Efficacy of EMG/Bioimpedance-Triggered Functional Electrical Stimulation on Swallowing Performance.

In order to support swallowing, the efficacy of functional electrical stimulation for different stimulation settings of the submental musculature has been investigated. The stimulation was administrated at rest and synchronously to voluntary initiated swallows. The onset of a swallow was detected in real-time by a combined electromyography/ bioimpedance measurement at the neck in order to trigger the stimulation. The amplitude and speed of larynx elevation caused by the FES has been assessed by the observed change in bioimpedance whereas a reduction of bioimpedance corresponds to an increase in larynx elevation. Study results from 40 healthy subjects revealed that 73% of the subjects achieved a larger and faster larynx elevation during swallowing with triggered FES and therefor a better protection of their airways. However, we also observed a decrease in larynx elevation compared to normal swallowing in 11 out of the 40 subjects what might not benefit from such a treatment. The largest improvement of larynx elevation and speed during swallowing could be achieved with three stimulation channels formed by four electrodes in the submental region.

Multisensor Classification System for Triggering FES in Order to Support Voluntary Swallowing.

In dysphagia the ability of elevating the larynx and hyoid is usually impaired. Electromyography (EMG) and Bioimpedance (BI) measurements at the neck can be used to trigger functional electrical stimulation (FES) of swallowing related muscles. Nahrstaedt et al.1 introduced an algorithm to trigger the stimulation in phase with the voluntary swallowing to improve the airway closure and elevation speed of the larynx and hyoid. However, due to non-swallow related movements like speaking, chewing or head turning, stimulations might be unintentionally triggered. So far a switch was used to enable the BI/EMG-triggering of FES when the subject was ready to swallow, which is inconvenient for practical use. In this contribution, a range image camera system is introduced to obtain data of head, mouth, and jaw movements. This data is used to apply a second classification step to reduce the number of false stimulations. In experiments with healthy subjects, the amount of potential false stimulations could be reduced by 47% while 83% of swallowing intentions would have been correctely supported by FES.

Automated detection and evaluation of swallowing using a combined EMG/bioimpedance measurement system.

INTRODUCTION: Developing an automated diagnostic and therapeutic instrument for treating swallowing disorders requires procedures able to reliably detect and evaluate a swallow. We tested a two-stage detection procedure based on a combined electromyography/bioimpedance (EMBI) measurement system. EMBI is able to detect swallows and distinguish them from similar movements in healthy test subjects. STUDY DESIGN: The study was planned and conducted as a case-control study (EA 1/019/10, and EA1/160/09, EA1/161/09). METHOD: The study looked at differences in swallowing parameters in general and in the event of penetration during swallows in healthy subjects and in patients with an oropharyngeal swallowing disorder. A two-stage automated swallow detection procedure which used electromyography (EMG) and bioimpedance (BI) to reliably detect swallows was developed. RESULTS: Statistically significant differences between healthy subjects and patients with a swallowing disorder were found in swallowing parameters previously used to distinguish between swallowing and head movements. Our two-stage algorithm was able to reliably detect swallows (sensitivity = 96.1%, specificity = 97.1%) on the basis of these differences. DISCUSSION: Using a two-stage detection procedure, the EMBI measurement procedure is able to detect and evaluate swallows automatically and reliably. The two procedures (EMBI + swallow detection) could in future form the basis for automated diagnosis and treatment (stimulation) of swallowing disorders.

Evaluation of an EMG bioimpedance measurement system for recording and analysing the pharyngeal phase of swallowing.

A neuroprosthetic device for treating swallowing disorders requires an implantable measurement system capable to analysing the timing and quality of the swallowing process in real time. A combined EMG bioimpedance (EMBI) measurement system was developed and is evaluated here. The study was planned and performed as a case-control study. The studies were approved by the Charité Berlin ethics committee in votes EA1/160/09 and EA1/161/09. Investigations were carried out on healthy volunteers in order to examine the usefulness and reproducibility of measurements, the ability to distinguish between swallowing and head movements and the effect of different food consistencies. The correlation between bioimpedance and anatomical and functional changes occurring during the pharyngeal phase of swallowing in non-healthy patients was examined using videofluoroscopy (VFSS). 31 healthy subjects (15♂, 16♀) were tested over the course of 1350 swallows and 19 (17♂, 2♀) non-healthy patients over the course of 54 swallows. The signal curves obtained from both transcutaneous and subcutaneous measurement were similar, characteristic and reproducible (r > 0.5) and correlated with anatomical and functional changes during the pharyngeal phase of swallowing observed using VFSS. Statistically significant differences between head movements and swallowing movements, food volumes and consistencies were found. Neither the conductivity of the food, the sex of the test subject nor the position of the measurement electrodes exerted a statistically significant effect on the measured signal. EMBI is able to reproducibly map the pharyngeal phase of swallowing and changes associated with it both transcutaneously and subcutaneously. The procedure therefore appears to be suitable for use in performing automated evaluation of the swallowing process and for use as a component of an implant.

The semisolid bolus swallow test for clinical diagnosis of oropharyngeal dysphagia: a prospective randomised study.

Contrary to clinical experience, clinical swallow tests are predominantly performed using water (water swallow tests, WST). In this study, we examine whether swallow tests performed using a bolus of semisolid food (bolus swallow test, BST) offer benefits. In a prospective, randomised, blind study, the results of a standardised saliva swallow test (SST), WST, BST, combinations of these tests and an endoscopic swallow test (FEES) in patients with oropharyngeal swallowing disorders of neurological (NEU) and non-neurological (NNEU) origin were compared. Sensitivity, specificity, test accuracy and inter-rater reliability were analysed. 62 patients (mean age = 64.68; range = 22-84) were included in the study (NEU = 40; NNEU = 22). A sensitivity of 70.7% (NEU = 70.3%, NNEU = 71.4%) and specificity of 82.5% (NEU = 92.3%; NNEU = 100%) were determined for the WST. The BST + SST was found to have a sensitivity of 89.6% (NEU = 66.7%; NNEU = 90.9%) and a specificity of 72.7% (NEU = 87.5%; NNEU = 90.9%). Analysis of test accuracy showed a statistically significant correlation between FEES and BST + SST. Only BST + SST exhibited statistically significant inter-rater reliability. BST in combination with SST was the sensitive clinical instrument for detecting aspiration both over the patient population as a whole and over the two sub-populations. Inter-rater reliability was found to be statistically significant. The results presented here demonstrate the benefit of semisolid food in investigating clinical dysphagia.