Coordination between respiration and deglutition in a preterm infant mammal, Sus scrofa

Preterm pigs for preterm birth research: reasonably feasible

Preterm birth will disrupt the pattern and course of organ development, which may result in morbidity and mortality of newborn infants. Large animal models are crucial resources for developing novel, credible, and effective treatments for preterm infants. This review summarizes the classification, definition, and prevalence of preterm birth, and analyzes the relationship between the predicted animal days and one human year in the most widely used animal models (mice, rats, rabbits, sheep, and pigs) for preterm birth studies. After that, the physiological characteristics of preterm pig models at different gestational ages are described in more detail, including birth weight, body temperature, brain development, cardiovascular system development, respiratory, digestive, and immune system development, kidney development, and blood constituents. Studies on postnatal development and adaptation of preterm pig models of different gestational ages will help to determine the physiological basis for survival and development of very preterm, middle preterm, and late preterm newborns, and will also aid in the study and accurate optimization of feeding conditions, diet- or drug-related interventions for preterm neonates. Finally, this review summarizes several accepted pediatric applications of preterm pig models in nutritional fortification, necrotizing enterocolitis, neonatal encephalopathy and hypothermia intervention, mechanical ventilation, and oxygen therapy for preterm infants.

Reduced Coordination of Hyolaryngeal Elevation and Bolus Movement in a Pig Model of Preterm Infant Swallowing

Preterm infants often have dysphagia. Because reducing lifetime cumulative exposure to radiation in the context of diagnosis and treatment is a continuing goal of all medical fields which use X-ray imaging, efforts exist to reduce reliance on the gold standard diagnostic tool for dysphagia, VFSS. Alternatives, such as video of external hyolaryngeal movement using video recordings of the anterior surface of the neck, must be evaluated and validated against videofluoroscopy, a task for which non-human animal models are appropriate. In this study, we tested the hypotheses that (1) swallows could be identified equally well from video of external hyolaryngeal movement and bolus movement in videofluoroscopy, and that (2) the two measures would be tightly temporally linked in both term and preterm infant pigs. We recorded 222 swallows in simultaneous and precisely synchronized high-speed videofluoroscopy and high-speed camera films of 4 preterm and 3 term infant pigs drinking milk from a bottle. In term pigs, the two measures consistently identified the same swallows in each image stream. However, in preterm pigs there was a high rate of false positives (~ 10% per feeding sequence) and false negatives (~ 27% per feeding sequence). The timing of hyolaryngeal elevation (external video) and bolus movement (videofluoroscopy) was correlated and consistent in terms pigs, but not in preterm pigs. Magnitude of hyolaryngeal elevation was less in preterm pig swallows than term pig swallows. Absence of epiglottal inversion in preterm pigs was not linked to variation in the timing of the two swallow events. Video of external hyolaryngeal movement, though a reliable swallow indicator in term infant pigs, was unreliable in preterm infant pigs. The coordination of swallowing events differs in preterm and term infant pigs. More research is needed into the distinctive biomechanics of preterm infant pigs.

Maturation of the Coordination Between Respiration and Deglutition with and Without Recurrent Laryngeal Nerve Lesion in an Animal Model

The timing of the occurrence of a swallow in a respiratory cycle is critical for safe swallowing, and changes with infant development. Infants with damage to the recurrent laryngeal nerve, which receives sensory information from the larynx and supplies the intrinsic muscles of the larynx, experience a significant incidence of dysphagia. Using our validated infant pig model, we determined the interaction between this nerve damage and the coordination between respiration and swallowing during postnatal development. We recorded 23 infant pigs at two ages (neonatal and older, pre-weaning) feeding on milk with barium using simultaneous high-speed videofluoroscopy and measurements of thoracic movement. With a complete linear model, we tested for changes with maturation, and whether these changes are the same in control and lesioned individuals. We found (1) the timing of swallowing and respiration coordination changes with maturation; (2) no overall effect of RLN lesion on the timing of coordination, but (3) a greater magnitude of maturational change occurs with RLN injury. We also determined that animals with no surgical intervention did not differ from animals that had surgery for marker placement and a sham procedure for nerve lesion. The coordination between respiration and swallowing changes in normal, intact individuals to provide increased airway protection prior to weaning. Further, in animals with an RLN lesion, the maturation process has a larger effect. Finally, these results suggest a high level of brainstem sensorimotor interactions with respect to these two functions.

Pre-pharyngeal Swallow Effects of Recurrent Laryngeal Nerve Lesion on Bolus Shape and Airway Protection in an Infant Pig Model

Recurrent laryngeal nerve (RLN) damage in infants leads to increased dysphagia and aspiration pneumonia. Recent work has shown that intraoral transport and swallow kinematics change following RLN lesion, suggesting potential changes in bolus formation prior to the swallow. In this study, we used geometric morphometrics to understand the effect of bolus shape on penetration and aspiration in infants with and without RLN lesion. We hypothesized (1) that geometric bolus properties are related to airway protection outcomes and (2) that in infants with RLN lesion, the relationship between geometric bolus properties and dysphagia is changed. In five infant pigs, dysphagia in 188 swallows was assessed using the Infant Mammalian Penetration-Aspiration Scale (IMPAS). Using images from high-speed VFSS, bolus shape, bolus area, and tongue outline were quantified digitally. Bolus shape was analyzed using elliptical Fourier analysis, and tongue outline using polynomial curve fitting. Despite large inter-individual differences, significant within individual effects of bolus shape and bolus area on airway protection exist. The relationship between penetration-aspiration score and both bolus area and shape changed post lesion. Tongue shape differed between pre- and post-lesion swallows, and between swallows with different IMPAS scores. Bolus shape and area affect airway protection outcomes. RLN lesion changes that relationship, indicating that proper bolus formation and control by the tongue require intact laryngeal sensation. The impact of RLN lesion on dysphagia is pervasive.