1. Effects of bolus rheology on aspiration in patients with dysphagia
Ashley Kish

2. outline Background Purpose of study Sample Methods Results
Strengths & weaknesses
Ideas for further research
Applicability in dietetics practice

3. 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.
Dysphagia – difficulty swallowing. Difficulty moving food, liquid, saliva or medication from mouth to stomach.

4. 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.

5. National dysphagia diet
centipoises

6. 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%)

7. All boluses nectar thick (51-350 cP), based on National Dysphagia Diet
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 ( cP), based on National Dysphagia Diet
THIN
STARCH
GUM
Viscosity
4 to 5 cP
290 to 330 cP
150 to 170 cP

8. Analyses Independently evaluated Primary outcome measure
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

9. results 23/100 patients aspirated on one or more of the bolus types
9 aspirated on three bolus types, 5 aspirated on 2 bolus types and 9 aspirated on only on bolus type.
56 incidents of aspiration
28 incidents (50%) on THIN, 16 incidents (28.5%) on STARCH, 12 incidents (21.5%) on GUM
23 out of 100 patients demonstrated aspiration on one or more of the three bolus types during the fluoroscopic study.

10. 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)

11. 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.

12. Mean ± standard deviation, *P<0.001
results
Significant difference in PAS scores between bolus types.
GUM vs THIN was statistically significant (P<0.001)
Mean ± standard deviation, *P<0.001

13. 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)

14. Strengths & weaknesses of study
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
Small sample size
Increased probability of type II error
No intention to treat analysis
Decreases external generalization
Prospective; follows individuals over time to look for outcomes
Double blind; overcome potential bias from the subjects or investigators
neither subjects nor persons administering the experiment know who is receiving treatment
SLPs don’t know order of bolus types administered
patients don’t know the order of bolus types administered
Independently evaluated
conducted by a third party
reduces bias
Level 1b clinical trial (likely reliable)
individual randomized controlled trials (with narrow confidence interval)
External validity: the generalizability of study findings; to whom the study findings apply
Internal validity: are the methods of the study appropriate? No major concerns with methodology.
no bias
WEAKNESSES
Sample size: could have been larger to reach greater significance
type 1 error: conclude there is a real difference, when it fact it was just due to chance alone.
type II error: conclude there is NOT a true difference, when in fact there was a difference (than/starch, starch/gum)

15. 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)

16. 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.

17. 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):
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,
Nelms, Marcia, Kathryn P. Sucher, Karen Lacey, Sara Long Roth. Nutrition Therapy and Pathophysiology. Belmont: Wadsworth, 2011.

18. Questions???

19. Thickening agents starch vs 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