Effects of age and viscosity on food transport and breathing–swallowing coordination during eating of two-phase food in nursing home residents

Aim: When eating food that contains both liquid and solid phases, the liquid component frequently enters the hypopharynx before swallowing and can increase the risk of aspiration. Thus, we examined whether the initial viscosity of mixed consistency food could alter pre-swallow food transport and breathing–swallowing coordination in older adults. Methods: Fiberoptic endoscopy was recorded while 18 healthy young adults and 19 older adults ate 5 g of steamed rice combined with 3 mL of blue-dye water. Liquid viscosity was set at three levels by the addition of a thickening agent (0 wt%, thin; 2 wt%, thicker; 4 wt%, higher-viscosity, respectively). We measured the timing of swallow initiation and its corresponding respiratory phase for each participant. Results: For thin mixed consistency food, whereas the timing of swallow initiation was comparable between young and older participants, swallowing was initiated during inspiration significantly more often in older participants (31.6 %) than in young participants (5.6 %). In contrast, the timing of swallow initiation was delayed in older participants for thicker and higher-viscosity foods, although swallowing was commonly initiated during expiration in both groups. Conclusions: In older adults, we observed that swallow initiation function was preserved for thin mixed consistency samples, but breathing–swallowing coupling was diminished. For higher-viscosity foods, swallow initiation was delayed in this group, but breathing–swallowing coordination was not disturbed, probably as a result of the slow bolus flow into the hypopharynx. Thus, it appears the initial viscosity of mixed consistency food profoundly affects food transport before swallowing as well as breathing–swallowing coordination in nursing home residents. Geriatr Gerontol Int 2017; 17: 2171–2177.