Surface Electromyographic Biofeedback and the Effortful Swallow Exercise for Stroke-Related Dysphagia and in Healthy Ageing

Dysphagia https://doi.org/10.1007/s00455-020-10129-8 ORIGINAL ARTICLE Surface Electromyographic Biofeedback and the Effortful Swallow Exercise for Stroke‑Related Dysphagia and in Healthy Ageing Sally K. Archer1,2,3 · Christina H. Smith4 · Di J. Newham1 Received: 15 November 2019 / Accepted: 5 May 2020 © The Author(s) 2020 Abstract Dysphagia is common after stroke, leading to adverse outcome. The Effortful Swallow (ES) is recommended to improve swallowing but it is not known if dysphagic patients can increase muscle activity during the exercise or if age affects performance. Providing surface electromyographic (sEMG) biofeedback during dysphagia therapy may enhance exercise completion, but this has not been investigated and the technique’s acceptability to patients is not known. Aims: To determine if age or post-stroke dysphagia affect the ability to increase submental muscle activity during the ES, if sEMG biofeedback improves ES performance and if sEMG is an acceptable addition to therapy. In a Phase I study submental sEMG amplitudes were measured from 15 people with dysphagia < 3 months post-stroke and 85 healthy participants aged 18–89 years during swallowing (NS) and when they performed the ES with and without sEMG biofeedback. Participant feedback was collected via questionnaire. Measurements were compared with repeated measures ANOVA and age effects were examined with linear regression. Both groups produced significantly greater muscle activity for the ES than NS (p < 0.001) and significantly increased activity with biofeedback (p < 0.001) with no effect of age. Participant feedback about sEMG was very positive; over 98% would be happy to use it regularly. The ES is a physiologically beneficial dysphagia exercise, increasing muscle activity during swallowing. sEMG biofeedback further enhances performance and is considered an acceptable technique by patients. These findings support the potential application of sEMG biofeedback and the ES in dysphagia therapy in stroke, justifying further investigation of patient outcome. Keywords Dysphagia · Deglutition · Deglutition disorders · Speech and language therapy · Biofeedback · Surface electromyography · Effortful swallow · Stroke Introduction Oropharyngeal dysphagia, or difficulty with swallowing, affects around 50% of acute stroke patients [1], is associated with an 11-fold increase in the risk of pneumonia [2], * Sally K. Archer 1 Centre of Human and Aerospace Physiological Sciences, King’s College London, London, UK 2 Speech and Language Therapy Department, Guy’s and St Thomas’ NHS Foundation Trust, Westminster Bridge Road, London SE1 7EH, UK 3 NIHR Biomedical Research Centre at Guy’s and St Thomas’ NHS Foundation Trust and King’s College London, London, UK 4 Division of Psychology and Language Sciences, University College London, London, UK is an independent predictor of mortality and is associated with poor nutrition, dehydration, increased length of stay, institutionalisation and poor quality of life [3–6]. Speech and language therapists (SLTs) recommend behavioural therapy techniques for dysphagia in which patients work to gain volitional control of previously automatic movements with the aim of restoring swallowing ability, airway protection and quality of life [7]. Frequently, patients are asked to learn and practise movements that are novel and/or difficult to monitor as part of behavioural swallowing rehabilitation [8]. Feedback is vital for motor learning to be successful as the learner adapts subsequent behaviour according to the difference between the actual and the desired output [9–11]. It is accepted that individuals generate motor commands that will maximise the reward they receive [11], so it follows that accurate feedback is essential and the right behaviour is rewarded to shape learning. However, feedback is 13 Vol.:(0123456789) S. K. Archer et al.: Surface Electromyographic Biofeedback and the Effortful Swallow Exercise challenging to deliver in dysphagia therapy when there is no overt sign of successful accomplishment of a target. Clinical swallowing assessments have poor reliability [12] so it likely that feedback provided during therapy may lack validity. This has implications for ensuring that optimal movements are reinforced and for motivating the patient to continue trying. A solution could be incorporating biofeedback into therapy programmes. This involves taking measurements of a chosen physical function and displaying them directly or through a feedback signal so that the patient can practise controlling the signal by altering their movement or behaviour. This enables small changes in physiological processes to be noticed and reinforced so that behaviour can be modified [13]. Surface electromyography (sEMG) provides a type of neuromuscular biofeedback by displaying a visual or auditory representation of muscle activity. Electrodes are placed on the skin and detect motor unit action potentials generated by muscle contraction. With increasing force of muscle contraction, there is successive activation of motor units and an increase in the firing rate of all motor units recruited [14] leading to an increase in the amplitude of the sEMG signal, which can be displayed graphically. By using this feedback, patients can work to increase muscle activity [15]. Biofeedback has been incorporated into stroke rehabilitation for decades [15] with good evidence to suggest it leads to improvements in limb function and gait following stroke [16–18]. It is thought to work best when used with functions that are not normally directly observable [19]. Therefore incorporating biofeedback in dysphagia rehabilitation would provide the patient with direct information on a complex and subtle process to improve motor control for swallowing, while potentially enabling more active involvement and thereby improving outcome [20]. Increased conscious control for swallowing with biofeedback was indicated by the results of an fMRI study in which visual feedback during swallowing led to increased activation in frontal regions of the brain, indicating that the feedback directed more attention to motor planning [21]. Several studies have reported benefits of swallowing therapy with adjunctive sEMG biofeedback in dysphagic stroke patients [8, 22–27]. However, many of these studies are retrospective and/or case studies and none used a control group, blinding or randomisation and the sample sizes are small. Furthermore, most do not follow a specified, structured treatment protocol, used mixed treatments [8, 22, 24] and include mixed populations [8, 20]. These methodological weaknesses limit the interpretation of the reported findings. Indeed, a recent robust systematic review and meta-analysis concluded that there was a paucity of good quality studies examining the effect of biofeedback in dysphagia therapy [28]. 13 The “effortful swallow” (ES) is a commonly recommended exercise [29] in which the patient i (...truncated)