Newborn Lamb as a New Model for Studying Gastroesophageal Reflux

Abstract

We aimed to determine whether the newborn lamb at term is a valid model for studying gastroesophageal reflux. Seven bottle-fed lambs, ages 2 to 3 days, underwent esophageal multichannel intraluminal impedance-pH monitoring (MII-pH). A total of 196 reflux episodes were recorded, including 73% alkaline and 27% weakly acidic. No acid refluxes were observed. Median bolus clearance time was 4 seconds (3; 5.5), and proximal reflux extent was 35% (26). This first report of MII-pH in the newborn mammal sets the foundations for future studies with physiological and clinical relevance to human neonates.

Nasal Continuous Positive Airway Pressure Inhibits Gastroesophageal Reflux in Newborn Lambs

“…In addition, two studies have shown a similar effect of nCPAP on acid GER in healthy adults using esophageal manometry and/or pH monitoring [5], [11]. The availability of our unique ovine neonatal model for the study of GER and esophagodeglutition [7], [8] allows for the first time to provide data in the neonatal period. The present study clearly shows that the inhibiting effect of nCPAP on GER is also present in early life and in the absence of esophageal disease.…”

“…Anatomical differences with regard to the extent of striated muscle along the esophagus (upper third only in humans vs. entire esophagus in the sheep) are manifest [32]. However, there are clear similarities between the two species, including i) a well-established LES, ii) the fact that the preruminant lamb is monogastric in the first week of life [33] and iii) the presence of spontaneous GER, with characteristics close to human infants [8]. While our study was only limited to a few hours, similar results in adult humans with OSA suggest that the effect can persist for at least one week [17].…”

“…The MII-pH catheter (diameter  = 2 mm, Unisensor, Portsmouth, USA) was inserted trans-nasally and its position confirmed by X-ray [8]. External lamb instrumentation included i) an electrocardiogram for monitoring heart rate; ii) a pulse oximeter probe (Masimo Radical, Irvine, CA) attached at the base of the tail for monitoring oxygen hemoglobin saturation; iii) thoracic and abdominal bands of respiratory inductive plethysmography for monitoring of respiratory rate.…”

“…In addition, we have established the newborn lamb as a unique model to study neonatal GER [8]. In keeping with our research program on nCPAP and gastroesophageal function in the neonatal period, the aim of the present study was to test the hypothesis that nCPAP decreases GER number in our neonatal ovine model, using Multichannel Intraluminal Impedance-pH monitoring (MII-pH).…”

Inhibitory Effect of Nasal Intermittent Positive Pressure Ventilation on Gastroesophageal Reflux

“…Over the past ten years, we have been able to gain unique and extensive expertise in non-invasive ventilatory support in lambs [ 8 , 9 , 11 , 19 , 20 ]. Our team has also been pioneer in GER recordings in a newborn animal model in which GERs can be readily characterized using MII-pH in non-sedated conditions [ 21 ]. The preruminant, monogastric newborn lamb has well-established upper and lower esophageal sphincters ([ 6 ] and unpublished observations) and presents spontaneous GERs, which bear several features similar to those of the human infant [ 21 ].…”