Comparison of Sequential Swallowing in Patients With Acute Stroke and Healthy Adults

Article Outline

• Abstract
• Methods
  • Participants
  • Radiographic Procedure
  • Radiographic Measures
  • Reliability
  • Statistical Analysis
• Results
• Discussion
  • Study Limitations
• Conclusions
• References
• Copyright

Abstract 

Murguia M, Corey DM, Daniels SK. Comparison of sequential swallowing in patients with acute stroke and healthy adults.

Objectives

To compare hyolaryngeal complex (HLC) movement and leading-edge-of-the-bolus location patterns of sequential swallowing in patients with stroke and healthy adults, and to determine whether these patterns affect swallowing safety.

Design

Between-groups comparison.

Setting

Veterans hospital.

Participants

Consecutively admitted patients with acute unilateral supratentorial stroke (right hemisphere damage, n=13; left hemisphere damage, n=16) and age-matched healthy participants (n=25).

Interventions

Not applicable.

Main Outcome Measures

HLC movement pattern, bolus location, Penetration-Aspiration (P-A) Scale score.

Results

No significant group differences were observed for HLC movement pattern, bolus location, and P-A Scale score. Specific HLC movement patterns and bolus location were not associated with a higher P-A Scale score. A significant correlation between HLC movement pattern and bolus location was observed. Bolus location was typically inferior to the valleculae between swallows when the HLC was partially elevated. Across all groups, P-A Scale scores were significantly higher during sequential swallowing than single swallows.

Conclusions

HLC movement pattern and bolus location do not appear related to airway invasion, at least in persons without significant dysphagia. Given higher P-A Scale scores during sequential swallowing as compared with single swallows, sequential swallowing should always be evaluated in all patients.

Key Words: Cerebrovascular disorders, Deglutition, Deglutition disorders, Rehabilitation

List of Abbreviations: ANOVA, analysis of variance, HLC, hyolaryngeal complex, LHD, left hemisphere damage, MRI, magnetic resonance imaging, NIHSS, National Institutes of Health Stroke Scale, P-A, penetration-aspiration, RHD, right hemisphere damage

DISCRETE, OR SINGLE, swallows of standard liquid volumes (eg, 5mL) have been the focus of study for normal deglutition. Discrete swallows, however, do not represent typical patterns of behavior seen for ingestion of liquids, as most people complete multiple, consecutive swallows (ie, sequential swallowing). Few studies of sequential swallowing have been conducted, but results indicate that sequential swallowing differs from single swallows in many important ways.¹, ², ³, ⁴

In a normal single swallow, the HLC elevates with epiglottic inversion during the swallow followed by HLC lowering with return of the epiglottis to upright upon completion of the swallow.⁵ During sequential swallowing, 2 distinct patterns of HLC movement have been identified when using a straw to ingest liquids: (1) HLC lowering with return of the epiglottis to upright between swallows, and (2) partial HLC elevation with the continued epiglottic inversion between swallows.¹, ² Most healthy young and older adults demonstrate a majority HLC movement pattern across the sequence. That is, rarely do people continuously switch from HLC lowering to HLC elevation during the sequence; they typically maintain a primary pattern during the sequential swallowing sequence. When identifying the majority HLC movement pattern across swallows in healthy older and younger persons during sequential swallowing using a straw, an equal incidence of either pattern was evident.² In a study³ of sequential swallowing using a cup, most participants demonstrated HLC lowering between swallows, with only 1 person demonstrating a majority partial HLC elevation pattern. Differences in findings may be related to the method of intake (straw vs cup), or more probably, differences may be related to the instructions given to participants in each study: “continually drink until I say stop”^2(p35) versus “drink in your usual manner.”^3(p1490) The second set of instructions was used during sequential swallowing via a cup and may have allowed for participants to pause between each swallow, thus yielding a greater incidence of HLC lowering.

Sequential swallowing differs from single, discrete swallows in terms of leading-edge-of-the-bolus location at the onset of the pharyngeal swallow. In single swallows, bolus location is generally level with or superior to the mandibular angle⁵ at the onset of the pharyngeal swallow, although recent research has identified variations in bolus location in healthy adults,⁶, ⁷ with bolus location frequently inferior to the mandibular angle with evocation of the swallow. During sequential swallowing, bolus location is generally in the hypopharynx with ingestion via either a cup⁴ or straw.¹, ² This supports findings of longer-stage transit duration (the period of transition from the oral stage to the pharyngeal stage of swallowing) and pharyngeal transit time in sequential swallowing as compared with single swallows.⁴ A relationship between bolus location and HLC movement pattern during sequential swallowing has also been identified.¹, ² When the HLC was partially elevated with continued epiglottic inversion between each swallow, bolus location was in the hypopharynx at the onset of the pharyngeal swallow. With HLC lowering and return of the epiglottis to upright between swallows, the bolus was not consistently located in any single anatomic area in the pharynx at the onset of the pharyngeal swallow.

Airway invasion appears to occur more frequently in sequential swallowing as compared with single swallows.⁴, ⁸ The relationship between patterns of sequential swallowing and laryngeal penetration and aspiration have been evaluated in healthy adults.² No one particular HLC movement pattern was associated with airway invasion, as it occurred equally with both HLC lowering and partial HLC elevation between swallows. Increased airway invasion, however, was related to bolus location. A greater frequency of laryngeal penetration was evident when bolus location was inferior to the valleculae as compared with when it was superior to or level with the valleculae, particularly in the elderly.

Swallowing is frequently impaired after acute supratentorial stroke, with approximately 50% of stroke patients having dysphagia.⁹, ¹⁰, ¹¹, ¹² As with healthy adults, swallowing in the stroke population has been generally studied with discrete swallows. This is due, in part, to patient safety issues to prevent large amounts of aspiration. Given the risk of dysphagia and aspiration in this population, it seems important to study sequential swallowing, particularly because this is the preferred mode of liquid ingestion. It is unclear how the hemisphere lesioned may impact sequential swallowing or how these apparent inherent patterns of HLC movement or bolus location, which are associated with sequential swallowing, may affect deglutitive safety. Aspiration is frequently evident for single liquid swallows after stroke and is often associated with bolus location inferior to the mandibular angle at the onset of the pharyngeal swallow.⁹, ¹⁰ It seems intuitive, therefore, to speculate that sequential swallowing would result in even greater aspiration, because bolus location is generally in the hypopharynx with evocation of the swallow.

The purpose of this study was to compare HLC movement and bolus location patterns of sequential swallowing in individuals with acute supratentorial stroke and in healthy adults, and to determine whether these patterns affect swallowing safety. It was hypothesized that HLC movement pattern and bolus location at the onset of the pharyngeal swallow would be similar in individuals with acute stroke and in healthy adults. We predicted higher P-A Scale scores in individuals with stroke as compared with healthy adults, and that airway invasion would be associated with bolus location inferior to the valleculae⁹, ¹⁰ but not with a specific HLC movement pattern.²

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Methods 

Participants 

Patients with stroke who completed a sequential swallowing sequence were selected from a cohort of consecutive patients with an acute supratentorial unilateral ischemic stroke (n=34) admitted to the Southeast Louisiana Veterans Healthcare System, New Orleans, LA, who participated in a large-scale stroke-dysphagia study. Acute infarction was confirmed in the diffusion-weighted imaging sequence of the MRI scan. The scan was completed on average, 1.31 days from admission. Participants also included healthy, age-matched adults (n=25) without complaints of dysphagia who participated in this large-scale stroke-dysphagia study and served as controls. Excluding current ischemic infarct in the stroke group, participants had no history of neurologic disease, head or neck structural damage, or prior dysphagia. Swallowing status after the current stroke was unknown at the time of recruitment. All participants underwent the radiographic evaluation of swallowing as part of the research protocol. In some patients who warranted this examination as part of their clinical care, the swallowing examination served dual purposes. Inclusion criteria for this subproject evaluating sequential swallowing were completion of the sequential swallowing task without use of compensatory strategies (eg, chin tuck, thickened liquids), completion of more than 2 consecutive swallows, and an ability to swallow sequentially without verbal instruction between swallows. After implementing the above inclusion criteria, data analysis was completed on 29 patients with stroke (RHD=13, LHD=16) and all control participants. Persons were excluded due to sequential swallowing not attempted because of severity of dysphagia on previously administered discrete swallows (n=1), required compensatory strategy to complete sequential swallowing (n=1), an inability to complete more than 2 consecutive sequential swallows because of aspiration (n=1), an inability to perform continuous ingestion of liquid (n=1), and incomplete data capture (n=1). All excluded participants had RHD. Language testing was completed on all patients with stroke. No participant was identified with significant auditory comprehension deficits (no aphasia, 23; anomic aphasia, 4; conduction aphasia, 1; transcortical motor aphasia, 1).

The study was initially approved by the institutional review board at Tulane University Health Sciences Center and the Southeast Louisiana Veterans Healthcare System. All participants provided written informed consent. Permission to continue data analysis for sequential swallowing was obtained from the institutional review board at Baylor College of Medicine and the Michael E. DeBakey Veterans Administration Medical Center.

Radiographic Procedure 

Videofluoroscopic swallowing samples were recorded with a resolution of 30 frames a second on a Panasonic AG-1980 Super-VHS videocassette recorder.^a Lateral radiographic views of swallowing were obtained with the fluoroscopic tube focus encompassing the oral cavity and the pharynx as participants swallowed 100 mL of liquid barium (Liquid E-Z-Paque^b) that was diluted 2:1, water to barium, and self-administered from a cup. Participants were instructed to “drink all of the liquid without stopping.” No participant demonstrated any difficulty after the verbal instruction. A single trial was completed to reduce radiation exposure, because sequential swallowing was part of an extended videofluoroscopic protocol. The videofluoroscopic swallow study was completed on average, 1.54 days from admission (range, 0–4d) in all patients with a stroke.

Radiographic Measures 

HLC movement pattern, location of the leading edge of the bolus at the onset of the pharyngeal swallow, and the P-A Scale score were measured for each swallow using slow motion and frame-by-frame analysis on the same videocassette recorder used to capture the study. The first swallow of the sequence was not included because this swallow represented an isolated swallow with the HLC lowered at onset. The last swallow was also not included if it represented a single, clearing swallow.⁴ After excluding first and last swallows, at least 3 consecutive swallows per participant were measured.

Swallowing measures as defined by Daniels et al² were used. HLC movement was scored categorically as (1) partial HLC elevation with continued epiglottic inversion (coded as 0), or (2) lowering of the HLC with the epiglottis returning to upright between swallows (coded as 1). Scores were averaged across swallows to obtain for each participant the proportion of swallows during the sequence in which the HLC was lowered. Proportions equal to 0 indicated that the HLC was partially elevated between all swallows, and proportions equal to 1 indicated that the HLC was lowered between all swallows.

The location of the leading edge of the bolus at the onset of the pharyngeal swallow was determined based on position of the bolus in relation to the valleculae and categorized as (1) superior or level (coded as 0), or (2) inferior (coded as 1). As bolus location was defined dichotomously as superior-level or inferior, we selected the valleculae rather than the ramus of the mandible as the cutoff location in order to distinguish between larger and potentially more critical locations. Scores were averaged across all swallows to obtain for each participant the proportion of swallows during the sequence in which the bolus was inferior to the valleculae. Proportions equal to 0 indicated that the bolus location was superior to or level with the valleculae for all swallows, and proportions equal to 1 indicated that the bolus location was inferior to the valleculae for all swallows. Onset of the pharyngeal swallow was identified as the first frame in which initiation of HLC movement toward maximum was observed.

The P-A Scale¹³ was used to score airway invasion for each swallow during the sequence (table 1). The P-A Scale yields scores on an 8-point ordinal scale used to measure depth, clearance, and participant's response to penetrated material. The average score was calculated across swallows completed during the sequence.

Table 1. The Penetration-Aspiration Scale

Reliability 

Coders were blinded to group. Rules were established by the third author (S.K.D.), who has extensive research experience measuring videofluoroscopic swallow studies. HLC movement and bolus location at the onset of the pharyngeal swallow were coded categorically by both a first rater (S.K.D.) and a second rater (M.M.), who was pretrained to criteria. Both coders measured 89 swallows including all swallows of 14 randomly selected participants (10 stroke, 4 control), and reliability was assessed via the kappa statistic. Kappa coefficients revealed interrater and intrarater reliabilities for HLC movement patterns (κ=.956 and κ=.933, respectively) and for bolus location (κ=.950 and κ=.975, respectively). P-A Scale score reliability was previously established by Daniels² and completed by 2 expert speech pathologists, 1 of whom contributed to the design of the P-A Scale. Kappa coefficients revealed intrarater and interrater reliabilities for the P-A Scale score (κ=.853 and κ=.685, respectively). Although P-A Scale score interrater reliability did not reach the desired level (κ=.80), 94.6% agreement between raters was evident and better than the reliability previously reported.¹³

Statistical Analysis 

Groups were initially compared on age, NIHSS, and number of swallows via 1-way between-groups ANOVA, with group (RHD, LHD, control) entered as a grouping factor.

Group differences in swallow characteristics were tested via 1-way between-groups ANOVA with group (RHD, LHD, control) entered as a grouping factor. Dependent variables HLC movement (proportional measure), bolus location (proportional measure), and mean P-A Scale score were examined in separate analyses.

Associations among HLC movement (proportional measure), bolus location (proportional measure), and mean P-A Scale score were assessed via correlation analyses. All statistical analysis was performed using SPSS version 16.0.^c

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Results 

No significant group differences were observed (P>.05) for all measures. Table 2 shows group means and SDs for all measures. Most participants demonstrated a partially elevated HLC movement pattern (fig 1). Most participants in all 3 groups demonstrated either consistent HLC lowering or consistent partial HLC elevation across all swallows. A single movement pattern across all swallows, however, was not observed in 11 (44%) of 25 controls, 3 (23%) of 13 patients with RHD, and 4 (25%) of 16 patients with LHD.

Table 2. Dependent Variables for Each Group

Group	Age (y)	NIHSS	No. of Swallows	HLC Movement	Bolus Location	P-A Scale Score
RHD	65.62±14.59	3.58±2.39	8.00±2.89	.37±.45	.90±.17	1.67±.81
LHD	62.81±9.17	4.54±3.69	6.81±1.91	.31±.41	.80±.35	1.83±.90
Control	67.20±9.11	NA	7.16±2.31	.35±.39	.70±.41	1.71±.97

Note. Values are mean ± SD.

Abbreviation: NA, not applicable.

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• Fig 1. 

  The proportion of HLC movement pattern across participants in each group.

Most participants demonstrated bolus location inferior to the valleculae at the onset of the pharyngeal swallow (fig 2). No patient with RHD demonstrated a consistent bolus location superior-level to the valleculae; most demonstrated a consistent location inferior to the valleculae. For patients with LHD, proportions were close to either 0 or 1, indicating minimal variation of bolus location at the onset of the swallow during the sequence. Controls demonstrated a greater range of bolus location, with 7 (28%) of 25 participants not demonstrating a 100% occurrence of either a superior-level or inferior-to-the-valleculae location between swallows during the sequence.

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• Fig 2. 

  The proportion of leading-edge-of-the-bolus location across participants in each group. Abbreviation: BL, bolus location.

The average P-A Scale score for all 3 groups was less than 2 (fig 3). At least 1 instance of airway invasion (P-A Scale score ≥2) occurred in 61% of the participants (14/25 control, 9/13 RHD, 10/16 LHD). Six control subjects demonstrated consistent scale scores of greater than or equal to 3 across the sequence, with 2 participants demonstrating a single occurrence of aspiration (P-A Scale score, 8; silent aspiration). One participant with RHD and 5 with LHD demonstrated scale scores consistently greater than or equal to 3; 1 patient with RHD demonstrated aspiration.

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• Fig 3. 

  The average P-A Scale score across participants in each group.

Because no significant between-group differences were detected in any measures, groups were collapsed to examine the correlation among measures. A significant correlation between HLC movement and bolus location was observed (r =–.498, P<.001); the leading edge of the bolus was primarily inferior to the valleculae when the HLC was partially elevated. Significant correlations were not detected between HLC movement pattern and P-A Scale score (r=–.169, P=.22) or between bolus location and P-A Scale score (r=.168, P=.23).

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Discussion 

Patterns of HLC movement and location of the leading edge of the bolus at the onset of the pharyngeal swallow have been identified for healthy adults during sequential swallowing.¹, ², ³ Sequential swallowing has, however, not been studied in disordered populations in which dysphagia is prevalent, such as stroke.⁹, ¹⁰, ¹¹, ¹² The purposes of this study were (1) to compare sequential swallowing in patients with an acute single supratentorial stroke with that of healthy adults, and (2) to evaluate the effects of specific swallowing characteristics on swallowing safety. Findings from our study offer no evidence that a single supratentorial stroke, regardless of hemisphere lesioned, alters HLC movement pattern or bolus location during sequential swallowing. Furthermore, we found no evidence that HLC movement or bolus location is associated with airway invasion. Patients with a posterior fossa infarct or multiple strokes were excluded because our focus was single supratentorial strokes. Moreover, sequential swallowing was not evaluated in people who could not safely swallow discrete volumes of thin liquids. This is common, judicious clinical practice that is the standard of care to prevent large amounts of aspiration. Given this exclusion from our sample of the most severely dysphagic potential participants, our findings are limited to stroke patients without significant dysphagia.

Analysis of proportions for HLC movement across groups revealed that a partially elevated HLC between swallows was the preferred pattern for healthy adults and both stroke groups. While patients with stroke were not studied preinfarction and postinfarction, the lack of significant differences between RHD, LHD, and age-matched control groups suggests no change in sequential swallowing patterns in patients with generally mild dysphagia after stroke. This supports previous research, which has identified a high occurrence of partial HLC elevation in healthy young and older adults during continuous liquid ingestion using a straw.² Results from our study expand this earlier finding to ingestion via a cup. Similar HLC movement patterns between healthy adults and patients with stroke suggest strong habituation of sequential swallowing patterns. Results contrast with those of Dozier et al,³ who found lowered HLC to be the preferred pattern with sequential cup drinking. This difference in findings may be associated with between-study variation in instructions to participants, with instruction such as “drink in your usual manner” being more likely to elicit multiple, albeit discrete, swallows.

Across groups, having the bolus location inferior to the valleculae at the onset of the pharyngeal swallow was the predominant pattern. This observation is consistent with findings in earlier studies of sequential swallowing in healthy young and older adults.¹, ², ⁴ In previous research using discrete swallows, patients with stroke demonstrated longer-stage transit duration than healthy adults and evoked the pharyngeal swallow inferior to the mandibular angle.⁹, ¹⁰ This was evident more often in patients with RHD as compared with LHD and was associated with aspiration in single swallows. Our results for sequential liquid ingestion also support the notion of a bolus location that is inferior to the mandibular angle at the onset of the pharyngeal swallow for patients after stroke; however, most healthy adults demonstrated this same pattern. Moreover, unlike findings in discrete swallows, the inferior bolus location was not associated with increased airway invasion during sequential swallowing in any group.

As with our previous research, bolus location was significantly associated with HLC movement pattern. When the HLC was partially elevated, the bolus location was inferior to the valleculae at the onset of the pharyngeal swallow. This finding was evident in patients with stroke as well as in healthy adults. When the HLC was lowered between swallows, the bolus location was less consistent. These data support our previous findings in healthy young and older adults¹, ² and suggest that the configuration of the HLC (partially elevated, lowered) before the onset of the pharyngeal swallow may influence the magnitude of receptor site stimulation necessary to induce a swallow; however, further research is warranted to confirm this notion.

Supratentorial stroke, regardless of hemisphere lesioned, was not associated with an increased risk of airway invasion as compared with age-matched healthy adults. This finding did not support our hypothesis and may be related to the dysphagia severity of the sample. While airway invasion was common in all 3 groups, the average P-A Scale score for all groups was less than 2. This indicated that the penetration with residual or increased depth (P-A Scale scores, 3–5) and aspiration were infrequent. Unlike findings from studies of single swallows,⁹, ¹⁰ patients with RHD did not demonstrate greater occurrences of penetration and aspiration as compared with persons with LHD. All individuals, however, who were excluded from either the sequential swallowing task or analysis had RHD, which may suggest that RHD stroke is associated with more severe dysphagia, at least in 4 of the 5 patients (1 person was not analyzed because of incomplete data). Stroke severity also may have contributed to deglutitive impairment. The mean NIHSS score was 12.75 in these 4 patients who could not or did not complete the sequential swallowing task, whereas the mean NIHSS score was notably lower in patients who completed sequential swallowing. Moreover, we did not study patients with posterior fossa or multiple infarcts, which are typically associated with more severe dysphagia.⁵, ¹¹ Hence, increased dysphagia or stroke severity and inclusion of additional stroke locations may have resulted in increased P-A Scale scores during sequential swallowing.

Findings of frequent airway invasion during sequential swallowing among all groups and an absence of group differences in average P-A Scale scores caused us to question whether sequential swallowing added additional information to our knowledge of swallowing function and deglutitive safety. Therefore, post-hoc comparisons of P-A Scale scores for single discrete swallows of liquid barium (3, 5, 10, and 20mL) and sequential swallowing were completed. Across groups, P-A Scale scores were significantly higher for sequential swallowing than for single swallows of any of the 4 volumes (P<.05 for all comparisons). Eight participants (6 stroke, 2 control) demonstrated P-A Scale Scores of 1 or 2 on single swallows, yet demonstrated multiple scores of greater than or equal to 3 during sequential swallowing. Six participants (2 stroke, 4 control) demonstrated P-A Scale scores greater than or equal to 3 both on discrete and sequential swallows. Only 2 participants (1 stroke, 1 control) demonstrated P-A Scale scores greater than or equal to 3 on single swallows and demonstrated lower scores during sequential swallowing. The 1 person who was omitted from analysis because of an inability to complete more than 2 swallows without aspiration demonstrated dysphagia and aspiration on earlier discrete swallow trials.

Airway invasion during sequential swallowing has previously been identified in healthy adults and has been shown to increase with age.², ⁸ In sequential drinking via a straw, 34% of participants across the older and young age groups demonstrated at least 1 instance of airway invasion during the sequence.² While only 3 (15%) of 20 young participants demonstrated any occurrence of laryngeal penetration, 10 (56%) of 18 older adults demonstrated entrance of material into the laryngeal vestibule. A single instance of aspiration (P-A Scale score, 7) was evident in 1 older person. During sequential cup ingestion of 3 oz of liquid barium, penetration (P-A Scale score ≥2) was evident in 59% of the cohort.⁸ Infrequent evidence of aspiration (scores 6–8) was also evident in the 2 older age groups (60–79y, >80y) (G. H. McCullough, personal communication, August 18, 2008). In our study, airway invasion during sequential swallowing was not uncommon and occurred in 61% of the participants. This occurrence in healthy adults further suggests that intermittent airway invasion is not atypical in aging adults during sequential swallowing. The occurrence of aspiration without evocation of a cough in 2 participants in our study and in participants in the study by McCullough et al⁸ is surprising. The amount was minimal, did not proceed deep into the trachea, and occurred in participants older than 65 years. While an MRI brain scan was not obtained in the healthy adults in our study or in the participants in the McCullough study, and thus the degree of white matter disease was unknown,¹⁴ no healthy participant reported any swallowing problem, and none had medical diagnoses associated with dysphagia.

Clinicians frequently test sequential swallowing in order to replicate a more normal pattern of swallowing and to stress the swallowing system in an attempt to identify breakdown of functioning. Recent research identified that the sequential swallowing sequence is more commonly preceded and followed by inspiration³ as compared with single swallows, which are typically bracketed by expiration.¹⁵, ¹⁶ Inspiration, particularly after swallowing, is associated with increased airway invasion after stroke¹⁷; thus, the notion that the risk of airway invasion would increase during sequential swallowing would seem intuitive.

Martin-Harris et al¹⁸ recently suggested that the addition of sequential swallowing to a clinical swallowing protocol does not provide additional information about swallowing physiology relative to single swallows of thin and thick liquid. Given the significant increase in airway invasion associated with sequential swallowing identified by our study and by others,⁸ we suggest that evaluating sequential swallowing may be critical, especially given that aspiration is a frequent occurrence in clinical populations including stroke patients.⁹, ¹⁰, ¹¹, ¹² In addition, because sequential swallowing is the typical method of ingesting thin liquids, evaluating sequential swallowing provides the clinician with information on bolus flow that is relevant to typical ingestive behavior that is performed outside the very structured and controlled radiologic environment. Given that healthy adults experience increased airway invasion during sequential swallowing as compared with single swallows, a person should not be defined as dysphagic based solely on airway invasion during sequential swallowing. Nor should persons be classified as dysphagic based on performance during a single discrete swallow.¹⁹, ²⁰ Swallowing function across a complete examination must be evaluated for adequate classification of individuals as dysphagic or nondysphagic. Identification of airway invasion is only part of the interpretation of the swallow study, albeit a very important piece. The P-A Scale focuses on depth of penetration, residual in the airway, and an individual's response to airway invasion. Although the P-A Scale represents significant improvement over the binary yes/no penetration or aspiration classification, other factors such as depth of aspiration (eg, just inferior to the vocal folds, deep into the trachea) and amount of material entering or remaining in the larynx or trachea may help distinguish between pathologic and more “normal” airway invasion during sequential swallowing.

Study Limitations 

Although no significant group differences were identified related to sequential swallowing, the significant increase in airway invasion with sequential swallowing cannot be ignored, particularly because we did not study patients with severe dysphagia or patients with brainstem or multiple stroke who are generally at greater risk for significant deglutitive dysfunction. Further studies of sequential swallowing patterns and their impact on swallowing safety in individuals with and without dysphagia are warranted. Moreover, studies are indicated to determine whether healthy adults with frequent airway invasion during sequential swallowing are at greater risk for dysphagia after disease.

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Conclusions 

Among persons without significant dysphagia, patterns of sequential swallowing were not found to differ between healthy adults and patients with a single supratentorial stroke. Neither patterns of HLC movement nor bolus location at the onset of the pharyngeal swallow was found to be associated with swallowing safety, at least in individuals with mild dysphagia. Airway invasion significantly increases in sequential swallowing as compared with single swallow. This increase is equally evident in people with and without stroke, supporting the necessity of including sequential swallowing as part of the instrumental assessment.

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• a Panasonic Corp of North America, 1 Panasonic Way, Secaucus, NJ 07094.
• b E-Z-EM Inc, 717 Main St, Westbury, NY 11590.
• c SPSS Inc, 233 S Wacker Dr, 11th Fl, Chicago, IL 60606.