Introduction Dysphagia is a common functional disorder after stroke. Most patients post-stroke are incapable of oral feeding, which often leads to complications such as malnutrition, aspiration pneumonia and dehydration that seriously affect the quality of life of patients. Oropharyngeal muscle strength training is a major method of swallowing training, and recent studies have focused on healthy adults, elderly persons, and patients with head and neck cancer or neurodegenerative diseases; but there have been few studies on such training in patients with post-stroke dysphagia. Our study aims to systematically review the safety and performance of oropharyngeal muscle strength training in the treatment of post-stroke dysphagia during oral feeding.
Methods and analysis The Cochrane Library, Web of Science, PubMed, Embase and ClinicalTrials.gov databases will be systematically searched, and all relevant articles in English from the establishment of the databases to January 2022 will be reviewed. The study will be conducted in accordance with the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions and will be reported in accordance with Preferred Reporting Items for Systematic Reviews and Meta Analyses guidelines. The primary outcome measures include the Penetration–Aspiration Scale and the Functional Oral Intake Scale. Two authors will independently screen the articles, extract the data and assess the study quality. Any disagreements during this process will be resolved by discussion or by consultation with a third author. Next, quantitative or qualitative, subgroup and sensitivity analyses of the included literature data will be performed as appropriate.
Ethics and dissemination Ethical approval is not required for this systematic review as no primary data collection will be required. The results of the present study will be published in a peer-reviewed journal in the field of deglutition disorders.
PROSPERO registration number CRD42022302471.
- Rehabilitation medicine
- Neuromuscular disease
This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.
Statistics from Altmetric.com
If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.
Strengths and limitations of this study
The study will be conducted in accordance with the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions and will be reported in accordance with Preferred Reporting Items for Systematic Reviews and Meta Analyses guidelines.
Five key databases will be searched: the Cochrane Library, Web of Science, PubMed, Embase and ClinicalTrials.gov.
Two reviewers will independently complete the study screening, selection, data extraction and quality rating, and any disagreements will be resolved via discussions or consultations with a third author.
Different types, intensity, frequency and time of oropharyngeal muscle strength training may lead to a large degree of heterogeneity; subgroup analyses of the effects of the onset time, stage and type of the stroke on the training outcome of people post-stroke will also be carried out.
Only studies published in English will be included.
Approximately 13.7 million people worldwide suffer from stroke annually,1 and nearly half of these people experience varying degrees of functional impairment that seriously affect their quality of life.2 3 Dysphagia is a notably common functional impairment in people post-stroke, with a reported incidence of up to 80%.4 Patients with dysphagia are often incapable of oral feeding, resulting in complications such as malnutrition, dehydration, aspiration pneumonia and prolonged hospitalisation, in addition to increased hospital costs. Although most patients spontaneously recover swallowing function, 11%–50% of patients still have dysphagia 6 months after stroke.5
The primary purpose of swallowing treatment is to reduce the incidence of aspiration and increase the level of oral feeding. Traditional dysphagia treatment includes oral facial massage,6 thermal tactile stimulation7 and various compensatory methods.8 9 Although they can help patients begin to attempt oral feeding promptly, they do not facilitate the recovery of neural networks in regions of the cerebral cortex associated with swallowing, and training efficacy is short-lived.10–12 Modalities for improving oropharyngeal muscle strength such as tongue-to-palate resistance training (TPRT),13 Shaker exercise,14 Iowa Oral Performance Instrument (IOPI),15 tongue-strengthening exercises (TSEs)16 and chin tuck against resistance (CTAR) exercise17 use isometric or isokinetic muscle contractions to improve the strength and endurance of swallowing-related muscles. Studies involving healthy adults and older adults have shown that maximum tongue pressure18 and suprahyoid muscle strength19 are significantly improved after oropharyngeal muscle strength training, but there have been few studies on such training in patients with post-stroke dysphagia.
Thus, our study is a comprehensive systematic review that aims to address the following questions through evidence-based medicine: (1) Compared with conventional swallowing treatment, what is the effect of oropharyngeal muscle strength training on the swallowing process in patients with post-stroke dysphagia with respect to (a) safety of swallowing, evaluated with Penetration–Aspiration Scale (PAS), and (b) performance of swallowing, evaluated with Functional Oral Intake Scale (FOIS)?; (2) Does training efficacy differ depending on the type, time, frequency or intensity of training?; (3) Does the training efficacy depend on the onset time, stage and type of the stroke?
Methods and analysis
This protocol was reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols (PRISMA-P)20 (see online supplemental appendix 1). The final study will be conducted in accordance with the recommendations of the Cochrane Handbook for Systematic Reviews of Interventions21 and will be reported in accordance with PRISMA 2020 checklist.22
Inclusion criteria for studies
Studies will be included in this systematic review if they meet the following criteria:
The participants will be initial-onset stroke aged 18 years or above, with oropharyngeal dysphagia diagnosed after videofluoroscopic swallowing study (VFSS), flexible endoscopic evaluation of swallowing or clinical evaluation. Those with a history of oropharyngeal cancer or head and neck trauma or surgery prior to onset will be excluded. There will be no restrictions on race, nationality or sex of the participants.
Interventions will include methods of oropharyngeal muscle strength training, including Shaker exercise, CTAR, IOPI, TPRT and TSE. Considered studies will include at least one of any of these methods, with no restrictions on time, frequency or intensity of training.
Control groups in selected studies would have undergone conventional swallowing treatment, including orofacial muscle exercises, thermal tactile stimulation, and therapeutic or compensatory manoeuvres, or placebo treatment (defined as using the same equipment as the intervention, but without resistance).
The primary outcome measures include (1) safety of swallowing evaluated with PAS23 through VFSS to compare the changes in aspiration before and after intervention; and (2) performance of swallowing assessed with FOIS24 to compare the changes in oral intake levels before and after intervention. The PAS is the primary tool to quantify swallowing safety. It is an 8-point scale used to characterise the depth and response to larynx passage and airway invasion during VFSS. A PAS score of 3 is frequently used as the cut-off for unsafe swallowing. The FOIS is a 7-point ordinal scale that documents the functional level of oral intake of food and liquid. It is a reliable and validated outcome parameter, to measure adequate oral intake.
Secondary outcome measures include (1) severity of dysphagia assessed through Functional Dysphagia Scale,25 Videofluoroscopic Dysphagia Scale,26 Dysphagia Outcome and Severity Scale27 and Dysphagia Rating Scale28; (2) swallowing biomechanics with changes in maximal excursion of the hyoid, muscle strength of suprahyoid muscles and tongue pressure; (3) swallow-related quality of life assessed through Swallow Quality of Life Questionnaire.29
Study design and language
The systematic review will only include randomised controlled trials published in English. Case–control studies, cohort studies, case reports or other studies that do not provide data for analysis will be excluded.
The Cochrane Library, Web of Science, PubMed and Embase databases will be searched for relevant studies from inception until January 2022, in addition to ClinicalTrials.gov (www.clinicaltrials.gov). Key search terms include the following: “deglutition disorders,” “dysphagia,” “shaker exercise,” “head lift exercise,” “chin tuck against resistance,” “Iowa oral performance instrument,” “isometric lingual exercise,” “tongue-to-palate resistance training,” “tongue-strengthening exercises.” For a detailed search strategy, see online supplemental appendix 2.
EndNote (V.X9) software will be used to store and manage all articles retrieved from the databases. First, duplicate documents will be identified and eliminated through the duplication checking function of EndNote, and then an author will manually identify and eliminate them. After eliminating duplicates, two authors will independently screen the titles and abstracts of the articles; those that did not meet the inclusion criteria will be excluded. After preliminary screening, two authors will independently conduct a detailed full-text review of potentially eligible articles, exclude articles that do not meet the inclusion criteria and record the reasons for the exclusion, and finally determine the studies to be included in the systematic review. During this process, any disagreements between the two authors on whether an article should be included will be resolved by discussion or consultation with the third author.
Data extraction and management
Two authors will independently extract relevant study data from the included studies using a data extraction form (see online supplemental appendix 3). The extracted data will then be subjected to a final review by the third author, and any discrepancies will be resolved through discussion or consultation. The extracted data will include the basic information of the study, research methods, characteristics of the research participants (demographic information, inclusion and exclusion criteria, baseline characteristics, sample size, etc), interventional measures (type, time, frequency, and intensity of training in the experimental and control groups), outcome measurement (definitions, methods of measurement, different time points, etc) and results (primary outcome measures, secondary outcome measures, losses to follow-up, missing data, etc).
Risk of bias assessment
The risk of bias of the included studies will be independently assessed by two authors using the Cochrane risk-of-bias tool,30 which covers seven domains of bias, including random sequence generation (selection bias), allocation concealment (selection bias), blinding of participants and personnel (performance bias), blinding of outcome assessment (detection bias), incomplete outcome data (attrition bias), selective reporting (reporting bias) and other biases. Each domain is judged as ‘high risk’, ‘low risk’ or ‘unclear risk’. During this process, disagreements will be resolved through discussion or consultation with the third author.
Data analysis and synthesis
Cochrane Review Manager software (V.5.3, The Cochrane Collaboration, London, UK) will be used in this review for the meta-analysis. If enough studies meet the inclusion criteria and have the same outcome, we will perform a meta-analysis of the primary and secondary outcome measures. If a given outcome measure has data from only one study, the results will be reported narratively.
Treatment efficacy will be measured using risk ratio and 95% CI for dichotomous data, mean difference or standardised mean difference and 95% CI for continuous data.
A low degree of overlap in the CI of the included studies will indicate heterogeneity. The χ2 test and the I2 statistic will be used for the analysis.31 If p>0.1 and I2 <50%, a fixed-effects model will be used; if p>0.1 and I2 ≥50%, a random-effects model will be used. If p≤0.1, the heterogeneity is large and will be considered statistically significant, and subgroup analysis will be used to investigate the reasons for the heterogeneity. Subgroup analysis will investigate factors such as the type, intensity, frequency, and time of oropharyngeal muscle strength training, and the onset time, stage and type of stroke. If necessary, sensitivity analysis of the primary outcome measure will be used to investigate the effect of bias on the study results.
If the number of articles included in this study is sufficiently large (n>10), funnel plot analysis will be used to assess potential publication bias.
This study will assess five factors determining the quality of evidence (study limitations, inconsistency of results, indirectness of evidence, imprecision and reporting bias) in accordance with the Grading of Recommendations Assessment, Development and Evaluation system.32 This system classifies the quality of evidence into four levels (very low, low, moderate or high). The evaluation process will be performed independently by two authors, and any disagreements will be resolved by discussion or consultation with the third author.
Patient and public involvement
Patients and the public will not be directly involved in the study. All data collected in this study will be derived from published data in databases or clinical trial registries.
Ethics and dissemination
Ethical approval is not required for this systematic review as no primary data collection is required. The results of the present study will be published in a peer-reviewed journal in the field of deglutition disorders.
Patient consent for publication
We gratefully acknowledge Professor Xueyong Liu for his management and support of this research. We wish to acknowledge Qijun Wu, Yu He and Zhan Zhang for their suggestions on this research. We would like to thank Editage (www.editage.cn) for English language editing.
Contributors MG, YW, LX and FZ designed the study and interventions. HW, JS and XY designed search strategies and will perform the study search. MG, YW, XW and FZ will perform data collection, analysis and synthesis. MG wrote the manuscript and all coauthors critically reviewed and approved the final manuscript. FZ is the guarantor of the protocol and the final review.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.
Provenance and peer review Not commissioned; externally peer reviewed.
Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.