Enrique P. Canilang

Noninvasive acceleration measurements to characterize the pharyngeal phase of swallowing

Swallowing disorder (dysphagia) presents a major problem in the rehabilitation of stroke and head injured patients. In the present investigation, a new technique is developed for noninvasive assessment of the pharyngeal phase of the swallowing mechanism. Acceleration was measured with two ultra-miniature accelerometers placed on the skin over the throat. Simultaneously, the swallow suction pressure was monitored. Swallowing in normal individuals gave rise to a characteristic acceleration pattern which was quite reproducible, and was in phase with the swallow pressure. In dysphagic patients, the acceleration response was either absent or significantly delayed. The accelerometry technique provides a tool for continuing patient assessment and demonstrating the clinical improvements.

Measurements of acceleration during videofluorographic evaluation of dysphagic patients

Accelerometry represents a noninvasive technique for the assessment of the swallowing mechanism. However, the underlying physiological events that give rise to the acceleration signal are poorly understood. In the present study, the acceleration signal was measured simultaneously during videofluorography examination. Preliminary results revealed that the signal occurred during laryngeal elevation and the magnitude of acceleration correlated well with the laryngeal displacement. Acceleration measurements present a potentially useful noninvasive tool.

Biomechanical measurements to characterize the oral phase of dysphagia

Several biomechanical parameters that characterize the oral musculature are identified and techniques for quantifying these parameters in normal and dysphagic patients are discussed. These parameters include lip closure pressure, lip interface shear force, tongue thrust, and swallow pressure. Significant differences were found in each of these parameters measured in normal and dysphagic patients. The quantitative measurements can aid the physician in choosing the appropriate therapy during the course of rehabilitation of stroke and head injured patients.<<ETX>>

A fuzzy logic diagnosis system for classification of pharyngeal dysphagia

Identification and classification of the dysphagic patient at risk of aspiration is important from a clinical point of view. Recently, we have developed techniques to quantify various biomechanical parameters that characterize the dysphagic patient, and have developed an expert system to classify patients based on these measurements. The purpose of the present investigation was to develop a fuzzy logic diagnosis system for classification of the patient with pharyngeal dysphagia into four categories of risk for aspiration. Non-invasive acceleration and swallow pressure measurements were obtained and five parameters were extracted from these measurements. A set of membership functions were defined for each parameter. The measured parameter values were fuzzified and fed to a rule base which provided a set of output membership values corresponding to each of the categories. The set of output values were defuzzified to obtain a continuous measure of classification. The fuzzy system was evaluated using the data obtained from 22 subjects. There was a complete agreement between the fuzzy system classification and the clinicians classification in 18 of the 22 patients. The fuzzy system overestimated the risk by half a category in two patients and underestimated by half a category in two patients. The fuzzy logic diagnosis system, together with the biomechanical measures, provides a tool for continued patient assessment on a daily basis to identify the patient who needs further videofluorography examination.

Surface EMG measurements at the throat during dry and wet swallowing

Within the sphere of dysphagia management, there is a growing need for the development of noninvasive methods of quantification of swallowing disorders. The purpose of the present investigation was to determine if surface electromyogram (EMG) at the throat could be measured during swallowing. Surface EMG was measured from 35 normal human subjects during dry and wet swallowing. The EMG signals recorded were highpass filtered using digital fourth order highpass Butterworth filter to eliminate baseline variations. Spectral analysis was performed on the filtered signals. The mean power values of the surface EMG signals were then calculated. Paired t-test between the mean power values of surface EMG during dry and wet swallowing showed a statistically significant difference (p<0.005). The results of the study confirmed the hypothesis that surface EMG at the throat during swallowing could be measured. Mean power of surface EMG measurement provides a reliable noninvasive measure of swallowing.

Design and development of portable biofeedback systems for use in oral dysphagia rehabilitation

The management of dysphagia presents a major problem in the comprehensive rehabilitation of stroke and head injury patients. Dysphagia is a disorder of the swallowing process. Oral dysphagia refers to abnormalities in the oral phase of the swallowing mechanism. The oral phase of the swallowing mechanism is important for the proper triggering of the swallowing reflex. Current techniques in oral dysphagia rehabilitation include oro-motor exercises using tongue depressors and mouth-care swabs. There is thus a need for a better therapeutic method for oral dysphagia. The purpose of this paper is to report the development of audio-visual biofeedback devices for treating oral dysphagia. Portable biofeedback devices rendering feedback of biomechanical parameters characterizing the oral phase were developed and evaluated in preliminary clinical trials. A patient progress index (PPI) was developed and used to quantify the overall patient progress. The devices demonstrated good patient acceptability.

Neural networks in computer-aided diagnosis classification of dysphagic patients

Dysphagia is a swallowing disorder observed in head injury and stroke patients. Impairment of the oral and pharyngeal phases of the swallowing mechanism often leads to aspiration. Clinically, it is essential to estimate the risk of aspiration in dysphagic patients so that safe feeding protocols can be established. The current clinical procedures of diagnosis are qualitative and involve videofluorography and bedside clinical evaluation. Videofluorography exposes the patient to X-ray radiation and therefore cannot be performed on a daily basis. Reddy, et al. [1–3], have developed non-invasive biomechanical techniques to quantify oral and pharyngeal phases. The biomechanical parameters measured to characterize oral phase were the lateral tongue thrust, the forward tongue thrust, the tongue elevation force and the lip pulling force. For the pharyngeal phase, accelerations of the throat were measured by placing ultraminiature accelerometers on the skin at the levels of cricoid and thyroid cartilages, and the swallow suction pressure was measured with a catheter placed at the base of the tongue. Thomas, et al.[4], have used these biomechanical parameters to classify dysphagic patients into four categories of risk of aspiration. The purpose of the present investigation was to develop and clinically evaluate neural network models for classification of patients based on the biomechanical measurements obtained from them.

Neural networks for recognition of acceleration patterns during swallowing and coughing

The acceleration signal during swallowing was filtered and segmented. The parameters extracted from the signal were used to develop and train two sets of neural network models. The first neural network model was developed to differentiate between the acceleration signals of normal, dysphagic and coughing. The second neural network model was developed to differentiate between acceleration during swallowing in normal, mild dysphagic, moderate dysphagic and severe dysphagic subjects.

Spectral analysis of acceleration signals during swallowing and coughing

The mean frequency of acceleration recorded during swallowing in dysphagic subjects was significantly lower compared to that in normal subjects. The acceleration signal recorded during coughing had higher mean frequency than that during swallowing.

Acceleration and EMG for sensing pharyngeal swallow

Swallowing disorders present a major problem in rehabilitation of stroke and head injury patients. Therefore, an accurate assessment of the swallowing ability is very important. Swallowing consists of three phases the oral phase, the pharyngeal phase and the esophageal phase. Dysfunction of the pharyngeal phase can lead to aspiration, choking and even death. In the current clinical practice, the patient assessment is qualitative based generally on videofluorography and clinical bed-side evaluation. Videofluorography exposes the patient to radiation and cannot be performed on a daily basis. Clinical bed-side evaluation is generally based on feeling. Reddy et. al [1,2] have developed quantitative methods to characterize the oral and the pharyngeal phase. For the pharyngeal phase they measured acceleration and swallow suction pressure [2]. These measurements showed good correlation with clinical evaluation. Investigators [3,4] have used Electromyography (EMG), using needle electrodes, to quantify the pharyngeal phase during swallowing. The objective of the present study was to investigate the relationship between the acceleration and surface EMG measured at the throat during swallowing in normal subjects.