Background

Choking incidents mostly occur while swallowing food and drinking and have been recognized as a cause of death among people with mental illness such as schizophrenia, bipolar disorder and depression.1-3 According to the National Safety Council in the United States, choking led to the death of 4800 people in 2014, and among 57% (2751) of them were older than 75 years. In 2016, choking was the fourth leading cause of unintentional injury death.4 A recent study from Ireland showed that over a 10-year period, 10% of sudden deaths caused by choking were among people with mental illness5 and mortality in this population caused by choking was 100 times higher than that in the general population.6 Another study done by Regan et al.7 reported that patients with schizophrenia and organic brain syndrome had a risk of death by choking 30 to 40 times higher than that of the general population. Three other studies showed that people with mental illness had a three- to five-fold,1 eight-fold8 and 20-fold9 higher risk of death by choking than people without mental illness, respectively. Based on the mortality rate of these studies, it is necessary for healthcare professionals to pay attention to the risk of choking in people with mental illness.

Factors contributing to the risk of choking in people with mental illness are still unclear although some factors have been suggested in the literature. Modifiable risk factors (which can be changed) such as side effects of antipsychotic medication, poor dentition and seizures have been suggested to contribute to choking.9,10 In addition, some non-modifiable risk factors (demographic factors which are non-changeable), such as young children,11 the elderly, especially those with dementia, neurological patients,12 alcoholics, and people with drug addiction issues,13 learning disabilities and intellectual disabilities,14 have also been suggested. Choking incidents may be preventable through implementation of effective strategies for identified causes.15 As people with mental illness in the inpatient settings are seldom confined to their beds, passively receiving treatment by health providers, helping them self-manage their conditions becomes extremely important. Strategies for choking prevention include education on poor eating habits and the signs and symptoms of the side effects of antipsychotic drugs.10 Caregivers should be alerted to the high risk of choking in people with mental illness.16 Training and providing appropriate emergency resuscitation to manage choking are essential.10,16

Although a review has been conducted on the prevalence of asphyxia and dysphagia caused by the use of antipsychotics,17 no other recent systematic review on pre-disposing factors of choking and strategies to manage choking risks and incidents was identified from a preliminary search of the Cochrane Library and the JBI Database of Systematic Reviews and Implementation Reports. Choking happens when normal breathing is compromised by obstruction of the airway,1 whereas in dysphagia, the airway may be obstructed without compromising normal breathing. Therefore, there is a dearth of evidence on risk factors and management of choking in people with mental illness. Although much of the choking-related mortality has included both inpatient and outpatient settings, the risk factors are highly varied and health professionals have limited opportunities to manage these risk factors, especially in outpatient settings. Hence, this systematic review will synthesize the best available evidence on pre-disposing factors of choking in the inpatient healthcare setting.

Choking is preventable; it could be reduced by identifying risk factors and implementing strategies to manage the risk factors accordingly. Hence, this systematic review, other than synthesizing the best available evidence on pre-disposing factors of choking, will also review the types and impact of non-pharmacological strategies to manage choking risk in people with mental illness in inpatient healthcare settings. Although pharmacological strategies may also be utilized to manage choking risk, this is not the focus of this review as such strategies are only available to specific groups of health professionals, namely, physicians and pharmacists.

Inclusion criteria

Types of participants

The current review will consider studies where participants are aged 18 years and over with any type of mental illness, based on the diagnostic criteria in the International Statistical Classification of Diseases and Related Health Problems18 and the Diagnostic and Statistical Manual of Mental Disorders,19,20 and are inpatients in healthcare settings (namely, acute and long-term inpatients settings, community residential care facilities such as nursing homes) who have also been exposed to choking incidents or injuries (refer to the "Outcomes" section).

Exposure

The modifiable and non-modifiable risk factors that pre-dispose adults with mental illness to choking incidents or injuries in inpatient settings during their hospitalization will be examined in this review. The risk factors that may be derived from this systematic review may include (but not limited to) the side effects of antipsychotic medications, eating behavior, poor dentition and seizures as contributing to choking in people with mental illness.

Types of intervention(s)

The current review will also include studies investigating non-pharmacological strategies such as (but not limited to) identification and management of risk factors, and educational, dietary and first aid training interventions in managing individuals at risk of choking or while a choking incident is occurring in healthcare settings (such as acute and long-term inpatient settings, residential care facilities and nursing homes). Studies that compare these strategies to one another or to usual care or a control group without specification of interventions to manage choking will be considered for this review.

Outcomes

The outcomes include choking incidents or frequencies, injuries (as a result of choking such as lesions to the esophagus), or mortality of individuals resulting from choking occurring in the healthcare settings.

Types of studies

Various types of quantitative studies will be considered to identify risk factors for choking.

Descriptive studies, such as case-series or time-series studies, comparable cohort, case-control, randomized controlled trials or pseudo-randomized trial studies, will also be considered to identify the effective non-pharmacological strategies to manage choking risk in adults with mental illness who are inpatients in healthcare settings.

Search strategy

The literature search aims to find published and unpublished studies reported in the English language. The search to retrieve articles will be limited from Jan 1, 2000 up to the present to identify current evidence in this current millennium. Moreover, it was only from the year 2000 that incidents of choking and "choking games", that is, self-strangulation, have been included in literature;21 hence the time limit for the literature search to ensure that all choking incidents will be captured. A three-stage search will be undertaken in this review. An initial search of the MEDLINE and CINAHL databases will be undertaken followed by analysis of the text words contained in the title and abstract, and of the index terms used to describe the articles. A second extensive search will be undertaken across all included databases (the keywords and related terms are listed in Appendix I). Third, the reference lists and bibliographies of all identified articles will be searched for additional studies.

Electronic databases to be searched include:

* CINAHL

* PubMed

* Ovid Nursing Database

* PsycINFO

* Cochrane Central Register of Trials

* ProQuest Dissertations and Theses Global.

The above stated databases to be searched are intended to retrieve completed studies where results are published and unpublished studies from dissertations. The search for unpublished studies and gray literature helps reduce publication bias by including studies with limited, negative or neutral outcomes that may otherwise not have been published.

The titles and abstracts identified from the search will be assessed independently according to the inclusion criteria. Full texts will be retrieved for studies that meet the inclusion criteria. Once the papers are retrieved, studies will again be assessed for their relevance to the review objectives. Studies where full text is not available will be excluded.

Assessment of methodological quality

Papers selected for retrieval will be assessed by two independent reviewers for methodological validity prior to inclusion in the review using standardized critical appraisal instruments from the Joanna Briggs Institute System for the Unified Management, Assessment and Review of Information (JBI-SUMARI).22 Any disagreements that arise between the reviewers will be resolved through discussion or with a third reviewer.

Data extraction

Data will be extracted by the two independent reviewers using the standardized data extraction tool from JBI-SUMARI. The data extracted will include specific details about the interventions, populations, study methods and outcomes of significance to the review question and specific objectives. Any disagreements that arise between the reviewers will be resolved through discussion or with a third reviewer.

Data synthesis

Where possible, quantitative study results will be pooled using JBI-SUMARI. All results will be double entered. Odds ratio (for categorical data such as choking incidents, and morbidity and mortality resulting from choking), weighted mean differences and their 95% confidence intervals (for continuous data such as choking frequencies or severity) will be calculated for analysis. Heterogeneity will be assessed using the standard Chi-square. Where statistical pooling is not possible, the findings will be presented in narrative form.

Should findings be synthesized in narrative form, we will consider stratifying the risk factors of choking. Articles that examine similar risk factors will be grouped under various categories of risk factors such as non-modifiable risk factors (for example, personal factors and types of mental illness) or modifiable risk factors (for example, dentition and eating behavior). The non-pharmacological strategies to manage choking risk may also be grouped based on the different healthcare settings where the strategies have been applied.

Acknowledgements

The reviewers acknowledge Institute of Mental Health, Singapore, for its support in the development of this systematic review protocol.

Appendix I: Search strategy

Keywords and related terms used to search literature in the databases

References