Cardiovascular responses to pacifier experience and feeding in newborn infants

Evaluation of Pulse Rate, Oxygen Saturation, and Respiratory Effort after Different Types of Feeding Methods in Preterm Newborns

BACKGROUND

During the initial days of hospitalization, preterm newborns are given combinations of breastfeeding, spoon/paladai feeding, and/or gavage feeding. Each method of feeding may have a different effect on vital parameters.

OBJECTIVE

To study changes in vital parameters in relation to different feeding methods and postmenstrual age (PMA) in preterm newborns. Study Design. This prospective observational study was carried out at a tertiary care neonatal unit. Participants. Physiologically stable preterm newborns with PMA less than 37 weeks on full enteral feeds were included in the study. Intervention. None. Outcomes. Respiratory rate (RR), pulse rate (PR), oxygen saturation (SPO2), nasal flaring, and lower chest indrawing were monitored before and up to 3 h after the breastfeeding/spoon (paladai) feeding/gavage feeding or their combinations. These vital parameters were assessed in relation to the feeding methods and PMA groups using ANOVA.

RESULTS

A total of 383 records were analyzed from 110 newborns. No infant developed chest indrawing or nasal flaring after any feeding method. During the 3 h period of monitoring, vital parameters changed significantly except in the gavage feeding group. The mean PR did not change, but the mean RR and SPO2 changed significantly at different PMA.

CONCLUSION

Vital parameters changed after different types of feeding methods and at different PMA. A further multicentric prospective study is needed to understand the effect of different feeding methods and PMA on vital parameters.

Neonatal Blood Pressure Standards: What Is "Normal"?

Blood pressure (BP) is routinely measured in newborn infants. Published BP nomograms demonstrate a rise in BP following delivery in healthy infants at all gestational ages (GA) and evidence that BP values are higher with increasing birth weight and GA. However, the complex physiology that occurs in newborn infants and range of BP values observed at all GA make it difficult to identify "normal" BP for a specific infant at a specific time under specific conditions. As such, complete hemodynamic assessment should include the physical examination, perinatal history, other vital signs, and laboratory values in addition to BP values.

Cardiovascular autonomic dysfunction in sudden infant death syndrome

A failure of cardiorespiratory control mechanisms, together with an impaired arousal response from sleep, are believed to play an important role in the final event of sudden infant death syndrome (SIDS). The 'triple risk model' describes SIDS as an event that results from the intersection of three overlapping factors: (1) a vulnerable infant, (2) a critical developmental period in homeostatic control and (3) an exogenous stressor. In an attempt to understand how the triple risk hypothesis is related to infant cardiorespiratory physiology, many researchers have examined how the known risk and protective factors for SIDS alter infant cardiovascular control during sleep. This review discusses the association between the three components of the triple risk hypothesis and major risk factors for SIDS, such as prone sleeping, maternal smoking, together with three "protective" factors, and cardiovascular control during sleep in infants, and discusses their potential involvement in SIDS.

Suck-Swallow-Breathe Dynamics in Breastfed Infants

Despite the importance of the suck-swallow-breathe reflex during breastfeeding, a large proportion of our understanding is derived from bottle-feeding studies. Given the differences in the delivery of milk during breast and bottle feeding, it is imperative that a more general view of the suck-swallow-breathe and milk removal process during breastfeeding is available. This systematic review aimed to assess the evidence for the mechanism of milk removal during breastfeeding; evaluate how the term infant coordinates sucking, swallowing, breathing (SSwB) and cardiorespiratory patterns; and how these patterns change with maturation during breastfeeding. A literature search of PubMed and MEDLINE was performed to assess the mechanism of milk removal and patterns of sucking, swallowing, breathing, and cardiorespiratory control during breastfeeding in healthy term infants. Seventeen studies were selected and a narrative synthesis was performed. Nine studies assessing the infant sucking mechanism consistently provided evidence that vacuum is essential to milk removal from the breast. The limited data on swallowing and breathing and cardiorespiratory control showed mixed results. Overall, results highlighted the high variability in breastfeeding studies and suggested that swallowing, breathing, and cardiorespiratory patterns change with maturation, and within a breastfeed. These findings show potential for devising breastfeeding interventions for populations at risk of SSwB problems. However, consistent methods and definitions of breastfeeding parameters are required before interventions can be adequately developed and tested.

A pilot study: the role of the autonomic nervous system in cardiorespiratory regulation in infant feeding

AIM

The purpose of this pilot study was to examine the interplay between the parasympathetic (PNS) and sympathetic nervous systems' (SNS) contributions to prefeeding, feeding and satiation in young, healthy infants.

METHOD

This prospective study was completed on eleven full-term infants, less than 6 months old. Respiratory rate, heart rate, heart rate variability (HRV), electrodermal activity and low-frequency/high-frequency heart rate variability ratio were sampled from the infant during prefeeding, feeding and satiation periods.

RESULTS

A repeated-measures ANOVA revealed a significant difference in respiratory patterning during the three feeding phases (p = .049); however, none of the other physiological measures reached significance. An emerging trend across physiological measures suggests that the feeding phase was influenced by the SNS with increasing respiratory rate, heart rate, low-frequency HRV, electrodermal activity and decreasing high-frequency HRV compared to the prefeeding and satiation phases, which were influenced predominantly by the PNS.

CONCLUSION

Respiration rate increased significantly during the feeding phase compared to prefeeding and postfeeding phases. Emerging trends indicate a pattern of alternating relative tone in PNS versus SNS across feeding phases - with SNS predominating the feeding phase. More clinical research examining the SNS and PNS contributions to feeding should be completed across patient populations.

Longitudinal changes in suck-swallow-breathe, oxygen saturation, and heart rate patterns in term breastfeeding infants

BACKGROUND

Despite the differences in breastfeeding and bottle-feeding, our understanding of how suck-swallow-breathe (SSwB), oxygenation, and heart rate patterns change as the infant ages is based predominantly on bottle-feeding studies. Therefore, this study aimed to measure how SSwB, oxygenation, and heart rate patterns changed during the first 4 months of lactation in term breastfeeding infants.

METHODS

Infants less than 1 month postpartum (n = 15) were monitored early in lactation and again later in lactation (2-4 months postpartum). Simultaneous recordings of vacuum, tongue movement, respiration, swallowing, oxygen saturation, and heart rate were made during both nutritive sucking and non-nutritive sucking during breastfeeding.

RESULTS

Infants transferred a similar amount of milk (P = .15) over a shorter duration later in lactation (P = .04). Compared to early lactation, suck bursts became longer (P < .001), pauses became shorter (P < .001), vacuum levels decreased (all P < .05), oxygen saturation increased (P < .001), and heart rate decreased (P < .001) later in lactation.

CONCLUSION

This study confirmed that term infants become more efficient at breastfeeding as they age, primarily by extending their suck bursts and pausing less. Although infants demonstrated satisfactory SSwB coordination during early lactation, they showed a level of adaption or conditioning at later lactation by applying weaker vacuum levels and demonstrating improved cardiorespiratory responses.

Autonomic nervous system function following prenatal opiate exposure

In utero exposure to opiates may affect autonomic functioning of the fetus and newborn. We investigated heart rate variability (HRV) as a measure of autonomic stability in prenatal opiate-exposed neonates (n = 14) and in control term infants (n = 10). Electrocardiographic data during both non-nutritive and nutritive sucking were evaluated for RR intervals, heart rate (HR), standard deviation of the consecutive RR intervals (SDRR), standard deviation of the differences of consecutive RR intervals (SDDRR), and the power spectral densities in low and high frequency bands. In controls, mean HR increased significantly, 143-161 per min (p = 0.002), with a trend toward a decrease in RR intervals from non-nutritive to nutritive sucking; these measures did not change significantly among exposed infants. Compared to controls, exposed infants demonstrated significantly greater HRV or greater mean SDRR and SDDRR during non-nutritive period (p < 0.01), greater mean SDDRR during nutritive sucking (p = 0.02), and higher powers in the low and high frequency bands during nutritive feedings. Our findings suggest that prenatal opiate exposure may be associated with changes in autonomic nervous system (ANS) functioning involving both sympathetic and parasympathetic branches. Future studies are needed to examine the effects of prenatal opiate exposure on ANS function.

Cardiovascular control during sleep in infants: Implications for Sudden Infant Death Syndrome

In infants the cardiorespiratory system undergoes significant functional maturation after birth and these changes are sleep-state dependent. Given the immaturity of these systems it is not surprising that infants are at risk of cardiorespiratory instability, especially during sleep. A failure of cardiovascular control mechanisms in particular is believed to play a role in the final event of Sudden Infant Death Syndrome (SIDS). The "triple risk model" describes SIDS as an event that results from the intersection of three overlapping factors: (1) a vulnerable infant, (2) a critical development period in homeostatic control, and (3) an exogenous stressor. This review summarises normal development of cardiovascular control during sleep in infants and describes the association of impaired cardiovascular control with the three overlapping factors proposed to be involved in SIDS pathogenesis.

Cardiorespiratory measures before and after feeding challenge in term infants are related to birth weight

AIM

This study tested the hypothesis that, within a few hours of delivery, cardiorespiratory measure taken during feeding provides markers of group differences related to birth weight. A secondary hypothesis was that high-frequency heart period variability would be related to underlying differences in autonomic control associated with birth weight.

METHODS AND SUBJECTS

One hundred four term infants in the lowest, middle, and highest birth weight quintiles were enrolled. Exclusion criteria were evidence of drug abuse, congenital anomalies, Apgar scores less than 7 or admission to the neonatal intensive care unit. Within 96 h of delivery, heart and respiratory rates, blood pressures and heart period variability were measured before, during and after feeding.

RESULTS

Term babies in the lowest quintile of birth weights have lower heart rates prior to feeding but greater increases in heart rate during the early postprandial period. Assessments of high-frequency heart period variability suggest that small term infants have greater parasympathetic tone before feeding and more sustained parasympathetic withdrawal following feeding.

CONCLUSION

Measurements of cardiorespiratory functions before and after feeding are related to birth weight and may provide markers that can help identify the most vulnerable of infants with small size at birth.

Effects of nutritive and non-nutritive sucking on infant heart rate variability during the first 6 months of life

The effects of eating on heart rate variability (HRV) differ between adults and newborns. This may reflect the impact of suckling on the overall psychophysiological and autonomic nervous system maturation. The purpose of the present study was to explore whether the reactions of HRV during feeding change towards the adult pattern during the first 6 months of life. In addition, the effects of non-nutritive and nutritive sucking on heart rate (HR) and HRV were compared. The participants were 23 infants on whom recordings were performed as newborns and at 6, 12 and 24 weeks old. Nutritive sucking caused an increase in HR and a decline in HRV. The results were consistent with previous reports of a decrease in high frequency components of HRV during feeding in newborns, reflecting a decrease in parasympathetic activity. This response was apparent in all four ages studied, and remained similar throughout the 6-month period. However, age as an independent factor seemed to influence both HR and HRV. Pacifier sucking had no significant effects on HRV at any age. The results demonstrate the physical strain that sucking imposes on the baby, with a specific autonomic nervous system response involved. We consider this response an essential part of the overall psychophysiological maturation of infants.

Blood pressure responses to feeding in infancy: spin-offs of serendipity

This article summarizes results from a program of research that has focused on understanding the characteristics of, and factors that shape, acute cardiovascular responses to feeding in infants. The work developed from behavioral observations in rats suggesting a linkage between variations in maternal behavior and adult blood pressure. However, the hypothesis that specific types of interactions, in particular those associated with feeding, might alter cardiovascular function was greatly influenced by a serendipitous observation made by Myron Hofer several years earlier. Myron discovered that nutrient availability is a key regulator of cardiovascular function in newborn rats. Our spin-off studies established that, in newborn rats and human infants, ingestion of nutrient is associated with robust increases in heart rate and blood pressure.

Pacifier use modifies infant's cardiac autonomic controls during sleep

OBJECTIVE

The risk for sudden infant death (SIDS) was postulated to decrease with the use of a pacifier and by conditions increasing parasympathetic tonus during sleep. We evaluated the influence of a pacifier on cardiac autonomic controls in healthy infants.

STUDY DESIGN

Thirty-four healthy infants were studied polygraphically during one night: 17 infants regularly used a pacifier during sleep and 17 never used a pacifier. Thumb users or occasional pacifier users were not included in the study. The infants were recorded at a median age of 10 weeks (range 6-18 weeks). Autonomic nervous system (ANS) was evaluated by spectral analysis of the heart rate (HR). The high frequency component of HR spectral analysis reflected parasympathetic tonus and the low frequency on high frequency ratio corresponded to the sympathovagal balance.

RESULTS

Most infants (63.6%) lost their pacifier within 30 min of falling asleep. Sucking periods were associated with increases in cardiac sympathovagal balance. During non-sucking periods, in both REM and NREM sleep, infants using a pacifier were characterized by lower sympathetic activity and higher parasympathetic tonus compared with non-pacifier users.

CONCLUSIONS

The use of pacifiers modifies cardiac autonomic controls during both sucking and non-sucking sleep periods. Non-nutritive sucking could regulate autonomic control in infants. These findings could be relevant to mechanisms implicated in the occurrence of sudden infant deaths during sleep.