EFFECTS OF BOLUS RHEOLOGY ON
ASPIRATION IN PATIENTS WITH
DYSPHAGIA
Ashley Kish
OUTLINE
 Background
 Purpose of study
 Sample
 Methods
 Results
 Strengths & weaknesses
 Ideas for further research
 Applicability in dietetics practice
BACKGROUND
Dysphagia
 Difficulty swallowing = unsafe swallowing
Who’s affected?
 Affects 8% of the world’s population
 30% of stroke patients, 60-80% with neurodegenerative diseases, 10-30% of adults 65+,
51% institutionalized elderly
Management: Food and beverages may be thickened to consistencies that are judged to be
safe and effective, based on results of clinical and instrumental assessments.
Few conclusive studies are available to support the widespread use of bolus rheology
manipulation in the clinical practice.
PURPOSE OF STUDY
 To investigate the effects of bolus viscosity on aspiration in patients with
dysphagia.
 Compare the effects of a thin liquid barium contrast fluid (THIN) to the same
barium material thickened with a conventional starch-based (STARCH) and a
xanthan gum-based (GUM) thickening agent on swallow function in patients with
dysphagia.
 Null hypothesis: no differences in rates of aspiration across the three bolus types.
NATIONAL DYSPHAGIA DIET
POPULATION SAMPLE
 Oral-pharyngeal dysphagia
 Considered all adults undergoing a comprehensive dynamic fluoroscopic swallow study
 Excluded pregnant women and individual under 18 years of age.
 Center for Voice and Swallowing of the University of California, Davis. (Nov ‘09 – Dec ‘10)
 118 individuals enrolled; 100 completed the study
 18 discontinued during fluoroscopic study for safety reasons (extreme aspiration, etc)
 58% men, 42% women
 Average age: 62 ± 13 years
 Variety of medical conditions:
 head and neck cancer (23%), history of GERD (22%), neuromuscular or neurogenic (20%), medical
connective tissue disease or diabetes (14%), structural anomaly (13%), trauma (8%)
METHODS
 Investigators prepared boluses before each fluoroscopic study
 Time allowed to thicken: 5 minutes GUM, 25 minutes STARCH
 Radiographic studies conducted by speech language pathologist (SLP) and
fluoroscopy technician.
 Studies were recorded.
 Bolus types presented in random order by SLP
All boluses nectar thick (51-350 cP), based on National Dysphagia Diet
Viscosity
THIN
STARCH
GUM
4 to 5 cP
290 to 330 cP
150 to 170 cP
ANALYSES
Independently evaluated
 Two investigators not involved with fluoroscopic studies, and unfamiliar with bolus
order presentation to participants
 Third investigator evaluated studies where aspiration was disputed
Primary outcome measure
 Presence or absence of aspiration
Secondary outcome measure
 Penetration-Aspiration Scale (PAS) score
RESULTS
23/100 patients aspirated on one or more
of the bolus types
56 incidents of aspiration
9 aspirated on three bolus types, 5 aspirated on 2 bolus types and 9
aspirated on only on bolus type.
28 incidents (50%) on THIN, 16 incidents (28.5%) on STARCH,
12 incidents (21.5%) on GUM
RESULTS
 Significantly less aspiration on GUM thickener vs THIN (P=0.016).
 Less aspiration on STARCH compared to THIN, but not statistically significant (P>0.18)
 Less aspiration on GUM than STARCH, but not statistically significant (P>0.05)
PENETRATION-ASPIRATION SCALE
 8 point scale
 Describes entrance of bolus material
into the airway, to which level (above
or below vocal folds), and the patients
response to penetration or aspiration
events.
 Penetration: bolus enters airway, but
remains above vocal folds.
 Aspiration: bolus passes through the
vocal folds.
RESULTS
Significant difference in PAS scores between bolus types.
• GUM vs THIN was statistically significant (P<0.001)
Mean ± standard deviation, *P<0.001
INTERESTING FINDINGS
 Thickened sample with the lower viscosity (GUM), was associated with less
aspiration than the thickened sample with the higher viscosity (STARCH).
 Thicker consistencies generally assumed to be more safe and effective
 Rheological properties (other than viscosity) may alter swallowing safety
 Thickened beverages = complex fluids; cannot be evaluated on single criteria
alone (viscosity)
STRENGTHS & WEAKNESSES OF STUDY
Strengths
 Prospective cohort
 Double blind
 Independently evaluated
 Level 1b clinical trial
 External validity - generalization
 All patients considered
 Many different medical conditions
 Internal validity
 Study design, statistical analysis
Weaknesses
 Small sample size
 Increased probability of type II error
 No intention to treat analysis
 Decreases external generalization
FUTURE RESEARCH
 Elaborate differences in rheological behaviors within individual National
Dysphagia Diet categories; ex differences across substances that are classified as
nectar thick.
 Differences in subgroups of populations with dysphagia (cerebrovascular
accidents, head and neck cancer, etc)
APPLICATION TO DIETETICS
 RDNs are an important part of the health are team in the treatment of patients
with dysphagia.
 RDNs consulted for many problems secondary to dysphagia, such as dehydration,
malnutrition, weight loss, poor appetite, etc.
 Be aware of different options for thickening agents, can make recommendations
to make food safer, more palatable.
RESOURCES
 Cichero, Julie A. Y., et al. “The Need for International Terminology and Definitions
for Texture-Modified Foods and Thickened Liquids Used in Dysphagia
Management: Foundations of a Global Initiative.” Current Physical Medicine and
Rehabilitation Reports 1 (2013): 280-291
 Leonard, R. J., White, C., McKenzie, S., Belafsky, P. C. (2013). Effects of Bolus
Rheology on Aspiration in Patients with Dysphagia. Journal of the Academy of
Nutrition and Dietetics, 114, 590-594.
 Nelms, Marcia, Kathryn P. Sucher, Karen Lacey, Sara Long Roth. Nutrition Therapy
and Pathophysiology. Belmont: Wadsworth, 2011.
QUESTIONS???
THICKENING AGENTS
STARCH VS GUM
STARCH
GUM
PROS
• Cheaper
• Not degraded by amylase in saliva; viscosity remains
stable
• Reach target viscosity rapidly
• Maintains stability in liquids over time
• Better for diabetics; does not contribute meaningful
amount of carbohydrates or calories
• May enhance swallowing safety in pts with dysphagia
CONS
• Do not work well in hot or carbonated
beverages
• Appear cloudy
• Taste “starchy”
• “grainy” texture
• Continues to thicken over time
• Contains 4kcal/g
• Slippery texture
• More expensive