Event Sequence Variability in Healthy Swallowing: Building on Previous Findings

This study builds on previous work by Kendall, Leonard, and McKenzie, which investigated event sequence variability for 12 paired events during swallowing by healthy volunteers. They identified four event pairs that always occurred in a stereotyped order and a most common occurring overall order of events during swallowing. In the current study, we investigated overall event sequencing and the same four paired events in a sample of swallows by healthy young (under 45 years old) volunteers. Data were collected during a 16-swallow lateral videofluoroscopy protocol, which included manipulations of bolus volume, barium density, bolus viscosity, and swallow cueing. Our results agreed with previous findings that variable event sequencing is found in healthy swallowing, and, in regard to obligatory sequencing of two paired events, movement of the arytenoids toward the base of the epiglottis begins prior to upper esophageal sphincter (UES) opening and maximum hyolaryngeal approximation occurs after UES opening. However, our data failed to replicate the previous findings that there is obligatory sequencing of maximum pharyngeal constriction after maximal UES distension and the UES opens before bolus arrival at the UES. The most common observed overall event sequence reported by Kendall et al. was observed in only 4/293 swallows in our dataset. Manipulations of bolus volume, bolus viscosity, barium concentration, swallow cueing, and swallow repetitions could not completely account for the differences observed between the two studies.     

Timing Differences Between Cued and Noncued Swallows in Healthy Young Adults

Temporal parameters such as stage transition duration, bolus location at swallow onset, and pharyngeal transit time are often measured during videofluoroscopy, but these parameters may vary depending on assessment instructions. Specifically, “command” (cued) swallows have been observed to alter timing compared to spontaneous (noncued) situations in healthy older adults. The aim of our study was to confirm whether healthy young people show timing differences for thin liquid swallows between cued and noncued conditions. Twenty healthy young adults swallowed 10-cc boluses of ultrathin barium in videofluoroscopy. The cued condition was to hold the bolus in the mouth for 5 s before swallowing. Three noncued swallows were also recorded. In the cued condition, bolus advancement to the pyriform sinuses prior to swallow initiation was seen significantly less frequently. Stage transition durations showed a nonsignificant trend toward being shorter. Pharyngeal transit times and pharyngeal response time (a measure capturing the interval between hyoid movement onset and bolus clearance through the upper esophageal sphincter) were both significantly longer in the cued condition. Our study in healthy young adults confirms findings previously observed in older adults, namely, that swallow onset patterns and timing differ between cued and noncued conditions. In particular, bolus advancement to more distal locations in the pharynx at the time of swallow onset is seen more frequently in noncued conditions. This pattern should not be mistaken for impairment in swallow onset timing during swallowing assessment.     

Pharyngeal clearance during swallowing: a combined manometric and videofluoroscopic study.

The deglutitive pharyngeal contraction was analyzed using simultaneous videofluoroscopic and manometric studies of eight volunteers. Anterior, posterior, and longitudinal movements of the pharyngeal surfaces, relative to the cervical vertebrae, were measured during swallows of 5 and 10 mL of liquid barium. Profound pharyngeal shortening during bolus transit through the pharynx eliminated access to the larynx and elevated the upper esophageal sphincter to within 1.5 cm of the retrolingual pharynx. Bolus head movement through the pharynx preceded the propagated pharyngeal contraction and registered manometrically as a slight intrabolus pressure before the major pressure complex. Contraction in the horizontal plane began after bolus head transit and culminated with stripping of the bolus tail through the pharynx. Prolonged upper sphincter opening with the larger-volume swallows resulted from a delayed onset rather than altered propagation of the horizontal pharyngeal contraction. It is concluded that the propagated pharyngeal contraction facilitates pharyngeal clearance but has a minimal role in the process of bolus propulsion during swallowing. The propagated contraction works in concert with profound pharyngeal shortening to minimize hypopharyngeal residue after a swallow.     

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.     

Manometry and radiology. Complementary studies in the assessment of esophageal motility disorders

The relationship between radiological and manometric findings in esophageal motility disorders is poorly understood. Therefore, 20 subjects (4 normal; 13 diffuse spasm; 3 other motility disorders) were studied using synchronous manometry and videofluoroscopy with alternate 5-ml and 10-ml barium swallows. A total of 181 swallows were analyzed. Concordance between manometry and fluoroscopy was excellent for individual swallows (98%), groups of 5 swallows (97%), and final diagnoses (90%). Contraction onset intervals less than 0.8 s apart over 5 cm (velocity greater than 6.25 cm/s) were critical in determining abnormal bolus transit (98% sensitivity and positive predictive value). Radiologically, segmental tertiary activity (complete luminal obliteration) was always associated with disrupted primary peristalsis, but nonsegmental tertiary activity was often seen with normal bolus transit and did not have a specific manometric correlate. Four patterns of interrupted peristalsis radiologically were found--segmental tertiary contractions, a generalized esophageal contraction, absence of motor activity, or discoordinated "to-and-fro" movement. Surprisingly, nearly complete barium clearance occurred by the first two mechanisms in two thirds of swallows. Thus, the authors believe radiology and manometry are both excellent studies for identifying abnormal esophageal peristalsis. In difficult cases, these tests give complementary information because radiology assesses bolus movement while manometry provides quantitative pressure data.     

Esophageal solid bolus transit: studies using concurrent videofluoroscopy and manometry

OBJECTIVE: Our aim was to assess the efficacy and mechanism of solid bolus transit through the esophagus. METHODS: Eight healthy volunteers were studied with concurrent manometry and videofluoroscopy while swallowing 5 ml liquid barium, a 5-6 mm diameter bread ball, and 4 g chewed bread in both a supine and upright posture. As many as four successive swallows were performed until clearance was achieved. RESULTS: The esophageal clearance of liquid barium was 100% with the first swallow. Clearance of the unchewed bread ball occurred with the first swallow in only 6.7% of trials in the upright posture and 5.9% in the supine posture. After four swallows, clearance was 100% and 52.9% in the upright and supine postures, respectively. Chewed bread was more readily cleared than unchewed bread, with 100% clearance after two swallows in the upright posture and 91% clearance after four swallows in the supine posture. The most common locus of bread stasis was at the aortic arch and carina. The bread boluses were noted to move more effectively when localized in the head as opposed to the tail of the bolus composite. Nonocclusive contractions often occurred at the bolus tail despite the increased peristaltic amplitude seen with the chewed bread. Failed peristalsis, a frequent cause for solid clearance failure, was observed during 30% of all bread swallows. This usually occurred distal to the stopping point of the bolus, suggesting it to be the result rather than the cause of impaired transit. CONCLUSIONS: Although infrequently perceived by these normal subjects and in contradistinction to liquid clearance, bread is rarely cleared from the esophagus with a single swallow. Mastication and an upright posture facilitate the esophageal transport of solids. Bolus composition and impaired bolus transit alter the amplitude and conductance of peristalsis. Manometric data pertaining to liquid clearance through the esophagus do not readily apply to bread.     

Experience with the Chin Tuck Maneuver in Postesophagectomy Aspirators

Aspiration is a common finding in the postesophagectomy barium swallow that often necessitates premature termination of the study prior to complete evaluation of the gastric conduit. More importantly, aspiration may play a significant role in the high incidence of postoperative pulmonary complications in this population. The chin tuck maneuver is a postural technique that reduces and often eliminates aspiration in swallowing-impaired patients. To evaluate the ability of the chin tuck maneuver to prevent aspiration during radiographic examination of the gastric conduit, the technique was used in 21 esophagectomy patients who aspirated during a swallowing evaluation combining the barium swallow and videofluoroscopy. Aspiration was eliminated in 81% of aspirators using the chin tuck maneuver. The results of this study demonstrate that the chin tuck maneuver is a simple technique that should be attempted in patients who aspirate postesophagectomy during radiographic imaging studies that require multiple swallows of contrast materials. Combining the barium swallow with the videofluoroscopic evaluation of swallowing provides objective documentation of both the structural integrity of the gastric conduit and swallowing function in patients after esophagectomies who are at high risk for postoperative morbidity.     

Kinematic and Temporal Factors Associated with Penetration–Aspiration in Swallowing Liquids

In this study we undertook careful analysis of 13 quantitative physiological variables related to oropharyngeal swallowing from a sample of 42 subacute patients referred for dysphagia assessment. Each patient underwent a videofluoroscopic swallowing examination in which they swallowed up to five boluses of 22 % w/v ultrathin liquid barium suspension administered by teaspoon. Our goal was to determine whether scores on 13 kinematic or temporal parameters of interest were independently associated with the presence of penetration–aspiration in the final compiled dataset of 178 swallows. Participants were classified as aspirators based on the presence of at least one swallow that demonstrated a Penetration–Aspiration Scale score of ≥3. The parameters of interest included six kinematic parameters for capturing hyoid position, three swallow durations [laryngeal closure duration, hyoid movement duration, and upper esophageal sphincter (UES) opening duration], and four swallow intervals (laryngeal closure to UES opening, bolus dwell time in the pharynx prior to laryngeal closure, stage transition duration, and pharyngeal transit time). Mixed-model repeated-measures ANOVAs were conducted to determine the association between each parameter and aspiration status. Only 1 of the 13 parameters tested distinguished aspirators from nonaspirators: aspirators demonstrated significantly shorter UES opening duration. In addition, a trend toward reduced maximum superior position of the hyoid was seen in aspirators. Limitations and future considerations are discussed.     

Effects of Barium Concentration on Oropharyngeal Swallow Timing Measures

Videofluoroscopy is commonly used for evaluating oropharyngeal swallowing but requires radiopaque contrast (typically barium). Prior studies suggest that some aspects of swallowing, including timing measures of oral and pharyngeal bolus transit, vary depending on barium concentration. The aim of our study was to identify timing differences in healthy swallowing between “thin” (40 % w/v concentration) and “ultrathin” (22 % w/v concentration) barium solutions. Twenty healthy adults (Ten women; mean age = 31 years) each performed a series of three noncued 5-ml swallows each of ultrathin and thin liquid barium solutions in videofluoroscopy. Timing measures were compared between barium concentrations using a mixed-model ANOVA. The measures of interest were stage transition duration, pharyngeal transit time, and duration of upper esophageal sphincter opening. Significant differences were observed in the timing measures of swallowing with respect to barium concentration. In all cases, longer durations were seen with the higher barium concentration. Barium concentration influences timing parameters in healthy swallowing, even between ultrathin and thin concentrations. Clinicians need to understand and control for the impact of different barium stimuli on swallowing physiology.     

Laryngeal Penetration During Deglutition in Normal Subjects of Various Ages

This study examined the frequency of penetration of liquid, paste, and masticated materials into the airway during videofluoroscopic studies of normal swallow in 98 normal subjects who were from 20 to 94 years of age. The purposes of the study were to define frequency and level of penetration using the penetration-aspiration scale as a result of age, bolus volume, viscosity, and gender, and to describe the body's sensorimotor response to the penetration based on audible coughs or throat clearing on the audio channel of each videotaped fluoroscopic study. Frequencies of penetration were defined in relation to bolus volume, age, gender, and bolus viscosity from swallows of 1, 3, 5, and 10 ml and cup-drinking of thin liquids; 3 ml of pudding; (1/4) of a Lorna Doone cookie; and a bite of an apple. Results showed that penetrations were significantly more frequent after age 50 and thick viscosities penetrated only in subjects age 50 and over. For persons under 50, 7.4% of swallows exhibited penetration, while for people age 50 and over, 16.8% of swallows showed penetration. Significantly more penetration occurred on larger liquid boluses. There was no relationship between gender and frequency of penetration. None of the subjects that penetrated showed a sensorimotor response to the penetration, which may relate to the relatively shallow depth of the penetration.     

Upper esophageal sphincter function during deglutition

Upper esophageal sphincter function was investigated during swallows of graded volumes in 8 normal volunteers. Concurrent recordings of video-fluoroscopic and manometric studies were obtained and correlated with each other by means of a videotimer. Maximal upper esophageal sphincter (UES) pressure was typically located 1.5 cm distal to the air-tissue interface between the hypopharynx and the proximal margin of the sphincter. The region in which UES pressure was greater than or equal to 50% maximal averaged 1.0 cm in length. Thus, the physiologic high-pressure zone of the UES corresponds in size and location to that of the cricopharyngeus muscle. Fluoroscopic analysis of sphincter movement indicated that the sphincter high-pressure zone moved 2.0-2.5 cm orally during swallowing and that the magnitude of the orad movement was directly related to the volume of barium swallowed. The maximal anterior-posterior diameter of sphincter opening during a swallow ranged from 0.9 to 1.5 cm and was also directly related to the volume swallowed. The intervals of UES opening and relaxation increased significantly with increasing bolus volume; the duration of UES relaxation ranged from a mean of 0.37 s for dry swallows to 0.65 s for 20-ml swallows. Thus, the dynamics of UES function during deglutition are dependent upon the volume of the swallowed bolus. Larger bolus volumes are accommodated by both an increased diameter of sphincter opening and by prolongation of the interval of sphincter relaxation. Analysis of the timing of other reference points within the pharyngeal swallow sequence indicated that as the manometric interval of UES relaxation increased, the period of laryngeal elevation was prolonged, the UES relaxed earlier and contracted later, and the interval between the onset of laryngeal elevation and hypopharyngeal contraction increased.     

Effects of Three Techniques on Maximum Posterior Movement of the Tongue Base

Effects of three techniques designed to improve maximum range of posterior movement of the base of tongue were investigated under videofluoroscopy in 20 subjects. Retraction of the tongue base during 3-ml pudding swallows, tongue pull-back, yawn, and gargle tasks was measured in millimeters, with the second cervical vertebra as a reference point and was judged subjectively as well. The gargle task was the most successful in eliciting most tongue base retraction for the group of subjects, although not in every subject. Gargle also resulted in greater tongue base movement than swallow more often than the other two voluntary tasks. Clinicians' subjective judgment of ``most' retracted tongue base position was generally reliable in comparison with actual measurements. The number of repeat swallows on each bolus correlated significantly with the approximate percentage of residue in the valleculae as judged clinically.     

Timing of videofluoroscopic,manometric events,and bolus transit during the oral and pharyngeal phases of swallowing

The aims of this study were to evaluate and quantify the timing of events associated with the oral and pharyngeal phases of liquid swallows. For this purpose, we recorded 0–20 ml barium swallows in three groups of volunteers using videoradiographic, electromyographic, and manometric methods. The study findings indicated that a leading complex of tongue tip and tongue base movement as well as onset of superior hyoid movement and mylohyoid myoelectric activity occurred in a tight temporal relationship at the inception of swallowing. Two distinct general types of normal swallows were observed. The common “incisor-type” swallow began with the bolus positioned on the tongue with the tongue tip pressed against the upper incisors and maxillary alveolar ridge. At the onset of the “dipper-type” swallow the bolus was located beneath the anterior tongue and the tongue tip scooped the bolus to a supralingual location. Beginning with tongue-tip peristaltic movement at the upper incisors, the two swallow types were identical. Swallow events that occurred after lingual peristaltic movement at the maxillary incisors showed a volume-dependent forward migration in time that led to earlier movement of the hyoid and larynx as well as earlier opening of the upper esophageal sphincter in order to receive the large boluses that arrived sooner in the pharynx during the swallow sequence than did smaller boluses. The study findings indicated that timing of swallow events should be considered in reference to both swallow type and bolus volume. The findings also indicated an important distinction between peristaltic transit and bolus clearance.     

Multiple swallows and piecemeal deglutition; Observations from normal adults and patients with head and neck cancer

The incidence of multiple swallows for liquid and paste, and the time delay between multiple swallows, was determined from videofluoroscopic records of modified barium swallow tests. In a comparison of liquid and paste, the overall incidence of multiple swallows did not differ, for either patients with head and neck cancer or normal controls. However, for liquid swallows the incidence in patients with cancer was abnormally high, predominantly in patients with pharyngeal cancer.     

Influence of Chin-down Posture on Tongue Pressure during Dry Swallow and Bolus Swallows in Healthy Subjects

The purpose of this study was to investigate the influence of chin-down posture and bolus size on tongue pressure during swallowing. Eleven healthy volunteers (7 men, 4 women; age range = 26–59 years) participated in the experiments. Tongue pressure during dry and 5- and 15-ml water swallows in neutral and chin-down postures was measured using a sensor sheet system with five measuring points on the hard palate. Sequential order, maximal magnitude, duration, and integrated value of tongue pressure at each measuring point were compared between postures and bolus sizes. Onset of tongue pressure at posterior-circumferential parts occurred earlier in dry swallow than in 5- and 15-ml water swallows in each posture. Chin-down posture was most effective for increasing tongue pressure in the 5-ml water swallow compared with dry swallow and the 15-ml water swallow, but it had almost no influence on tongue pressure with the 15-ml water swallow. These results suggest that chin-down posture increases the tongue driving force for small boluses in healthy subjects, which can be interpreted to mean that oropharyngeal swallowing in a chin-down posture requires more effort.     

Preliminary observations on the effects of age on oropharyngeal deglutition

Swallows of 4 bolus volumes (1, 5, 10, 20 ml) were examined in three groups of subjects: 6 subjects 20–29 years of age, 12 subjects 30–59 years of age, and 6 subjects 60–79 years of age. A simultaneous manometric and videofluoroscopic data collection protocol permitted measurement of bolus transit, temporal aspects of the oropharyngeal swallow, and pharyngeal peristalsis. Statistically significant effects of increasing bolus volume were oral transit of the bolus head (decreased) and duration of cricopharyngeal opening (increased). Five measures were significantly changed with increasing age: duration of pharyngeal swallow delay (increased), duration of pharyngeal swallow response (decreased), duration of cricopharyngeal opening (decreased), peristaltic amplitude (decreased), and peristaltic velocity (decreased).     

Bolus Location at the Initiation of the Pharyngeal Stage of Swallowing in Healthy Older Adults

This study characterized the vertical position of the bolus head at the onset of the pharyngeal swallow in healthy older adults. Lateral-view videofluoroscopic (VF) images were obtained from ten healthy volunteers (age-71.6 ± 7.5 years, mean± SD) as they swallowed 5-cc thin liquid barium aliquots. For each swallow, the bolus head and several anatomic landmarks were digitally recorded from the image in which pharyngeal swallow-related hyoid bone elevation began. Vertical distance between the bolus head and the intersection of the tongue base and mandibular ramus (TMI) was computed. Bolus head position at swallow onset ranged from 47.4-mm above to 34.9-mm below the TMI (2.2 ± 14.4-mm, mean ± SD). Although the bolus head was below the level of the TMI for the majority of swallows, neither penetration nor aspiration occurred. For individual subjects, mean bolus head position ranged from 25.8 ± 5.0-mm above to 15.5 ± 6.5-mm below the TMI. Whereas five of ten subjects initiated the pharyngeal swallow with the bolus head consistently above or consistently below the TMI, five subjects initiated swallowing with the bolus head either above or below the TMI across trials. Older adults commonly initiate thin-liquid swallows with the bolus head well below the TMI without associated penetration or aspiration. Thus, bolus position alone does not differentiate between normal and pathologic swallowing within the healthy elderly. Bolus position at pharyngeal swallow onset can vary substantially from trial to trial within an individual, suggesting that the triggering of swallowing depends on multiple influences. This research was supported by NSERC grant No. 0GPO171208 and an Ontario Ministry of Health Career Scientist Award to REM.     

Preterm Infant Swallowing of Thin and Nectar-Thick Liquids: Changes in Lingual–Palatal Coordination and Relation to Bolus Transit

Tongue–soft palate coordination and bolus head pharyngeal transit were studied by means of postacquisition kinematic analysis of videofluoroscopic swallowing images of ten preterm infants referred from hospital NICUs due to poor oral feeding and suspicion of aspiration. Sequences of coordinated tongue–soft palate movements and bolus transits during swallows of thin-consistency and nectar-thick-consistency barium were digitized, and time series data were used to calculate continuous relative phase, a measure of coordination. During swallows of nectar-thick compared to thin barium, tongue–soft palate coordination was more likely to be antiphase, bolus head pharyngeal transit time was longer, and coordination was significantly correlated with bolus head pharyngeal transit. Analysis of successive swallows indicated that tongue–soft palate coordination variability decreased with nectar-thick but not with thin-consistency barium. Together, the results suggest that slower-moving bolus transits may promote greater opportunity for available sensory information to be used to modulate timing of tongue–soft palate movements so that they are more effective for pumping liquids.     

Unilateral Superior Laryngeal Nerve Lesion in an Animal Model of Dysphagia and Its Effect on Sucking and Swallowing

We tested two hypotheses relating to the sensory deficit that follows a unilateral superior laryngeal nerve (SLN) lesion in an infant animal model. We hypothesized that it would result in (1) a higher incidence of aspiration and (2) temporal changes in sucking and swallowing. We ligated the right-side SLN in six 2–3-week-old female pigs. Using videofluoroscopy, we recorded swallows in the same pre- and post-lesion infant pigs. We analyzed the incidence of aspiration and the duration and latency of suck and swallow cycles. After unilateral SLN lesioning, the incidence of silent aspiration during swallowing increased from 0.7 to 41.5 %. The durations of the suck containing the swallow, the suck immediately following the swallow, and the swallow itself were significantly longer in the post-lesion swallows, although the suck prior to the swallow was not different. The interval between the start of the suck containing a swallow and the subsequent epiglottal movement was longer in the post-lesion swallows. The number of sucks between swallows was significantly greater in post-lesion swallows compared to pre-lesion swallows. Unilateral SLN lesion increased the incidence of aspiration and changed the temporal relationships between sucking and swallowing. The longer transit time and the temporal coordinative dysfunction between suck and swallow cycles may contribute to aspiration. These results suggest that swallow dysfunction and silent aspiration are common and potentially overlooked sequelae of unilateral SLN injury. This validated animal model of aspiration has the potential for further dysphagia studies.     

Videofluoroscopic Evaluation of Swallowing in Chagas�� Disease

Dysphagia is the most common digestive symptom reported by patients with Chagas’ disease. The condition results from abnormalities of esophageal motility. Our hypothesis is that there are also alterations of oral and pharyngeal transit during swallowing. We studied by videofluoroscopy the oral and pharyngeal transit during swallowing in 17 patients with dysphagia, a positive serologic test for Chagas’ disease, and radiologic demonstration of esophageal involvement. The study also included 15 asymptomatic healthy volunteers. Each subject swallowed in duplicate 5 and 10 ml of liquid and paste barium boluses. Chagas’ disease patients had a longer oropharyngeal transit with the 5-ml liquid bolus (p = 0.03), and a longer oral transit (p = 0.01) and pharyngeal transit (p = 0.04) with the 10-ml liquid bolus than controls. There was no difference between patients and controls with swallows of the 5-ml paste bolus. With swallows of the 10-ml paste bolus, the oropharyngeal transit (p = 0.05), pharyngeal transit (p = 0.04), pharyngeal clearance (p = 0.02), and UES opening (p = 0.01) took a longer amount of time in Chagas’ disease patients than in controls. We conclude that the duration of pharyngeal transit is longer in patients with Chagas’ disease than in normal subjects, especially with a bolus of pasty consistency and a volume of 10 ml.