The safety and effectiveness of techniques to assist coughing in people with chronic neuromuscular disorders

Review question

We reviewed the evidence on the effectiveness and safety of techniques used to assist coughing in people with chronic neuromuscular disorders (cough augmentation techniques).

Background

People with neuromuscular disorders (nerve-related conditions that affect the muscles) may have difficulty coughing and clearing mucous from the airways, placing them at risk of choking, recurrent chest infections, and ongoing lung disease. Cough augmentation techniques, such as manually assisted cough, bagging (using a self-inflating bag commonly used for resuscitation), mechanical Cough Assist (a device that clears secretions by applying a positive pressure to the airway, then rapidly shifting to a negative pressure), 'frog' breathing (a method of breathing to help a person take in a bigger volume of air), and breathstacking (the person takes a number of sequential breaths in, stacking one breath on top of the other without breathing out in between breaths) aim to improve cough effectiveness, with the eventual aim of reducing the number or severity (or both) of chest infections, and improving the ability of people to perform daily activities (functional ability) and quality of life.

Methods

We carried out a wide database search for studies of cough augmentation techniques in adults and children with chronic neuromuscular disorders. We selected studies that assigned people to the treatment(s) or treatment order by chance, as this study type provides the best evidence.

Results and quality of the evidence

We found 11 studies with 287 people and several cough augmentation techniques. One study measured the long-term effects of treatment, but was only published as an abstract without enough information to accurately analyse the study findings. Many included studies had problems with how they were performed, how their findings were reported, or both, which made it difficult to fully interpret their results. None of the studies reported on the outcomes we thought were the most important for making decisions about the effectiveness and safety of cough augmentation techniques. For example, the studies did not report on the number or duration of unscheduled hospital admissions for chest infections, survival, functional ability, or quality of life. The safety of cough augmentation techniques could not be determined. Some studies suggested that cough augmentation techniques may be better than an unassisted cough, but the results are very uncertain. There was not enough evidence to show that any one technique was better than another in improving cough effort.

Conclusions and recommendation

The findings of this review provided insufficient information to make decisions about when and how to use cough augmentation techniques in people with chronic neuromuscular disorders. There is currently very low certainty evidence for or against the safety and effectiveness of cough augmentation techniques in people with chronic neuromuscular diseases and more studies are needed.

The evidence is up-to-date to 13 April 2020.

Authors' conclusions: 

We are very uncertain about the safety and efficacy of cough augmentation techniques in adults and children with chronic neuromuscular disorders and further studies are needed.

Read the full abstract...
Background: 

People with neuromuscular disorders may have a weak, ineffective cough predisposing them to respiratory complications. Cough augmentation techniques aim to improve cough effectiveness and mucous clearance, reduce the frequency and duration of respiratory infections requiring hospital admission, and improve quality of life.

Objectives: 

To determine the efficacy and safety of cough augmentation techniques in adults and children with chronic neuromuscular disorders.

Search strategy: 

On 13 April 2020, we searched the Cochrane Neuromuscular Specialised Register, CENTRAL, MEDLINE, Embase, CINAHL, and ClinicalTrials.gov for randomised controlled trials (RCTs), quasi-RCTs, and randomised cross-over trials.

Selection criteria: 

We included trials of cough augmentation techniques compared to no treatment, alternative techniques, or combinations thereof, in adults and children with chronic neuromuscular disorders.

Data collection and analysis: 

Two review authors independently assessed trial eligibility, extracted data, and assessed risk of bias. The primary outcomes were the number and duration of unscheduled hospitalisations for acute respiratory exacerbations. We assessed the certainty of evidence using GRADE.

Main results: 

The review included 11 studies involving 287 adults and children, aged three to 73 years. Inadequately reported cross-over studies and the limited additional information provided by authors severely restricted the number of analyses that could be performed.

Studies compared manually assisted cough, mechanical insufflation, manual and mechanical breathstacking, mechanical insufflation-exsufflation, glossopharyngeal breathing, and combination techniques to unassisted cough and alternative or sham interventions. None of the included studies reported on the primary outcomes of this review (number and duration of unscheduled hospital admissions) or listed 'adverse events' as primary or secondary outcome measures.

The evidence suggests that a range of cough augmentation techniques may increase peak cough flow compared to unassisted cough (199 participants, 8 RCTs), but the evidence is very uncertain. There may be little to no difference in peak cough flow outcomes between alternative cough augmentation techniques (216 participants, 9 RCTs).

There was insufficient evidence to determine the effect of interventions on measures of gaseous exchange, pulmonary function, quality of life, general function, or participant preference and satisfaction.

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