The following chapter describes the methods and the protocols, which are
undertaken to direct the systematic review. It also states the procedure
involved in data collection, concluding with a description of how data was
prepared for analysis (Calabrese, 2009). The procedure followed the guidelines
provided by the Cochrane Collaboration Handbook for Systematic Review of
Interventions (Higgins & Green, 2011) where it is appropriate.
Methodology and Design
The type of research methodology,
which is utilized in this study, is a Systematic review. A Systematic Review is
a means of identifying, evaluating and drawing conclusions from available
research pertaining to a topic of interest (Kitchenham, 2004). The selection of the most appropriate study design relies on an
understanding of the project’s purpose and complexities, and subsequently
choosing the design which best accommodates these parameters (Kennedy N. Otwombe, 2014). Using inappropriate studies can lead to gathering of improper results
and drawing of improper or biased conclusions. The objectivity of the research
is to investigate the effectiveness of the chin
tuck manoeuvre in reducing or preventing aspiration in individuals with
neurological impairment, in order to identify if this practice is justified in
a clinical setting. Also, there continues to be a discrepancy in its use for
neurologic population. Therefore the systematic review process provides a
methodology through which the specific objectives of this study can be
addressed, and was thus the chosen methodology.
for considering studies for this review
2.2.1 Types of studies
thoroughly designed systematic review limits inclusion criteria to randomized
controlled trials (RCTs) and Controlled Clinical Trials (CCTs) as they are
thought to provide a higher level of unbiased information regarding
differential intervention effects than other study designs(O’Connor, 2011). All
published and non-published RCTs and CCTs were evaluated for this systematic
were defined as all trials that involved at least one test treatment aimed at
improving or eliminating aspiration and one control treatment; or no treatment
with concurrent enrolment and follow up of the test and control treated groups;
as well as trails in which the treatment to be administered is selected by a
random process, such as a random number tables (Lefebvre, 2011).
were classed as all trials that involved at least one test treatment aimed at
improving or eliminating aspiration and one control treatment; or no treatment
with a non-randomized but bias free method of assigning patients to the test
treatment (Lefebvre, 2011).
is the most serious threat to credibility of evidence, RCT studies have been
considered as having the highest level of evidence (Level 1). The trials for
inclusion were not restricted by language or date filter so as to make sure
that all trials examining this intervention were found. Studies from past and
trials in different languages were not excluded as evidence from all studies
that needs to be assessed. Studies from inception to the date of analysis of
research were included.
criteria for including and excluding studies in a review (eligibility criteria)
is an important feature of systematic reviews (O’Connor, 2011). People above
18 years of age were included in the review because of biological plausibility
and the existing controversy, which are present within adults (Terre? R, 2012;
Macrae P, 2014; Solazzo A, 2012; Shanahan TK, 1993). Adults with a clinical
diagnosis of any neurological disorder, who have symptoms and signs of
difficulty swallowing and in whom aspiration or penetration has been confirmed
by a full clinical bedside evaluation, video-fluoroscopy or fiber-optic
examination of swallowing (FEES) using valid reliable measures, where
available, such as the Penetration-Aspiration Scale (Rosenbek 1996).
Participants who suffer any type and severity of the neurological disorder were
included in the review. Also, Patient with head and neck cancer were excluded
from the review because of the post-operative changes in the anatomy and
physiology, which results in the change of swallowing pattern (McCulloch,
aged 18 and over (male and female) seen in any setting.
under 18 years of age.
with a clinical diagnosis of any neurological disorder.
with history of head and neck cancer.
with any type and severity of neurological disorder
having history of radiation therapy.
2.2.3 Types of Interventions
intervention included in this systematic review was chin tuck, which aimed to reduce
or prevent aspiration. This intervention was allowed to practice in any setting
(generally in a medical setting for e.g. clinic, hospitals), and must have been
delivered by trained individual or team. Immediate, medium or long-term
improvements in drooling, as well as any positive or negative effects to chin
tuck intervention were taken into consideration.
intervention considered in this review includes:
versus no intervention (i.e. chin tuck versus normal swallow)
vs. other intervention (i.e. Chin tuck versus other compensatory strategies for
e.g. head back, head rotation)
2.2.4 Types of outcome measures
primary outcome of this systematic review was to see the positive or negative
change in aspiration for individuals with dysphagia with neurological
aetiology. Both the desirable and undesirable effects of these outcomes were
considered in relation to the current intervention. Loke, Price and Herxheimer
(2011), reported that in order to achieve a balanced perspective; all reviews
should consider the adverse aspects of intervention. The secondary outcomes in
the review were to see the positive or negative changes to oral and pharyngeal
phase functions, which are measured using Video-fluoroscopic evidence. Also,
positive or negative changes to lip, tongue and other structural movements
involved in swallowing.
in aspiration for individuals with dysphagia with neurological aetiology
to oral and pharyngeal phase functions
to lip, tongue and other structures
2.3 Search methods for identification of studies
search strategy aimed to identify all available studies, published and
unpublished. Search for studies were not restricted to electronic databases,
but were expanded to other sources in order to maximize the accuracy of the
search and minimize publication bias. This ensured that the search strategy was
thorough and detailed, covering all relevant studies.
search words like “chin”, “dysphagia”, “dysphagic”, “deglutition”,
“swallow”, “swallows”, “swallowing”, “swallowed”, “deglutition disorder”, “chin
down”, “chin tuck”, “head forward”, “manoeuvre”, “posture”, “effectiveness”,
“evaluation”, “video fluoroscopy”, “Neurological” were used
and these words were entered into the controlled vocabulary for indexing,
specific to each database search. These terms were combined using standard
Boolean operators “OR” and “AND”. It was seen that these search term cover the
relevant studies that were needed for this review. The main purpose of the
database indexing is to yield the accuracy of search results (Murphy, 2003). A comprehensive Title/Abstract search
including medical subject headings (MeSH) terms were completed in PubMed to
begin the search. MeSH terms are controlled, indexed vocabulary used to capture
all possible interpretations of a concept (Cooper, 2014).
following twelve electronic databases search were included for the review;
Academic Search Complete; AMED; CINAHL; the Cochrane Library; EMBASE; Google
Scholar; HSE Library; PsycINFO; Cochrane Central Register of Controlled Trials
(CENTRAL); SCOPUS; MEDLINE; and Web of Science. Ongoing clinical trials were
searched on the clinical trials website (http://clinicaltrials.gov) and
ongoing controlled trials were searched
on (http://www.isrctn.com/). The
ProQuest Dissertation and Thesis was reviewed for relevant abstracts. Database
were searched from inception up to and including May 2018. It was addressed
that biased conclusion from studies could result from reviews that omit studies
with delayed publication (Guyatt, 2011); a fact often termed “Time Lag
bias” (Hopewell et al., 2007). Therefore, a
repeated search in all the database was conducted just before the completion of
2.3.2 Searching other resources
single data search is not sufficient as it can introduce the risk of omitting
large quantities of relevant literature. Additional search methods are also
required. Searches were not limited to electronic searches, to avoid
publication bias. Publication bias is defined as a selective publication of
studies with a particular outcome, usually those that are statistically
significant, at the expense of null studies (Ferguson & Brannick, 2011). Grey literature, defined by Happe and Walker
(2013) as information, which is not controlled by commercial publishing, it was
also explored. These measures were taken as a part of the search strategy for this
systematic review in order to further minimize the risk of publication bias.
Also, additional separate searches in many of the above sources were done to
ensure that we get the most up to date information.
For the review grey literature search were:
· ISI web
of knowledge conference proceedings
The following Journals were hand searched:
journal of Speech-Language Pathology
American Journal of Occupational Therapy
Journal of Therapy and Rehabilitation
of Medical Speech-Language Pathology
of Oral Rehabilitation
International Journal of Language and Communication Disorders.
The “related article” function in PubMed was
used in order to enhance the search
ProQuest Database was searched for unpublished
thesis and dissertations abstracts.
Lastly, the reference list from all other
included studies was searched to identify other relevant studies.
Data collection and analysis
researcher initially screened all the titles and/or abstracts of studies
retrieved using the search strategy and those from additional sources were
screened independently by two review authors to identify studies that
potentially meet the inclusion criteria outlined above.
search results were merged using reference management software and duplicated
records of the same report were removed. Results from the search were
categorized as either ‘relevant’, ‘potentially relevant’ or ‘not relevant’. Studies
that were unclear from titles and abstracts of whether it should be included,
the third reviewer was told to obtain copies of the study for further analysis.
Any kind of disagreement on the selection of studies was resolved by consensus
eligibility of the study was in question, we contacted the authors of the study
for additional information. The review team was not blinded to information
about authors, institution, and journal of publication or results.
PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses;
Moher, Liberati, Tetzlaff, & Altman, 2009) flow diagram was used to map out
the inclusion and exclusion of studies.
2.4.2 Data extraction and management
designed standardized data form was used to extract data from the included
studies for assessment of studies quality and for evidence synthesis. For
eligible studies, two authors extracted the data using the standard form. The
data was entered in Review manager software (Revman 2012); to check the
accuracy of the data. Two authors will extracted the data independently, and
discrepancies were identified and resolved through discussion (with a third
author where necessary).
data will be requested from study authors. If no response is received from the
authors, then the studies were eliminated from the meta-analysis but they were
retained for further discussion.
aimed to reduce risk of bias at the stage of data extraction. No attempts were
made to mask for authorship, journal name, or institution.
2.5 Assessment of risk of bias in included
These five domains of bias were examined: selection bias,
performance bias, attrition bias, detection bias and reporting bias. The “Cochrane
Collaboration’s Tool for Assessing Risk of Bias” (Higgins & Green, 2011)
was used to assess the criteria for risk of bias for each individuals study
which were included. The “Downs and Black checklist” (Downs SH, Black N, 1998) was
used to assess the quality of the Non- Randomized Controlled Trial studies.
This data was then entered into Review Manager (RevMan:
Computer program Version 5.3, and a risk of bias table was generated. Any
further data analysis in this review was carried out using RevMan.
of treatment effect
of treatment effect involves combining results from different studies to create
one overall numerical estimate to increase statistical power and lead to more
precise estimates of treatment effect (Lau, 1997). It was
decided that in this Systematic Review to create forest plots to display effect
estimates for the outcomes considered in included studies using RevMan.
2.7 Unit of
of analysis is the level at which researchers collect data and compare outcomes
(Pieper, Mathes and Eikermann, 2014). The unit of analysis, which was of
importance in this study, were the individuals participants having Dysphagia
with Neurological origin. For studies where only group data was available, it
was planned to contact the authors of the studies, to provide the individual
with missing data
percentage of missing data may undermine the scientific credibility of
conclusions and decrease the potential statistical power (Little, 2012). It was
decided that the authors would be contacted in possible cases where there was
noted to be missing data from included studies.
heterogeneity occurs when the total variation across study results is
beyond that predicted by chance (Higgins, 2002). Authors of this article planned
to conduct heterogeneity test using the Chi² test (significance: p < 0.1). Also, with the estimated impact of variation due to heterogeneity calculated using the I² statistic. This describes the percentage of variability in point estimates caused by heterogeneity rather than sampling error (Higgins, 2002). If statistical heterogeneity is identified, a number of analysis were used to address this. If there is evidence of heterogeneity, then which factor caused it were explored and a sensitivity analysis was performed based on the possible reasons. The trials, which did not show heterogeneity a meta-analysis was conducted as, planned by authors. This involves meta-analysis of primary and secondary end-points via calculation of risk ratio and 95% confidence intervals for dichotomous outcomes, and standardized mean differences and 95% confidence interval for continuous outcomes. 2.10 Data synthesis Meta-analysis is used to systematically review and combine results of similar studies, producing an overall summary estimate (Munn Z, 2014). Meta-analysis is widely employed in systematic reviews of intervention effectiveness, when the intervention is well accepted and explained(Felix Achana, 2014). It was intended to conduct a meta-analysis if a minimum of two sufficiently homogenous studies were defined (Ryan & Cochrane Consumers and Communication Review Group, 2013) in this review. 2.11 Subgroup analysis and investigation of heterogeneity Subgroup analysis allows exploration of heterogeneity within studies and can allow researchers to answer specific clinical questions regarding particular intervention effects (Deeks, 2011). A subgroup analysis considering the treatment effects was planned taking into consideration the aetiology of individuals with dysphagia. If substantial heterogeneity (indicated by a Chi² test p < 0.1 or an I² value >50%) was found to be present. Then the researchers intended to explore possible
causes of heterogeneity (e.g. patient age).
Sensitivity analysis of methodological quality allows researchers to assess
stability and robustness of conclusion made during primary analysis (Deeks, 2011).
Sensitivity analysis requires repeated calculations with inclusion/exclusion of
particular subsets of studies to assess if this effects overall results (Taylor, 2009). The author
planned to conduct a sensitivity analysis to explore potential influences of
methodological quality on effect sizes, if appropriate.
This chapter presented the research methodology employed in
this systematic review. Considerations of study design; data collection,
synthesis and analysis were discussed. The following chapter presents the
findings of the systematic review.