Reconstruction of the cervical esophagus: free jejunal transfer versus gastric pull-up

Use of enteric grafts is a popular method for reconstruction of the cervical esophagus and hypopharynx. Free jejunal transfer (FJT) and gastric pull-up (GP) are the most popular methods used. This discussion is a retrospective review of our experience with 50 cases of free jejunal transfer and 15 cases of gastric pull-up. The graft survival rate was 94 percent (47 of 50) for free jejunal transfer and 87 percent (13 of 15) for gastric pull-up. Successful swallowing was achieved in 88 percent (44 of 50) of free jejunal transfers and 87 percent (13 of 15) of gastric pull-ups. Patients with free jejunal transfers were able to swallow and leave the hospital sooner: 10.6 versus 16.0 days and 22.3 versus 29.0 days, respectively. Fistulas occurred in 16 percent (8 of 50) of free jejunal transfers, most of which (6 of 8) healed spontaneously. Fistulas occurred in 20 percent (3 of 15) of gastric pull-ups, only one of which healed spontaneously. Stricture was the most common late complication for free jejunal transfers, 22 percent (11 of 50), whereas reflux was most common in gastric pull-ups, 20 percent (3 of 15). In patients with advanced cancer, extensive esophageal resection into the chest is often required, and gastric pull-up seems to be an easier and more direct form of reconstruction. In limited resection of the hypopharynx and esophagus, especially with proximal lesions, free jejunal transfer is simpler and avoids mediastinal dissection. This concept as well as other advantages and disadvantages of both techniques will be discussed.     

Assessment of intraluminal impedance for the detection of pharyngeal bolus flow during swallowing in healthy adults

Intraluminal impedance, a nonradiological method for assessing bolus flow within the gut, may be suitable for investigating pharyngeal disorders. This study evaluated an impedance technique for the detection of pharyngeal bolus flow during swallowing. Patterns of pharyngoesophageal pressure and impedance were simultaneously recorded with videofluoroscopy in 10 healthy volunteers during swallowing of liquid, semisolid, and solid boluses. The timing of bolus head and tail passage recorded by fluoroscopy was correlated with the timing of impedance drop and recovery at each recording site. Bolus swallowing produced a drop in impedance from baseline followed by a recovery to at least 50% of baseline. The timing of the pharyngeal and esophageal impedance drop correlated with the timing of the arrival of the bolus head. In the pharynx, the timing of impedance recovery was delayed relative to the timing of clearance of the bolus tail. In contrast, in the upper esophageal sphincter (UES) and proximal esophagus, the timing of impedance recovery correlated well with the timing of clearance of the bolus tail. Impedance-based estimates of pharyngoesophageal bolus clearance time correlated with true pharyngoesophageal bolus clearance time. Patterns of intraluminal impedance recorded in the pharynx during bolus swallowing are therefore more complex than those in the esophagus. During swallowing, mucosal contact between the tongue base and posterior pharyngeal wall prolongs the duration of pharyngeal impedance drop, leading to overestimation of bolus tail timing. Therefore, we conclude that intraluminal impedance measurement does not accurately reflect the bolus transit in the pharynx but does accurately reflect bolus transit across the UES and below.     

Role of physical bolus properties as sensory inputs in the trigger of swallowing

Background

Swallowing is triggered when a food bolus being prepared by mastication has reached a defined state. However, although this view is consensual and well supported, the physical properties of the swallowable bolus have been under-researched. We tested the hypothesis that measuring bolus physical changes during the masticatory sequence to deglutition would reveal the bolus properties potentially involved in swallowing initiation.

Methods

Twenty normo-dentate young adults were instructed to chew portions of cereal and spit out the boluses at different times in the masticatory sequence. The mechanical properties of the collected boluses were measured by a texture profile analysis test currently used in food science. The median particle size of the boluses was evaluated by sieving. In a simultaneous sensory study, twenty-five other subjects expressed their perception of bolus texture dominating at any mastication time.

Findings

Several physical changes appeared in the food bolus as it was formed during mastication: (1) in rheological terms, bolus hardness rapidly decreased as the masticatory sequence progressed, (2) by contrast, adhesiveness, springiness and cohesiveness regularly increased until the time of swallowing, (3) median particle size, indicating the bolus particle size distribution, decreased mostly during the first third of the masticatory sequence, (4) except for hardness, the rheological changes still appeared in the boluses collected just before swallowing, and (5) physical changes occurred, with sensory stickiness being described by the subjects as a dominant perception of the bolus at the end of mastication.

Conclusions

Although these physical and sensory changes progressed in the course of mastication, those observed just before swallowing seem to be involved in swallowing initiation. They can be considered as strong candidates for sensory inputs from the bolus that are probably crucially involved in the triggering of swallowing, since they appeared in boluses prepared in various mastication strategies by different subjects.     

Upper esophageal sphincter impedance as a marker of sphincter opening diameter

The measurement of the physical extent of opening of the upper esophageal sphincter (UES) during bolus swallowing has to date relied on videofluoroscopy. Theoretically luminal impedance measured during bolus flow should be influenced by luminal diameter. In this study, we measured the UES nadir impedance (lowest value of impedance) during bolus swallowing and assessed it as a potential correlate of UES diameter that can be determined nonradiologically. In 40 patients with dysphagia, bolus swallowing of liquids, semisolids, and solids was recorded with manometry, impedance, and videofluoroscopy. During swallows, the UES opening diameter (in the lateral fluoroscopic view) was measured and compared with automated impedance manometry (AIM)-derived swallow function variables and UES nadir impedance as well as high-resolution manometry-derived UES relaxation pressure variables. Of all measured variables, UES nadir impedance was the most strongly correlated with UES opening diameter. Narrower diameter correlated with higher impedance (r = -0.478, P < 0.001). Patients with <10 mm, 10-14 mm (normal), and ≥ 15 mm UES diameter had average UES nadir impedances of 498 ± 39 Ohms, 369 ± 31 Ohms, and 293 ± 17 Ohms, respectively (ANOVA P = 0.005). A higher swallow risk index, indicative of poor pharyngeal swallow function, was associated with narrower UES diameter and higher UES nadir impedance during swallowing. In contrast, UES relaxation pressure variables were not significantly altered in relation to UES diameter. We concluded that the UES nadir impedance correlates with opening diameter of the UES during bolus flow. This variable, when combined with other pharyngeal AIM analysis variables, may allow characterization of the pathophysiology of swallowing dysfunction.     

Noninvasive Mechanical Ventilation Improves Breathing-Swallowing Interaction of Ventilator Dependent Neuromuscular Patients: A Prospective Crossover Study

Background

Respiratory involvement in neuromuscular disorders may contribute to impaired breathing-swallowing interactions, swallowing disorders and malnutrition. We investigated whether the use of non-invasive ventilation (NIV) controlled by the patient could improve swallowing performances in a population of neuromuscular patients requiring daytime NIV.

Methods

Ten neuromuscular patients with severe respiratory failure requiring extensive NIV use were studied while swallowing without and with NIV (while ventilated with a modified ventilator allowing the patient to withhold ventilation as desired). Breathing-swallowing interactions were investigated by chin electromyography, cervical piezoelectric sensor, nasal flow recording and inductive plethysmography. Two water-bolus sizes (5 and 10ml) and a textured yogurt bolus were tested in a random order.

Results

NIV use significantly improved swallowing fragmentation (defined as the number of respiratory interruption of the swallowing of a single bolus) (p = 0.003) and breathing-swallowing synchronization (with a significant increase of swallows followed by an expiration) (p <0.0001). Patient exhibited piecemeal swallowing which was not influenced by NIV use (p = 0.07). NIV use also significantly reduced dyspnea during swallowing (p = 0.04) while preserving swallowing comfort, regardless of bolus type.

Conclusion

The use of patient controlled NIV improves swallowing parameters in patients with severe neuromuscular respiratory failure requiring daytime NIV, without impairing swallowing comfort.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT01519388","term_id":"NCT01519388"}}NCT01519388     

Respiration during feeding on solid food: alterations in breathing during mastication, pharyngeal bolus aggregation, and swallowing.

During feeding, solid food is chewed and propelled to the oropharynx, where the bolus gradually aggregates while the larynx remains open and breathing continues. The aggregated bolus in the valleculae is exposed to respiratory airflow, yet aspiration is rare in healthy individuals. The mechanism for preventing aspiration during bolus aggregation is unclear. One possibility is that alterations in the pattern of respiration during feeding could help prevent inhalation of food from the pharynx. We hypothesized that respiration was inhibited during bolus aggregation in the valleculae. Videofluorography was performed on 10 healthy volunteers eating solid foods with barium. Respiration was monitored concurrently with plethysmography and nasal air pressure. The timing of events during mastication, food transport, pharyngeal bolus aggregation, and swallowing were measured in relation to respiration. Respiratory cycle duration decreased during chewing (P < 0.001) but increased with swallowing (P < 0.001). During 66 recordings of vallecular bolus aggregation, there was inspiration in 8%, expiration in 41%, a pause in breathing in 17%, and multiple phases (including inspiration) in 35%. Out of 98 swallows, 47% started in the expiratory phase and 50% started during a pause in breathing, irrespective of bolus aggregation in the valleculae. Plethysmography was better than nasal manometry for determining the end of active expiration during feeding and swallowing with solid food. The hypothesis is rejected in that respiration was not inhibited during bolus aggregation. These findings suggest that airflow through the pharynx does not have a role in preventing aspiration during bolus aggregation in the oropharynx.     

The coordination and interaction between respiration and deglutition in young pigs

The anatomical pathways for inspired air and ingested food cross in the pharynx of mammals, implying that breathing and swallowing must be separated either in space or in time. In this study we investigated the time relationship between swallowing and respiration in young pigs, as a model for suckling mammals. Despite the high morphological position of the larynx in young mammals, allowing liquid to pass in food channels lateral to the larynx, respiration and swallowing are not wholly independent events. Although, when suckling on a veterinary teat, the swallows occurred at various points in the respiratory cycle, there was always a period of apnea associated with the swallow. Finally, an increase in the viscosity of the milk altered this coordination, changing respiratory cycle length and also restricting the relative rate at which swallows occurred in some parts of the respiratory cycle. These results suggest that the subsequent changes in respiratory activity at weaning, associated with passage of a solid bolus over the larynx, is preceded by the ability of the animal to alter coordination between respiration and swallowing for a liquid bolus. Accepted: 29 September 1997     

Laryngeal activity during upright vs. supine swallowing.

Previous investigations of human pharyngeal muscle activation patterns during swallowing found a relatively invariant muscle activation onset sequence in the upright position. However, different gravitational forces influence a liquid bolus when supine and could modify the central timing control of laryngeal airway protection during swallowing. The purpose of this study was to determine whether laryngeal muscle onset timing during swallowing differed between the supine and upright positions. Nine subjects performed six swallowing trials with a 2-ml water bolus in each position. Simultaneous electromyographic recordings were obtained from the submental complex (SMC) and the right and left thyroarytenoid (TA) muscles. Regardless of body position, the timing, amplitude, and duration of the TA muscles did not vary relative to the SMC. Therefore, the sequence of TA muscle activation relative to the SMC during swallowing appeared unaffected by gravitational influences.     

An optimization model for mastication and swallowing in mammals.

Mammalian mastication is a process combining simultaneous food comminution and lubrication. The initiation of swallowing, which is voluntary, has been thought to depend on separate thresholds for food particle size and for particle lubrication. Instead of this duality, we suggest that swallowing is initiated when it is sensed that a batch of food particles is binding together under viscous forces so as to form a bolus. Bolus formation ensures that when the food mass is swallowed, it will pass the pharyngeal region safely without risk of inhaling small particles into the lower respiratory tract. Crucial for bolus formation is food particle size reduction by mastication. This allows the tongue to pack particles together tightly by pressure against the hard palate. A major function of salivation is to fill the gradually reducing spaces between particles, so increasing viscous cohesion and promoting bolus formation. If swallowing is delayed, excessive saliva floods the bolus, separating particles and reducing cohesion. Swallowing then becomes more precarious. Our model suggests that there is an optimum moment for a mammal to swallow, defined in terms of a peak cohesive force between food particles. The model is tested on human mastication with two foods, brazil nut and raw carrot, which have very different particle size breakdown rates. The peak cohesive force is much greater with brazil nuts but both foods are predicted to be swallowed after similar numbers of chews despite the very different food particle size reductions achieved at that stage. The predicted number of chews to swallow is in broad agreement with published data.     

Adaptation of swallowing hyo-laryngeal kinematics is distinct in oral vs. pharyngeal sensory processing

Before a bolus is pushed into the pharynx, oral sensory processing is critical for planning movements of the subsequent pharyngeal swallow, including hyoid bone and laryngeal (hyo-laryngeal) kinematics. However, oral and pharyngeal sensory processing for hyo-laryngeal kinematics is not fully understood. In 11 healthy adults, we examined changes in kinematics with sensory adaptation, sensitivity shifting, with oropharyngeal swallows vs. pharyngeal swallows (no oral processing), and with various bolus volumes and tastes. Only pharyngeal swallows showed sensory adaptation (gradual changes in kinematics with repeated exposure to the same bolus). Conversely, only oropharyngeal swallows distinguished volume differences, whereas pharyngeal swallows did not. No taste effects were observed for either swallow type. The hyo-laryngeal kinematics were very similar between oropharyngeal swallows and pharyngeal swallows with a comparable bolus. Sensitivity shifting (changing sensory threshold for a small bolus when it immediately follows several very large boluses) was not observed in pharyngeal or oropharyngeal swallowing. These findings indicate that once oral sensory processing has set a motor program for a specific kind of bolus (i.e., 5 ml water), hyo-laryngeal movements are already highly standardized and optimized, showing no shifting or adaptation regardless of repeated exposure (sensory adaptation) or previous sensory experiences (sensitivity shifting). Also, the oral cavity is highly specialized for differentiating certain properties of a bolus (volume) that might require a specific motor plan to ensure swallowing safety, whereas the pharyngeal cavity does not make the same distinctions. Pharyngeal sensory processing might not be able to adjust motor plans created by the oral cavity once the swallow has already been triggered.     

Functional oromandibular reconstruction with the microvascular composite groin flap

Ten patients were reconstructed with the microvascular osteocutaneous groin flap for oromandibular defects with the objective of improving function. The flap was based on the superficial and deep circumflex iliac vessels for optimal positioning of the bone and contouring of the skin. Patients with major glossectomies and arch resections had intelligible speech and were able to eat a soft diet without aspirating. Cineradiographic studies to evaluate swallowing in selected patients showed that the shape of the intraoral flap and the location of the bone graft played an important role in swallowing and prevention of aspiration.     

The traditional Chinese medicine banxia houpo tang improves swallowing reflex.

A marked depression of swallowing reflex has been found in patients with aspiration pneumonia. We have examined the effects of Banxia Houpo Tang (BHT, Hange Koboku-To in Japanese), on swallowing reflex among the elderly. Thirty-two patients, mean age 74.2 +/- 1.7 years who had at least one episode of aspiration pneumonia, were divided into two groups. Twenty patients took BHT extracts of 7.5 g per day for four weeks, and the other 12 patients took a placebo. The swallowing reflex was measured by a bolus injection of 1 ml of distilled water into the pharynx through a nasal catheter. The reflex was evaluated by the latency time of response, which was the time from the injection to the onset of swallowing. The latency of response decreased significantly from 11.6 +/- 3.0 sec to 2.6 +/- 0.4 sec in the group treated with BHT (p < 0.01), while in the other group with placebo it was from 11.0 +/- 4.0 to 10.8 +/- 3.6 (p > 0.5). Depletion of substance P in the pharynx causes impairments of the swallowing reflex. Substance P in the saliva of treated patients increased from 9.2 +/- 2.5 fmol/ml to 15.0 +/- 2.2 fmol/ml after BHT treatment (p < 0.01), while levels were 8.0 +/- 4.0 fmol/ml before and 7.1 +/- 3.1 fmol/ml after among the placebo group (no significant difference). We suggest that BHT improves the impaired swallowing reflex and may help to prevent aspiration pneumonia in the elderly.     

A biomechanical model of swallowing for understanding the influence of saliva and food bolus viscosity on flavor release

After swallowing a liquid or a semi-liquid food product, a thin film responsible for the dynamic profile of aroma release coats the pharyngeal mucosa. The objective of the present article was to understand and quantify physical mechanisms explaining pharyngeal mucosa coating. An elastohydrodynamic model of swallowing was developed for Newtonian liquids that focused on the most occluded region of the pharyngeal peristaltic wave. The model took lubrication by saliva film and mucosa deformability into account. Food bolus flow rate and generated load were predicted as functions of three dimensionless variables: the dimensionless saliva flow rate, the viscosity ratio between saliva and the food bolus, and the elasticity number. Considering physiological conditions, the results were applied to predict aroma release kinetics.Two sets of conditions were distinguished. The first one was obtained when the saliva film is thin, in which case food bolus viscosity has a strong impact on mucosa coating and on flavor release. More importantly, we demonstrated the existence of a second set of conditions. It was obtained when the saliva film is thick and the food bolus coating the mucosa is very diluted by saliva during the swallowing process and the impact of its viscosity on flavor release is weak. This last phenomenon explains physically in vivo observations for Newtonian food products found in the literature. Moreover, in this case, the predicted thickness of the mix of food bolus with saliva coating the mucosa is approximately of 20 μm; value in agreement with orders of magnitude found in the literature.     

Surface electromyograph activity of submental muscles during swallowing and expiratory muscle training tasks in Huntington’s disease patients

IntroductionHuntington’s disease (HD) patients have difficulty in swallowing, leading to aspiration pneumonia, which is a major cause of death. It seems possible that submental muscles that are crucial for preventing an escape of a bolus into the airway, are affected by HD, but no previous studies have investigated this.ObjectiveTo assess surface electromyograph (sEMG) activity of submental muscles during swallowing and expiratory muscle training (EMT) tasks in HD patients in comparison to healthy volunteers.MethodssEMG activities of submental muscles during saliva, water swallowing, EMT tasks performed at 25% and 75% of maximum expiratory pressure were recorded and normalised by the sEMG activity during an effortful swallow in 17 early to mid stage HD patients and 17 healthy volunteers.ResultssEMG activity was greater (p < 0.05) during EMT tasks than saliva and water swallowing, but was not significantly different between groups for saliva, water swallowing and EMT at 25%. HD patients had lower sEMG activity for EMT at 75% (p < 0.05).ConclusionDecreases in submental muscle activity were not evident in HD patients except during EMT at 75%. This suggests that relative submental muscle weakness is observed only during a high intensity task in early to mid stage HD patients.     

Mechanical basis for lingual deformation during the propulsive phase of swallowing as determined by phase-contrast magnetic resonance imaging.

The tongue is an intricately configured muscular organ that undergoes a series of rapid shape changes intended to first configure and then transport the bolus from the oral cavity to the pharynx during swallowing. To assess the complex array of mechanical events occurring during the propulsive phase of swallowing, we employed tongue pressure-gated phase-contrast MRI to represent the tissue's local strain rate vectors. Validation of the capacity of phase-contrast MRI to represent local compressive and expansive strain rate was obtained by assessing deformation patterns induced by a synchronized mechanical plunger apparatus in a gelatinous material phantom. Physiological strain rate data were acquired in the sagittal and coronal orientations at 0, 200, 400, and 600 ms relative to the gating pulse during 2.5-ml water bolus swallows. This method demonstrated that the propulsive phase of swallowing is associated with a precisely organized series of compressive and expansive strain rate events. At the initiation of propulsion, bolus position resulted from obliquely aligned compressive and expansive strain, vertically aligned compressive strain and orthogonal expansion, and compressive strain aligned obliquely to the styloid process. Bolus reconfiguration and translocation resulted from a combination of compressive strain occurring in the middle and posterior tongue aligned obliquely between the anterior-inferior and the posterior-superior regions with commensurate orthogonal expansion, along with bidirectional contraction in the distribution of the transversus and verticalis muscle fibers. These data support the concept that propulsive lingual deformation is due to complex muscular interactions involving both extrinsic and intrinsic muscles.     

A new method of subcutaneous placement of free jejunal flaps to reconstruct a diversionary conduit for swallowing in complicated pharyngoesophageal injury

Choking is a serious problem in pharyngoesophageal reconstruction, which may occur following tumor ablation of the pharynx or following corrosive injury involving the epiglottis and other parts of the upper airway. To prevent choking and the risk of severe pulmonary complications, patients have to give up oral intake and assume feeding via jejunostomy for the rest of their lives. After reconstruction of the esophagus, eight patients experienced frequent choking and aspiration. With a free jejunal flap, the inlet for food could be separated from the route of the upper airway by a diversion technique. The jejunum segment was transferred microsurgically to reconstruct the cervical esophagus, with its inlet at the buccogingival sulcus. There were no surgical complications related to either the free jejunal flap transfer or the donor site. Postoperatively, patients require re-education of their pattern of swallowing, but after the rehabilitation period all patients reported a satisfactory oral intake through the reconstructed esophagus to the abdomen without choking. There were no episodes of aspiration following reconstruction. With this new method to create a separate food pathway, patients can resume oral intake safely without choking and without permanent jejunostomy. This technique offers a useful solution for patients who suffer from recurrent choking and aspiration following injury or ablation of the pharynx.     

Textural evaluation of rice cake by chewing and swallowing measurements on human subjects

The difficulty in masticating and swallowing rice cake was quantified. Healthy subjects ate pieces of rice cake (9 g and 3 g) and a modified product (9 g). We used electromyography to measure the activity of the jaw-closing and -opening muscles during chewing, as well as the suprahyoid muscle activity, laryngeal movement, and sound during swallowing. The smaller the rice cake, the shorter the mastication time, the fewer the number of chews, and the less the jaw-closing muscle activity. A modified rice cake product (9 g) was consumed with less mastication effort than the standard rice cake (9 g) and with the same effort as the standard (3 g). Both the sample amount and texture influenced mastication, although neither factor caused a significant difference in swallowing characteristics. These observations suggest that swallowing was induced when the bolus properties became suitable for swallowing, as healthy subjects could adjust their mastication technique according to the food amount and texture.     

Neural control of deglutition and esophageal motility in mammals

Swallowing is a complex motor sequence involving the coordinated contraction of many muscles of the buccopharyngeal cavity, the larynx and the oesophagus. Most of the muscles are striated except those of the distal oesophagus which, in human and some other species, are of the smooth type. During swallowing, usually divided into a buccopharyngeal and an oesophageal stage (peristalsis), the sequential activity of the muscles results from motor orders programmed by a rhombencephalic swallowing centre and conveyed to the periphery by efferent fibres belonging to various pairs of cranial nerves (Vth, VIIth, IXth, Xth). Apart from the motor nuclei of the cranial nerves, the swallowing centre contains an nuclei of the cranial nerves, the swallowing centre contains an interneurone network responsible for the programming of deglutition. During swallowing, these interneurones (INs) exhibit a sequential activity quite parallel to that of muscles, and persisting in the absence of sensory feedback. The "swallowing INs" are located in two medullary regions: a dorsal region including the nucleus of the solitary tract and the adjacent reticular formation, a ventral region corresponding to the reticular formation surrounding the nucleus ambigus. The dorsal INs are involved in the initiation and the programming of swallowing. The ventral INs receive their swallowing input from the dorsal neurones and are probably switching neurones that distribute the swallowing excitation to the various pools of motoneurones. The swallowing program can be triggered by inputs originating from either the peripheral reflexogenic areas or the supramedullary structures (cerebral cortex in particular). Under physiological circumstances, the swallowing program is continuously modified by peripheral afferents (especially muscular) that adjust the force and the timing of contractions to the size of the swallowed bolus. In addition, an important operating feature of the programming network consists of a functional polarization so that the activity of proximal portions of the swallowing tract inhibits that of distal portions. This polarization implies the existence of inhibitory connections between interneurones, that could constitute "time-lag lines" responsible for the series of delays typical of the swallowing contractile sequence. Lastly, although the smooth muscle oesophagus contains its own programming system (intramural nervous system), motility of this area during deglutition also depends on the medullary program that combines with the intramural program by ways not yet elucidated.     

Correspondence between food consistency and suprahyoid muscle activity, tongue pressure, and bolus transit times during the oropharyngeal phase of swallowing.

This study aimed to evaluate the effects of food texture and viscosity on the swallowing function by measuring tongue pressure and performing a videofluorographic (VF) examination. Eleven normal adults were recruited for this study. Test foods with different consistencies and liquid contents, i.e., a half-solid nutrient made of 0.8 and 1.5% agar powder, syrup, and a liquid containing 40 wt/vol% barium sulfate, were swallowed, and the anterior (AT) and posterior tongue pressures (PT) and electromyographic (EMG) activity of the suprahyoid muscles were recorded, together with VF images. The timing of each event obtained from EMG, tongue pressure, and VF recordings was measured and then compared. We found that the AT and PT activity patterns were similar and showed a single peak. The peak, area, and time duration of all of the variables for AT and PT and EMG burst increased with increasing hardness of the bolus. The onset of the EMG burst always preceded those of the AT and PT activities, while there were no significant differences in peak and offset times among EMG burst, AT, and PT. Total swallowing time and oral ejection time were significantly longer during the swallowing of 1.5% agar than any other boluses, while pharyngeal transit time and clearance time were significantly longer during the swallowing of syrup, which was as hard as the liquid, but showed a higher viscosity than the liquid. The results suggested that the major effects of food hardness were to delay oral ejection time, which strongly delays total swallowing time. In addition, pharyngeal bolus transit is not dependent on the hardness of food but on its viscosity.     

Lung volume effects on pharyngeal swallowing physiology.

The experiment was a prospective, repeated-measures design intended to determine how the variation of lung volume affects specific measures of swallowing physiology. Swallows were recorded in 28 healthy subjects, who ranged in age from 21 to 40 yr (mean age of 29 yr), by using simultaneous videofluoroscopy, bipolar intramuscular electromyography, and respiratory inductance plethysmography. Each subject swallowed three standardized pudding-like consistency boluses at three randomized lung volumes: total lung capacity, functional residual capacity, and residual volume. The results showed that pharyngeal activity duration of deglutition for swallows produced at residual volume was significantly longer than those occurring at total lung capacity or at functional residual capacity. No significant differences were found for bolus transit time or intramuscular electromyography of the superior constrictor. The results of this experiment lend support to the hypothesis that the respiratory system may have a regulatory function related to swallowing and that positive subglottic air pressure may be important for swallowing integrity. Eventually, new treatment paradigms for oropharyngeal dysphagia that are based on respiratory physiology may be developed.