Sequential stimulator for dysphagic patients
เครื่องกระตุ้นไฟฟ้าชนิดลำดับก่อนหลังสำหรับรักษาผู้ป่วยกลืนลำบาก
Vitoon Leelamanit, Assoc. Prof., D. of Otolaryngology, F. of Medicine, PSU.
Chusak Limsakul, Asst. Prof., D. of Electrical Eng., F. of Eng., PSU.
Alan Geater, Epidemiology Unit, F. of Medicine, PSU.
Corresponding e-mail : lvitoon@ratree.psu.ac.th
Grant : NECTEC
Published : Research Report
Key words : sequential stimulator, dysphagic patients, myoelectrical activity (EMG)
The objective of this research is to build the sequential stimulator for assisting the swallowing function in dysphagic patients. The typical character of this stimulator is its property of stimulating contraction of thyrohyoid muscle during deglutition. It is already known that in normal swallowing contraction of thyrohyoid will help opening the pharynx and cricopharyngeus. Therefore, the function of sequential stimulator alleviates the dysphagia symptom of the patients. This research also studied the possibility of using the myoelectrical activity (EMG) of those muscles function during swallowing as a trigger to the stimulator. The study included the EMG of temporalis, posterior tongue and mas-
seter muscles and was found that EMG of the posterior tongue was the most appropriate while the second most was temporalis muscle. In recording the EMG, disc surface electrodes were used instead of needle and hook-wire electrodes because it is more convenience to the patients especially when
using repeatedly for a long time. The next step was to find an algorithm having the property of detect-ing swallowing initiation in the recorded surface EMG. The ideal algorithm must have the property
of real time processing with 100% accuracy. Thus many algorithms had been tried and found that the mean of the signal power 2 is the best one and provided 80% accuracy in swallowing detection and
60-120 msec delay time. The character of the stimulating pulse used in this study was twin-peak high voltage pulse. The twin-peak pulse was designed in the order that the time spacing between two consecutive pulses was 75 msec and the stimulation duration was 1 sec long with ramp at the beginning. The sequential stimulator is compsed of two parts, the calculation/decision making part and the sti-mulating part. The function of the calculation/decision making part is to calculate the recorded EMG signal and compared it to the reference signal that can be adjusted from 0-2 volt. If the amplitude of
the calculated signal is higher than the reference signal, the output will be high and the trigger will be sent to command the stimulating part to release the high voltage (1-150 volt) stimulating pulse to stimulate contraction of the thyrohyoid muscle in assisting swallowing. The sequential stimulator
was used to treat 23 patients suffering reduced laryngeal elevation dysphagia. The treatment duration ranged from 2-30 days (mean 6 days). Videofluoroscopic examination was done to compare the result before and after treatment in every patient. Twenty-patients had favorable outcome while three showed failure treatment. Patients with favorable outcome showed improved dysphagia symptom without difficulty swallowing, obstruction or aspiration. Six of this group showed relapse symptom after the first course of treatment and the second course was applied with favorable outcome. Of the three patients who showed failure treatment, one received radiation treatment for head and neck cancer
with severe fibrosis of thyrohyoid muscle, one suffering multiple sites cerebrovascular accident with severe degree weakness of tongue. The other showed no improvement but after using the sequential stimulator it was found to have been inoperative. Neither complication nor adverse reaction was
found in any treated patients using sequential stimulator.
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