QUANTIFICATION OF PRETERM INFANT FEEDING COORDINATION: AN ALGORITHMIC APPROACH

Oral feeding competency is a primary requirement for preterm infant hospital release. Currently there is no widely accepted method to objectively measure oral feeding. Feeding consists primarily of the integration of three individual feeding events: sucking, breathing, and swallowing, and the objective of feeding coordination is to minimize aspiration. The purpose of this work was to quantify the infant feeding process from signals obtained during bottle feeding and ultimately develop a measure of feeding coordination. Sucking was measured using a pressure transducer embedded within a modified silicone bottle block. Breathing was measured using a thermistor embedded within nasal cannula, and swallowing was measured through the use of several different piezoelectric sensors. In addition to feeding signals, electrocardiogram (ECG) signals were obtained as an indicator of overall infant behavioral state during feeding. Event detection algorithms for the individual feeding signals were developed and validated, then used for the development of a measurement of feeding coordination. The final suck event detection algorithm was the result of an iterative process that depended on the validity of the signal model. As the model adapted to better represent the data, the accuracy and specificity of the algorithm improved. For the breath signal, however, the primary barrier to effective event detection was significant baseline drift. The frequency components of the baseline drift overlapped significantly with the breath event frequency components, so a time domain solution was developed. Several methods were tested, and it was found that the acceleration vector of the signal provided the most robust representation of the underlying breath signal while minimizing baseline drift. Swallow signal event detection was not possible due to a lack of available data resulting from problems with the consistency of the obtained signal. A robust method was developed for the batch processing of heart rate variability analysis. Finally a method of coordination analysis was developed based on the event detection algorithm outputs. Coordination was measured by determining the percentage of feeding time that consisted of overlapping suck and breath activity

Coordination of airway protective behaviors and swallow: effects of afferent feedback and sex.

This dissertation represents a series of studies describing mechanisms related to breathing, upper airway behaviors and their coordination in man and animal. Chapter two transformed the cough swallow aspiration protocol from the cat (previous work) to the human introducing a new strategy, volume targeting, in swallow breathing coordination. Chapter three evaluated swallow breathing coordination at increasing altitudes. As respiratory drive altered due to hypoxia and hypocapnia, swallow breathing coordination shifted toward inspiration occurring during the transition from inspiration and expiration. The collection of the two previous studies led to development of an animal model to evaluate volume targeting and mechanisms involved in this strategy. Chapter four highlights presence of vagal spinal feedback on breathing characteristics and chapter five the same for swallow behavior and swallow breathing coordination. Chapter four and five also introduce sex differences in breathing and swallow breathing coordination when vagal and spinal balance is perturbed. In conclusion, this work has furthered the knowledge of swallow breathing coordination and suggested mechanisms responsible for these behaviors. Describing basic swallow parameters in human could lead to potential detection of pathologic changes in the upper airway as well as further the understanding of pulmonary complications such as aspiration pneumonia. The influence of the thoracic cavity spinal feedback could lead to new therapeutic techniques for breathing, swallow and their coordination in spinal cord injured patients

Airway protection and coordination of breathing and swallowing : in health and anesthesia

Swallowing and breathing is coordinated to ensure that the airway is protected from aspiration. During the pharyngeal phase of swallowing, breathing is interrupted to allow safe passage of bolus. However, details on the complex coordination of breathing and swallowing and their precise temporal relationship are not fully understood. Respiratory complications are common in the postoperative period and drugs used in anesthesia impair pharyngeal function and airway protection in young adults. The aims of this thesis were first to characterize key mechanisms for airway protection, i.e. pharyngeal function and coordination of breathing and swallowing and secondly to describe the impact of age and drugs used in anesthesia. A newly developed airflow discriminator was validated by comparisons with spirometry, diaphragmal and abdominal EMG and integrated with pharyngeal manometry and videoradiography into a multimodal platform recording swallowing and breathing simultaneously with high temporal resolution. Normal coordination of breathing and swallowing was studied in young volunteers, while swallowing different bolus types, changing body position and during hypercapnia. Moreover, effects of morphine and midazolam were studied at two occasions during spontaneous decay of drug concentration. Effects of partial neuromuscular block were examined during rocuronium infusion in elderly volunteers (>65 years) at steady state adductor pollicis train-of-four ratios of 0.70, 0.80 and >0.90. The airflow discriminator proved highly reliable and provided detailed information on timing of respiratory airflow unambiguously in relation to pharyngeal and diaphragmatic activity. The diaphragm was activated in the apneic period during swallowing, presumably a mechanism for preserving respiratory volume and to promote expiratory airflow after swallowing. This finding has to our knowledge not been described in humans before. Coordination between breathing and swallowing remained mostly unchanged regardless of age, body position, bolus characteristics, respiratory drive or partial neuromuscular block. In contrast, morphine and midazolam dys-coordinated breathing and swallowing, increasing the incidence of inspiration immediately after swallowing. Moreover, clinically relevant doses of morphine and midazolam caused pharyngeal dysfunction and impaired airway protection in young adults. Partial neuromuscular block profoundly aggravated age-dependent pharyngeal dysfunction by predominantly impairing mechanical properties of the pharynx. In conclusion, swallowing occurs during expiration in young and elderly individuals and drugs used in anesthesia cause pharyngeal dysfunction and dys-coordination of breathing and swallowing, ultimately compromising the protection of the airway against aspiration

Training Clinical Judgment Skills for Interpreting Feeding Behavior in Preterm Infants: A Comparison of Video and In Vivo Simulation

Health and feeding outcomes for preterm infants depend upon healthcare providers’ ability to recognize non-verbal signs of distress during bottle-feeding. Methods of training future providers’ to interpret feeding behavior in preterm infants are unclear. This study used a pre-test/post-test design to compare the effects of in- vivo simulation and video-simulation training on students’ knowledge of feeding abnormalities, clinical judgment, and documentation accuracy. Fifty-two graduate level speech-language pathology students were assigned to the in-vivo (N= 27) or video-simulation (N= 25) group. Results revealed that both methods proved beneficial for increasing knowledge and clinical judgment skills. Participants trained using video-simulation training documented a greater number of distress signs. The use of patient simulators to train graduate level speech-language pathology students to use correct clinical judgment for managing abnormal feeding behavior is efficacious

Autonomic control in preterm infants - what we can learn from mathematical descriptions of vital signs

Background: Preterm birth is a major burden, affecting approximately 15 million infants each year. Recent advances in reproductive medicine increases that number even more. The population of preterm infants in particular suffers from autonomic dysregulation that manifests as temperature instability and poor control of heart rate and breathing. Thermal care, monitoring of vital signs in a neonatal intensive care unit, pharmacotherapy, and respiratory support over weeks to months is necessary. Improvements in neonatal care in the past years lead to a decrease in mortality, especially in very preterm infants. However, former preterm infants still are a high-risk population for acute and chronic sequelae as a result of the interruption of the physiological development. A better understanding of the pathophysiology of the autonomic dysregulation in that population would be very useful. Unfortunately, accurate diagnostic tools that objectively assess and quantify the immature autonomic control in neonates are lacking. Methods: In this PhD thesis we examined different effects of the immature autonomic control in very preterm infants under clinically relevant conditions. We conducted a prospective single center observational study, where we assessed fluctuations in body temperature, sleep behavior, and heart rate variability in very preterm infants. We described the different regulatory systems using distinct mathematical expressions, such as detrended fluctuation analysis and sample entropy. We assessed associations between these outcome parameters and relevant factors of the infant’s history, such as demographic parameters and co-morbidities. Besides that, we analyzed lung function measurements of preterm infants and healthy term controls at a comparable postconceptional age, to describe respiratory control. Results: This study is systematically assessing different physiological signals of autonomic dysregulation in preterm infants during their first days of life. We found associations between parameters describing the complexity of time series analysis and maturity or relevant co-morbidities of the infants. In the analysis of heart rate variability we even found that parameters derived from time series analysis, assessed during the infants first days of life, improve our ability to predict future evolution of the infants’ autonomic stability. Lastly, several weeks after the expected due date, tidal breathing pattern of preterm infants showed a different reaction in response to a sigh when compared to term born controls at equivalent postmenstrual age indicating that autonomic dysregulation in preterm infants is still present well beyond the expected due date. Conclusion: A better understanding about the resolution of autonomic dysregulation in this population is not only important for the infant and its family but has the potential to support resource allocation and identification of patients with elevated risk for future deterioration. We thus think that the insights about the immature autonomic control in preterm infants, gained through this PhD work, are of substantial scientific and clinical relevance

Effect of Laser-Cut Slow-Flow Nipples on Preterm Feeding Performance

Background: Dysphagia of prematurity is a highly prevalent condition that carries negative developmental, social, and financial implications. Although the modification of bottle nipple properties is a widely used treatment for dysphagia of prematurity, there have been a paucity of investigations examining the effect of this intervention on refined measures of feeding performance. Methods: Healthy preterm infants were evaluated for measures of milk ingestion and respiratory performance during oral intake on a laser-cut slow-flow and standard-flow nipple. Time to achieve hospital discharge milestones was recorded. Results: Few differences were observed in feeding performance between slow-flow and standard-flow nipples. Characteristics of respiration during oral intake and at rest were correlated with time to hospital discharge. Conclusions: Slow-flow nipples may reduce the need for skilled feeders that are able to adapt feeding method based on infant feeding performance; when broadly applied to all infants by skilled feeders the clinical benefits are in question

Supporting Public Health Nurses with Breastfeeding Interventions for Late Preterm Infants

Late preterm infants often experience feeding difficulty post discharge from hospital. While breast milk is especially important for late preterm infants, they have lower exclusive breastfeeding rates than full term infants. This is because mothers of late preterm infants often do not receive sufficient amount of breastfeeding support in the postpartum period. Furthermore, in the Canadian context, guidelines do not exist for health care providers to use to assist them in providing breastfeeding support for mothers of late preterm infants in the community setting. We used a modified Delphi approach to begin to fill this gap. We present information relating to physiological development in systems, its significance to feeding, and potential interventions for public health nurses. This information will assist PHNs in their clinical reasoning and decision-making when supporting mothers and their LPIs to exclusively breastfeed in the community

Oxygen Saturation and Suck-Swallow-Breathe Coordination of Term Infants during Breastfeeding and Feeding from a Teat Releasing Milk Only with Vacuum

Background. Vacuum is an important factor in milk removal from the breast, yet compression is the predominant component of milk removal from bottle teats. Since bottle-feeding infants have lower oxygen saturation, vacuum levels, and different suck-swallow-breathe (SSwB) coordination to breastfeeding infants, we hypothesised that when infants fed from a teat that required a vacuum threshold of −29 mmHg for milk removal, that oxygen saturation, heart rate, and suck-swallow-breathe (SSwB) patterns would be similar to those of breastfeeding. Study Design. Infants (=16) were monitored during one breastfeed and one feed from the experimental teat. Simultaneous recordings were made of oxygen saturation, heart rate, vacuum, tongue movement, respiration, and swallowing. Results. There were no differences in oxygen saturation and heart rate between the breast and the teat. Infants displayed fewer sucks and breaths per swallow during nutritive sucking (NS) compared to non-nutritive sucking (NNS). The number of sucks per breath was similar for NS and NNS although respiratory rates were slower during NS. These patterns did not differ between the breast and the teat. Conclusion. These results suggest that vacuum may be conducive to safe and coordinated milk removal by the infant during both breast and bottle-feeding

Mechanisms of Respiratory-Swallow Coordination and the Effects of Skill Training on Swallowing Rehabilitation in Parkinson’s Disease

Respiratory-swallow coordination (RSC) is critical for safe and efficient swallowing. In healthy adults, RSC is most frequently characterized by an exhale-swallow-exhale pattern initiated within the mid-lung volume range with a respiratory pause of approximately one second. This combination in RSC behaviors is thought to be most optimal for swallowing-related bolus clearance and airway protection. Deviations from these RSC behaviors are observed at disproportionately higher rates in people with Parkinson’s disease (PD) when compared to non-dysphagic, healthy adults. However, little is known about which variables influence RSC in PD, if the RSC behaviors that are most optimal for swallowing in healthy adults are also most optimal for swallowing in PD, and if respiratory-swallow training can be used to successfully rehabilitate suboptimal RSC, swallowing safety, and swallowing efficiency in PD. This dissertation document includes a series of four studies that address these important clinical research questions. Chapter 1 will begin by reviewing the current body of literature as it relates to dysphagia in PD, RSC in healthy adults and PD, respiratory-swallow training as a skill-based treatment for dysphagia rehabilitation, and motor learning considerations for respiratory-swallow skill training in PD. Chapter 2 will be used to examine the relationships among RSC with patient- and swallowing-specific factors in PD. Chapter 2 will also be used to assess the influence of RSC behaviors on measures of swallowing safety (penetration-aspiration) and swallowing efficiency (pharyngeal residue) in PD. Chapter 3 will then evaluate the effects of verbal cueing on RSC in PD as a method of determining if RSC is stimulable for rehabilitative change. Chapter 4 will explore the effects of respiratory-swallow training on swallowing safety and efficiency rehabilitation in a person with mid-stage PD and severe dysphagia within the context of a single-subject experimental design. Chapter 5 will then examine the effects of respiratory-swallow training on dysphagia and RSC rehabilitation within the context of a cohort study. Chapter 5 will also be used to compare the effects of constant versus variable practice in order to explore how principles of motor learning can be used to enhance respiratory-swallow training outcomes. This document will then conclude by synthesizing the results from Chapters 2-5 and by discussing directions for future research