Rationale: Swallowing during inspiration and swallowing immediately followed by inspiration increase the chances of aspiration and may cause disease exacerbation. However, the mechanisms by which such breathing–swallowing discoordination occurs are not well-understood.Objectives: We hypothesized that breathing–swallowing discoordination occurs when the timing of the swallow in the respiratory cycle is inappropriate. To test this hypothesis, we monitored respiration and swallowing activity in healthy subjects and in patients with dysphagia using a non-invasive swallowing monitoring system.Measurements and Main Results: The parameters measured included the timing of swallow in the respiratory cycle, swallowing latency (interval between the onset of respiratory pause and the onset of swallow), pause duration (duration of respiratory pause for swallowing), and the breathing–swallowing coordination pattern. We classified swallows that closely follow inspiration (I) as I-SW, whereas those that precede I as SW-I pattern. Patients with dysphagia had prolonged swallowing latency and pause duration, and tended to have I-SW or SW-I patterns reflecting breathing–swallows discoordination.Conclusions: We conclude that swallows at inappropriate timing in the respiratory cycle cause breathing–swallowing discoordination, and the prolongation of swallowing latency leads to delayed timing of the swallow, and results in an increase in the SW-I pattern in patients with dysphagia.
IntroductionImpaired coordination between breathing and swallowing (breathing–swallowing discoordination) may be a significant risk factor for the exacerbation of chronic obstructive pulmonary disease (COPD). We examined breathing–swallowing discoordination in patients with COPD using a non-invasive and quantitative technique and determined its association with COPD exacerbation.MethodsWe recruited 65 stable outpatients with COPD who were enrolled in our prospective observational cohort study and did not manifest an apparent swallowing disorder. COPD exacerbation was monitored for 1 year before and 1 year after recruitment. Swallowing during inspiration (the I-SW pattern) and swallowing immediately followed by inspiration (the SW-I pattern) were identified.ResultsThe mean frequency of the I-SW and/or SW-I patterns (I-SW/SW-I rate) was 21.5%±25.5%. During the 2-year observation period, 48 exacerbation incidents (25 patients) were identified. The I-SW/SW-I rate was significantly associated with the frequency of exacerbation. During the year following recruitment, patients with a higher I-SW/SW-I frequency using thicker test foods exhibited a significantly higher probability of future exacerbations (p=0.002, log-rank test).ConclusionsBreathing–swallowing discoordination is strongly associated with frequent exacerbations of COPD. Strategies that identify and improve breathing–swallowing coordination may be a new therapeutic treatment for patients with COPD.
In Japan, the viscosity of thickened liquids is different among hospitals and nursing homes. In order to standardize viscosity of thickened liquids, the dysphagia diet committee of the Japanese Society of Dysphagia Rehabilitation developed the Japanese Dysphagia Diet 2013 (JDD2013). To decide on a definition of thickened liquids, the committee reviewed categories from other countries. Especially, the criteria of the USA and Australia were used as references. The definition had three levels: mildly thick, moderately thick, and extremely thick. Then a sensory evaluation by health care workers was carried out to decide the viscosity range of each level, and a draft document was made. After collecting public comments, follow-up experiments using thickened water with thickeners using xanthan gum were performed, and the JDD2013 (Thickened Liquid) was determined. The JDD2013 (Thickened Liquid) evaluated the drinking properties, visual properties, and viscosity values of each level. The shear rate of 50 s was adopted to measure the viscosity with a cone and plate type viscometer to duplicate the measurement criteria used by the USA. We also set the values of the JDD2013 with the Line Spread Test to promote the use of guidelines in clinical practice. We believe the JDD2013 standards help hospitals and other settings that care for people with dysphagia to use the same thickness level and the same labels. In the future, the JDD2013 levels will be compared with new international guidelines to help with international understanding of the JDD2013 levels.
Thickening agents are usually added to thin liquids administered to dysphagic patients to prevent aspiration. In this study, we aimed to identify the viscosity best suited for easy swallowing in elderly people and to examine the optimal shear rate for measuring, through sensory evaluation, these thickening liquids. Ten elderly participants were selected for sensory evaluation of diluted solutions for ease of swallowing and stickiness. Diluted solutions containing > 2.0% xanthan gum-based product were judged to be significantly more difficult to swallow than solutions containing < 2.0%. Fifty-two healthy panelists were selected for sensory evaluation of oral viscosity to compare sensory evaluation with instrument-based viscosity measurement. We found that the optimal shear rate was approximately 100 s -1 . These findings indicate that the thickening agent-diluted solutions that the elderly found difficult to swallow exceeded 120 mPa·s at a shear rate of 100 s -1 .Keywords: viscosity, thickening agents, TOROMI, shear rate *To whom correspondence should be addressed. E-mail: kayashita@pu-hiroshima.ac.jp IntroductionDysphagic patients with delayed pharyngeal swallow response or reduced lingual control find it difficult to swallow thin liquids safely (O'Gara, 1990). Thickening agents may promote safer swallowing as they lower the risk of aspiration (Kuhlemeier et al., 2001). Compared to thin liquids, thickened liquids are associated with higher values of some swallowing parameters, such as the total swallowing duration (Chi-Fishman and Sonies, 2002), number of swallowing movements (Hamlet et al., 1996), and peak lingual force amplitude (Miller and Watkin, 1996); however, the range of liquid viscosity suitable for dysphagic patients remains unclear.In Japan, thickeners in a dry mix powder form are used to provide instant viscosity to liquids, and the products formed are called "TOROMI". Although Japanese people favor thinner liquids, clinical staff prepare thicker TOROMI to prevent aspiration in dysphagic patients; however, they are often unsure how to adjust the liquid consistency for each individual dysphagic patient.In 1994, the Japanese Ministry of Health, Labour and Welfare defined the "Foods for the elderly with difficulty in masticating or swallowing," and categorized them as "Food for Special Dietary Uses (FOSDU)." This criterion indicates a lower limit of viscosity and states that the viscosity of soltype foods should be measured using a Brookfield-type viscometer, commonly known as the B-type viscometer, at a rotor rotation rate of 12 rpm at 20℃. This rotor rotation rate is calculated to an approximate shear rate of 2 − 3 s -1 (Kumagai et al., 2009). In 2009, FOSDU was changed to "Foods for the elderly with difficulty in swallowing," which denotes a new measuring standard for gel-type foods, but the sol-type foods criterion was excluded because there was insufficient evidence for the measuring method of sol-type foods in Japan. As a result, the old method involving measurement at 12 rpm by a B-type viscomete...
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