Effects of bolus volume, viscosity, and repeated swallows in nonstroke subjects and stroke patients

This study examined the effects of bolus volume and viscosity and the variability of repeated swallows in ten stroke patients and ten age-matched nonstroke subjects. The ten stroke patients demonstrated single unilateral cortical (three subjects), subcortical (six subjects), or brainstem (one subject) infarcts on computed tomography or magnetic resonance imaging scans at three weeks post-ictus. All subjects underwent videofluoroscopic swallow studies in which seven temporal pharyngeal swallow measures were examined. Despite the dissimilarity in lesion locations, the swallow physiology in the stroke patients was relatively homogeneous, ie, no swallowing disorders severe enough to prevent oral intake. As bolus volume increased, pharyngeal delay time diminished in stroke patients, but not in nonstroke subjects. Increasing bolus volume affected three other pharyngeal swallow measures similarly in nonstroke and stroke subjects: laryngeal closure durations and cricopharyngeal (CP) opening durations increased and duration of tongue base contact to posterior pharyngeal wall decreased. On viscosity comparisons (liquid vs paste), both subject groups displayed longer duration of base of tongue contact to posterior pharyngeal wall. On paste swallows, nonstroke subjects had longer CP opening and lower swallow efficiency, whereas stroke patients did not. This study found no statistically significant learning/repetition effect for repeated swallows in either subject group, or both groups combined.