A method for simultaneous physiological and radiographic recordings from sleeping neonatal piglets

A healthy neonatal piglet model was developed to investigate the effects of simulated gastro-esophageal reflux (GER) on airway protective mechanisms in different sleep states. Piglets were chosen for the model because there are similarities in esophageal morphology, development of the cardiorespiratory system and sleep-wakefulness cycle between the piglet and the human infant. Unanesthetized piglets were instrumented and trained to sleep in a radiolucent, temperature-controlled box. Physiologic recordings of sleep (electroencephalogram, 'ear-o-gram', behavioral observations), cardiorespiratory function (end-tidal CO2, O2 saturation, heart rate, respiratory movements), swallowing (pharyngeal or esophageal pressures) and GER (signaled by a fall in esophageal pH) were displayed and stored on a computer. An image intensifier was used for radiographic observations. The outputs from the computer and image intensifier were synchronized and recorded on videotape. The method enabled simultaneous physiologic and radiographic observations to be made during the simulation of GER by the injection of normal NaCl, distilled water or HCl (pH 2 and 3) into either the pharynx or different sites in the esophagus. The piglet model appears to accurately reflect the normal physiologic responses of the healthy sleeping neonate.