Introduction Anecdotal clinical evidence supports the use of carbonated liquids in reducing the likelihood of aspiration in dysphagic patients (Bulow et al. Acta Radiol 2003; Sdravou et al. Dysphagia 2011). Repetitive transcranial magnetic stimulation (rTMS) delivered at 1-Hz can induce transient focal suppression of pharyngeal motor cortex (Mistry S, et al. J Physiol 2007). Here we investigated whether swallowing of carbonated water can reverse the inhibitory effects of a virtual lesion to pharyngeal motor cortex, compared to still water and saliva swallowing.
Methods In 14 healthy subjects (7 male, mean age 34±15 (SD)) pharyngeal electromyographic responses were recorded using an intraluminal catheter after the application of Transcranial Magnetic Stimulation (TMS) over pharyngeal motor cortex, as a measure of cortico-bulbar excitability. On three randomised visits, subjects were cued by a visual feedback software to perform a total of 40 swallows over 10 min (swallows every 15 s) of either carbonated water or still water vs 10 min of saliva swallowing ad libitum (control), before and after an unilateral 1-Hz virtual lesion of the pharyngeal motor cortex. Cortical excitability (presented as mean±SEM) was then reassessed bilaterally for 60 min post-interventions and analysed with repeated measures ANOVA (SPSS V.14).
Results A three-way ANOVA showed a significant interaction of Hemisphere × Intervention × Time [F(1,13)=5.82, p=0.03]. Compared to saliva swallowing (control), there was significant increase in cortical excitability bilaterally following swallowing of carbonated water (lesioned pharyngeal motor cortex [F(1,13)=7.5, p=0.017], with a maximum increase of 81±38% at 30 min post intervention (Abstract PWE-057 figure 1A); unlesioned [F(1,13)=4.75, p=0.04], with a maximum of 46±16%, immediately post intervention, Abstract PWE-057 figure 1B), not seen with still water swallowing.
Conclusion Carbonation reverses the effects of a unilateral virtual lesion with significant increases in cortical excitability not limited to the lesioned hemisphere. These data support the notion that chemesthetic stimuli of carbonation may provide the required peripheral sensory information that can influence brain swallowing activity compared to still water swallowing. These data provides the platform for considering the use of carbonation as facilitating stimuli in dysphagic patients who aspirate thin liquids.
Competing interests None declared.
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