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.     

Bolus position at swallow onset in normal adults: Preliminary observations

A “delayed swallowing reflex/response” (i.e., when the swallow reflex is not triggered when the bolus passes the back of the tongue at the anterior faucial arch) Logemann [8] has been widely accepted as an abnormality. Careful review of the literature supports the premise that a “delayed swallowing reflex/response” may in fact be a variation of normal. This paper describes swallowing in normal adults. We report the videofluoroscopic measurements of bolus position at the onset of swallow. A radiopaque marker was affixed to the anterior faucial arch and the distance between the head of the bolus and the anterior faucial arch was measured at the onset of swallow. A statistically significant proportion of swallows (22 of 30) occurred after the head of the bolus passed the anterior faucial arch. This finding suggests that there may be diverse sites for elicitation of the swallowing response/reflex rather than a single site (i.e., the anterior faucial arch). The relevance of this finding to treatment using thermal stimulation is discussed, as is the versatility of the normal pharynx.     

Pressure-flow dynamics of the oral phase of swallowing

In 5 healthy volunteers, we studied the pressure-flow kinetics of the oral phase of swallowing. The regional profile within the oral cavity during swallowing was recorded, at the tongue tip (T₁), dorsum of the tongue (T₂), 3 cm from the tongue tip, oral floor, buccal cavity, and between the lips during swallows of water (0–20 ml) and 5 ml of mashed potato. Two strain gauge (SG) probes, each with two transducer recording sites 3 cm apart, were used for recording pressure. Supralingual and sublingual pressure were recorded concurrently. The relationship between transit of a barium bolus and deglutitive oral pressure phenomena was determined by concurrent videoradiography and manometry. Lingual pressure with the SG facing the tongue showed the most consistent recording and highest pressure: 193±16 (SE) mmHg at T₁ and 214±18 mmHg at T₂ for dry swallows. Pressures were similar for water swallows. However, mashed potato swallows produced a pressure of 383±30 mmHg at T₁ and 485±52 mmHg at T₂ that were greater than for water swallows (p<0.01). Pressure recorded with the transducers facing the hard palate and, to a lesser extent, laterally, was low and inconsistent. Oral-floor pressure was greatest with the transducers oriented upwards and averaged 64±2.9 mmHg proximally and 173±36 mmHg distally. At all sites the pressure waves propagated sequentially, toward the pharynx. Minimal pressure increases occurred in the buccal cavity. Lip squeeze varied from 0 to 90 mmHg. We can draw the following conclusions. The oral phase of swallowing includes contraction of the oral floor, which provides a platform for tongue movement. Oral pressure waves propagate toward the pharynx so that a swallowed bolus is propelled ahead of the point of lingual-palatal closure. Lingual peristalsis exhibits a wide range of pressures, with lower pressure for dry and liquid boluses than for a semisolid bolus. Buccal and lip contractions act as stabilizing forces, but do not contribute to bolus propulsion. Significant differences exist in the radial pressure profile of lingual peristalsis, with maximal pressure oriented toward the tongue.     

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.     

Upper esophageal sphincter opening and modulation during swallowing

Studies were done on 8 normal subjects with synchronized videofluoroscopy and manometry to facilitate a biomechanical analysis of upper esophageal sphincter opening and volume-dependent modulation during swallowing. Movements of the hyoid and larynx, dimensions of sphincter opening, and intraluminal sphincter pressure were determined at 1/30th-s intervals during swallows of 1, 5, 10, and 20 ml of liquid barium. Our analysis subdivided upper esophageal sphincter activity during swallowing into five phases: (a) relaxation, (b) opening, (c) distention, (d) collapse, and (e) closure. Sphincter relaxation occurred during laryngeal elevation and preceded opening by a mean period of 0.1 s. Opening occurred as the sphincter was pulled apart via muscular attachments to the hyoid such that the hyoid coordinates at which sphincter opening and closing occurred were constant among bolus volumes. Sphincter distention after opening was modulated by intrabolus pressures rather than graded hyoid movement. The generation of intrabolus pressure coincided with the posterior thrust of the tongue that culminated in pharyngeal wall contact and the initiation of pharyngeal peristalsis. Larger volume swallows were associated with greater intrabolus pressure and increased bolus head velocity. The duration of sphincter opening increased in conjunction with a prolongation of the anterior-superior excursion of the hyoid and a delay in the onset of pharyngeal peristalsis (the event that determined the timing of sphincter closure). We conclude that transsphincteric transport of increasing swallow bolus volumes is accomplished by modulating sphincter diameter, opening interval, and flow rate (reflected by bolus head velocity). Furthermore, upper esophageal sphincter opening is an active mechanical event rather than simply a consequence of cricopharyngeal relaxation.     

Volume accommodation during swallowing

Bolus volume is an important modifier of the biomechanical events of the oropharyngeal swallow. The biomechanical events comprising a swallow can be divided into events associated with the reconfiguration of the pharynx into a swallow pathway and events associated with bolus transport from the oropharynx into the esophagus. Volume modification is achieved differently for the events of reconfiguration and propulsion. In the case of reconfiguration, a longer time is allocated to the process, as exemplified by sustained laryngeal elevation and hyoid excursion during larger volume swallows. On the other hand, in the case of bolus expulsion, volume accommodation is accomplished within the same period of time by utilizing increased vigor of expulsion. The result of deglutitive volume accommodation is a remarkably different fluoroscopic appearance of a small vs. a large volume swallow. The larger volume swallow seemingly takes longer and results in much more vigorous bolus expulsion than a small volume. However, this is more related to the bolus than the swallow.     

Durational aspects of the oral-pharyngeal phase of swallow in normal adults

We present durational data on normal oral-pharyngeal swallows in adults obtained using ultrasound imaging. The effects of normal aging on the oral-pharyngeal phase of swallowing were studied in 47 healthy adults. Timing of the oralpharyngeal phase of swallow was determined from frame-by-frame analysis of ultrasound videos of the motion of the tongue and hyoid bone from initial rest to final resting position. Duration of unstimulated (dry) swallows was compared to stimulated (wet) swallows across four age groups and by sex and age. For most subjects, dry swallows were longer than wet swallows; moreover, swallow duration was longest for older women than any other group. As age increased (55+), oral swallows were accompanied by extralingual gestures. Ability to produce a timed series of continuously dry swallows was somewhat influenced by age. Findings are suggestive of an age change more typical in women, with a pattern of multiple lingual gestures commonly seen after age 55 in both sexes. We suggest that subtle, subclinical, oral neuromotor changes occur with normal aging to cause these findings.     

Speed of peristalsis in pharyngeal constrictor musculature: Correlation to age

In order to define the influence of age on pharyngeal constrictor peristalsis, four groups of individuals were examined with cineradiography (50 frames/s) during barium swallow. The speed varied between 6.3 and 21.3 cm/s (mean, 10.5). There was no significant difference between young nondysphagic volunteers and the three groups of dysphagic patients ages under 40, between 50 and 60, and over 75 years of age). However, the intrapersonal variation of peristaltic speed during three different swallows was small in young nondysphagic volunteers and large in dysphagic patients. The variation increased with age. Variation in speed is easy to register during cineradiography and should be considered as a criterion for definition of pharyngeal motor performance in dysphagic patients. Supported by grants from the “Gun and Bertil Stohnes Foundation”     

Coordination of mastication and swallowing

The coordination of mastication, oral transport, and swallowing was examined during intake of solids and liquids in four normal subjects. Videofluorography (VFG) and electromyography (EMG) were recorded simultaneously while subjects consumed barium-impregnated foods. Intramuscular electrodes were inserted in the masseter, suprahyoid, and infrahyoid muscles. Ninety-four swallows were analyzed frame-by-frame for timing of bolus transport, swallowing, and phases of the masticatory gape cycle. Barium entered the pharynx a mean of 1.1 s (range −0.3 to 6.4 s) before swallow onset. This interval varied significantly among foods and was shortest for liquids. A bolus of food reached the valleculae prior to swallow onset in 37% of sequences, but most of the food was in the oral cavity at the onset of swallowing. Nearly all swallows started during the intercuspal (minimum gape) phase of the masticatory cycle. Selected sequences were analyzed further by computer, using an analog-to-digital convertor (for EMG) and frame grabber (for VFG). When subjects chewed solid food, there were loosely linked cycles of jaw and hyoid motion. A preswallow bolus of chewed food was transported from the oral cavity to the oropharynx by protraction (movement forward and upward) of the tongue and hyoid bone. The tongue compressed the food against the palate and squeezed a portion into the pharynx one or more cycles prior to swallowing. This protraction was produced by contraction of the geniohyoid and anterior digastric muscles, and occurred during the intercuspal (minimum gape) and opening phases of the masticatory cycle. The mechanism of preswallow transport was highly similar to the oral phase of swallowing. Alternation of jaw adductor and abductor activity during mastication provided a framework for integration of chewing, transport, and swallowing.     

Hyoid-Bolus Transit Latencies in Normal Swallow

Pharyngeal swallow delay is frequently found in dysphagic patients and is thought to be a factor in a range of swallowing problems, including aspiration. Implicit in notions of swallow “delay” is a temporal interval between two events that is longer than normal. However, there appears to be little agreement about which referent events should be considered in determining delay. A number of pharyngeal bolus transit points and various pharyngeal gestures have been used in delays determined from fluoroscopic evidence, and other referents have been used in electromyographic and manometric studies of swallow. In this study latencies between the first movement of the hyoid and several pharyngeal bolus transit points were calculated from fluoroscopic swallow studies in normal nondysphagic adults. Means and standard deviations of these latencies are provided for a 3-cc and a 20-cc bolus and for both nonelderly and elderly adults. The data may be a useful resource for relating the specific latencies investigated to concepts of pharyngeal swallow delay, in particular, when assessing videofluoroscopic studies using a similar protocol.     

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.     

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.     

Relation of bolus size and pharyngeal swallow

To study the influence of bolus size on pharyngeal swallow, 20 dysphagic patients and 10 nondysphagic volunteers were examined cineradiographically while swallowing a bolus of 2.5, 5, 10, and 20 ml. Ten patients and 10 volunteers swallowed boluses in increasing volume while 10 patients swallowed boluses of decreasing volume. The movement of the hyoid bone occurred in a two-step fashion irrespective of the bolus size, and in all individuals. The speed of the apex of the bolus through the pharynx, measured by frame counting, increased with increasing size of the bolus. The speed of the peristaltic wave, as measured between vallecula and the PE segment, did not change with bolus size. Boluses of 10 or 20 ml caused penetration of barium into the larynx in 7 of the patients but in none of the volunteers. Our results suggest that pharyngeal constrictor activity, in terms of speed of peristalsis, is constant and not influenced by bolus volume.     

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.     

The Influence of Orolingual Pressure on the Timing of Pharyngeal Pressure Events

This study explored the influence of two methods of effortful swallow execution on the timing of pharyngeal pressure events. Participants were asked to either emphasize or minimize tongue-to-palate contact during performance of the maneuver. Twenty healthy participants were evaluated using concurrent submental surface electromyography (sEMG), orolingual manometry, and pharyngeal manometry. Each subject performed three repetitions of three counterbalanced tasks (noneffortful dry swallows, effortful dry swallows with tongue-to-palate emphasis, and effortful dry swallows with tongue-to-palate de-emphasis). Four variables were measured: Onset Lag vs. sEMG Peak, Peak Lag vs. sEMG Peak, Total Duration, and Percent Rise Time to Peak. Compared to noneffortful swallows, the effortful swallow task elicited significantly earlier onsets and peaks of pharyngeal pressures relative to the submental sEMG peak. Total pressure event durations were greater and rise times were significantly shorter. When comparing the two methods of effortful swallow execution, a longer latency to peak proximal pharyngeal pressure was found in the tongue-to-palate emphasis condition. These results support the interpretation that the effortful swallow maneuver involves generation of higher velocity bolus driving forces that propel the bolus into and through the pharynx with greater efficiency and that pressure is then sustained to facilitate more complete bolus clearance. Work performed at the Van der Veer Institute for Parkinson’s and Brain Research, Christchurch, New Zealand     

Effects of systematic bolus viscosity and volume changes on hyoid movement kinematics

Using ultrasonography with head and transducer stabilization, this study examined the effects of maximally controlled, systematic changes in bolus viscosity (thin juice-like, 7 cP; nectar-like, 243–260 cP; honey-like, 724–759 cP; spoon-thick, 2760–2819 cP) and volume (5, 10, 20, 30 cc) on hyoid kinematics in 31 healthy subjects (16 male, 15 female) in three age groups (20–39, 40–59, 60–79 years). Frame-by-frame hyoid displacements were tracked from digitized images of 612 swallows. Measures of movement durations, maximal amplitudes, total distances, and peak velocities were subjected to repeated measures multivariate analyses of variance with viscosity, volume, age, and gender as factors. Results showed that (1) spoon-thick swallows had the greatest preswallow gesture and total movement durations; (2) larger-volume swallows had significantly greater maximal amplitudes, forward peak velocity, and total vertical distance; (3) older subjects had longer start-to-max duration (though shorter preswallow gesture and total movement durations), greater maximal vertical amplitude, longer total vertical distance, and greater backward peak velocity than younger subjects; (4) males had greater values for all kinematic parameters except preswallow gesture, hyoid-at-max, and max-to-end durations. The results illustrate the importance of examining the interrelations among kinematic variables to better understand task accommodation and motor control strategies. The evidence also supports the concept of suprahyoid–infrahyoid functional adaptation and compensation in the healthy elderly.     

Maximal Hyoid Excursion in Poststroke Patients

Reduced maximal hyoid excursion has been suspected as one of the primary physiologic causes of aspiration after a stroke. Vertical and anterior displacement of hyoid excursion is critical to epiglottic closure for airway protection and the opening of the upper esophageal sphincter (UES). Without these carefully timed and well-executed components, the bolus cannot pass safely through the pharynx. The purpose of this study was to evaluate vertical and anterior displacement of the hyoid bone during oropharyngeal swallowing in two groups of subjects: (1) 16 stroke patients who aspirate before or during the swallow (aspirators), and (2) 33 stroke patients who do not aspirate (nonaspirators). Means and standard deviations for anterior and vertical displacement were analyzed for 5- and 10-ml thin-liquid boluses using the ImageJ program (136 swallows). A two-way analysis of variance (ANOVA) was run with group and volume as independent variables. There was no significant difference between the two groups for vertical or anterior displacement. Maximal anterior displacement of the hyoid bone was slightly longer in nonaspirators than in aspirators. Aspiration before and during the swallow may be related more to the triggering of pharyngeal swallow than to the maximal extent of hyoid excursion.     

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.     

A Randomized Study Comparing the Shaker Exercise with Traditional Therapy: A Preliminary Study

Seven institutions participated in this small clinical trial that included 19 patients who exhibited oropharyngeal dysphagia on videofluorography (VFG) involving the upper esophageal sphincter (UES) and who had a 3-month history of aspiration. All patients were randomized to either traditional swallowing therapy or the Shaker exercise for 6 weeks. Each patient received a modified barium swallow pre- and post-therapy, including two swallows each of 3 ml and 5 ml liquid barium and 3 ml barium pudding. Each videofluorographic study was sent to a central laboratory and digitized in order to measure hyoid and larynx movement as well as UES opening. Fourteen patients received both pre-and post-therapy VFG studies. There was significantly less aspiration post-therapy in patients in the Shaker group. Residue in the various oral and pharyngeal locations did not differ between the groups. With traditional therapy, there were several significant increases from pre- to post-therapy, including superior laryngeal movement and superior hyoid movement on 3-ml pudding swallows and anterior laryngeal movement on 3-ml liquid boluses, indicating significant improvement in swallowing physiology. After both types of therapy there is a significant increase in UES opening width on 3-ml paste swallows.     

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.