Voluntary and Reflex Influences on the Initiation of Swallowing Reflex in Man

The electrophysiological features of voluntarily induced and reflexive/spontaneous swallows were investigated. In normal subjects, swallows were elicited by infusing water either into the mouth (1–3 ml) or directly into the oropharyngeal region through a nasopharyngeal cannula (0.3–1 ml). For water infused orally, subjects were either requested to swallow voluntarily or instructed to resist swallowing and maintain the horizontal head position until swallowing occurred reflexively. Spontaneous saliva swallowing was investigated in patients with severe dysphagia who had a prominent clinical picture of suprabulbar palsy. Comparisons between different swallowing types were made by measuring the time interval between the onset of submental electromyographic activity (SM-EMG) and the onset of the upward movement of the larynx recorded by a movement sensor. This interval was less than 100 ms, even frequently less than 50 ms, in reflexive/spontaneous swallows, while in voluntarily induced swallows it was substantially longer. The rising time of submental muscle's excitation was also shorter in reflexive/spontaneous swallows. It was suggested that the triggering of voluntarily induced swallows commences more than 100 ms before the onset of swallowing reflex and that this mechanism is under the control of corticobulbar–pyramidal pathways. If the swallowing reflex is triggered within such a short period of time following the onset of SM-EMG, the central control by the bulbar swallowing center should be effective until the end of oropharyngeal swallowing.     

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.     

Food Transport and Bolus Formation during Complete Feeding Sequences on Foods of Different Initial Consistency

Food movements during complete feeding sequences on soft and hard foods (8 g of chicken spread, banana, and hard cookie) were investigated in 10 normal subjects; 6 of these subjects also ate 8 g peanuts. Foods were coated with barium sulfate. Lateral projection videofluorographic tapes were analyzed, and jaw and hyoid movements were established after digitization of records for 6 subjects. Sequences were divided into phases, each involving different food management behaviors. After ingestion, the bite was moved to the postcanines by a pull-back tongue movement (Stage I transport) and processed for different times depending on initial consistency. Stage II transport of chewed food through the fauces to the oropharyngeal surface of the tongue occurred intermittently during jaw motion cycles. This movement, squeeze-back, depended on tongue–palate contact. The bolus accumulated on the oropharyngeal surface of the tongue distal to the fauces, below the soft palate, but was cycled upward and forward on the tongue surface, returning through the fauces into the oral cavity. The accumulating bolus spread into the valleculae. The total oropharyngeal accumulation time differed with initial food consistency but could be as long as 8–10 sec for the hard foods. There was no predictable tongue–palate contact at any time in the sequence. A new model for bolus formation and deglutition is proposed.     

A Study of Interrater Reliability when Using Videofluoroscopy as an Assessment of Swallowing

Videofluoroscopic assessment of swallowing is widely used in clinical settings. The interpretation of such assessments depends on subjective visual judgments but the reliability of these judgments has been poorly researched. This study measured interrater reliability of judgments, made by speech pathologists, of videofluoroscopic images of subjects swallowing liquid and semisolid boluses. A 5-point rating scale was used in three conditions: individually after careful reading; together with other speech pathologists in group discussion; and individually after the group discussion. Analysis of the ratings for the three conditions revealed that the level of agreement among raters was generally higher for semisolid swallows than for liquid swallows. The highest levels of agreement occurred for ratings made after group discussions. The levels of agreement were lowest when raters worked alone, relying only on reading the scale. Individual rating after group discussion resulted in higher levels of agreement than sole reliance on reading the scale. Factors influencing the levels of interrater agreement, including the timing of observations, bolus consistency, the quality of the image, and the complexity of the task, are discussed.     

Swallowing Physiology of Toddlers with Long-Term Tracheostomies: A Preliminary Study

This study investigated the swallowing physiology of toddler-aged patients with long-term tracheostomies. Structural movements and motility of the pharyngeal stage of swallowing were studied in four toddlers ranging in age from 1:2 (years:months) to 2:9 with long-term tracheostomies. A patient aged 1:2 years with no tracheostomy served as a toddler model for comparison. Videofluoroscopic recordings of the patients' liquid and puree bolus swallows were analyzed for a) onset times for pharyngeal stage events, laryngeal vestibule closure, and tracheostomy tube movement; b) timeliness of swallow response initiation; and c) pharyngeal transport function. Results found differences in timing of pharyngeal stage movements between the tracheostomized patients and the patient with no tracheostomy. Laryngeal vestibule closure occurred before or within the same 0.033-s video frame as onset of upper esophageal sphincter (UES) opening in the patient with no tracheostomy, but occurred 0.033–.099 s after onset of UES opening in the tracheostomized patients. The time line required to close the laryngeal vestibule once the arytenoids began their anterior movement was longer in the tracheostomized patients than in the patient with no tracheostomy and was associated with laryngeal penetration. The patient with no tracheostomy displayed superior excursion of the arytenoid and epiglottis during the swallowing; the tracheostomized patients did not. No association was found between onset of tracheostomy tube movement and laryngeal vestibule closure. Delayed swallow response initiation was observed across tracheostomized patients at a mean frequency of 45% with associated penetration. Pharyngeal dysmotility was not observed. Findings supported the concept that long-term tracheostomy in toddler-aged patients affects swallowing physiology.     

Lateral Pharyngeal Wall Motion during Swallowing Using Real Time Ultrasound

B-mode ultrasound imaging has been used primarily to detect temporal and spatial movements of the tongue during the oral preparatory and oral stages of swallowing. The purpose of this study was to investigate the application of M-mode (motion mode) ultrasound imaging as a method to quantify the duration and displacement of single regions along the lateral pharyngeal wall during swallows of two bolus volumes and during three swallow maneuvers (supraglottic, super-supraglottic and Mendelsohn maneuver). In 5 normal subjects, simultaneous B/M-mode images were captured at two regions along the lateral pharyngeal wall. Computer-assisted video analysis of each swallow sequence provided spatial coordinates and durational measures. Results indicated no significant differences in displacements of the lateral pharyngeal wall across bolus volumes, swallow maneuvers, or recording sites. Significant differences (p < 0.001) in lateral pharyngeal wall duration occurred as a function of volitional swallow maneuvers. Greater durations (p < 0.05) were found for the Mendelsohn and super-supraglottic swallow maneuvers. The data demonstrate that B/M-mode ultrasound imaging provides a simple, noninvasive method to visually examine movements of the lateral pharyngeal wall and may provide a clinical method for assessing the effects of direct swallowing therapies at the level of the mid-oropharynx.     

Exploration of Pharyngeal Swallowing by Audiosignal Recording

The aims of this study were to analyze the following by audiorecording of swallows: (1) the influence on the volume and consistency of ingested substances on the audiosignal recorded during separate swallows; and (2) the characteristics of successive swallows during ingestion of 100 ml of the same substances to define deglutitive behaviors. Volunteers followed two protocols. Protocol (P) 1 comprised ingestion of 100 ml of water or yoghurt in successive swallows and Protocol 2 comprised separate swallows of different volumes of the same substances. Audiosignal recordings were made with a dynamic microphone. The following parameters were measured in P1: total time of ingestion (TT), number of swallows necessary for ingestion (N), and spontaneous swallowing intervals (SI). In P2 the duration (d) of each signal was measured according to consistency and volume. Mean (m) values were then calculated (TTm, Nm, SIm, and dm). During P1, TTm for yoghurt was significantly longer than for water (23.1 vs. 6.5 sec (men) and 21.8 vs. 7.8 sec (women). Nm was also greater for yoghurt (10.1 vs. 4.3 (men) and 10.0 vs. 4.8 (women). Three types of swallowing behavior were defined according to SI: swallowing at regular intervals (Reg) with increasing intervals during ingestion (Prog) and swallowing at variable intervals (Irreg). These patterns did not differ significantly according to sex. In P2 the increase in volume swallowed increased the duration (dm) of the signal for water (600 msec for 5 ml and 960 msec for 15 ml). The dm for yoghurt was significantly less than for water (580 msec for 5 ml and 920 msec for 15 ml). Our technique of recording sounds of pharyngeal swallowing is simple, reproducible, and not expensive. It permitted the analysis of each swallow according to volume and consistency and the determination of three swallowing patterns (Reg, Prog, and Irreg), taking into account the spontaneous swallowing interval. Ingestion by successive swallows could be used to characterize certain pharyngoesophageal motor dysfunctioning in relation to this reference population and to integrate this into a deglutition rehabilitation program.     

Proposed Catheter Standards for Pharyngeal Manofluorography (Videomanometry)

With the recent introduction of commercially available pharyngeal manofluorography systems, catheter design should be standardized. Catheters of different designs can produce different data because of their design characteristics. A standard catheter design should make results between investigators comparable and facilitate acceptable normal values. The authors' combined laboratory experience with many catheter designs was reviewed and the literature consulted. For pharyngeal manofluorography, the proposed standard catheter should be 2 × 4 mm in diameter, ovoid, and 100 cm long. The catheter should be marked in centimeters with an anterior and posterior orientation. There should be a slightly malleable, 3- to 4-cm length without sensors beyond the most distal sensor. Solid state transducer sensors should be three or four in number and placed in the pharyngoesophageal segment, midhypopharynx, and tongue base (esophagus for fourth sensor). Sensor spacing should be 3 cm, except 2 cm between the midhypopharynx and tongue base. Unidirectional, in-line, posteriorly oriented sensors with the option of a single circumferential sensor in the cricopharyngeus are currently preferred over circumferential sensors because of their small diameter (patient comfort).     

Effects of Age, Gender, Bolus Volume, and Trial on Swallowing Apnea Duration and Swallow/Respiratory Phase Relationships of Normal Adults

The effects of age, gender, bolus volume, and trial on swallowing apnea duration (SAD) and swallow/respiratory phase relationships were examined. Sixty adults, composed of ten males and ten females in each of three age groups (i.e., 20–39, 40–59, and 60–83 years), participated. SAD was assessed via nasal airflow during saliva swallows and 10-, 15-, 20-, 25-mL bolus volumes across three trials. Results revealed SAD is consistent across trial (p>0.05). Significant main effects of age, gender, and bolus volume were found (p<0.05), i.e., elderly adults had longer SAD than young and middle-aged adults; women had longer SAD than men; and SAD increased as bolus volume increased. With respect to saliva swallows, a significant interaction of age by gender was found (p<0.05), i.e., males exhibited a decrease in SAD with increasing age while females exhibited an increase in SAD with increasing age. Concerning swallow/respiratory phase relationships, the pattern of exhale–swallow–exhale was evident during 62% of participants' swallows. Furthermore, age, gender, or bolus volume did not predict the pattern of exhale–swallow–exhale (p>0.05). Submitted February 23, 2000; accepted October 2, 2000     

Dynamic aspects of lingual propulsive activity in swallowing

This investigation concerned the effect of different bolus volumes on the characteristics of lingual propulsive activity in swallowing. Young normal subjects were asked to perform dry swallows and swallows of 5, 10, and 15 ml of water. Tongue activity was recorded by tracking multiple gold pellets affixed to the tongue, utilizing the specialized research capabilities of the X-ray Microbeam facility at the University of Wisconsin. The major differences were between dry and liquid swallows, with dry swallows showing smaller range of movement, higher tongue position at the initiation of lingual propulsive activity, a slightly different direction of motion, a humped or flat rather than grooved cross-sectional contour of the tongue, lower peak velocity of motion, and slower progression of activity from tongue blade to dorsum. Within the 5–15 ml range of liquid bolus volumes, fewer consistent differences were found as a function of bolus size, and some marked individual differences in swallowing patterns were seen. Data are presented on normal within-subject variability in swallowing, with discussion of the possible contribution of sensory assessment of bolus size to the modification of oral and pharyngeal characteristics of swallowing.     

Videofluorographic Study of Swallowing in Parkinson's Disease

We studied 16 patients with Parkinson's disease (PD) with dysphagia and 8 young and 7 elderly normal controls videofluorographically to evaluate the nature of swallowing disorders in PD patients. In 13 patients, abnormal findings in the oral phase were residue on the tongue or residue in the anterior and lateral sulci, repeated pumping tongue motion, uncontrolled bolus or premature loss of liquid, and piecemeal deglutition. Thirteen patients showed abnormal findings in the pharyngeal phase, including vallecular residue after swallow, residue in pyriform sinuses, and delayed onset of laryngeal elevation. Ten of these patients also showed abnormal findings in both the oral and pharyngeal phases. Aspiration was seen in 9 patients. The oral transit duration was significantly longer in the patients with and without aspiration than in the control subjects. The stage transition duration, pharyngeal transit duration, duration of the upper esophageal sphincter (UES) opening, and total swallow duration were significantly longer in the patients with and without aspiration than in the young controls, but were not longer than in the elderly controls. These durational changes in the pharyngeal phase of swallowing were similar to those in the elderly controls. The findings suggest that the disturbed motility in the oral phase of swallowing may be due to bradykinesia. Although PD patients with dysphagia evince a variety of swallowing abnormalities, the duration of pharyngeal swallowing may remain within the age-related range until the symptoms worsen.     

Electromyographic Response of the Labial Muscles during Normal Liquid Swallows Using a Spoon, a Straw, and a Cup

In this investigation, surface electromyographic (EMG) recordings were used to make qualitative and quantitative analyses of labial muscle activity during three swallowing tasks, incorporating the use of various drinking implements. EMG was recorded from four quadrants of the perioral region and from the submental muscle complex in 11 normal adult females. Swallowing tasks included liquid extraction from a spoon, a straw, and a cup and posterior bolus propulsion of a 5 ml, thin liquid. Average EMG values obtained during a maximal lip compression task were used to normalize labial muscle responses for each subject thus allowing between-subject comparisons. Variable activity patterns were noted in the perioral muscles once the lips were contacted by a drinking implement. Subjects used a greater percentage of maximal labial muscle activity to remove liquid from an implement than to swallow the liquid. A greater level of EMG was recorded in the lips during straw usage as compared with spoon or cup usage. Significant intrasubject and intersubject variability in labial function occurred during liquid removal using a drinking implement and during the oral swallow in these normal subjects.     

Oral Sensory Discrimination of Fluid Viscosity

This study was designed to investigate the ability of normal young adult volunteers to sensorially identify Newtonian fluids of specified viscosities. Twenty subjects, 10 men and 10 women between the ages of 18 and 29 years participated. Seven stimuli, consisting of combinations of corn syrup and water, with viscosities ranging from 2 to 2,240 centipoise (cP) were prepared and characterized using a coaxial rotational viscometer. Subjects were presented with two anchor stimuli representing the extremes of the range of viscosities as a basis from which the experimental stimuli were judged. The seven experimental stimuli were randomly presented to each subject 10 times. The accuracy with which the subjects identified the viscosity of the fluid was significant at p < 0.01. The pattern of response was not significantly different across subjects nor gender. There were no differences in performance throughout the duration of the study. The repeat presentation of the anchor points did not significantly affect performance. Further research on oral perception of viscosity, and the processes that mediate changes in swallow physiology resulting from changes in viscosity is required.     

Dysphagia following Anterior Cervical Spine Surgery

Although previous reports have identified dysphagia as a potential complication of anterior cervical spine surgery (ACSS), current understanding of the nature and etiologies of ACSS-related dysphagia remains limited. The present study was undertaken to describe the patterns of dysphagia that may occur following ACSS. Thirteen patients who exhibited new-onset dysphagia following ACSS were studied retrospectively by means of chart review and videofluoroscopic swallow study analysis. Results indicated that a variety of swallowing impairments occurred following ACSS. In 2 patients, prevertebral soft tissue swelling near the surgical site, deficient posterior pharyngeal wall movement, and impaired upper esophageal sphincter opening were the most salient videofluoroscopic findings. In another 5 patients, the pharyngeal phase of swallowing was absent or very weak, with resulting aspiration in 3 cases. In contrast, an additional 4 patients exhibited deficits primarily of the oral preparatory and oral stages of swallowing including deficient bolus formation and reduced tongue propulsive action. Finally, 2 patients exhibited impaired oral preparatory and oral phases, a weak pharyngeal swallow, as well as prevertebral swelling. Thus, a variety of swallowing deficits, due possibly to neurological and/or soft tissue injuries, may occur following ACSS.     

Inter- and Intrajudge Reliability of a Clinical Examination of Swallowing in Adults

This study investigates inter- and intrajudge reliability of a clinical examination of swallowing in adults. Several investigations have sought correlations between clinical indicators of dysphagia and the actual presence of dysphagia as determined by videofluoroscopy. Whereas some investigations have reported interjudge reliability for the videofluoroscopic measures employed, none have reported reliability for clinical measures. Without established reliability for rating clinical measures, conclusions drawn regarding the utility of a measure for detecting aspiration can be called into question. Results of the present study indicate that fewer than 50% of the measures clinicians typically employ are rated with sufficient inter- and intrajudge reliability. Measures of vocal quality and oral motor function were rated more reliably than were history measures or measures taken during trial swallows. There is a need to define more clearly the measures employed in clinical examinations and to be consistent in reporting reliability for clinical measures of swallowing function in future research.     

Structural Displacements in Normal Swallowing: A Videofluoroscopic Study

Dynamic videofluoroscopic swallow studies were performed on 60 normal adult volunteers to establish normative data for displacement of upper aerodigestive tract structures during deglutition. Variables evaluated included hyoid bone displacement, larynx-to-hyoid bone approximation, pharyngeal constriction, and the extent of pharyngoesophageal sphincter (PES) opening during liquid swallows of 1, 3, and 20 cc. Results showed direct relationships between bolus size and hyoid displacement, between bolus size and PES opening, and between bolus size and pharyngeal constriction. Only hyoid-to-larynx approximation remained unchanged across bolus sizes. Sex differences were noted for all variables except PES opening. Reliability for most measurement variables was excellent. To our knowledge, normative data for pharyngeal constriction and larynx-to-hyoid approximation have not previously been described.     

Isolated Lower Esophageal Sphincter Relaxation as ``Wave-Suppressed' Secondary Peristalsis

Esophageal venting following air insufflation may occur by secondary peristalsis or by isolated transient lower esophageal sphincter relaxation (TLESR). To identify factors determining venting by these two mechanisms, we analyzed the responses to esophageal air insufflation in 4 infants and in 2 adults. We used a nine-lumen dual-Dent-sleeve manometric catheter with an air insufflation esophageal side hole, identifying swallowing by pharyngeal manometry or submental electromyography. The time from the venting lower esophageal sphincter relaxation (whether part of a secondary peristalsis or an isolated TLESR) to the next swallow (whether spontaneous, in the infants, or on command, in the adults) was characterized as ≥15 sec or <15 sec. Of the 25 evaluable trials, the subsequent swallow was ≥15 sec after the venting response in 9 instances and <15 sec afterward in 16 instances. Eight of the 9 trials with delayed swallows (≥15 sec) were vented by secondary peristalsis, whereas 11 of the 16 with early swallows (<15 sec) were vented by TLESR (X² p < 0.01). TLESRs may be induced by esophageal stimuli, in which case they may represent ``wave-suppressed' secondary peristaltic complexes.     

Difference in the Burst Patterns of Digastric and Mylohyoid Activities during Feeding in the Freely Behaving Rabbit

Burst patterns in the digastric, mylohyoid, and masseter muscles and the resultant jaw movement orbits during chewing and swallowing were investigated in the freely behaving rabbit. Activities in the posterior mylohyoid fibers consisted of two continuous bursts. Peaks in the first burst of the posterior fibers occurred in the middle part of opening and preceded the digastric burst. Peaks in the second burst occurred in the final part of opening and coincided with those in the working side of the digastric burst. After removal of the bilateral digastric muscles, the gape size during chewing was largely reduced in the final part of opening and in the early part of closing. The results suggest that (a) the digastric may have a role in opening the mandible widely beyond the rest position but may not have a major role in the control of the horizontal (mediolateral) jaw movement, (b) the posterior mylohyoid fibers may have a function as an elevator of the tongue in the early part of opening, and (c) the posterior mylohyoid fibers may have a function as a depressor of the jaw in the late part of opening. Electromyographic burst in the mylohyoid muscle began with marked activity in the mid-closing phase. The results support a role for the mylohyoid muscle as a leading muscle of swallowing. Swallowing events in the rabbit are easily distinguished from the activities of the mylohyoid muscle and the thyrohyoid muscle.     

Videomanometric Analysis of Supraglottic Swallow, Effortful Swallow, and Chin Tuck in Healthy Volunteers

Simultaneous videoradiography and solid-state manometry (videomanometry) was applied in eight healthy volunteers (four women, four men; age range 25–64 years, mean age 41 years) without swallowing problems. Three different swallowing techniques were tested; supraglottic swallow, effortful swallow, and chin tuck. Seven videoradiographic variables and six manometric variables were analyzed. The supraglottic swallowing technique did not differ significantly from that of the control swallows. The effortful swallow had a significantly (p= 0.0001) reduced hyoid–mandibular distance preswallow due to an elevation of the hyoid and the larynx, which caused a significantly (p= 0.007) reduced maximal hyoid movement and a significantly (p= 0.009) reduced laryngeal elevation during swallow. The chin tuck swallow had a significantly (p= 0.001) reduced laryngohyoid distance and also a significantly (p= 0.004) reduced hyoid–mandibular distance. The chin tuck swallow also displayed significantly (p= 0.003) weaker pharyngeal contractions. Videomanometry allows for analysis of bolus transport, movement of anatomical structures, and measurement of intraluminal pressures. These variables are important when evaluating swallowing techniques. In the present study, we made a few observations that never have been reported before. When healthy volunteers performed supraglottic swallow, they performed the technique somewhat differently. Therefore, we assume dysphagic patients would need a substantial period of training to perform a technique efficiently. Chin tuck could impair protection of the airways in dysphagic patients with weak pharyngeal constrictor muscles.     

Videofluoroscopic Evaluation of Aspiration with Visual Examination of the Gag Reflex and Velar Movement

The purpose of the present study was to investigate the relationship between prevalence of aspiration as determined by videofluoroscopic evaluation and prevalence of the gag reflex and velar movement as determined by direct visual examination. One hundred adult patients underwent a videofluoroscopic evaluation of aspiration with either an esophagram (n = 31), upper gastrointestinal series (n = 18), small bowel series (n = 23), or modified barium swallow procedure (n = 28), and concomitant evaluation of the gag reflex and velar movement on phonation. All studies were performed using the lateral, upright position, and all patients drank at least 5 cc of single contrast barium. Aspiration was defined as penetration of material below the level of the true vocal folds. A normal gag reflex and normal velar movement on phonation were observed in 14 of 15 (93%) patients who exhibited objective documentation of aspiration with videofluoroscopy. Conversely, 19 of 20 (95%) patients without a gag reflex were observed with videofluoroscopy to be without aspiration. Normal velar movement on phonation was observed in 99 of 100 (99%) patients. There was no significant age difference between patients with or without a gag reflex. No relationship was found between the prevalence of aspiration and the gag reflex or velar movement on phonation. It was concluded that the presence of a gag reflex does not protect against aspiration, and the absence of a gag reflex does not predict aspiration.