Abstract: 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. 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.

Plain-language summary: 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.