Pressure and Timing Differences Between Volitional and Non-Cued Saliva Swallows Measured with Pharyngeal High-Resolution Manometry

Abstract Volitional and spontaneous swallowing occur regularly throughout the day, yet most research has primarily focused on cued volitional swallowing. Differences in sensory input and degree of cortical involvement between swallow types may contribute to differences in swallowing physiology. Pharyngeal high-resolution manometry provides an opportunity to characterize both swallow types. Pressure generation and timing events during cued volitional (2 cc thin liquid) and non-cued saliva swallowing were evaluated in 50 healthy adults (n = 25 per sex). Paired t-tests revealed that on average, significantly greater pressures were generated during volitional swallows than non-cued saliva swallows in the velopharynx ( p < 0.0001), tongue base ( p = 0.045), and UES (post-closure) regions ( p = 0.0058), while no significant differences were noted in the hypopharynx ( p > 0.05). Positive linear relationships between swallow types were identified for velopharyngeal and tongue base pressures. Additionally, volitional swallows demonstrated longer UES relaxation durations than non-cued saliva swallows ( p = 0.0003). While C2-C4 size differed between males (larger) and females ( p < 0.0001), sex was not associated with any swallowing outcome measures. Overall, healthy adults generated higher pressures during volitional than non-cued saliva swallows in most pharyngeal regions, whereas the hypopharynx appeared less influenced by swallow type. Positive relationships between swallow types suggest that volitional assessments can serve as useful proxies for spontaneous function and may provide clinically relevant information when standard bolus swallows are difficult to obtain. The absence of sex effects supports uniform interpretation of manometric results across adults. These results underscore the importance of considering swallow type when evaluating swallowing physiology and designing clinical interventions.