Respiratory and acoustic signals associated with bolus passage during swallowing.

In order to advance our understanding of the relation between respiration and deglutition, simultaneous videofluoroscopy and respirodeglutometry was performed. Fifteen normal, healthy, young adults (20-29 years of age) were connected to a respirodeglutometer and positioned for simultaneous videofluoroscopic assessment in the lateral plane. Subjects performed three swallows each of a 5-ml and a 10-ml bolus of liquid barium and a 5-ml bolus of paste barium, for a total of nine swallows per subject. Location of the bolus head as identified with videofluoroscopy was associated with eight respirodeglutometric variables. In addition, temporal relations for seven respirodeglutometric variables were calculated as a function of bolus volume and viscosity. Significant temporal differences were found for five of the variables by volume. No significant temporal differences were noted by viscosity. Expiration occurred before 79% and after 96% of the swallows. The number of inspirations preceding a swallow suggested a possible effect resulting from the need to hold a bolus in the mouth before receiving instructions to swallow during videofluoroscopic assessment. This effect may be important during patient evaluation. For a significant number of swallows, respiratory flow ceased before the velum was fully elevated.

Temporal and durational patterns associating respiration and swallowing.

This study obtained initial normative data on the temporal coordination of respiration and swallowing events in 12 young adults using a first-generation Respirodeglutometer. In addition, direction of airflow before and after deglutive apnea was obtained. Three swallows of two viscosities of bolus material were performed by each subject, yielding a total of 72 swallows. Qualitative and quanitative analyses were performed. Time of onset of submental surface electromyography and time of laryngeal movement were found to differ between males and females. Males began submental muscle contraction before females and laryngeal movement after females. Duration of deglutition apnea for all swallows was 0.75 +/- 0.14 sec. Expiration occurred before the deglutition apnea 93% of the time and after the deglutition apnea 100% of the time. A modal pattern of events obtained with the Respirodeglutometer was present in 42% of the swallows, and an additional 47% had only one event differ from that order.

Electromyographic activity from human laryngeal, pharyngeal, and submental muscles during swallowing.

The durations and temporal relationships of electromyographic activity from the submental complex, superior pharyngeal constrictor, cricopharyngeus, thyroarytenoid, and interarytenoid muscles were examined during swallowing of saliva and of 5- and 10-ml water boluses. Bipolar, hooked-wire electrodes were inserted into all muscles except for the submental complex, which was studied with bipolar surface electrodes. Eight healthy, normal, subjects produced five swallows of each of three bolus volumes for a total of 120 swallows. The total duration of electromyographic activity during the pharyngeal stage of the swallow did not alter with bolus condition; however, specific muscles did show a volume-dependent change in electromyograph duration and time of firing. Submental muscle activity was longest for saliva swallows. The interarytenoid muscle showed a significant difference in duration between the saliva and 10-ml water bolus. Finally, the interval between the onset of laryngeal muscle activity (thyroarytenoid, interarytenoid) and of pharyngeal muscle firing patterns (superior pharyngeal constrictor onset, cricopharyngeus offset) decreased as bolus volume increased. The pattern of muscle activity associated with the swallow showed a high level of intrasubject agreement; the presence of somewhat different patterns among subjects indicated a degree of population variance.

Laryngeal activity during swallow, phonation, and the Valsalva maneuver: an electromyographic analysis.

To better understand the mechanisms of airway protection during swallow, the authors of this study performed an electromyographic (EMG) analysis on the thyroarytenoid (TA) and interarytenoid (IA) muscles during a variety of tasks. The tasks included high, low, and comfortable pitch phonation, the Valsalva maneuver, saliva swallow, and 5- and 10-mL water swallows. Raw EMG signals were analyzed to obtain root mean square data, which correspond to a relative magnitude of muscle activation. The data show that both TA and IA muscles generate a similar level of relative activation, with the greatest electrical activity observed during swallow tasks followed by the Valsalva maneuver and phonation. The duration, onset, offset, and pattern of activity during the swallowing tasks also showed close synchronization between the two muscles. These data can be used in designing therapy for voice disorders and pharyngeal dysphagia.

Quantitative assessment of hyoid bone displacement from video images during swallowing.

Given the relationship between hyoid displacement and aspiration, a simple, accurate, clinically useful method for identification of reduced hyoid displacement is needed. The purpose of this investigation was to validate a quantitative method for clinically assessing hyoid bone movement during swallowing. Videofluoroscopic evaluations of 20 male subjects--10 who had been subjectively assessed as demonstrating normal hyoid displacement during swallowing, and 10 who had been subjectively assessed as demonstrating reduced displacement during swallowing--were analyzed. A video measuring gauge was used, and a software spreadsheet was developed to perform trigonometric calculations for determination of anterior/superior hyoid trajectories. Statistically significant differences were found between groups in both the anterior and superior directions of hyoid movement. No significant differences were found between liquid and paste swallows within groups. This method is simple in that it is necessary to identify only three to five points on two video images. Those values are then input onto a preprogrammed spreadsheet that automatically performs the necessary calculations. Although the present investigation focused on the movements of the hyoid bone during swallowing, this method of tracking displacement can be used for virtually any task or structure whose movements can be captured on videotape.

Intrinsic fibre architecture and attachments of the human epiglottis and their contributions to the mechanism of deglutition.

Two mechanisms have been proposed which address the downfolding of the epiglottis during swallowing. The passive mechanism (Fink et al. 1979) focuses on passive mechanical forces transmitted through the median hyoepiglottic ligament and pre-epiglottic adipose tissue to the epiglottis. The active mechanism (Ekberg & Sigurjonsson, 1982) expands the passive mechanism to include active contributions from the aryepiglotticus and thyroepiglotticus muscles. By means of laryngeal microdissection and whole mount orcein staining, distinct bands of fascial condensations were identified running from the lateral edge of the epiglottis just superior to the attachment of the median hyoepiglottic ligament to the hyoid bone near the ends of the greater horns. Neither the proposed active nor the passive mechanisms address the possible contribution of these paired lateral hyoepiglottic ligaments to epiglottic downfolding. Computer image analysis of videofluoroscopic examinations of swallowing was then used to assess the dynamic movements of the larynx during swallowing. It was observed that the downfolding of the epiglottis occurred in the same video frame as initiation of anterior displacement of the hyoid bone and thyrohyoid approximation. Based on the anatomical and dynamic relationship of the epiglottis to other laryngeal structures, we propose that as the larynx elevates and the hyoid bone moves anteriorly, these lateral ligaments exert traction preferentially on the upper third of the epiglottis to bring it to a position below the horizontal.

Laryngeal movement, oropharyngeal pressure, and submental muscle contraction during swallowing.

This study examined temporal relationships of laryngeal movement, oropharyngeal pressure and submental muscle contraction during swallowing. Techniques used to obtain the temporal measures were electroglottography (EGG), oropharyngeal manometry, and submental surface electromyography. Liquid bolus swallows were performed by 40 normal subjects evenly divided by young and elderly, men and women. Results of this investigation suggest that the EGG waveform is reflective of the temporal aspects of laryngeal movement during swallowing and that the EGG has potential as a behavioral modification technique in swallowing therapy. A case study is presented to illustrate the use of the electroglottograph for biofeedback.

Videofluoroscopic predictors of aspiration in patients with oropharyngeal dysphagia.

The purpose of this investigation was to determine the relationship between aspiration and seven other variables indicative of pharyngeal stage dysphagia. Additionally, we looked at the relationship between aspiration and oral stage dysphagia. Multiple logistic regression analysis identified five independent predictors of aspiration that were significant at the p = 0.05 level: vallecular stasis, reduced hyoid elevation, deviant epiglottic function, diffuse hypopharyngeal stasis, and delayed initiation of the pharyngeal stage of the swallow. A linear trend was observed in that, as the severity of vallecular stasis, pyriform sinus stasis, diffuse hypopharyngeal stasis, or delayed initiation of the pharyngeal stage of the swallow increased, the proportion of patients who aspirated also increased. A stepwise logistic regression model furnished estimates of the odds ratio for each independent variable and can be used by clinicians to calculate the risk of aspiration in patients who demonstrate pharyngeal stage dysphagia.

Effects of age, gender, bolus volume, and bolus viscosity on oropharyngeal pressure during swallowing.

Oropharyngeal pressure during swallowing was studied in a total of 40 healthy adult males and females in two age groups (21-27 yr and 62-75 yr). Effects of bolus volume, bolus viscosity, age, and gender were analyzed, and dry and bolus swallows were compared. The duration of the intrabolus pressure, reflecting the pressure exerted by the tongue on the bolus and preceding the generation of the pharyngeal pressure, was significantly affected by bolus volume. The duration of oropharyngeal pressure was affected by age, gender, and bolus type (bolus vs. dry swallow). Peak oropharyngeal pressure was not affected by any of the test factors, although there was a tendency for older subjects to have higher pressures than young subjects.

The relationship of vallecular residue to oral involvement, reduced hyoid elevation, and epiglottic function.

The purpose of this investigation was to identify certain variables that may result in vallecular residue after swallowing. The relationship between vallecular residue and oral-stage dysphagia, reduced hyoid elevation, and movement of the epiglottis was assessed in 330 patients referred to the speech pathology section for evaluation of oropharyngeal swallowing function. Patients with vallecular residue were more likely to have oral involvement or deviant epiglottic function, characterized by an absence of epiglottic inversion or incomplete inversion, than patients without vallecular residue. Although the primary focus of the study was between vallecular residue and the other select variables, the interrelationships among the three other variables were also studied. Patients with deviant epiglottic function were more likely to have oral involvement, reduced hyoid elevation, or vallecular residue than patients without deviant epiglottic function and patients with reduced hyoid elevation were more likely to have oral involvement than those with normal hyoid elevation. Multivariate analysis revealed that the relationship between oral involvement and deviant epiglottic function, present in the bivariate analysis, was not significant when controlling for other relationships in the model. The relationship between primary medical diagnostic category and the presence/absence of vallecular residue as well as the other dichotomous variables varied between and within diagnostic categories.

Frequency response of the Fourcin electroglottograph and measurement of temporal aspects of laryngeal movement during swallowing.

The purpose of this investigation was to study the frequency response of a modified Fourcin EGG at frequencies associated with the slow varying laryngeal movement of swallowing and to compare those findings with the response characteristics of the EGG at frequencies associated with phonation. Frequency-dependent differences were found. At very low frequencies the EGG output was found to be the derivative of the changes in neck impedance; at higher frequencies the EGG output directly represented the changes in neck impedance. Three of the four phases of the pharyngeal stage of the swallow are represented by the EGG signal.

Tetanic response of the cricothyroid muscle.

Tetanic response of canine cricothyroid muscle tissue was investigated through a series of experiments conducted in vitro. Two separate portions of the cricothyroid muscle, namely the pars recta and pars oblique, were studied. Samples of the muscle were dissected from dog larynges excised a few minutes before death and kept in Krebs-Ringer solution at a temperature of 37 degrees +/- 1 degrees C and a pH of 7.4 +/- 0.05. Tetanic contraction of the muscle samples was obtained by field stimulation to the muscle through a pair of parallel-plate platinum electrodes and with a train of square pulses of 0.1-millisecond duration and 85-V amplitude. Isometric force responses of the pars recta and pars oblique muscles were obtained electronically with a dual servo system (ergometer). The effect of tissue elongation on the active and passive responses was quantified by stimulation of the sample during cyclic elongation. Both active and passive responses as a function of elongation were obtained on the same sample.

The effects of a maxillary speech-aid prosthesis for the combined tongue and mandibular resection patient.

The purpose of this investigation was to develop a protocol for the fabrication of a prosthesis that would improve speech in individuals who have undergone complete removal of the tongue and mandible. A 60-year-old man was suffering from severe xerostomia and was unable to produce intelligible speech. Speech analysis without the prosthesis revealed a profound articulatory disorder. With the prosthesis, xerostomia was eliminated and the subject had fewer articulatory errors of severity. Improvement in speech intelligibility was significant at p less than 0.001.

Use of the electroglottograph for measurement of temporal aspects of the swallow: preliminary observations.

The electroglottograph (EGG) is a non-invasive, electrical impedance device that was developed for observing vocal fold contract during phonation. After a thorough study of the frequency response characteristics of the EGG, we found that the EGG output can be used to identify maximum laryngeal displacement and the duration of laryngeal movement during swallowing. With a small intranasal pressure transducer placed beneath the velum and the EGG electrodes placed externally on the thyroid cartilage, additional information on the temporal aspects of the swallow can be measured. The EGG has direct clinical application when teaching such techniques as the safe swallow and Mendelsohn maneuver and it is useful as a research technique when using repeated measures designed to study the swallow reflex.

Electrical activity from the superior pharyngeal constrictor during reflexive and nonreflexive tasks.

The purpose of this investigation was to determine, in a quantitative manner, which, if any, nonswallowing tasks produce significant levels of activation in the superior pharyngeal constrictor muscle of normal human subjects. Bipolar hooked wire electrodes were inserted in the superior pharyngeal constrictor muscle of 15 healthy subjects. Electrode placement was controlled. Each subject performed two reflexive tasks, six voluntary tasks requiring phonation, and four nonspeech voluntary tasks. The electromyogram (EMG) was rectified and integrated. The resulting number was then transformed by taking its natural logarithm. An ANOVA was performed and a linear model was estimated. The magnitude of the EMG activity was related to the location of the electrodes. The largest values were recorded in the lateral-superior placement, followed by the lateral-inferior, medial-inferior and medial-superior. The superior pharyngeal contrictor was found to be a muscle activated primarily during reflexive activity. There was a general trend in the amplitude of EMG activity in relationship to task. Swallowing produced the greatest amount of activity and a gag produced about 60% of the activity produced by the swallow. Two tasks, production of the work /hok/ in which the phoneme /k/ was stressed, and a "modified Valsalva," which was actually a hard /k/ held for several seconds, produced the next greatest level of EMG.

Tetanic contraction in vocal fold muscle.

Active properties of canine vocalis muscle tissue were investigated through a series of experiments conducted in vitro. Samples of the vocalis muscle were dissected from dog larynges excised a few minutes before death and kept in Krebs solution at a temperature of 37 +/- 1 degree C and a pH of 7.4 +/- 0.05. Isometric and isotonic tetanic responses of the vocalis muscle were obtained electronically with a Dual Servo System (ergometer). Isometric tension was recorded at various levels of elongation and stimulation rate. Isotonic shortening was recorded at various levels of force, and shortening velocity was obtained by numerical analysis of recorded data. It was found that fused tetanus occurred at stimulation rates of about 90 Hz, where the isometric tetanic force saturates. Repeated stimulation of the muscle in vitro not only caused nonrecoverable fatigue in the tissue, but also decreased its passive tension. The combined active and passive isometric tension increased with elongation of the muscle. Results of isometric active responses were normalized with respect to average passive response. This normalization allowed for better comparison between tetanic contraction and twitch contraction. It was found that maximum tetanic contraction was 6.4 times greater than maximum twitch contraction obtained in a previous study. A tetanic contraction period was defined and investigated for eight samples of vocalis muscle tissue from different dogs. The tetanic contraction period showed a linear increasing trend with strain.

Development of an in vitro technique for measuring elastic properties of vocal fold tissue.

The purpose of this investigation was to develop an in vitro technique for measurement of elastic properties of isolated vocal fold tissue. Larynges were excised from anesthetized dogs, immediately submerged in a Krebs-Ringer solution, and aerated with 95% oxygen and 5% carbon dioxide. The tissue was maintained in the aerated electrolyte solution throughout the experiment. The vocalis muscle was carefully dissected, with attachments to the arytenoid and thyroid cartilages maintained. The preparation was then subjected to isometric (constant length) force-elongation measures, which were converted to stress-strain values. Stage I of the investigation identified the dog model with the least intrastudy variability relative to the age, sex, and breed of the research animal, as well as to the effects of curare. Stage II investigated the effects of different instrumentation, definitions of reference length, methods of elongation, and effects of electrical stimulation. Once the procedure had been refined, the effects of age and sex were retested. There was a significant interaction between sex and strain and between age and strain. The least variability was obtained with curarized tissue from one sex of young, mixed-breed dogs, where an arbitrary 1 gram of initial force was the criterion for establishing "zero" strain. Problems associated with determination of reference length and various approaches to this problem are discussed.