NNS) and NNS-breathing coordination, which are crucial to prevent aspiration related-cardiorespiratory events. Eighteen newborn lambs (6 per group) were randomly exposed to either 10 cigarettes/day, 20 cigarettes/day or room air for 15 days. Lambs were instrumented for recording states of alertness, swallowing, electrocardiogram and breathing; recordings were performed in non-sedated lambs at the end of ETS exposure. Urinary cotinine/creatinine ratio confirmed relevant real-life exposure. Postnatal ETS exposure had no effect on NNS frequency but tended to decrease inspiratory NNS (p=0.07) during quiet sleep. No effect on respiratory or heart rate (p>0.6), apnea index (p=0.2) or sleep states (p=0.3) was observed. In conclusion, postnatal ETS exposure in lambs had only mild effects on NNS-breathing coordination.

Effects of caffeine and/or nasal CPAP treatment on laryngeal chemoreflexes in preterm lambs

Current knowledge suggests that laryngeal chemoreflexes (LCR) are involved in the occurrence of certain neonatal apneas/bradycardias, especially in the preterm newborn. While caffeine and/or nasal continuous positive airway pressure (nCPAP) are the most frequent options used for treating apneas in preterm newborns, their effects on LCR-related apneas/bradycardias are virtually unknown. The aim of the present study was to test the hypothesis that caffeine and/or nCPAP decreases LCR-related cardiorespiratory inhibition in a preterm ovine model. Seven preterm lambs were born vaginally on gestational day 133 (normal gestation: 147 days) after intramuscular injections of betamethasone and mifepristone. Five days after birth, a chronic surgical instrumentation was performed to record states of alertness, electrocardiogram, systemic arterial pressure, and electromyographic activity of a laryngeal constrictor muscle, as well as to insert a transcutaneous supraglottal catheter. LCR were induced in quiet sleep under four conditions: 1) control (without caffeine or nCPAP); 2) nCPAP (5 cmH2O, without caffeine); 3) caffeine (10 mg/kg infused intravenously for 30 min, without nCPAP); and 4) nCPAP + caffeine. Our results showed that nCPAP consistently blunted LCR-related cardiorespiratory inhibition vs. control condition, contrary to caffeine whose overall effect was nonsignificant. In addition, nCPAP condition was characterized by a more consistent and rapid arousal after HCl injection. No significant differences were observed between all tested conditions with regard to swallowing and cough. It is concluded that nCPAP should be further assessed for its usefulness in treating neonatal apneas linked to LCR.