The Manifestation of Surface EMG of Swallowing Muscles in Stroke Patients With Respiratory Muscle Training

Stroke patients commonly to have respiratory muscle weakness and swallowing disturbance. Their cardiorespiratory function could be markedly impaired within 7 weeks after a stroke, and maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) reduced. Dysphagic patients usually had reduced hyolaryngeal excursion. The contraction of submandibular hyolaryngeal muscles (geniohyoid, mylohyoid, anterior digastric) and thyohyoid muscles can influence on the hyoid bone and largynx . The decreased excursion and elevation of hyolaryngeal complex has been considered as one of cause of penetration and aspiration in patients with dysphagia.

Respiratory muscle training (RMT) could improve cough effectiveness and reduce the incidence of pneumonia in acute stroke. RMT could significantly increase in MIP and MEP with training intensity of inspiratory muscle training (IMT) varied from 30% to 60% of MIP, duration of 3 to 7 times per week and duration of each session from 10-30 minutes for a period of training from 6 to12 weeks in subacute stroke patients.

Expiratory muscle strength training (EMST) had potential benefit for respiratory muscle strength, swallowing and cough function. EMST could significantly increase duration of activation with higher peak amplitudes of EMG signal of the submental muscles as compared to dry and wet swallowing in stroke patients(Wheeler, et al. 2007) and it also had promising outcomes for airway protection in persons with dysphagia second to neuromuscular impairment.

Swallowing phase including oral phase, pharyngeal phase, pharyngeal and initial esophageal pahased. Surface EMG (sEMG), a simple, noninvasive, radiation-free and reliable method, can be used to screen and differentiate the swallowing disturbance by recording activity of surface EMG over the swallowing muscles, including orbicularis oris, masseters, submental muscles and infrahyoid muscles. The electric activity of sEMG can be filtered and rectified as EkG-looking line. It can provide complementary information to assess the dysphagia.

Correlation of sEMG signals during swallowing in healthy adults has been reported And stroke patients with middle cerebral artery infarction had delayed swallowing onset, pretrigger duration of hyoid bone. The sEMG showed shorter duration of sEMG activity, latency between the start of EMG activity and actual movement, shortened submental muscle activity, and prolonged pretrigger duration during swallowing.

Hypothesis Respiratory muscle training can activate the respiratory muscles, stimulate motor cortex of central nervous system of speech, swallowing and respiratory function through the certain process of neuroplasticity in brain and spinal cord. EMST could facilitate submental muscle contraction, increase submental muscle force and elevate the hyolaryngeal complex during swallowing.

However, rare reports regarding the relationship between the respiratory muscle training and swallowing dysfunction in stroke patients. And stroke patients with different lesions may have specific sEMG patterns; the differentiation of sEMG pattern of swallowing muscles in different stroke disease with dysphagia is not explored yet, and also short of standards to study the sEMG of swallowing muscles.

In this study, we will use a simple respiratory muscle training device(Threshold type) to train respiratory muscles and follow up its effect on swallowing, cough, voice quality in stroke patients with respiratory muscle weakness and/or swallowing disturbance.

Forty-six stroke patients with respiratory muscle weakness, age between 35 to 80 years, will be enrolled. The participants will be randomly assigned by a computer random number generator into two groups, including the experimental group (RMT group plus usual rehabilitation) and the control group (usual rehabilitation alone). All allocations will be concealed in the opaque envelopes. The research assistant will enroll the participants, generate the allocation sequence, and assign participants to their groups after obtaining the informed consent.

The patient will be randomized into 3 groups:

Group I: IMST only: inspiratory muscle training for patients with inspiratory muscle weakness (MIP less than 70% of normal range).

Group II: EMST: for patients with swallowing disturbance.

Group III: Control group will receive regular rehabilitation.

Each subject with respiratory muscle weakness or swallowing disturbance, baseline characteristics, including height, weight, body mass index, duration of the disease, neurological level (Brunnstrom's stage), spirometry, peak cough flow, resting heart rate, systolic and diastolic blood pressure, resting oxyhemoglobin saturation (SpO2), MIP, MEP, Borg's scale (0.5 to 10), 6-minute walking test, cough function, fatigue assessment scale and caregiver stress scale. Pulmonary function and respiratory muscle strength will be assessed by an experienced technician in our pulmonary functional room as a baseline at the begin of training program, and at end of program(6 weeks).

Training protocol:

Group I: IMST only:

IMT will commence from 30% to 60 % of MIP and then adjust one level of training loading according to the tolerance of continuously breathing through a respiratory trainer for two sets of 30 breaths or 6 sets of 10 repetitions with one or two minute of rest between sets, once per day, 5 days per week. Training resistance will be adjusted as tolerated. The loading will be performed with the previous resistance setting or even lower if training load is not tolerated or not completed.

During IMT, patients will be instructed to place their lips around breathing trainer in a sitting position with a nose-clip, inhale with enough force to open the valve (inhale deeply and forcefully), exhale through the mouthpiece (exhale slowly and gently), and then continue inhaling and exhaling without removing the device from their mouths. The training load and training program will be instructed by an experienced respiratory technician.

Group II: EMST: for patients with only swallowing disturbance EMST will commence from 15% to 75% of threshold load of an individual's MEP, 5 sets, 5 repetition with one or two minute of rest between sets, twice per day, 5 days per week. And training resistance will be adjusted accordingly. The loading will be performed with the previous resistance setting or even lower if training load is not tolerated or not completed. Each patients with swallowing disturbance will receive swallowing screen test, Functional Oral Intake Scale, voice quality analysis and surface electromyography by an experience physician and experienced speech therapist to evaluate the functional level of oral intake of food and liquid, voice quality and measurement of submental muscle strength respectively. And swallowing training program will be conducted by an experienced speech therapist.

GroupIII：Control group will receive regular rehabilitation.

Outcome measurements:

Each subject's baseline characteristics, including height, weight, body mass index, and duration of the disease, neurological level (Brunnstrom's stage), spirometry, resting heart rate, rest respiratory rate, blood pressure, resting oxyhemoglobin saturation (SpO2), MIP, MEP, or the lowest resting SpO2, Borg's scale, six-minute walk work value and distance, six-minute upper extremity ergometry, peak cough flow, non-affected upper limb strength, fatigue assessment scale etc.

For rectified and filtered sEMG, swallowing duration (the time lapse between the start and the end of swallowing. In second), mean peak amplitude (inμsec), and shape of contraction patterns of different stage of swallowing will be analyzed.

The timing of serial evaluation including the assessment at baseline, 6 weeks and 3 month later.