The Influence of Surface Electromyography Visual and Clinician Verbal Feedback on Swallow Effort Ratio at Different Bolus Volumes in a Healthy Population

Abstract

Background/aims: The effortful swallow is a common treatment intervention requiring increased intensity to facilitate adaptations and modify swallow kinematics. The type of feedback and bolus volume provided may influence the intensity of the effortful swallow. To determine the increased effortful swallow intensity, a clinician can collect the peak amplitude of an effortful swallow and a typical swallow and compute a "swallow effort ratio" (SER). Dividing the effortful swallow surface electromyography (sEMG) peak amplitude by the typical swallow sEMG peak amplitude derives the SER. A higher SER suggests increased intensity. An increase in the SER may have clinical relevance in swallowing therapy as a threshold of intensity is required to elicit neuroplastic change. The purpose of this investigation was to determine whether sEMG visual and clinician verbal feedback increases the SER. Additionally, the investigation examined whether the SER is influenced by different liquid bolus volumes.

Methods: Eighty-two nondysphagic, healthy adults were assigned at random to 2 groups. One group received no feedback, and the other received verbal and visual feedback while performing typical and effortful swallows at 3 liquid volumes.

Results: An analysis of covariance compared the typical and effortful peak swallow amplitudes among 3 volumes in the 2 feedback groups. There was a significant effect on the peak amplitude values by feedback group F(2, 79) = 22.82, p < 0.001. There were no differences in peak amplitude by volume regardless of feedback F(2, 78) = 0.413, p = 0.663.

Conclusion: It appears that sEMG visual and clinician verbal feedback increases the SER, which may be a surrogate for intensity. An increased SER may have a positive effect on swallow intervention as intensity is known to influence outcomes of exercise and elicit neuroplastic change.

Keywords: Biofeedback; Effortful swallow; Swallow effort ratio; Swallowing.