Tohoku J. Exp. Med., 2015 May, 236(1)

Isolated Pharyngeal Swallow Exists during Normal Human Feeding

HITOSHI KAGAYA,¹ MICHIO YOKOYAMA,¹ EIICHI SAITOH,¹ DAISUKE KANAMORI,¹ CHIAKI SUSA,¹ REBECCA Z. GERMAN² and JEFFREY B. PALMER³

¹Department of Rehabilitation Medicine I, School of Medicine, Fujita Health University, Toyoake, Aichi, Japan
²Department of Physical Medicine and Rehabilitation, Johns Hopkins University, Baltimore, MD, USA
³Department of Otolaryngology, Head and Neck Surgery, and Center for Functional Anatomy and Evolution, Johns Hopkins University, Baltimore, MD, USA

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.

keywords —— consecutive pharyngeal swallow; deglutition; isolated pharyngeal swallow; model; videofluoroscopic examination of swallowing

© 2015 Tohoku University Medical Press

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Tohoku J. Exp. Med., 2015, 236, 39-43

Correspondence: Hitoshi Kagaya, M.D., DMSc, Department of Rehabilitation Medicine I, School of Medicine, Fujita Health University, 1-98 Dengakugakubo, Kutsukake, Toyoake, Aichi 470-1192, Japan.

e-mail: hkagaya2@fujita-hu.ac.jp