Viscosity and volume of bolus. Standard practice consists in modifying the consistency of food and liquids administered to patients with dysphagia, based on the findings of the clinical exploration and/or videofluoroscopy. In general, foods with greater consistency prevent aspiration, while thin liquids favour it.
Several studies have described changes in swallowing physiology using liquid thickening agents. As the viscosity of the bolus increases, it moves more slowly in response to the effect of compression and gravity. Therefore, the more viscous the bolus, the less motor agility: the bolus does not deform so easily and is less likely to pass into the airway in case of airway closure impairment. In terms of bolus volume, a smaller size is safer and is less likely to be aspirated in the case of laryngeal incompetence.
The aim of these manoeuvres is to modify pharyngeal dimensions and redirect the flow of the bolus. One of the most important of these is the cervical flexion manoeuvre. This consists of swallowing in a chin tuck position, thereby enabling airway closure during swallowing and reducing the risk of aspiration. In a study conducted by our unit we found that this prevents aspiration in 50% of patients.
Techniques for increasing sensory feedback
The aim of these techniques is to increase sensation and alert the central nervous system prior to swallowing. They are indicated in swallowing apraxia, delayed onset of the oral phase, sensory deficit and delayed triggering of the swallowing reflex. They include tactile stimulation, by pressing a spoon against the tongue, or gustatory stimulation (acidic taste) and thermal (cold) stimulation. The size, viscosity and texture of the bolus may also provide additional tactile feedback.