Mechanical insufflation-exsufflation to improve mucus clearance in people with neuromuscular disorders

Review question

Our aim in this review was to find out how well mechanical insufflation-exsufflation (MI-E) works and how safe it is to use in people with neuromuscular disorders (diseases of the peripheral nerves or muscles) who have breathing problems.


People with neuromuscular disorders (NMDs) sometimes have weak breathing muscles. This can make it difficult for them to cough and clear mucus from the lungs well, putting them at risk of repeated chest infections and ongoing lung disease. MI-E is one of a number of methods used to improve cough and mucus clearance. MI-E is given through a mask, mouthpiece, or via a tracheostomy (an opening in the neck into the windpipe). MI-E acts like a cough by first pushing air into the lungs when the person breathes in (insufflation), then sucking it out again (exsufflation).


We carried out a wide database search for trials of MI-E in people with NMDs. We only included trials in which people were assigned to the treatments by chance, as these studies provide the best quality evidence.

Results and quality of the evidence

We found five trials, with 105 people. They all studied the immediate effects of a single treatment with MI-E. The studies compared MI-E to other ways of helping people cough, or normal cough without help. One trial studied MI-E when added to other treatment. Based on three trials, MI-E may improve the outwards flow of air during coughing compared to a normal cough without help. MI-E was not clearly better than other methods of improving cough. None of the studies measured the outcomes that we thought were important for making decisions about the usefulness of MI-E. For example, the studies did not report on survival, length of hospital stay, quality of life, or serious side effects. One study reported extreme tiredness as a side effect of MI-E. There was often not enough information in the reports to tell whether the studies were well run; in some we found design problems that could have affected the results.

The findings of this review do not give enough evidence on which to make decisions. We were unable to find any information from trials on important short- and long-term effects, including side effects of MI-E in NMDs.

There is currently insufficient evidence for or against the use of MI-E to help people with NMDs clear mucus from their lungs. Further studies are needed to better understand the benefits and risks of MI-E in relation to other methods of cough assistance.

The evidence in the review is up to date as of 7 October 2013.

Authors' conclusions: 

The results of this review do not provide sufficient evidence on which to base clinical practice as we were unable to address important short- and long-term outcomes, including adverse effects of MI-E. There is currently insufficient evidence for or against the use of MI-E in people with NMDs. Further randomised controlled clinical trials are needed to test the safety and efficacy of MI-E.

Read the full abstract...

People with neuromuscular disorders (NMDs) may have weak respiratory (breathing) muscles which makes it difficult for them to effectively cough and clear mucus from the lungs. This places them at risk of recurrent chest infections and chronic lung disease. Mechanical insufflation-exsufflation (MI-E) is one of a number of techniques available to improve cough efficacy and mucus clearance.


To determine the efficacy and safety of MI-E in people with NMDs.

Search strategy: 

On 7 October 2013, we searched the following databases from inception: the Cochrane Neuromuscular Disease Group Specialized Register, CENTRAL (The Cochrane Library), MEDLINE, and EMBASE. We also searched and the WHO International Clinical Trials Registry Platform for ongoing trials. We conducted handsearches of reference lists and conference proceedings.

Selection criteria: 

We considered randomised or quasi-randomised clinical trials, and randomised cross-over trials of MI-E used to assist airway clearance in people with a NMD and respiratory insufficiency. We considered comparisons of MI-E with no treatment, or alternative cough augmentation techniques.

Data collection and analysis: 

Two authors independently assessed trial eligibility, extracted data, and assessed risk of bias in included studies according to standard Cochrane methodology. The primary outcome was mortality throughout follow-up or at six months follow-up.

Main results: 

Five studies with a total of 105 participants were found to be eligible for inclusion in this review. All included trials were short-term studies (two days or less), measuring immediate effects of the interventions. There was insufficient detail in the reports to assess methods of randomisation and allocation concealment. All five studies were at a high risk of bias from lack of blinding. The studies did not report on mortality, morbidity, quality of life, serious adverse events or any of the other prespecified outcomes. One study was a randomised cross-over trial conducted over two days, in which investigators applied two interventions twice daily in randomly assigned order, with a reverse cross-over the following day. Four studies applied multiple interventions for cough augmentation to each participant, in random order. One study reported fatigue as an adverse effect of MI-E, using a visual analogue scale. Peak cough expiratory flow (PCEF) was the most common outcome measure and was reported in four studies. Based on three studies, MI-E may improve PCEF compared to an unassisted cough. All interventions increased PCEF to the critical level necessary for mucus clearance. The included studies did not clearly show that MI-E improves cough expiratory flow more than other cough augmentation techniques. Based on one study, which was at risk of assessor bias, the addition of MI-E may reduce treatment time when added to a standard airway clearance regimen with manually assisted cough. MI-E appeared to be as well tolerated as other cough augmentation techniques, based on three studies which reported comfort visual analogue scores.