In patients with dysphagia, it has been a practice to thicken fluid food to prevent aspiration—the transport of a bolus into the trachea instead of the oesophagus. In these patients, aspiration is a risk behaviour and is closely related to pneumonia (caused by the aspiration of oral bacteria into the lungs). Since excessive thickening of fluids can cause adverse effects, such as lowering the palatability of food, subsequent reduction of liquid intake, dehydration and malnutrition, identifying the optimum thickening level is vital. Thickening might not only increase fluid viscosity, but could also modify its cohesiveness, which is another key factor affecting aspiration. Even though cohesiveness is more of a concept than a well-defined measurable parameter, this property describes the degree of coherency provided by the internal structure of a material against its fractional breakup. In fluids, this concept is less explored than in solids, powders and granules, and during the last decade few scientists have tackled this topic. Although the role of cohesiveness in the swallowing of heterogeneous solid foods is briefly overviewed, the aim of the present paper is to introduce the concept of cohesiveness for a relatively homogeneous fluid bolus and its effect on swallowing. Cohesiveness is highly correlated with the extensibility and yield stress of the fluid, suggesting that a high cohesiveness could have an important role in preventing aspiration.

对于吞咽困难的患者，一种做法是使液体食物变稠以防止误吸——将食团输送到气管而不是食道。在这些患者中，误吸是一种危险行为，与肺炎（由口腔细菌误吸至肺部引起）密切相关。由于液体过度稠化会导致不利影响，例如降低食物的适口性、随后减少液体摄入量、脱水和营养不良，因此确定最佳稠化水平至关重要。增稠不仅可能增加液体粘度，还可能改变其内聚性，这是影响抽吸的另一个关键因素。尽管内聚性更多地是一个概念而不是明确定义的可测量参数，但该属性描述了材料内部结构针对其分数破裂提供的内聚程度。在流体中，这个概念比在固体、粉末和颗粒中更少被探索，并且在过去十年中，很少有科学家解决这个话题。尽管简要概述了粘性在异质固体食物吞咽中的作用，但本文的目的是介绍相对均匀的液体丸的粘性概念及其对吞咽的影响。内聚性与流体的延伸性和屈服应力高度相关，这表明高内聚性可能在防止误吸方面发挥重要作用。