Cough reflex attenuation and swallowing dysfunction in sub-acute post-stroke patients: prevalence, risk factors, and clinical outcome

Effect of high-frequency repetitive transcranial magnetic stimulation on swallowing function and pneumonia in poststroke dysphagia in rats

BACKGROUND

Post-stroke dysphagia (PSD) is a common symptom of stroke. Clinical complications of PSD include malnutrition and pneumonia. Clinical studies have shown that high-frequency repetitive transcranial magnetic stimulation (HF-rTMS) can improve the swallowing function in stroke patients. However, few studies have elucidated the underlying molecular mechanisms.

METHODS

A PSD rat model was established using transient middle cerebral artery occlusion (tMCAO). Rats were randomly divided into sham-operated groups, PSD groups, PSD + sham-rTMS groups, PSD + 5 Hz-rTMS groups, PSD + 10 Hz-rTMS groups and PSD + 20 Hz-rTMS groups. Rats were weighed and videofluoroscopic swallowing studies were conducted. Pulmonary inflammation, levels of substance P (SP) and calcitonin gene-related peptide (CGRP) in the serum, lung, and nucleus tractus solitarius (NTS), brain-derived neurotrophic factor (BDNF) and 5-hydroxytryptamine (5HT) in NTS were evaluated.

RESULTS

Rats in the PSD group experienced weight loss, reduced bolus area and pharyngeal bolus speed, and increased pharyngeal transit time (PTT) and inter-swallow interval (ISI) on day 7 and day 14 after operation. Moreover, PSD rats showed pulmonary inflammation, reduced levels of SP in the lung and serum, increased levels of CGRP in the lung and NTS, reduced levels of BDNF and 5HT in the NTS. There was no significant difference between the PSD group and the PSD + sham-rTMS group in the results of weight and VFSS. Comparing with the PSD group, there significant increases in the bolus area, decreases in PTT of rats following 5 Hz rTMS intervention. HF-rTMS at 10 Hz significantly increased the weight, bolus area, pharyngeal bolus speed and decreased the PTT and ISI of rats. There were also significant increases in the bolus area (p < 0.01) and pharyngeal bolus speed, decreases in PTT and ISI of rats following 20 Hz rTMS intervention. Furthermore, compared with the PSD + 5 Hz-rTMS group, there were significant increases in the bolus area and pharyngeal bolus speed, decreases in ISI in the swallowing function of rats in the PSD + 10 Hz-rTMS group. Besides, compared with the PSD + 5 Hz-rTMS group, there were significant decreases in ISI in the swallowing function of rats in the PSD + 20 Hz-rTMS group. HF-rTMS at 10 Hz alleviated pulmonary inflammation, increased the levels of SP in the lung, serum, and NTS, CGRP in the serum and NTS, 5HT in the NTS of PSD rats.

CONCLUSION

Compared with 5 Hz and 20 Hz rTMS, 10 Hz rTMS more effectively improved the swallowing function of rats with PSD. HF-rTMS at 10 Hz improved the swallowing function and alleviated pneumonia in PSD rats. The mechanism may be related to increased levels of SP in the lung, serum and NTS, levels of CGRP in the serum and NTS, 5HT in the NTS after HF-rTMS treatment.

Predictors of medical staff's knowledge, attitudes and behavior of dysphagia assessment: A cross-sectional study

PURPOSE

This study aimed to explore the predictors of medical staff's Knowledge, Attitudes and Behavior of dysphagia assessment, to provide reference suggestions for constructing the training program and improving the rate of dysphagia assessment.

METHODS

This study was a cross-sectional study. A total of 353 nurses and doctors from four provinces (Guangdong, Hunan, Guangxi, and Shaanxi) who were selected by convenience sampling and invited to complete the questionnaire through WeChat, DingTalk, and Tencent instant messenger from May 23 to 31, 2022. A self-reported questionnaire was used to assess participants' Knowledge, Attitude and Behavior regarding dysphagia assessment. Participants' sociodemographic, training, and nursing experience were measured using the general information sheet and analyzed as potential predictors of medical staff's Knowledge, Attitudes and Behavior of dysphagia assessment. A multiple linear regression model was used to identify the predictors.

RESULTS

The mean scores for Knowledge, Attitudes and Behavior of dysphagia assessments were (15.3±2.7), (35.9±4.9) and (41.4±14.4) respectively. Knowledge and Behavior of medical staff were medium, and attitude was positive. Multiple linear regression results indicated that experience in nursing patients with dysphagia, related training for dysphagia, working years in the field of dysphagia related diseases, specialized training (geriatric, swallowing and rehabilitation) and department (Neurology, Rehabilitation, Geriatrics) were significant predictors of Behavior, accounting for 31.5% of the variance. Working years in the field of dysphagia related diseases, department (Neurology, Rehabilitation, Geriatrics) and title were significant predictors of medical staff's knowledge, accounting for 7.8% of variance. Education, experience in nursing patients with dysphagia, department (Neurology, Rehabilitation, Geriatrics) and related training for dysphagia were significant predictors of medical staff's attitude, accounting for 12.9% of variance.

CONCLUSIONS

The study findings implied that nursing experience, training, and work for patients with swallowing disorders could have positive effects on the Knowledge, Attitudes and Behavior of medical staff regarding dysphagia assessment. Hospital administrators should provide relevant resources, such as videos of dysphagia assessment, training centers for the assessment of dysphagia, and swallowing specialist nurses.

Transcutaneous auricular vagus nerve stimulation alters cough sensitivity depending on stimulation parameters: potential implications for aspiration risk

Background

Transcutaneous auricular vagus nerve stimulation (taVNS) is considered a safe and promising tool for limb rehabilitation after stroke, but its effect on cough has never been studied. It is known that the ear and larynx share vagal afferent pathways, suggesting that stimulating the ear with taVNS might have effects on cough sensitivity. The specific stimulation parameters used can influence outcomes.

Objective

To investigate the effect of various stimulation parameters on change in cough sensitivity, compared to the reference parameter of 25 Hz stimulation at the left concha (most commonly-used parameter for stroke rehabilitation). Design, setting, and participants: Randomized, single-blind, active-controlled, eight-period cross-over design conducted March to August 2022 at a New Zealand research laboratory with 16 healthy participants.

Interventions

All participants underwent eight stimulation conditions which varied by stimulation side (right ear, left ear), zone (ear canal, concha), and frequency (25 Hz, 80 Hz). Main outcome measures: Change in natural and suppressed cough threshold (from baseline to after 10 min of stimulation) assessed using a citric acid cough reflex test.

Results

When compared to the reference parameter of 25 Hz stimulation at the left concha, there was a reduction in natural cough threshold of -0.16 mol/L for 80 Hz stimulation at the left canal (p = 0.004), indicating increased sensitivity. For the outcome measure of suppressed cough threshold, there was no significant effect of any of the stimulation conditions compared to the active reference.

Conclusion

Since stroke patients often have cough hyposensitivity with resulting high risk of silent aspiration, using 80 Hz taVNS at the left canal may be a better choice for future stroke rehabilitation studies than the commonly used 25 Hz taVNS at the left concha. Treatment parameters should be manipulated in future sham-controlled trials to maximize any potential treatment effect of taVNS in modulating cough sensitivity.

Clinical trial registration

ACTRN12623000128695.

Complications and Mortality after Surgeries in Patients with Prior Stroke Who Received General and Neuraxial Anesthesia: A Propensity-Score Matched Study

Patients who previously suffered a stroke have increased risks of mortality and complications after surgeries, but the optimal anesthesia method is not fully understood. We aimed to compare the outcomes after surgeries for stroke patients who received general anesthesia (GA) and neuraxial anesthesia (NA). Using health insurance research data, we identified 36,149 stroke patients who underwent surgeries from 1 January 2008 to 31 December 2013. For balancing baseline covariates, the propensity-score-matching procedure was used to select adequate surgical patients who received GA and NA at a case–control ratio of 1:1. Multiple logistic regressions were applied to calculate adjusted odds ratios (ORs) with 95% confidence intervals (CIs) for postoperative mortality and complications between surgical patients with prior stroke who received GA and NA. Among the 4903 matched pairs with prior stroke, patients with GA had higher risks of pneumonia (OR 2.00, 95% CI 1.62–2.46), pulmonary embolism (OR 3.30, 95% CI 1.07–10.2), acute renal failure (OR 3.51, 95% CI 1.13–2.10), intensive care unit stay (OR 3.74, 95% CI 3.17–4.41), and in-hospital mortality (OR 2.02, 95% CI 1.16–3.51) than those who received NA. Postoperative adverse events were associated with GA in patients aged more than 60 years and those who received digestive surgery (OR 3.11, 95% CI 2.08–4.66). We found that stroke patients undergoing GA had increased postoperative complications and mortality after surgery compared with those who received NA. However, these findings need more validation and evaluation by clinical trials.

Impaired Nutritional Condition After Stroke From the Hyperacute to the Chronic Phase: A Systematic Review and Meta-Analysis

Background

Malnutrition is common after stroke and can affect rehabilitation and healthcare costs. A comprehensive overview of stroke patients' nutritional condition from the hyperacute to the chronic phase is lacking. This systematic review aimed to investigate the prevalence of impaired nutritional condition (INC) across the continuum of care in specific phases after stroke.

Methods

CAB ABSTRACTS, Embase, MEDLINE, were used to collect studies published between 01-01-1999 and 26-08-2020. Primary and secondary outcomes were prevalence of INC and prevalence of malnutrition, respectively. Exploratory outcomes were prevalence of INC at follow-up, nutritional examination methods, prevalence of dysphagia, stroke severity, adverse events, and continent-specific prevalence of INC. A random-effects meta-analysis model was used to estimate the phase-specific pooled prevalence of INC and malnutrition.

Results

The dataset consisted of 78 study groups selected over a total of 1,244 identified records. The pooled prevalence of INC and malnutrition were 19% (95%CI:7–31) (N = 4) and 19% (95%CI:9–29) (N = 3), 34% (95%CI:25–43) (N = 34) and 26% (95%CI:18–35) (N = 29), 52% (95%CI:43–61) (N = 34) and 37% (95%CI:28–45) (N = 31), 21% (95%CI:12–31) (N = 3) and 11% (95%CI:0–24) (N = 3) and 72% (95%CI:41–100) (N = 3) and 30% (95%CI:0–76) (N = 2) in the hyperacute, acute, early subacute, late subacute, and chronic phase, respectively.

Conclusion

INC and malnutrition are highly prevalent in all stages of stroke care. Since malnutrition has been shown to negatively affect clinical outcomes, mortality, and overall healthcare expenditure in stroke survivors, it is essential to examine and monitor the nutritional status of stroke patients throughout their care journey to guide and plan, timely nutritional support and dietary modification.

Global Physiology and Pathophysiology of Cough: Part 2. Demographic and Clinical Considerations: CHEST Expert Panel Report

BACKGROUND

Cough characteristics vary between patients, and this can impact clinical diagnosis and care. The purpose of part two of this state-of-the-art review is to update the American College of Chest Physicians (CHEST) 2006 guideline on global physiology and pathophysiology of cough.

STUDY DESIGN AND METHODS

A review of the literature was conducted using PubMed and MEDLINE databases from 1951 to 2019 using prespecified search terms.

RESULTS

We describe the demographics of typical patients with cough in the clinical setting, including how cough characteristics change across age. We summarize the effect of common clinical conditions impacting cough mechanics and the physical properties of mucus on airway clearance.

INTERPRETATION

This is the second of a two-part update to the 2006 CHEST cough guideline; it complements part one on basic phenomenology of cough by providing an extended clinical picture of cough along with the factors that alter cough mechanics and efficiency in patients. A greater understanding of the physiology and pathophysiology of cough will improve clinical management.

A Systematic and a Scoping Review on the Psychometrics and Clinical Utility of the Volume-Viscosity Swallow Test (V-VST) in the Clinical Screening and Assessment of Oropharyngeal Dysphagia

(1) Background: The volume-viscosity swallow test (V-VST) is a clinical tool for screening and diagnosis of oropharyngeal dysphagia (OD). Our aims were to examine the clinical utility of the V-VST against videofluoroscopy (VFS) or fiberoptic endoscopic evaluation of swallow (FEES) and to map the V-VST usage with patients at risk of OD across the years since it was described for the first time, carrying a systematic and a scoping review. (2) Methods: We performed both a systematic review (SR) including studies that look at the diagnostic test accuracy, and a scoping review (ScR) with articles published from September 2008 to May 2020. Searches were done in different databases, including PubMed and EMBASE from September 2008 until May 2020, and no language restrictions were applied. A meta-analysis was done in the SR to assess the psychometric properties of the V-VST. Quality of studies was assessed by Dutch Cochrane, QUADAS, GRADE (SR), and STROBE (ScR) criteria. The SR protocol was registered on PROSPERO (registration: CRD42020136252). (3) Results: For the diagnostic accuracy SR: four studies were included. V-VST had a diagnostic sensitivity for OD of 93.17%, 81.39% specificity, and an inter-rater reliability Kappa = 0.77. Likelihood ratios (LHR) for OD were 0.08 (LHR-) and 5.01 (LHR+), and the diagnostic odds ratio for OD was 51.18. Quality of studies in SR was graded as high with low risk of bias. In the ScR: 34 studies were retrieved. They indicated that V-VST has been used internationally to assess OD's prevalence and complications. (4) Conclusions: The V-VST has strong psychometric properties and valid endpoints for OD in different phenotypes of patients. Our results support its utility in the screening and clinical diagnosis and management of OD.

Delayed Dysphagia May Be Sarcopenic Dysphagia in Patients After Stroke

OBJECTIVE

In many cases, swallowing function is impaired after the onset of stroke and gradually improves. However, delayed dysphagia has been reported in some post-stroke patients. Recently, several studies have reported that low muscle strength and decreased muscle mass cause dysphagia. This study aimed to investigate whether these conditions are associated with delayed dysphagia after stroke.

DESIGN

A multicenter prospective observational cohort study.

SETTING AND PARTICIPANTS

Participants included 165 patients with post-stroke dysphagia (mean age 79.1 ± 8.0 years, 53.3% women) admitted to rehabilitation wards for post-stroke rehabilitation.

METHODS

Swallowing function was assessed using the Functional Oral Intake Scale. Delayed dysphagia was defined as dysphagia that occurred more than 7 days after stroke onset. We used logistic regression to examine the independent association between low muscle strength and decreased muscle mass and delayed dysphagia development. Furthermore, we examined the relationship between improvement in dysphagia and delayed dysphagia.

RESULTS

Delayed dysphagia was observed in 18 (10.9%) patients. The combination of severely low muscle strength and decreased muscle mass was independently associated with the development of delayed dysphagia (adjusted odds ratio: 4.423, 95% confidence interval: 1.400-13.974, P = .011). Delayed dysphagia had an adverse effect on the improvement of dysphagia during in-hospital rehabilitation (adjusted odds ratio: 0.278, 95% confidence interval: 0.078-0.986, P = .047).

CONCLUSIONS AND IMPLICATIONS

The development of delayed dysphagia was influenced by a combination of severely low muscle strength and decreased muscle mass. Furthermore, delayed dysphagia adversely affects the improvement of dysphagia in patients with stroke and needs to be identified early. Identifying delayed dysphagia using the methods proposed in this study and incorporating early intervention may prevent or delay dependency conditions in this population.

Detection of airway protective level of the cough reflex in acute stroke patients

Background

The most common respiratory complications in cerebrovascular strokes were respiratory infection, pulmonary edema, acute lung injury (ALI) acute respiratory distress syndrome (ARDS) and pulmonary embolism (PE). The inhalation cough challenge facilitates the quantification of cough.

Objectives

To detect the level of cough reflex that is enough to protect against respiratory infection in stroke patients, and to identify predictors of post-stroke respiratory infection.

Patients and methods

One hundred and one of cerebrovascular stroke patients were assessed in the first week of symptoms by National Institutes of Health Stroke Scale (NIHSS) Arabic version, Mann Assessment of Swallowing Ability (MASA), cough challenge test, cough flow meter, and A2DS2 score. Then, follow up after 1 week.

Results

Post-stroke respiratory infection was higher in older patients and those who were not working. Respiratory infection was significantly associated with high A2DS2 and NIHSS score (p value < 0.001). A highly significant increase in the levels of the inflammatory markers was detected in patients with a respiratory infection. Eighty percent of stroke patients with no cough developed a respiratory infection. The Mann total scores and the peak cough flow were lower in patients who had a respiratory infection.

Conclusion

Preserved cough reflex is essential in preventing aspirations and consequent respiratory infections.

Cut-off Values of the Respiratory Muscle Power and Peak Cough Flow in Post-Stroke Dysphagia

Background and objectives: This study aimed to determine the cut-off values of the following three respiratory pressure meters; the voluntary peak cough flow (PCF), maximal expiratory pressure (MEP) and maximal inspiratory pressure (MIP); associated with post-stroke dysphagia and assess which of these parameters show good diagnostic properties associated with post-stroke dysphagia. Materials and Methods: Retrospective analysis of a prospectively maintained database. Records of patients with first-ever diagnosed dysphagia attributable to cerebrovascular disease, who had performed spirometry measurements for the PCF, MIP and MEP. Results: From a total of 237 stroke patients, 163 patients were diagnosed with dysphagia. Those with dysphagia had significantly lower PCF values than those without dysphagia (116.3 ± 75.3 vs. 219.4 ± 91.8 L/min, p < 0.001). In addition, the former group also had lower MIP (30.5 ± 24.7 vs. 41.6 ± 25.7 cmH₂O, p = 0.0002) and MEP (41.0 ± 27.9 vs. 62.8 ± 32.3 cmH₂O, p < 0.001) values than the latter group. The receiver operating characteristic curve analysis showed that the PCF cut-off value of 151 L/min (area under the receiver operating characteristic curve [AUC] 0.81; sensitivity 72%; specificity 78.8%) was associated with post-stroke dysphagia. The optimum MEP and MIP cut-off were 38 cmH₂O (AUC 0.70, sensitivity 58%; specificity 77.7%) and 20 cmH₂O (AUC 0.65, sensitivity 49%; specificity 84%). PCF showed the highest AUC results. Results from the univariate analysis indicated that PCF values of ≤151 L/min increased risk of dysphagia by 9.51-fold (4.96–18.23). Multivariable analysis showed that after controlling of other clinical factor, the PCFs at this cut-off value still showed increased risk of by 4.19 (2.02–83.69) but this was not observed with the MIPs or MEPs. Conclusions: Our study has provided cut-off values that are associated with increased risk of dysphagia. Among the three parameters, PCF showed increased association with post-stroke dysphagia.

Effect of Brain Lesions on Voluntary Cough in Patients with Supratentorial Stroke: An Observational Study

Patients with stroke are known to manifest a decreased cough force, which is associated with an increased risk of aspiration. Specific brain lesions have been linked to impaired reflexive coughing. However, few studies have investigated whether specific stroke lesions are associated with impaired voluntary cough. Here, we studied the effects of stroke lesions on voluntary cough using voxel-based lesion-symptom mapping (VLSM). In this retrospective cross-sectional study, the peak cough flow was measured in patients who complained of weak cough (n = 39) after supratentorial lesions. Brain lesions were visualized via magnetic resonance imaging (MRI) at the onset of stroke. These lesions were studied using VLSM. The VLSM method with non-parametric mapping revealed that lesions in the sub-gyral frontal lobe and superior longitudinal and posterior corona radiata were associated with a weak cough flow. In addition, lesions in the inferior parietal and temporal lobes and both the superior and mid-temporal gyrus were associated with a weak peak cough flow during voluntary coughing. This study identified several brain lesions underlying impaired voluntary cough. The results might be useful in predicting those at risk of poor cough function and may improve the prognosis of patients at increased risk of respiratory complications after a stroke.

Natural History of Swallow Function during the Three-Month Period after Stroke

Oropharyngeal dysphagia is a prevalent complication following stroke (PS-OD), and one that is sometimes spontaneously recovered. This study describes the natural history of PS-OD between admission and three months post-stroke, and the factors associated with its prevalence and development. PS-OD was assessed with the volume-viscosity swallow test (V-VST) in all stroke patients on admission and at the three-month follow-up. We analyzed clinical, demographic, and neuroanatomical factors of 247 older post-stroke patients (National Institute of Health Stroke Scale (NIHSS) = 3.5 ± 3.8), comparing among those with PS-OD the ones with and without spontaneous recovery. PS-OD prevalence on admission was 39.7% (34.0% impaired safety; 30.8%, efficacy) and 41.7% (19.4% impaired safety; 39.3%, efficacy) at three months. Spontaneous swallow recovery occurred in 42.4% of patients with unsafe and in 29.9% with ineffective swallow, associated with younger age and optimal functional status. However, 26% of post-stroke patients developed new signs/symptoms of ineffective swallow related to poor functional, nutritional and health status, and institutionalization. PS-OD prevalence on admission and at the three-month follow-up was very high in the study population. PS-OD is a dynamic condition with some spontaneous recovery in patients with optimal functional status, but also new signs/symptoms can appear due to poor functionality. Regular PS-OD monitoring is needed to identify patients at risk of nutritional and respiratory complications.

The impact of lesion location on dysphagia incidence, pattern and complications in acute stroke. Part 2: Oropharyngeal residue, swallow and cough response, and pneumonia

BACKGROUND AND PURPOSE

Dysphagia is a well-known complication of acute stroke. Given the complexity of cerebral swallowing control it is still difficult to predict which patients are likely to develop swallowing dysfunction based on their neuroimaging. In Part 2 of a comprehensive voxel-based imaging study, whether the location of a stroke lesion can be correlated with further dysfunctional swallowing patterns, pulmonary protective reflexes and pneumonia was evaluated.

METHODS

In all, 200 acute stroke cases were investigated applying flexible endoscopic evaluation of swallowing within 96 h from admission. Lesions were mapped using patients' computed tomography/magnetic resonance images and these were registered to a standard space. The percentage of lesioned volume of 137 anatomically defined brain regions was determined on a voxel basis (FSL5.0). Region-specific odds ratios (ORs) were calculated with respect to the presence of oropharyngeal residue, delayed swallow response, insufficient cough reflex and occurrence of pneumonia during hospital stay. Colour-coded lesion location maps of brain regions with significant ORs were created (P < 0.05).

RESULTS

Lesion maps for residue and impaired swallow response depicted parietal-temporal areas of the right hemisphere. Limbic structures in the right hemisphere and sensory regions on the left were associated with cough reflex disturbance. There was no overlap of lesion maps for impaired swallow response and insufficient cough reflex or pneumonia, but substantial overlap between the last two conditions.

CONCLUSIONS

This study gives new insights on the cortical representation of single components of swallowing and airway protection behaviours. The lesion model may help to risk-stratify patients for dysphagia and pneumonia based on their brain scan.