Fig. 1

Schematic diagram showing the method of pharyngeal stimulation used in this study, which illustrates the balloon position before (a) and during (b) stimulation. a Original position of the balloon. The balloon inserted from the mouth was placed in the oral cavity approximately 3 cm caudal from the rostral end of the mandible. b Balloon position during pharyngeal stimulation. The balloon was pushed, manually via the catheter connected, into the pharyngeal cavity to apply a mechanical stimulation of the pharyngeal areas, including the epiglottis