title: Isolated pharyngeal swallow exists during normal human feeding.
abstract: Swallowing is one of the basic activities in humans. The pharynx functions as an airway and a food channel, and a pharyngeal swallow usually occurs after bolus transport from the oral cavity. However, direct fluid infusion through a catheter into the hypopharynx produces a pharyngeal swallow without the oral stage in experimental situations. The purpose of this study was to examine whether a pharyngeal swallow, which is not accompanied by bolus transport, can occur during normal human feeding. Fifty-three healthy volunteers (25-89 years) were recorded, via videofluoroscopic examination of swallowing, during 3 different swallowing trials: command swallow of 10 ml liquid barium, chew-swallow of corned beef, and chew-swallow of a mixture of corned beef and liquid barium. Subsequently each swallow was classified as being either a consecutive pharyngeal swallow (CPS), following transport, or an isolated pharyngeal swallow (IPS), without immediately prior transport. The location of the bolus at swallow initiation was also noted. Of 307 trials, 681 swallows were identified, which included 43 IPS and 638 CPS. IPS only occurred as the first swallow of a trial, but the frequency of IPS did not differ between 28 younger (< 60 years) and 25 older (≥ 60 years) people. Of the three food types, IPS occurred more frequently with the mixed food than with liquid. These results suggest that IPS may represent an airway protective mechanism. In conclusion, IPS occurs in normal swallowing during a daily eating situation. Swallowing is more complex than a simple reflex.
authors.affiliation: Department of Rehabilitation Medicine I, School of Medicine, Fujita Health University.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Kagaya
authors.forename: Michio
authors.initials: M
authors.lastname: Yokoyama
authors.forename: Eiichi
authors.initials: E
authors.lastname: Saitoh
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kanamori
authors.forename: Chiaki
authors.initials: C
authors.lastname: Susa
authors.forename: Rebecca Z
authors.initials: RZ
authors.lastname: German
authors.forename: Jeffrey B
authors.initials: JB
authors.lastname: Palmer
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D003679:Deglutition / Q000502:physiology*; D004435:Eating / Q000502:physiology*; D005260:Female; D005502:Food; D006801:Humans; D008297:Male; D008875:Middle Aged; D010614:Pharynx / Q000502:physiology*; D014741:Video Recording