Does What I Say Matter? The Influence of Verbal Instruction and Delivery Method on Bolus Size

Bolus manipulation, such as volume reduction, is a common treatment strategy for managing dysphagia and reducing aspiration risk. However, limited evidence exists regarding the effects of specific verbal instructions on reducing bolus size. This prospective, randomized, repeated measure study aimed to establish reference points for bolus size based on different instructions (i.e., take a drink; take a comfortable sip; take a small sip; take a small sip like it is hot coffee), cup size (4-oz size cup vs. 8-oz size cup) and delivery methods (straw vs. cup) using room temperature water. This study hypothesized there would be differences observed in bolus size consumed based upon the verbal instruction, cup size, and delivery method. A total of 100 participants, including 50 healthy controls and 50 patients, participated in this study, consuming 8 boluses each for a total of 800 boluses. Statistical analysis revealed significant differences in volume consumed among the four instructions (F = 191.578, p ≥ .0001). Participants consumed the largest volumes following the instruction "take a drink" (mean bolus size 27.88 mL; SD = 17.58) and the smallest volumes following the instruction "take a small sip like it is hot coffee" (mean bolus size 5.57 mL, SD = 4.72). The results provide evidence to support that specific verbal instruction influences bolus size. It is crucial for the dysphagia rehabilitation team to understand the potential impact of verbal instruction and cueing on bolus size to facilitate a safe swallow.